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i | P a g e St. Croix Watershed Management Plan WATERSHED MANAGEMENT PLAN FOR THE DIAMOND WATERSHED ST. CROIX, USVI JUNE 2022 ii | P a g e Diamond, St. Croix Watershed Management Plan ACKNOWLEDGEMENTS This document was prepared by Watershed Consulting Associates, LLC (Watershed Consulting) with assistance from the Virgin Islands Department of Planning and Natural Resources (DPNR) and funding provided by the Federal Emergency Management Authority Hazard Mitigation Grant Program (FEMA HMGP). Special thanks are extended to Hilary Lohmann, DPNR Coastal Resilience Coordinator, for her guidance and expertise. Notable contributions to this document were made by the Center for Watershed Protection, the Green Piece Engineering & Environment, the Virgin Islands Conservation Society, Inc., Bioimpact, Inc., Ocean Systems Laboratory, and the University of Vermont Spatial Analysis Lab. Special thanks are also extended to the local residents, business owners, USVI government employees, and other watershed stakeholders that shared their knowledge of watershed conditions and their vision for watershed management planning. iii | P a g e Diamond, St. Croix Watershed Management Plan LIST OF ACRONYMS APR Area of Protection or Restoration APC Areas of Particular Concern AU Assessment Unit BMP Best Management Practice CEKA Cyril E. King Airport CN Curve Number CWA Federal Clean Water Act CWP Center for Watershed Protection, Inc. DEM Digital Elevation Model DPNR Department of Planning and Natural Resources DPW USVI Department of Public Works DSM Digital Surface Model EPA Environmental Protection Agency FEMA Federal Emergency Management Agency GIS Geographic Information System(s) GSI Green Stormwater Infrastructure HMGP Hazard Mitigation Grant Program HUC Hydrologic Unit Code HSG Hydrologic Soil Group H&H Hydrologic & Hydraulic LID Low Impact Development MS4 Municipal Separate Storm Sewer System MGD Million Gallons per Day nDSM Normalized Digital Surface Model NOAA National Oceanic and Atmospheric Administration NPDES National Pollutant Discharge Elimination System NRCS National Resource Conservation Service NWI National Wetlands Inventory OSDS On-Site Disposal Systems PAD-US U.S. Geological Survey’s Protected Areas Database iv | P a g e Diamond, St. Croix Watershed Management Plan USGS United States Geological Survey USVI (or VI) United States Virgin Islands UVI University of the Virgin Islands SCS Soil Conservation Service SSO Sanitary Sewer Overflow STP Sewage Treatment Plants TMDL Total Maximum Daily Load TN Total Nitrogen TP Total Phosphorus TPDES Territorial Pollutant Discharge Elimination System TSS Total Suspended Solids VIWMA Virgin Islands Waste Management Authority WAPA USVI Water and Power Authority WMP Watershed Management Plan WHPP Wellhead Protection Plan WTM Watershed Treatment Model v | P a g e Diamond, St. Croix Watershed Management Plan Table of Contents Acknowledgements ....................................................................................................................................... ii List of Acronyms ........................................................................................................................................... iii 1 Executive Summary ............................................................................................................................... 1 2 Project Overview ................................................................................................................................... 4 Introduction ................................................................................................................................. 5 Background .................................................................................................................................. 7 2.2.1 Introduction to Watersheds and Guts .................................................................................. 7 2.2.2 Watershed Management Planning ..................................................................................... 10 Community Outreach ................................................................................................................. 12 2.3.1 Media Outreach .................................................................................................................. 13 2.3.2 Community Meetings .......................................................................................................... 14 2.3.3 Site Visits ............................................................................................................................. 18 2.3.4 Short Educational Videos .................................................................................................... 20 2.3.5 Educational Outreach ......................................................................................................... 20 Existing Regulations, Policies and Programs .............................................................................. 24 2.4.1 Current Policies & Legal Framework ................................................................................... 24 2.4.2 USVI Regulatory Agencies ................................................................................................... 25 2.4.3 Coastal Zone Management Tier Structure .......................................................................... 26 2.4.4 Survey .................................................................................................................................. 27 3 Diamond Watershed ........................................................................................................................... 28 Watershed Introduction............................................................................................................. 29 Physical & Natural Features ....................................................................................................... 30 3.2.1 Soils & Topography ............................................................................................................. 30 3.2.2 Hydrology ............................................................................................................................ 33 3.2.3 Habitat & Ecology ................................................................................................................ 43 Population Characteristics & Land Cover ................................................................................... 45 3.3.1 Watershed Demographics .................................................................................................. 45 3.3.2 Land Cover Mapping ........................................................................................................... 49 3.3.3 Zoning .................................................................................................................................. 51 3.3.4 Housing Development Age.................................................................................................. 54 3.3.5 Publicly Owned Areas ......................................................................................................... 54 3.3.6 Predicted Future Land Cover .............................................................................................. 55 vi | P a g e Diamond, St. Croix Watershed Management Plan Problem Definitions ................................................................................................................... 60 3.4.1 Impaired Waterbodies ........................................................................................................ 60 3.4.2 Stormwater ......................................................................................................................... 64 3.4.3 Wastewater ......................................................................................................................... 66 3.4.4 Point Source Pollution ......................................................................................................... 68 3.4.5 Solid Waste Management ................................................................................................... 68 3.4.6 Other Issues of Concern ...................................................................................................... 70 Data Collection ........................................................................................................................... 73 3.5.1 Stormwater Infrastructure Mapping................................................................................... 73 3.5.2 Existing Stormwater BMPs .................................................................................................. 76 3.5.3 Updates to Existing Data ..................................................................................................... 76 3.5.4 UAS Data Collection ............................................................................................................ 78 Water Quality Monitoring of Guts ............................................................................................. 79 3.6.1 Monitoring Overview .......................................................................................................... 79 3.6.2 Rainfall Monitoring ............................................................................................................. 81 3.6.3 Grab Sampling ..................................................................................................................... 83 3.6.4 Flow Measurements ........................................................................................................... 85 3.6.5 Sediment Sampling ............................................................................................................. 86 3.6.6 Results & Discussion ........................................................................................................... 87 Identification and Ranking of Stormwater BMPs ..................................................................... 105 3.7.1 Identification of Potential BMP Project Sites .................................................................... 105 3.7.2 Preliminary Ranking of BMP Project Sites......................................................................... 109 3.7.3 Final Ranking of BMP Project Sites ................................................................................... 113 3.7.4 30% Design Sites ............................................................................................................... 117 Watershed Modeling ............................................................................................................... 121 3.8.1 Modeling Overview ........................................................................................................... 121 3.8.2 Existing Conditions ............................................................................................................ 123 3.8.3 Existing Conditions with Future Development ................................................................. 125 3.8.4 Top 10 Proposed BMPs ..................................................................................................... 127 3.8.5 Proposed Conditions with Future Development .............................................................. 131 4 Recommendations & Conclusions .................................................................................................... 133 Proposed Management Measures ............................................................................................ 134 4.1.1 Stormwater Management and Non-Stormwater Discharges ........................................... 134 vii | P a g e Diamond, St. Croix Watershed Management Plan 4.1.2 Watershed Planning .......................................................................................................... 136 4.1.3 Land Use Planning and Resource Protection .................................................................... 138 4.1.4 Site Design Guidelines ....................................................................................................... 141 4.1.5 Solid Waste Management ................................................................................................. 142 4.1.6 Research Topics ................................................................................................................. 144 4.1.7 Watershed Stewardship Programs ................................................................................... 145 Financial and Technical Assistance Needs, Timeline, and Costs ............................................... 147 4.2.1 Stormwater Management and Non-Stormwater Discharges ........................................... 148 4.2.2 Watershed Planning .......................................................................................................... 150 4.2.3 Land Use Planning and Resource Protection .................................................................... 151 4.2.4 Site Design Guidelines ....................................................................................................... 153 4.2.5 Solid Waste Management ................................................................................................. 155 4.2.6 Research Topics ................................................................................................................. 157 4.2.7 Watershed Stewardship Programs ................................................................................... 158 Implementation Strategy .......................................................................................................... 159 4.3.1 Funding Mechanisms ........................................................................................................ 159 4.3.2 Monitoring Program ......................................................................................................... 164 Conclusions ............................................................................................................................... 165 5 References ........................................................................................................................................ 166 1 | P a g e Diamond, St. Croix Watershed Management Plan 1 EXECUTIVE SUMMARY Executive Summary 2 | P a g e Diamond, St. Croix Watershed Management Plan The United States Virgin Islands Department of Planning and Natural Resources (USVI DPNR) obtained grant funding in 2019 through the Federal Emergency Management Authority Hazard Mitigation Grant Program (FEMA HMGP) to develop comprehensive Watershed Management Plans (WMPs) for eight high priority watersheds of concern, three on St. Thomas and five on St. Croix. This watershed management plan (WMP) summarizes watershed-specific assessments and provides recommendations and design details to reduce flooding and improve water quality and resiliency. The five watersheds assessed on St. Croix include Bethlehem, Diamond, Hovensa, Long Point Bay, and Salt River Bay (Figure 1). The concurrent study on St. Thomas includes the watersheds of Bolongo Bay, Cyril E. King Airport, and St. Thomas Harbor. This plan is intended to be used to guide actions to: 1. Remedy current water quality issues, 2. Inform future development and improvement projects, and 3. Increase resiliency for existing and future land, water, and climate conditions. Figure 1. The five study watersheds on St. Croix are outlined in red. Executive Summary 3 | P a g e Diamond, St. Croix Watershed Management Plan This WMP provides a detailed summary of existing regulations, policies, and programs related to water quality on St. Croix. This is paired with a watershed-specific characterization that includes geology, hydrology, habitat, ecology, and demographics. To fully understand current watershed conditions, several datasets were developed or refined. Existing watershed boundaries and mapped guts were revised to better reflect drainage patterns. Stormwater infrastructure and existing stormwater best management practices were mapped and now reflect the most comprehensive dataset for the watershed. A detailed land cover dataset was developed utilizing high-resolution imagery from 2019. To identify areas of development change since the 2019 imagery was collected, an unmanned aircraft system (UAS) was flow over key areas in March 2022 to capture these areas and update the land cover dataset. This information was then used to predict future development through 2100. Within each of the priority watersheds, synoptic sampling of major guts during storm events was conducted to establish a baseline of water quality data. This gut monitoring is the most comprehensive assessment carried out in the territory and, in addition to characterizing the major guts, it also provided important information to guide future monitoring efforts. The WMP also details the drivers of declining water quality and increasing flooding including a lack of stormwater best management practices (BMPs), unmaintained or absent stormwater infrastructure, unstable slopes, poorly planned development, failing wastewater infrastructure, solid and hazardous waste management, and climate change influenced changes in rainfall patterns. Other issues of concern are also summarized including point source pollution, sea level rise, mangrove health, coral health, air pollution, sargassum, and pollution from marinas. A critical component in the development of this plan was community outreach and community and stakeholder input. A project website was developed so that easy to understand information, meeting invitations, and project deliverables could be shared. Several public outreach meetings were completed at pivotal stages of the development of this plan to inform and solicit feedback on areas of concern, utilizing critical local knowledge. As this WMP and other water quality driven efforts in the USVI span many years, it is important that the next generation take on the mantle of environmental stewardship. As such, a teaching curriculum was developed to educate students about watersheds, water quality issues, and green stormwater infrastructure. An in person teaching session with students on St. Croix was carried out, completing many learning objectives from this curriculum. Likewise, a series of three educational videos were developed to educate a broad audience about these important topics. Finally, a more concise project summary website and print document were also created to convey the key information from this plan to a non-technical audience. To improve water quality, reduce flooding, and improve resilience, a suite of recommendations was presented. A key component of the recommendations involved the identification, field and desktop assessment, water quality and hydrologic modeling, and ranking of stormwater BMPs. Preliminary (30%) engineering designs were advanced for two priority projects in the watershed and cost estimates were provided so that funding can be sought for final design and implementation. Other recommendations include changes to policies regarding solid waste management, watershed planning, site design, and stewardship. As this plan is meant to be actionable, financial and technical assistance needs, proposed timelines, and preliminary costs are also provided. Project Overview Introduction 4 | P a g e Diamond, St. Croix Watershed Management Plan 2 PROJECT OVERVIEW Project Overview Introduction 5 | P a g e Diamond, St. Croix Watershed Management Plan INTRODUCTION The United States Virgin Islands Department of Planning and Natural Resources (USVI DPNR) obtained grant funding in 2019 through the Federal Emergency Management Authority Hazard Mitigation Grant Program (FEMA HMGP) to develop comprehensive Watershed Management Plans (WMPs) for: • Five (5) high priority watersheds of concern on St. Croix and • Three (3) high priority watersheds of concern on St. Thomas. This WMP summarizes the assessment of the five priority watersheds on St. Croix: Bethlehem, Diamond, Hovensa, Long Point Bay, and Salt River Bay (Figure 2). From the Salt River Bay National Historic Park and Ecological Preserve to the Limetree Bay Refinery, these watersheds encompass a variety of different land uses with important commercial, residential, governmental, and agricultural resources. Figure 2. The five high priority watersheds assessed on St. Croix. Project Overview Introduction 6 | P a g e Diamond, St. Croix Watershed Management Plan The high priority study watersheds were selected based on their importance to Virgin Islanders as places where the negative impacts of development (Figure 3) have led to decreasing water quality and increased flood risk. The recommendations of this report will equip the Virgin Islands with the means to reduce consequences of climate change as the region is expected to experience more intense rainfall events with long stretches of drought. The goal of this WMP is to summarize watershed-specific issues, propose attainable solutions to improve water quality and reduce flooding, outline the technical and financial resources required to do so, and create a proposed implementation timeline. This plan will be used to inform local agencies and institutions on site-specific options for flood reduction, stormwater management, and water reuse as well as larger programmatic changes that would improve water quality and resiliency. Figure 3. Significant development on St. Croix, such as the Lime Tree Oil Refinery pictured, has impacted water quality and altered natural drainage patterns on the island. Project Overview Background 7 | P a g e Diamond, St. Croix Watershed Management Plan BACKGROUND 2.2.1 Introduction to Watersheds and Guts A watershed is an area of land where rainfall drains to a common body of water such as a bay or harbor. There are 27 primary watersheds on St. Croix, separated from each other by the crests of hills, ridgelines, and constructed infrastructure that guide the movement of water across the land (Figure 6). Each of these watersheds is made up of smaller drainage systems called subwatersheds that are also determined by topography and water flow. Figure 4. The 27 primary watersheds of St. Croix. Project Overview Background 8 | P a g e Diamond, St. Croix Watershed Management Plan A healthy watershed is one that conserves and cleans water, maintains aquatic ecosystems, supports healthy soils, and provides habitat for wildlife and plants. One of the most critical processes in maintaining healthy watersheds is infiltration, that is, the process by which water absorbed into the ground. This process provides many benefits, from recharging groundwater reservoirs to acting as a natural filtration system and removing pollutants. When the rate of rainfall exceeds the rate of infiltration, stormwater runoff is produced. This happens more readily and with smaller rainfall amounts when rain falls on impervious surfaces such as parking lots, roofs, roads, and driveways that do not allow water to soak into the ground (Figure 5). In its wake, stormwater runoff can scour the landscape, causing erosion and flooding that can damage local ecosystems and communities alike. This becomes more likely as native vegetation, which stabilizes and protects the native soil, is removed. As stormwater moves across the land, it can pick up harmful pollutants like trash, chemicals, nutrients, and excessive sediment before inevitably depositing these pollutants into the harbors and bays. Figure 5. Runoff from impervious surfaces such as a road contributes to flooding and water quality problems. Project Overview Background 9 | P a g e Diamond, St. Croix Watershed Management Plan The dominant water conveyance system within the watersheds of St. Croix are guts (Platenberg, 2006). A gut (occasionally spelled “ghut”) is a stream with a reasonably well-defined channel (Figure 6). The guts of St. Croix are ephemeral, flowing only when there has been enough rain for the accumulation of water within the defined gut channel. Historically, there were many guts that flowed year-round, fed by the groundwater reserves of the island. Now, guts primarily only flow following storm events, and this ephemeral nature has impacted the public perception of guts as only being useful as stormwater conveyances and not as a functional amenity of the island (Gardner et al., 2008). Guts provide a variety of critical ecosystem services to St. Croix. They provide habitats to many rare flora and fauna, are sources of food and recreational opportunities to members of the community, and provide fresh water for agricultural, industrial, and domestic purposes (Gardner et al., 2008). While other types of wetlands are present on St. Croix and serve vital functions, the absence of large freshwater resources means that guts form the basis for watershed management in the territory (USVI DPNR, 2020). Figure 6. Illustration of a gut (University of the Virgin Islands, Cooperative Extension Service (left)) and a picture of gut (right). Project Overview Background 10 | P a g e Diamond, St. Croix Watershed Management Plan 2.2.2 Watershed Management Planning When Hurricane Maria hit St. Croix during the 2017 hurricane season, the impacts were devastating. High winds and flooding catastrophically damaged infrastructure across St. Croix including homes, schools, hospitals, roads, and private businesses. Many residents were left with limited access to food, water, or electricity (Cox et al., 2019). The significant flooding also led to surges in nutrients and sediment entering the coastal ecosystems, causing serious damage to the coral reef communities (Hernández et al., 2020). Events like these underline the need for proper watershed management, which is vital to maintaining healthy watersheds. There are many management practices that a community can employ to address stormwater runoff and prevent pollution at its source. Public education and outreach can be used to communicate the importance of responsible landscaping and proper use and storage of toxic household materials. Land use controls and/or incentives can be used to manage the development of impervious surfaces. Best management practices (BMPs) such as low impact development (LID) and green stormwater infrastructure (GSI) can be designed to clean and store stormwater. At the heart of watershed management is the underlying philosophy that everything is interconnected. Every component of a watershed is interrelated and interdependent, bound together by the same shared water system. A successful watershed management framework supports partnerships and uses sound multidisciplinary science to identify and complete well-planned, connected actions to achieve results. In developing this WMP, the guidelines established in the U.S. Environmental Protection Agency’s (EPA) Handbook for Developing Watershed Plans to Restore and Protect our Waters (the Handbook) were followed (U.S. EPA, 2008). The Handbook details a six-step process for watershed planning as outlined in Figure 7. The contents of this WMP are the product of Steps 1-4, that is, build partnerships (Step 1), inventory watershed (Step 2), set goals and identify solutions (Step 3), and design an implementation program (Step 4). Recommendations for implementation of the WMP (Step 5) and measurement of progress and making adjustments as progress is made (Step 6) are also provided within this WMP. It is important to note that the process of watershed management is dynamic and iterative. As more information is collected and lessons are learned, the implementation program should be reassessed, refined, and modified accordingly. Figure 7. Conceptual drawing of the WMP and implementation process. Project Overview Background 11 | P a g e Diamond, St. Croix Watershed Management Plan One key component of this process is its incorporation of the nine minimum elements from the Clean Water Act section 319 Nonpoint Source Program’s funding guidelines. Each of these elements are embedded within the six-step process for watershed planning as shown in Figure 7. The nine elements are designated by the EPA as the most critical for an effective watershed planning process and are generally required for watershed projects funded under section 319. The nine elements, included in EPA’s Handbook for Developing Watershed Plans to Restore and Protect Our Waters (2008), are: 1. Identify causes and sources of pollution 2. Estimate load reductions expected 3. Describe management measures and targeted critical areas 4. Estimate technical and financial assistance needed 5. Develop an information and education component 6. Develop a project schedule 7. Describe interim, measurable milestones 8. Identify indicators to measure progress 9. Develop a monitoring component Project Overview Community Outreach 12 | P a g e Diamond, St. Croix Watershed Management Plan COMMUNITY OUTREACH An essential component in the creation of this WMP is following the principles of community-driven development. Broad public education and engagement in the planning process is essential to the success of watershed management. This requires deliberate efforts to develop public participation in a shared analysis of both the problems and solutions for a given watershed. Communities most vulnerable to the effects of flooding and degraded water quality have relevant direct experience and can provide first-hand accounts and information not typically available by other means of investigation. It is also these same communities that are likely to be the most directly affected by the outcomes of the WMP. The more residents that are engaged in their own community solutions, the more effective those solutions will be. In the development of this WMP, a variety of mediums were utilized for the purposes of community outreach and engagement. This included virtual meetings, site visits, social media engagement, short educational videos, and teaching sessions. One key component of community outreach was the development of a project website designed using the ESRI Story Map platform (Figure 8). The purpose of the Story Map is to provide a comprehensive resource for DPNR, partners, and community members to learn about the project, provide input, and access updates on project events and deliverables. One of the primary features of the Story Map is a tab that allows the public to submit reports of flooding or other water quality issues in a geographic format. This feature enables citizens to engage with the project continuously and to act as citizen scientists. A link to the Story Map is provided here: Visioning Story Map. It can also be accessed and promoted via tinyurl.com/StormwaterUSVI. Figure 8. A screenshot from the Project Overview section of the project website. Project Overview Community Outreach 13 | P a g e Diamond, St. Croix Watershed Management Plan 2.3.1 Media Outreach To inform community members about upcoming events and increase general awareness of the project, media outreach through radio, the DPNR website, and social media posts on the project’s Facebook page was completed. The project piqued the interest of a number of local independent news organizations, resulting in several articles being written about the project. A summary of the press coverage and media outreach associated with project is summarized in Table 1. Table 1. A summary of the media outreach and press coverage for the project. Media Outreach Medium Organization Date Brief Description Radio NPR/WTJX / 93.1 FM March 29th, 2021 Interview for promotion of community kickoff meetings WSTX/ 100.3 FM March 29th, 2021 Interview for promotion of community kickoff meetings DaVybe/WLDV/107.9 FM March 30th, 2021 Interview for promotion of community kickoff meetings Radio One / WVWI / 1000 AM March 30th, 2021 Interview for promotion of community kickoff meetings Phone Interviews V.I. Daily News April 8th, 2021 Interview V.I. Daily News April 12th, 2021 Interview Press Coverage Organization Author Date Title & Link U.S. Virgin Islands Hotel & Tourism Association Laurel Kaufmann April 1st, 2021 USVI Watershed Management Plan Town Hall Announcement The Virgin Islands Consortium Staff Consortium April 6th, 2021 Town Halls to Discuss Impact of Stormwater Runoff on Local Communities Set for Wednesday and Thursday The St. Thomas Source, US Virgin Islands Susan Ellis April 7th, 2021 Watershed Project Aims to Improve Water Quality in the Territory The St. Thomas Source, US Virgin Islands Sian Cobb April 9th, 2020 Community’s Input Sought for Watershed Plans The Virgin Islands Daily News Patricia Borns April 14th, 2021 Stormwater USVI asks residents to identify territory water issues The Virgin Islands Free Press VI Free Press Staff June 23rd, 2021 Town Hall Meeting On Long Point Watershed In St. Thomas Is Tonight The St. Thomas Source, US Virgin Islands Don Buchanan June 30th, 2021 Rain Runoff Causes Problems, Project Seeks Solutions Project Overview Community Outreach 14 | P a g e Diamond, St. Croix Watershed Management Plan 2.3.2 Community Meetings To engage with communities of St. Croix, a combination of kickoff meetings, community visioning meetings and watershed-specific meetings were organized. The meetings were held virtually to maximize attendance and in consideration of the mitigating circumstances of the COVID-19 pandemic. The initial kickoff meeting (Kickoff Meeting #1) was intended to introduce USVI DPNR staff to the project, confirm goals and schedule, determine water quality sampling locations, and solicit general input. The second kickoff meeting (Kickoff Meeting #2) followed a similar format but was made available to all agencies and departments of the USVI territory government. In both meetings, project partners solicited important feedback on what can make a project of this nature successful and what important resources are available. The intent of the community visioning meetings was to identify how individuals and agencies can lead, participate in, and collaborate on watershed improvements to achieve the goals of the WMP and the community vision for the future. Two community visioning meetings were held for the island of St. Croix (Figure 9), one for residents and one for local business leaders. During these meetings, local stakeholders shared their perspective on environmental challenges within the study watersheds. Amongst business leaders, there was almost unanimous consensus that poor water quality and/or flooding has directly impacted their business and that they would benefit from a water quality friendly marketing campaign. This was echoed by several residents who have been directly impacted by the repercussions of storm- driven flood events. One resident voiced concern about the deteriorated road condition near their food products supplier, “Quality Food”, and additionally noted the build up of trash and sediment within the neighboring gut. Figure 9. Two virtual town hall meetings were held for St. Croix. Project Overview Community Outreach 15 | P a g e Diamond, St. Croix Watershed Management Plan Two watershed-specific community meetings were held for each of the study watersheds (Table 2). In the first round of the watershed-specific virtual town hall meetings (Figure 10), the discussions were focused on key areas of concern and best management practice opportunities as they pertain to each individual watershed. It was during these meetings that stakeholders within the community identified specific locations that would benefit the most from improved stormwater management practices. Maps of the watersheds were presented, and community members pointed to specific locations where they have observed flooding or water quality issues firsthand. In the second round of town hall meetings, which occurred in February of 2022, the discussions focused on the progress of the project in the last year (Figure 11). This included presentations of the top ranked BMP practices and the processes that went into selecting these, as well as the water quality monitoring conducted and the final steps that will be taking steps in the coming months. Further discussions were held in these meetings about other potential areas of impact that should be assessed. Figure 10. Flyers used to advertise the first watershed town hall meetings Project Overview Community Outreach 16 | P a g e Diamond, St. Croix Watershed Management Plan Figure 11. A second round of town hall meetings were held in February of 2022. Project Overview Community Outreach 17 | P a g e Diamond, St. Croix Watershed Management Plan Table 2. A summary of community presentations and meetings. Presentations and Meetings Events Date Brief Description Project Kickoff Meetings Project Kickoff Meeting #1 - USVI DPNR Stakeholders February 26th, 2021 The meetings were held to discuss the project, confirm project goals, confirm the project schedule, determine water quality sampling locations, and solicit general input. Project Kickoff Meeting #2 - USVI Government Stakeholders March 3rd, 2021 Community Visioning Meetings Community Visioning Meeting - Local Residents April 7th, 2021 The meetings were held to provide local residents and businesses with an introduction to watershed management and project summary. An in-depth watershed discussion was held to identify high risk areas and address local concerns. Community Visioning Meeting - Local Businesses April 7th, 2021 Events First Meeting Date Second Meeting Date Events Watershed Town Hall Meetings Bethlehem Watershed Town Hall June 14th 2021 February 7th, 2022 The meetings were held to discuss key areas of concern and best management practice opportunities as they pertain to each individual watershed. It was during these meetings that stakeholders within the community identified specific locations that would benefit the most from improved stormwater management practices. Salt River Bay Watershed Town Hall June 21h, 2021 February 16th, 2022 Long Point Bay Watershed Town Hall June 23rd, 2021 February 15th, 2022 Diamond Watershed Town Hall June 24th, 2021 February 10th, 2022 Hovensa Watershed Town Hall June 30th, 2021 February 14th, 2022 Project Overview Community Outreach 18 | P a g e Diamond, St. Croix Watershed Management Plan 2.3.3 Site Visits Property damage and limited access to roadways caused by flooding and erosion were the most prevalent concerns brought up by community members. Locations identified as concerns by community members on the project website interactive map can be found in Figure 12. In response to many of those who contacted the project team or our partners about site specific issues, representatives from our team conducted site visits to assess damage or issues, meet with community members in-person, and develop proposed solutions. Often a relatively recent infrastructure development was cited as the source of aggravated flooding within a neighborhood or on a specific property. Community members noted how the construction of housing developments, walls, and sidewalks led to the flow of runoff being redirected onto their property. This highlights the need for careful planning that considers stormwater management in any type of development. Figure 12. Flooding and water quality problem areas identified by community members. Project Overview Community Outreach 19 | P a g e Diamond, St. Croix Watershed Management Plan In one specific incident, a community member detailed the excavation of old growth trees within an existing gut and along its banks (Figure 13). The community member noted how the trees used to provide shade and shelter to many species of mammals, birds, and reptiles. The area was once a place he would take his family to recreate. He stated that the excavation of the gut and its riparian buffer destroyed this ecosystem, and there has been no follow up to amend the environmental consequences of the destruction. Figure 13. Photos of a gut taken by a resident before (left) and after (right) excavation. Project Overview Community Outreach 20 | P a g e Diamond, St. Croix Watershed Management Plan 2.3.4 Short Educational Videos A series of three short educational videos were developed as a part of this project. The purpose in the development of these videos was to provide DPNR with educational outreach content that they could share on their social media and with local stakeholders. Educational Video #1: An Introduction to Watersheds This video provides an introduction to watersheds. The video introduces viewers to the fundamentals of watershed science, providing them with the knowledge to identify the basics of what constitutes a healthy watershed and what potential threats may compromise that health. The video goes on to describe watershed management as a practice, why it is important and what that means for residents of a watershed. The narrator in this video is Olasee Davis, an assistant professor in the Natural Resources Program at the University of the Virgin Islands (UVI). Educational Video #2: Threats to Watersheds and Potential Solutions The second educational video dives a little deeper into the threats that watersheds in the Virgin Islands face and management strategies that can be used to address them. It provides an introduction to the specific water quality constituents (i.e., nutrients, sediment, and bacteria) that threaten human and environmental health. This was followed by an introduction to hydrologic dynamics, specifically the methods of water movement including infiltration, interception, storage, and transport and how land use plays an influential role in these dynamics. The video summarizes common types of stormwater best management practices and explains how these practices utilize hydrologic dynamics to address pollutants of concern. Educational Video #3: Community Action The last video of the educational series focused on community action. Specifically, how local residents and businesses can engage in reducing contamination and improving the overall health of USVI watersheds. The primary premise of this video is that watershed protection is everyone’s responsibility and there are impactful ways that individuals can contribute to improved watershed management. The first subject of focus is vegetation, emphasizing the value of utilizing vegetation to minimize erosion and reducing fertilizer and pesticide use to minimize nutrient pollution. This is followed by a discussion of hazardous chemicals and solid waste, and how residents can properly dispose of them. Next, the video describes the value in building a rain garden and keeping new structures out of flood zones. The video ends with a discussion of community action groups and local clean ups where community members can volunteer and get involved. 2.3.5 Educational Outreach 2.3.5.1 Curriculum Development A teaching curriculum was developed to be used by educators in the Virgin Islands. The curriculum is divided into three sections that align with the learning objectives. In Section 1, students learn about stormwater and its movement through watersheds and the types of pollutants that stormwater can carry to surface waters. In Section 2, students learn to monitor and measure stormwater and they are introduced to green stormwater infrastructure as a mechanism to treat and reduce stormwater runoff from a property. Activities are designed to engage students to make recommendations about green Project Overview Community Outreach 21 | P a g e Diamond, St. Croix Watershed Management Plan stormwater infrastructure practices for their school grounds and local communities. In Section 3, students engage in a stormwater stewardship project. Teachers have the option to carry out the curriculum in its entirety or to use guidance provided to engage students in any individual activity or grouping of activities. Each section includes an overview with guiding questions, student learning objectives, a list of activities and materials, preparation guidelines for educators, activity descriptions, resources for additional information, and background reading and worksheets for students. Key terms are listed in bolded red font and defined in a glossary at the end of the curriculum. Background information and worksheets designed for student use are provided within the document. 2.3.5.2 Teaching Sessions An in person teaching session was held at the St. Croix Educational Complex High School in mid-March 2022 (Figure 14). The project team met with Ms. Linda James’s Marine Biology class and the school’s Eco Club (combined) to complete the learning objectives for six of the ten activities found in the U.S. Virgin Islands Stormwater Education & Stewardship Curriculum (Appendix A). A seventh activity was partially completed. These activities, the learning objectives, and how they were completed are summarized below. Figure 14. Students learned about concepts related to watershed planning and green stormwater infrastructure. Activity 1.1B: Knowledge Assessment This activity was focused on ensuring that students understand key terms and concepts about watersheds, impervious surfaces, stormwater runoff, and best management practices. A group quiz game was completed. The students were asked: Project Overview Community Outreach 22 | P a g e Diamond, St. Croix Watershed Management Plan o What is a watershed? o What is an impervious surface? o What is a pervious surface? o What is stormwater runoff? o How does stormwater runoff and development impact water quality? o What is a rain garden? If students were unable to answer a question, the presenters helped guide them to the correct answers. Activity 1.3: Delineating a Watershed The goal of this activity is to understand how to delineate a watershed and understand a topographic map. At the teaching session, a location where a rain garden is proposed was assessed. The students walked to that location and a discussion was held about how water flows in that area. Students were asked to consider the area that drained to the point of interest. Students then returned to the classroom. The map of the school area was displayed on the smart screen at the front of the classroom so that students could view the watershed they described. Activity 1.4: Stormwater in Your Community A discussion was held regarding pollutant sources, impervious surfaces, and pervious surfaces with a focus on the drainage area for the proposed rain garden at each school. A discussion was also held about what other harmful pollutants could be carried by stormwater like oil from cars or trash. Students were asked if they have seen “muddy” water flowing over the ground when it rains. The topics of erosion and sediment pollution were introduced. Students were asked to consider how pollutant sources while looking at the drainage area for the proposed rain garden outside. Activity 1.5: Stormwater Flow Path Map A discussion was held about how stormwater moves over land and how slope, and land cover, and soil compaction can impact that flow. Students discussed how the stormwater flows while looking at the site outside. The map was presented on the smart board at the front of the classroom so they could visualize this on the map. Activity 1.6: Stormwater Pollution Map A discussion was held regarding impervious surfaces and pervious surfaces with a focus on the drainage area for the proposed rain garden at each school. Students were asked to point out these areas outside and discuss the impacts of these land cover types. Students were asked to consider how stormwater moves over impervious and pervious surfaces and define those areas for the drainage area to the proposed rain garden while outside. Activity 2.1: Getting to Know Green Stormwater Infrastructure (partial completion) The topic of best management practices and green stormwater infrastructure (GSI) were introduced to students. As the school has a proposed rain garden, the discussion was focused on this one practice. A brief discussion on the benefits, the design, and the maintenance of rain gardens was held. Activity 2.2: Recommend a GSI Practice A rain garden was recommended by the school group for their school property. A discussion was held regarding the practice design, how to direct water to the practice, and what issues the rain garden will Project Overview Community Outreach 23 | P a g e Diamond, St. Croix Watershed Management Plan address. Considerations include the size of the practice, plants to be installed, maintenance, and aesthetics. The group also discussed the importance of designing the rain garden to be an appropriate size for the drainage area. Section 1 Recap: It was confirmed that the students were able to: • Describe a watershed. • Describe stormwater and how it impacts watersheds. • Identify examples of nonpoint source pollution, discuss how it occurs, and compare and contrast it with point source pollution. This completes the student learning objectives for Section 1. Section 2 Recap: The student learning objectives for Section 2 are: • Students will learn about green stormwater infrastructure design solutions. • Students will be able to calculate impervious area and volume estimates for stormwater design. • Students will identify design criteria and make recommendations. Students learned about rain gardens and impervious surfaces as well as some of the considerations for design in the in-person teaching session. This completes the student learning objectives for Section 2. Section 3 Recap: Stewardship activities will be completed in the future through rain garden design and maintenance. Discussion about the practice was held. Project Overview Existing Regulations, Policies and Programs 24 | P a g e Diamond, St. Croix Watershed Management Plan EXISTING REGULATIONS, POLICIES AND PROGRAMS Existing regulations, policies, and programs related to water quality have a profound impact on the success of current and future watershed planning efforts. Strong regulations and programs provide a solid base for watershed planning efforts and can establish potential sources of funding for staffing and training. As part of this WMP, an evaluation of current codes and a survey of staff to better understand current challenges for staff and where code language may be adjusted to enhance water quality and protect natural resources was conducted. The complete methods and findings from the evaluation are documented in the U.S. Virgin Island Regulatory Review Report found in Appendix A. A summary of this information targeted at DPNR staff is also provided in Appendix A. 2.4.1 Current Policies & Legal Framework In the USVI, both federal and local policies and procedures are in place for environmental protection. The USVI government implements or enforces the following federally mandated environmental programs: • Clean Water Act (CWA) o Ambient Water Quality Monitoring o Section 319 Nonpoint Source Pollution o Section 402 Territorial Pollutant Discharge Elimination System (TPDES) o Beaches Environmental Assessment and Coastal Health (BEACH) Act • Safe Drinking Water Act (SDWA) • Clean Air Act (CAA) o Air Pollution Prevention and Control o Title V Operating Permits o New Source Performance Standards o Risk Management Program (RMP) o Section 112 Air Toxics, including National Emission Standards for Hazardous Air Pollutants • Energy Policy Act of 2005 The Virgin Islands Code currently contains the policies for water resources management and watershed planning in the USVI. The 2019 Code includes measures to ensure that some level of protection is provided for available water resources since development activities on land can result in direct impacts on coastal waters and marine resources due to the islands physiography. The USVI has several watershed protection codes in place (i.e., buffers, erosion, and sediment control) but are still experiencing negative water quality impacts. The surveys conducted through this regulatory audit and needs/capabilities assessment helped to identify how implementation of the codes could be improved. The regulatory review (see Project Overview Existing Regulations, Policies and Programs 25 | P a g e Diamond, St. Croix Watershed Management Plan Appendix A, report Table 1) highlights the sections of the Virgin Islands Code that have direct influence on water resources and watershed planning efforts. 2.4.2 USVI Regulatory Agencies The institutions with regulatory responsibilities related to watershed management and planning in the USVI are as follows: 2.4.2.1 Department of Planning & Natural Resources (DPNR) The Department of Planning and Natural Resources (DPNR) was established in 1987 and serves as the agency responsible for the administration and enforcement of all laws pertaining to the preservation and conservation of fish and wildlife, trees and vegetation, coastal zones, cultural and historical resources, water resources, and other environmental concerns. Prior to 1987 the agency was known as the Department of Conservation and Cultural Affairs. The responsibilities of the DPNR include oversight and compliance for land subdivision, development and building permits, code enforcement, earth change permits, zoning administration in the coastal zone, boat registration, and mooring and anchoring of vessels within territorial waters. DPNR is comprised of ten primary operating divisions, each with its own regulatory mandate. The divisions with responsibilities relevant to watershed management can be found in Appendix A’s regulatory review. 2.4.2.2 VI Department of Agriculture (VIDA) The Virgin Islands Department of Agriculture (VIDA) is responsible for soil conservation practices on agricultural lands including maintaining buffer zones along guts. VIDA exercises its authority for earth change activities conducted on sites over which they have authority They also support the activities of the Virgin Islands Conservation District (VICD) to provide for the conservation and development of the soil, water, and other natural resources of the Virgin Islands. 2.4.2.3 Department of Public Works (DPW) The Department of Public Works (DPW) routinely impacts watershed health and planning efforts through several program areas including: 1. Infrastructure Maintenance: DPW is mandated to plan, construct, and maintain public roads, highways, storm drainage systems, buildings, transportation systems, parking facilities, and cemeteries. 2. Gut Cleaning Program: DPW operates a program to clean guts to avoid nuisance flooding especially during the hurricane season. Guts are cleared and maintained in accordance with the guidelines stipulated by the DPNR and may involve bushing the sides of the guts and removal of solid waste. DPW has also partnered with the Waste Management Authority (WMA) to address guts that have been affected by sewage. 3. Flood Mitigation: DPW undertakes flood mitigation work for roads, as well as general flood mitigation for properties in floodplains. Examples include the Smith Bay Road stormwater mitigation project (USVI ODR, 2020) and the St. Andrews Flood Mitigation Project (FEMA, 2021). 2.4.2.4 Waste Management Authority (WMA) This agency provides waste collection, treatment, and disposal services to protect public health and preserve the environment of the USVI. They regulate the landfills, convenience centers, and bin locations where solid waste is collected. The agency is also responsible for the public sewer system and addressing sanitary sewer overflows (SSOs) and combined sewer overflows (CSOs). Project Overview Existing Regulations, Policies and Programs 26 | P a g e Diamond, St. Croix Watershed Management Plan 2.4.2.5 Water and Power Authority (WAPA) This agency produces and distributes electricity and drinking water to residential and commercial customers in the territory. This includes the islands’ wells that may be impacted by pollutants from runoff. The DPNR DEP’s groundwater program also has a role in in drinking water through their public water systems supervision program that regulates well management and new well drilling. 2.4.3 Coastal Zone Management Tier Structure The entirety of the USVI is in the coastal zone because they are small islands. For planning and permitting considerations, the coastal zone is divided into two tiers: Tier 1 and Tier 2. Tier 1 extends landward from the outer limit of the territorial sea, including all offshore islands and bays, to distances inland as specified in an approved map that was first developed in 1979 (NOAA, 2018). Figure 15 shows the extent of the Tier 1 areas for St. Croix as provided by the Coastal Zone Management (CZM) program. Tier 2 includes the remainder of the USVI - interior portions of the Islands of St. Thomas, St. John, and St. Croix, including all watersheds and adjacent land areas not included in Tier 1. Figure 15. CZM Tier 1 areas (courtesy of CZM). Areas designated as Tier 1 have a more stringent permitting process than those in Tier 2. Permits for development can be for either minor activities or major activities and permitting development responsibilities are assigned based on the activity type. The DPNR Commissioner issues permits for all minor activities. A Coastal Zone Management Commission committee for each of the three major islands issues all permits for major activities within Tier 1. A more comprehensive coastal zone permit process is focused only on proposals in Tier 1, and Section 906 of the VICZMA is focused on specific policies applicable to the tier. Major construction permit applications for Tier 1 projects are reviewed by CZM staff who then issue a report with recommendations that trigger a public hearing process. After the public hearing, the project must be approved by the local Coastal Zone Management Commission committee for the specific island, and then by the USVI legislature and the governor. Tier 2 permit applications have fewer requirements for applicants during the DPNR review process and are handled entirely by DPNR. The Division of Building Permits issues permits for activities under the Earth Change law, while the Division of Planning issues zoning and subdivision permits. No public hearing is currently required for Tier 2 projects unless a zoning change is required. Although development projects in Tier 2 are required to be consistent with the goals of the VICZMA and reviewed by the relevant Project Overview Existing Regulations, Policies and Programs 27 | P a g e Diamond, St. Croix Watershed Management Plan authorities, compliance monitoring and enforcement by DPNR personnel is typically limited to permitted activities within Tier 1 only. 2.4.4 Survey DPNR staff were surveyed to identify programmatic strengths and gaps in watershed protection strategies. The review used multiple online survey tools to best understand current practices and procedures and to allow staff an opportunity to weigh in on programmatic issues they encounter while performing their jobs. The review was conducted to document current conditions, not as a critique of past management efforts. The results of the surveys informed the watershed plan recommendations and were instrumental in developing optimum management standards and strategies to reduce the impacts of urbanization and new development. Understanding the current state of development strategies and practices allows for an assessment of strengths and weaknesses, guides future watershed planning strategies, and highlights changes and additions to current codes that help design effective watershed plans and protect important water resources. A total of four surveys were completed by DPNR and WMA staff. They included: 1. Eight Tools of Watershed Protection Audit This audit tool, developed by CWP, identifies programmatic strengths and gaps in watershed protection strategies and helps inform watershed planning recommendations. 2. Needs and Capabilities Assessment The Needs and Capabilities Assessment explores programmatic needs and existing capacity pertaining to the process of plan reviews and inspection of stormwater Best Management Practices (BMPs). 3. Future Land Use Questions These questions were designed to obtain more information on future watershed development. It was intended to answer questions about planned future projects and the protections provided to certain land uses and physical topographies to reduce the impact of development. 4. Better Site Design Questions for WMA Other agencies outside of DPNR also have programs or practices that influence watershed protection planning. A set of questions was provided to WMA staff to provide their insight into how their current practices influence watershed resources. The links to three of the surveys were provided to DPNR staff in early May 2021 and respondents were given several weeks to provide input. All survey instruments were closed on May 28th, 2021 to allow time for processing. Some tools had better response rates than others, and some questions received no response since the preceding question was answered with a no or a response that that meant there was no additional information. The Needs and Capabilities Assessment had four responses (compared to eight responses to the Eight Tools Audit survey), but the responses did provide additional input from staff on the development review process. Appendix A includes the results of the assessment. There was no response to the Post-Construction Management questions, which may indicate that post construction inspection and maintenance may be a tool that should be adopted in the future. Diamond Watershed Existing Regulations, Policies and Programs 28 | P a g e Diamond, St. Croix Watershed Management Plan 3 DIAMOND WATERSHED Diamond Watershed Watershed Introduction 29 | P a g e Diamond, St. Croix Watershed Management Plan WATERSHED INTRODUCTION The Diamond watershed is a 4.57 sq. mile watershed located on the southwestern coast of St. Croix (Figure 16). Diamond watershed is largely characterized as a residential. The watershed is home to the St. George Village Botanical Garden located on an old sugar plantation. The watershed also encompasses the Rasahai Hill Top hiking trail and the Breids Bay shoreline. The watershed population is 3,585, a majority of which are minorities based on 2010 US Census data. The watershed contains 7.6 miles of guts and 1.3 miles of shoreline. It includes 32.4 acres of wetlands, of which 76% are classified as riverine. Soils generally have a slow rate of infiltration and a high runoff potential. The total impervious cover of the watershed is approximately 9%, and the watershed has a high tree canopy cover of 65%. The primary zoning categories are low-density residential (52.6%) and medium- density residential (15.8%). Housing development in the watershed occurred throughout the 1970s – 2000s. Data from the U.S. Virgin Islands Department of Planning and Natural Resources (DPNR) ambient and beach water quality monitoring programs categorizes three assessment units as Class B, with two not monitored, and one with impairments for transparency/clarity, pH, and turbidity. See Appendix B1 for the complete watershed characterization. Figure 16. Overview map of the watershed. Diamond Watershed Physical & Natural Features 30 | P a g e Diamond, St. Croix Watershed Management Plan PHYSICAL & NATURAL FEATURES 3.2.1 Soils & Topography 3.2.1.1 Soils When rain falls over land, a portion runs into guts and the stormwater system while the remaining infiltrates into the soil or evaporates into the atmosphere. The hydrologic soil group (HSG) is a soil property that represents the rate at which water infiltrates into a type of soil. Soils are classified into seven soil groups, including four HSGs (A, B, C, and D) based on the soil’s infiltration capacity, and three “dual classifications” (A/D, B/D, and C/D) where a soil’s infiltration capacity is influenced by a perched water table (Table 3). Data was obtained from the USVI Department of Planning and Natural Resources (DPNR) soil boundaries and the gridded National Soil Survey Geographic Database (gNATSGO), which is developed and maintained by the U.S. Department of Agriculture’s Natural Resource Conservation Service (USDA NRCS). Table 3. Overview of Hydrologic Soil Groups (HSG)1. Hydrologic Soil Group (HSG) Description HSG-A HSG-A soils consist of deep, well-drained sands or gravelly sands with high infiltration and low runoff rates. HSG-B HSG-B soils consist of deep, well-drained soils with a moderately fine to moderately coarse texture and a moderate rate of infiltration and runoff. HSG-C HSG-C consists of soils with a layer that impedes the downward movement of water or fine-textured soils and a slow rate of infiltration. HSG-D HSG-D consists of soils with a very slow infiltration rate and high runoff potential. This group is composed of clays that have a high shrink-swell potential, soils with a high-water table, soils that have a clay pan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. HSG-A/D HSG-A/D soils naturally have a very slow infiltration rate due to a high-water table, but they will have high infiltration and low runoff rates if drained. HSG-B/D HSG-B/D soils naturally have a very slow infiltration rate due to a high-water table, but they will have a moderate rate of infiltration and runoff if drained. HSG-C/D HSG-C/D soils naturally have a very slow infiltration rate due to a high-water table, but they will have a slow rate of infiltration if drained. No HSG Assigned2 Data not available in gNATSGO. 1 Source: NRCS, 2007 https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=17757.wba 2 Indicates HSG data was not available within a particular soil boundary. Diamond Watershed Physical & Natural Features 31 | P a g e Diamond, St. Croix Watershed Management Plan Figure 17 shows the distribution of HSG classes within the Diamond watershed and Table 4 provides a breakdown of the acres and percentages. The watershed consists predominantly of low infiltration soils in the flatter sloped, developed portion of the watershed, with 14.6% HSG-C and 83.9% HSG-D, indicating a high potential for stormwater runoff. As shown in Table 4, the percentage of total area attributed to HSG classes amounts to 99.9% of the watershed. The final 0.1% can be attributed to surface water in the watershed. Table 4. Hydrologic Soil Groups (HSG) in the Diamond watershed. Hydrologic Soil Group (HSG) Area in Watershed (acres) Percentage of Total Area (%) A 0.0 0.0% B 0.0 0.0% C 425.4 14.6% D 2452.6 83.9% A/D 0.0 0.0% C/D 0.0 0.0% No HSG Assigned 41.2 1.4% Total 2919.2 99.9% Figure 17. Hydrologic Soil Groups (HSG) in the Diamond watershed. Diamond Watershed Physical & Natural Features 32 | P a g e Diamond, St. Croix Watershed Management Plan 3.2.1.2 Topography Development on steep slopes is highly susceptible to erosion that carries sediment to nearby waterways and ultimately local bays. In excess, sediment has harmful impacts on aquatic ecosystems, including but not limited to 1) reduced light penetration, which inhibits coral and seagrass growth, 2) clogging of gills and filters in fish and shellfish, and 3) decline of commercial and recreation fishing success (Schueler, 1987). Impacts of sediment deposition in coastal waters smothers seagrass beds and coral reefs, increases sedimentation of channels and harbors (requiring more frequent dredging), changes bottom composition, and leads to loss of use for recreational purposes like swimming and snorkeling (U.S. EPA, 1993). To date, there is no steep slope ordinance in the USVI to limit development on steep slopes and ensure adequate soil and erosion control practices are used. Soil surveys produced by the U.S. Department of Agriculture categorize soil types, in part, based on typical slope ranges shown in Table 5 below. These ranges, along with a slope data layer developed for this project using 2018 topographical data, were used to summarize slopes in the watershed, which are also outlined in Table 5 and displayed on Figure 18. Slopes in the watershed are predominantly either less than 8% or between 16-50%. Figure 18 shows the greatest slopes are in the northern portion of the watershed associated with the gut headwaters. The soils associated with the steeper slopes have low infiltration and high runoff potential. During a rain event, the runoff flows down these slopes to the floodplain below, often resulting in flooding. Figure 24 shows the locations of floodplains in the Diamond watershed. Figure 18 shows the location of the developed areas in relation to the slope percentages. Development areas, based on data from 2019, are defined as areas containing greater than 20% impervious cover. There are approximately 512 acres of developed area in the Diamond watershed, which equates to 18% of the total watershed area. Most development has occurred in areas with flatter slopes located in the central and southern portions in residential areas. Table 5. Slope percentages in the Diamond watershed. Slope Percentage Area in Watershed (acres) Percentage of Total Area (%) 0% – 3% 978.3 33.5% 4% – 8% 721.2 24.7% 9% – 15% 410.1 14.0% 16% – 25% 468.8 16.0% 26% – 50% 338.3 11.6% > 51% 5.1 0.2% Total 2,921.8 100% Diamond Watershed Physical & Natural Features 33 | P a g e Diamond, St. Croix Watershed Management Plan 3.2.2 Hydrology 3.2.2.1 Rainfall The average annual rainfall at Christiansted, St. Croix is 43.3 inches (ClimaTemps, n.d.). During a normal year, weather is characterized by a dry season, which spans from December – June, and a wet season, which spans from July – November. The wettest period, hurricane season, occurs between June and November (Alderson et al., 2018). Rainfall patterns vary significantly from year to year, with above average precipitation and flooding one year and drought or near-drought conditions the following year (RMSI Private Limited, 2021). The average annual rainfall at Christiansted, St. Croix is 43.3 inches (ClimaTemps, n.d.). During a normal year, weather is characterized by a dry season, which spans from December – June, and a wet season, which spans from July – November. The wettest period, hurricane season, occurs between June and November (Alderson et al., 2018). Rainfall patterns vary significantly from year to year, with above average precipitation and flooding one year and drought or near-drought conditions the following year (RMSI Private Limited, 2021). Figure 18. Developed areas and slope percentages in the Diamond watershed. Diamond Watershed Physical & Natural Features 34 | P a g e Diamond, St. Croix Watershed Management Plan 3.2.2.2 Surface Water Features In the U.S. Virgin Islands, waterways are called guts, which historically—as late as the 1950s—were perennial streams (Gardner et al., 2008). “Gut" is a local term, derived from the Danish word “ghut,” meaning stream or creek (Macdonald et al., 1997). U.S. Virgin Island Code defines a gut as a natural or constructed waterway or any permanent or intermittent stream (2019 U.S. Virgin Islands Code Title 29, Chapter 3, Subchapter I, § 225). Increased development activity resulted in guts that currently flow only after heavy rainfall or during the rainy season (May – November). Portions of the guts are piped underground to allow for development. There are no perennial streams on the USVI (USVI DPNR, 2016). In the 18th and 19th centuries, guts served as the primary drinking water source; they also served as a drinking water source to a limited degree in the 20th century through the 1960s (Gardner et al., 2008). Currently, desalination plants and bottled water have replaced guts as the primary drinking water source. Guts were also used for hunting, freshwater fishing, bathing, and hiking (Gardner et al., 2008). Guts with permanent pools of freshwater can serve as habitat for rare species of aquatic animals (e.g., Mountain Mullet and American Eel). In addition, guts form corridors that facilitate the movement of wildlife species (Gardner et al., 2008). Over time, increased development led to their degradation as they were seen as dumping grounds. Today, they are still used as a source of freshwater for agriculture and to recharge groundwater. Due to the ephemeral nature of guts, the water quality monitoring programs in the U.S. Virgin Islands focus on coastal waters and beaches, so information concerning water quality in guts is sparse. Within the Diamond watershed, there are 7.6 miles of guts, 5.0 acres of freshwater ponds, and 1.3 miles of shoreline along the Caribbean Sea (Figure 19). None of the coastal waters bordering any of the study watersheds on St. Croix fall within the jurisdiction of the National Park Service. Surface water feature data were obtained from USVI’s DPNR and from the National Wetlands Inventory (NWI) dataset. Diamond Watershed Physical & Natural Features 35 | P a g e Diamond, St. Croix Watershed Management Plan Figure 19. Surface water features in the Diamond watershed. Diamond Watershed Physical & Natural Features 36 | P a g e Diamond, St. Croix Watershed Management Plan 3.2.2.3 Riparian Zones Existing land cover was summarized within a 25-foot buffer surrounding the guts in the watershed. These buffers are commonly referred to as riparian zones, transitional areas occurring between guts and the neighboring land. Riparian zones are characterized by distinctive hydrology, soil, and biotic conditions, and while they are often proportionally a small component of a watershed, they play a significant role in ecosystem process and local fauna composition (Heartsill‐Scalley, 2021). In the watershed, 84% of the existing land-cover within the riparian buffer zone is composed of tree canopy with the remaining riparian area consisting primarily of grass and shrub. It is noteworthy that only 1% of the riparian buffer zone consists of impervious cover (buildings, roads, and other paved areas), indicating minimal development along the guts (Figure 20). Figure 20. Existing land cover within a 25-foot buffer of guts in the Diamond watershed. 3.2.2.4 Wetlands According to the NWI, the Diamond watershed includes 32.4 acres of wetlands (Figure 21 and Table 6). Approximately 76% of those wetlands are classified as riverine and 21% are freshwater forested/scrub. The remaining 1% are classified as estuarine and marine located along the shoreline. Table 6. Summary of wetlands in the watershed. Wetland Type Area in Watershed (acres) Estuarine and Marine Wetland 1.1 Freshwater Emergent Wetland 0.0 Freshwater Forested/Shrub Wetland 6.9 Lacustrine 0.0 Riverine 24.5 Total 32.4 Diamond Watershed Physical & Natural Features 37 | P a g e Diamond, St. Croix Watershed Management Plan Figure 21. Wetlands in the Diamond watershed. Diamond Watershed Physical & Natural Features 38 | P a g e Diamond, St. Croix Watershed Management Plan 3.2.2.5 Freshwater Resources Freshwater is a scarce resource in the U.S. Virgin Islands. Water is supplied to housing units through a combination of the public water supply, cisterns, and wells, in addition to bottled water purchased by residents. Figure 22 shows the distribution of water sources (public, cistern, or other) by estate based on 2010 U.S. Census data. The public water supply is provided by the USVI Water and Power Authority (WAPA), which operates two desalination plants (Estate Richmond Power Plant) that can produce 3.6 million gallons per day of potable water using energy efficient reverse osmosis. The WAPA pipe distribution system primarily serves Frederiksted and Christiansted and does not cover the entire island. The water main pipes that deliver water to residents are old and fragile ductile iron types installed as far back as the 1940s. This has resulted in leaks in the system with approximately 30 percent of water lost in the distribution system on St. Croix (USVI Hurricane Recovery and Resilience Task Force, 2018). Recent work has begun to replace the aging pipes in both Frederiksted and Christiansted. Most of the islands’ population uses cisterns to collect rainwater for general use and purchases bottled water for drinking. The USVI Code Title 29 Chapter 5 requires that all buildings except commercial development dwellings and single unit apartments already connected to potable water systems be constructed with a self-sustaining water system such as a cistern or water collection system (USVI, 2019). This includes a requirement to have a certain minimum usable capacity of gallons per square foot of roof area based on building type. Bottled water is from either WAPA or well water that is re-filtered, bottled, and certified by the Department of Health. Many hotels and condominiums in the USVI use small reverse osmosis units to produce their own water (USVI Hurricane Recovery and Resilience Task Force, 2018). Private water haulers also purchase potable water from WAPA, and several have built their own reverse osmosis production system (Alderson et al., 2018). Most residents collect and store rainwater from the rooftop drainage system into cisterns attached to their homes or businesses. Cisterns are either concrete holding tanks lined in waterproof coating and placed underground, or plastic tanks located either above ground or buried. Electric pumps are used to connect to the existing plumbing system and provide water used for toilets, sinks, dishwashers, washing machines, and showers. Generally, they are not used for drinking water as they are typically not sealed and subject to contamination. Mesh screens are used to keep out larger animals and debris, but mosquitoes and frogs are often found in cisterns. Cistern water is commonly treated with chlorine bleach to kill any animals, insects, or pathogens as recommended by CDC guidelines. Several drinking water treatment technologies are available for household use including treatment of cistern water that include filtration, reverse osmosis systems, distillation systems, and ultraviolet treatment systems (CDC, n.d.). During a drought, residents purchase water from WAPA or a private water hauler to fill their cisterns (USVI Hurricane Recovery and Resilience Task Force, 2018). Private water haulers treat groundwater from wells through reverse osmosis as a secondary source of drinking water (USVI DPNR, 2018). The major aquifer underlying the central portion of the island is a limestone aquifer called Kingshill aquifer (USVI DPNR, 2018). Principal aquifer locations from the U.S. Geological Survey are shown in Figure 23 below. Water quality data for the wells was not available. While the development of a Wellhead Protection Plan (WHPP) is vital to ensure the availability of uncontaminated groundwater for the future, one currently does not exist. Diamond Watershed Physical & Natural Features 39 | P a g e Diamond, St. Croix Watershed Management Plan Figure 22. Housing unit water sources by estate in the Diamond watershed (Source: 2010 U.S. Census data). Diamond Watershed Physical & Natural Features 40 | P a g e Diamond, St. Croix Watershed Management Plan Figure 23. Aquifers in the Diamond watershed. Diamond Watershed Physical & Natural Features 41 | P a g e Diamond, St. Croix Watershed Management Plan 3.2.2.6 Flood Zones Flood zones in the U.S. Virgin Islands are characterized by the impact associated with the 100-year and 500-year flood events. As indicated in Table 7, most of the mapped flood zone is in the “A” zone which is associated with the gut floodplains. Immediately adjacent to the “A” zone are areas in the “X” zone. The shoreline is prone to hazards from storm-induced velocity wave action, as defined by the “VE” flood zone (Figure 24). The “AE” zone also occurs along the shoreline. No data are available for the 10-, 25-, or 50- year flood events on the U.S. Virgin Islands. Table 7. Flood zones in the watershed. Flood Zone Definition* Area in Watershed (acres) A Areas subject to inundation by the 1-percent-annual-chance (100-year) flood event where no hydraulic analyses have been performed. 356.3 AE Areas subject to inundation by the 1-percent-annual-chance (100-year) flood event where hydraulic analyses have been performed. 7.4 AO Areas subject to inundation by the 1-percent-annual-chance (100-year) shallow flooding where average depths are between one and three feet. 0.0 VE Areas subject to inundation by the 1-percent-annual-chance (100-year) food event with additional hazards due to storm-induced velocity wave action. 7.4 X An area of minimal to moderate flood hazard that is outside of the Special Flood Hazard Area and either 1) between the limits of the base flood and the 0.2-percent-annual chance (500-year) flood, or 2) above the elevation of the 0.2-percent-annual-chance (or 500-year) flood. 36.2 *Definitions adapted from https://floodpartners.com/flood-zones/ Total: 407.4 Diamond Watershed Physical & Natural Features 42 | P a g e Diamond, St. Croix Watershed Management Plan Figure 24. Flood zones in the Diamond watershed. Diamond Watershed Physical & Natural Features 43 | P a g e Diamond, St. Croix Watershed Management Plan 3.2.3 Habitat & Ecology St. Croix is home to many species of protected and endangered plants, birds, fish, reptiles, mammals, and coral. The U.S. Endangered Species Act of 1973 provides for the conservation of endangered or threatened species and all or portions of their required habitats and ecosystems. A species is considered ‘endangered’ if it is likely to become extinct in a significant portion of its range. A species is considered ‘threatened’ if it is likely to become endangered in the near future (UVI, 2009). Coral reefs consist of a community of coral polyps that form some of the most diverse ecosystems and provide habitat for at least 25% of all marine species (UVI, 2009). Global stressors to the reefs include ocean warming and other impacts related to climate change. Local threats include pollutants associated with runoff from development, unsustainable land use and fishing pressure, physical damage from anchors, boat groundings, and marine debris. Strategic priorities for coral reef management are documented in Rothenberger & Henderson (2019). Coral reefs are important to the USVI economy; they provide food, jobs, recreation, and culture, as reef products are incorporated in streets and buildings. Corals also provide a natural defense to coastal property and protect the islands from hurricane-induced flooding, providing an estimated $47 million dollars in annual flood protection benefits (Storlazzi et al., 2019). They also help support recreation, as they contribute to swimmable and aesthetic bays and beaches as well as diving locations for tourists. According to the U.S. Fish and Wildlife Service’s spatial datasets, the Diamond watershed does not contain critical habitat for rare, threatened, or endangered species. There is a small amount of this habitat along the edges of St. Croix, but none falls within the Diamond watershed boundary. No spatial datasets for wildlife corridors, Areas of Protection or Restoration (APR), coral reef management locations, or mangroves were available for the island of St. Croix. These areas may exist on the island, and possibly within this watershed; however, data was unable to be obtained. A spatial dataset of Areas of Particular Concern (APCs), including APCs specific to coral reefs, was provided by DPNR. Within the Diamond watershed, there are no coral reef-specific APCs; however, 196.3 acres of the “Southshore Industrial Area” APC are within the Diamond watershed. Figure 25 below illustrates the APCs within and surrounding the Diamond watershed. Protected areas on St. Croix are available from the U.S. Geological Survey’s (USGS) Protected Areas Database (PAD-US). The PAD-US is a national inventory of protected areas including areas dedicated to the preservation of biological diversity, and other natural uses—such as recreational or cultural uses, including extraction—managed for these purposes through legal or other effective means (GreenInfo Network, 2016). Based on USGS PAD-US data, there are no protected areas in the Diamond watershed. There were no protected areas within Diamond Watershed. Diamond Watershed Physical & Natural Features 44 | P a g e Diamond, St. Croix Watershed Management Plan Figure 25. Areas of Particular Concern (APCs) within and surrounding the Diamond watershed. Diamond Watershed Population Characteristics & Land Cover 45 | P a g e Diamond, St. Croix Watershed Management Plan POPULATION CHARACTERISTICS & LAND COVER 3.3.1 Watershed Demographics Various demographics were summarized for the study watersheds using 2010 U.S. Census data because 2020 Census data was not yet released for the USVI at the time of this report. Data was obtained from the U.S. Census Bureau’s Virgin Islands webpage and summarized by USVI estate boundaries. Estates that intersected watershed boundaries were summarized according to the proportion of each estate within the study watershed. The demographic data categories include: • Total Population o Total number of people of any age. o This value was adjusted to account for the proportion of the estate that is contained within the study watershed. • Percent Minority o Percentage of population with a racial status other than white alone and/or non- Hispanic or Latino (i.e., all people other than non-Hispanic-or-Latino, white-alone individuals). The minority population in the USVI is primarily African American and West Indian. • Percent Linguistically Isolated o Percentage of population over 5 years old who speak a language other than English and who speak English less than “very well” • Percent Low Income o Percent of families with income in 2009 below the poverty level • Percentage of occupied households with no vehicles Diamond Watershed Population Characteristics & Land Cover 46 | P a g e Diamond, St. Croix Watershed Management Plan Table 8 provides a summary of the above-listed demographics in the Diamond watershed. Approximately 7.1% of the total population of St. Croix is located within the Diamond watershed, a majority of which are minorities. By analyzing the Census data at the estate scale, the data indicate differences between different portions of the watershed, in terms of population density, minority percentage, linguistic isolation, poverty, and mobility (see Figure 26 and Figure 27 below). Table 8 Overview of selected 2010 U.S. Census demographics data summarized for estates in the Diamond watershed. Demographic Value Total Population* 3,585 Percent Minority** 76.7% Percent Linguistically Isolated** 6.9% Percent Low Income** 16.5% Average Number of Vehicles per Occupied Household** 1.1 * This is the area-adjusted total, which accounts for portions of some estates being not entirely within the Diamond watershed boundary. ** These values are averages weighted by estate area. Figure 26 below illustrates the population density of the estates in the Diamond watershed. Populations are shown in people per square mile. The most densely populated areas are associated with medium- density residential development in the watershed. Figure 27 below illustrates (A) the percent minority of the population of each estate, (B) the percent of the population in each estate that is linguistically isolated, (C) the percent of the families whose 2009 earnings were below the poverty line and (D) the percentage of occupied households with zero vehicles in the estates within the watershed. The estate with gray fill has a population of zero, and therefore has no associated metrics. Low-income families make up a large proportion of residents within the main downtown urban development. These regions also coincide with a large percentage of minority populations, those who are linguistically isolated, and households with zero vehicles. Diamond Watershed Population Characteristics & Land Cover 47 | P a g e Diamond, St. Croix Watershed Management Plan Figure 26. Population density (people per square mile) in estates within the Diamond watershed. Diamond Watershed Population Characteristics & Land Cover 48 | P a g e Diamond, St. Croix Watershed Management Plan Figure 27. Minority (A), linguistically isolated (B), low-income (C), and zero vehicle household (D) demographics in estates within the Diamond watershed. D A B C Diamond Watershed Population Characteristics & Land Cover 49 | P a g e Diamond, St. Croix Watershed Management Plan 3.3.2 Land Cover Mapping Land cover was mapped from high-resolution, remotely sensed data yielding the most complete, precise, and accurate mapping ever carried out for the US Virgin Islands. The primary source data sets used consisted of aerial imagery obtained through the Hexagon imagery program and publicly available LiDAR sourced from NOAA Digital Coast. The aerial imagery, collected in 2019, had a spatial resolution of 15 cm with spectral coverage in the blue, green, red, and near-infrared portions of the electromagnetic spectrum. The LiDAR data, which was collected in 2018 using a discrete return sensor, had a point spacing that exceeded 90 points per square meter in some locations. Supplementing these remotely sensed data sets were vector layers representing roads and hydrologic features. The imagery data were processed to create seamless mosaics for each island. The LiDAR was processed to create normalized and classified point clouds in addition to raster surface models. The surface models consisted of a Digital Elevation Model (DEM), Digital Surface Model (DSM), and a Normalized Digital Surface Model (nDSM). The DEM was derived from the LiDAR ground classified points, with each pixel value representing the ground surface topographic elevation relative to sea level. The DSM was derived from the LiDAR first returns, with each pixel representing the height of features relative to sea level. The nDSM was obtained by subtracting the DEM from the DSM, yielding a model in which each pixel represented the height above ground. All the raster surface models were produced at a resolution of half a meter. Some editing was performed on these vector data sets to improve their consistency and quality prior to incorporating them into the land cover mapping. Land cover feature extraction was carried out using a semi-automated process at a resolution of half a meter. The automated part of the mapping centered on an object-based feature extraction approach that incorporated the imagery, LiDAR point clouds, LiDAR surface models, and supporting vector data sets to map land cover features using a combination of artificial intelligence and expert systems. The output from the automated workflow was then manually reviewed by technicians at a scale of 1:1000 to correct visible errors. The final landcover data set contained eight classes: 1) bare soil, 2) buildings, 3) grass/herbaceous vegetation, 4) other paved/impervious surfaces, 5) roads, 6) shrubs, 7) tree canopy, and 8) water. The height threshold for tree canopy was 2 meters. See Figure 28 below for an example of the imagery, nDSM, and land cover classifications for an example area on St. Thomas. Figure 28. Imagery displayed as color infrared (left), LiDAR nDSM (center), and resulting land cover (right) on an example area. Diamond Watershed Population Characteristics & Land Cover 50 | P a g e Diamond, St. Croix Watershed Management Plan The existing land cover in the Diamond watershed is predominantly tree canopy (64.8%), grass shrub (cumulatively 22.0%), impervious surfaces including roads, buildings, and other paved areas (9.0%) and bare soil (4.0%). Figure 29 and Table 9 present the existing land cover within the Diamond watershed. Total impervious cover is approximately 9%, placing the watershed in the “Sensitive” category, based on the Impervious Cover Model. According to this classification system, non-supporting watersheds have between 0% and 10% of their area in impervious cover. Within this range, the streams support hydrologic function and support good to excellent aquatic diversity (Schueler et al., 2009). Table 9. Existing land cover in the Diamond watershed on St. Croix. Land Cover Category Area in Diamond Watershed (acres) Percentage of Total Area Bare Soil 117.9 4.0% Buildings 73.2 2.5% Grass 347.8 11.9% Other Paved 99.7 3.4% Roads 91.9 3.1% Shrub 295.4 10.1% Tree Canopy 1,894.4 64.8% Water 2.7 0.1% Total 2,923.0 100% Figure 29. Existing land cover in the watershed. Diamond Watershed Population Characteristics & Land Cover 51 | P a g e Diamond, St. Croix Watershed Management Plan 3.3.3 Zoning The USVI Zoning Code defines how property in specific zones can be used. The document details whether specific geographic zones are acceptable for residential, commercial, or industrial purposes. Zoning codes may regulate lot size, placement, density, setbacks, acceptable uses, and the height of structures. The U.S. Virgin Islands have 18 distinct zoning districts: two agricultural districts, five residential districts, four business districts, one commercial district, two industrial districts, two waterfront districts, one public district, and one special district. Zoning information is available for the USVI as part of a parcel layer that contains the current, previous, and proposed zoning districts. However, the zoning districts in the spatial dataset do not match those in DPNR’s “Virgin Islands Zoning District Requirements” document, which can be found on their website. The zoning districts in the spatial dataset were revised to represent land use categories that are: 1) more meaningful from a planning sense, and 2) more consistent with the Watershed Treatment Model, which will be used in later phases of plan development for the watershed. In general, the zoning districts were categorized based on the use category (e.g., all agricultural zones characterized as “Agricultural”). Residential zoning districts were subdivided based on their densities, with “Waterfront Pleasure” classified as Low Density Residential due to the zoning density being the same as the Low-Density Residential category. Figure 30 illustrates the breakdown of the revised zoning districts throughout the parcels in the Diamond watershed. Most of the watershed is characterized as low-density residential (52.6%) and medium-density residential (15.8%). The southern portion of the watershed characterized as public (11.3%) is part of the Henry E. Rohlsen Airport. It is important to note that neither the revised zoning districts, nor the original zoning districts on which they are based, are necessarily reflective of all uses occurring in the parcel. Original zoning districts appear to be designated based on the parcel’s majority use. As such, a parcel may contain areas that do not match its overall zoning district. The pie charts in Figure 31 below summarizes the relationship between existing land cover and area of the revised zoning districts in the watershed. Most of the land-use in residential development zoning areas is green space, most notably in low-density developments and to a lesser degree in medium and high- density developments. Business, industrial, commercial, and public zoning areas also show to be predominated by green space. Land cover mapping and predicted future land cover can be found in Sections 3.3.2 and 3.3.6 respectively. Diamond Watershed Population Characteristics & Land Cover 52 | P a g e Diamond, St. Croix Watershed Management Plan Figure 30. Revised zoning districts within the Diamond watershed. Diamond Watershed Population Characteristics & Land Cover 53 | P a g e Diamond, St. Croix Watershed Management Plan Figure 31. Land cover in revised zoning districts in the Diamond watershed. Diamond Watershed Population Characteristics & Land Cover 54 | P a g e Diamond, St. Croix Watershed Management Plan 3.3.4 Housing Development Age Median decade of housing unit development by estate in the watershed was sourced from the 2010 U.S. Census data. As shown in Figure 33, the decades of residential development in the watershed ranged throughout the decades from the 1970s to early 2000s. 3.3.5 Publicly Owned Areas Figure 33 and Table 10 below display the federal- and USVI- owned areas within the Diamond watershed on St. Croix. Most of the USVI-owned parcels are owned by the Government of the Virgin Islands, the Virgin Islands Housing Finance Authority, or the Virgin Islands Port Authority. Most of the federal-owned parcels are owned by the “Federal Government” or the “United States of America Forest Service.” Figure 32. Median decade of housing unit development by estate in the Diamond watershed. Diamond Watershed Population Characteristics & Land Cover 55 | P a g e Diamond, St. Croix Watershed Management Plan Table 10. Area of parcels owned by federal and USVI government entities. Ownership Category Area in Watershed (acres) Percentage of Area in Watershed (%) Federal 2.1 0.1% USVI 440.4 15.1% Other 2,021.5 69.2% None Listed 458.5 15.7% Figure 33. Federal and USVI-owned parcels in the Diamond watershed on St. Croix 3.3.6 Predicted Future Land Cover Future land cover scenarios for 2030, 2050, 2080, and 2100 were developed based upon 2019 land cover data (see Section 3.3.6) and predicted development based on past trends within the watershed to assess the impacts of this growth. Feature engineering was employed to predict where this future development will occur based on observed development patterns. The study watershed was divided into grid cells, each representing 5.56 acres. Grid Cells with 20% impervious surface or more were defined as “Urban”, and all other grid cells were defined as “Other”. Land cover change between the 2012 and 2019 data was calculated to identify regions where change Diamond Watershed Population Characteristics & Land Cover 56 | P a g e Diamond, St. Croix Watershed Management Plan occurred during the specified time frame. This step was repeated to identify regions where development change occurred between 2002 and 2019. An exploratory analysis was performed to identify common characteristics associated with the grid cells experiencing development change. Characteristics explored included population density, income, distance to tourist attractions, distance from highway, zoning designation, distance to previously urban areas, elevation, slope, flood zone designation, distance to shoreline, watershed designation, parcel size, percent of previous agriculture land use in each grid cell, percent previous impervious land cover in each grid cell, percent previous wetland in each grid cell, and percent previous bare soil in each grid cell. The following notable findings were found during the feature engineering process: 1. Distance to shoreline does not appear to play a factor in the current development pattern while distance to highways was a more significant in predictor of where development will occur. 2. A large majority of newly created impervious surface is occurring in residential zoning designations 3. Most of recent development tends to occur at lower elevations. 4. 20.8% of grid cells designated as “new development” intersect a FEMA designated Flood zone. Features associated with development change were inserted into a logistic regression model. Features were removed if they were directly correlated to another feature in the model. The logistic regression model was used to predict development change between 2012-2019 and 2002-2019. Within the model, the dependent variable was binary, representing if a grid cell experienced development gain or not. At a 10% probability threshold, the 2012-2019 model’s overall accuracy is calculated at 96.8%. The 2002-2019 model’s overall accuracy is calculated at 89.5%. The 2012-2019 model was generalized to 10 years, distributing the new projected development across the study area. A 10% probability threshold was defined, which can be interpreted as having a 10% risk of development between 2019 and 2030. This same process was repeated for the 2002-2019 model, which was generalized to 20 years, to retrieve development risk predictions for 2040. The model was run iteratively on both the 10-year and 20-year model outputs to retrieve predictions for 2050, 2080, and 2100. The model’s features were updated where applicable. Lastly, the model output was manually corrected for any discrepancies between models. Each grid cell identified as at-risk for development was assigned a predicted amount of impervious surface if development were to occur. The amount of impervious was calculated as the mean percent impervious surface in the current urban grid cells bordering a given grid cell identified as at risk for development (Figure 34). The assumption is that the new development grid cells reflect the land use composition of nearby grid cells. The calculation was repeated for forest cover, shrub cover, grass cover, and bare cover. The future land cover model makes several assumptions. First and most significantly, the model assumes that the development pattern in the future will be consistent with the development pattern observed in present day. Significant changes in climate and the development market over the next 80 years can significantly impact future development patterns. Additionally, USVI’s population trajectory is highly dependent on the territory’s ability to mitigate future environmental damage. The model does not guarantee that any individual grid cell will be further developed. Instead, each identified grid cell should be thought of as being at risk for development and may require additionally monitoring for development in the future. The longer the model’s time frame, the higher the error potential. The new land cover for Diamond Watershed Population Characteristics & Land Cover 57 | P a g e Diamond, St. Croix Watershed Management Plan each newly defined urban grid cell is assumed to have the same land use composition as the urban grid cells surrounding each newly developed cell. Second, the model assumes that all currently classified urban grid cells will remain urban and grid cells not predicted to be developed will have the same land use composition as present day. Hence, a presently developed grid cell will remain developed in the future with a similar land use composition while undeveloped grid cells that are expected to remain undeveloped will have similar future land use composition as present day. Third, aggregating data into grid cells may result in discrepancies in the land use composition of grid cells bordering the watershed’s edge. Since each grid cell is assigned a percentage for each land use type, the land use composition of each grid cell is assumed to be spatially dispersed across the grid cell. Finally, the model fails to account for conserved areas, meaning that development may be predicted in conservation regions. Future land cover datasets for 2030, 2050, 2080, and 2100 consisted of approximately five-acre grid cells containing percentages for the following land cover categories: water, bare soil, green space, and impervious cover. The land cover area in each grid cell was summarized within the Diamond watershed boundary. Impervious surface in the watershed is expected to increase by approximately 4% from the existing condition of 9% in 2019 to 13% in 2100. In comparison, green space is expected to decrease by 4% from the existing condition of 87% in 2019 to 83% in 2100. New development is predicted to be most likely to occur adjacent to existing development clusters. The modeled results indicated that there as time passes, there is greater risk of development in regions with more open green space. The land cover breakdown for the existing and future land cover scenarios is provided in Figure 35. Diamond Watershed Population Characteristics & Land Cover 58 | P a g e Diamond, St. Croix Watershed Management Plan Figure 34. Grid Cells at risk of development in 2030, 2050, 2080 and 2100. Diamond Watershed Population Characteristics & Land Cover 59 | P a g e Diamond, St. Croix Watershed Management Plan Figure 35. Existing land cover (2019) and future land cover (2030, 2050, 2080, and 2100) in the Diamond watershed. Diamond Watershed Problem Definitions 60 | P a g e Diamond, St. Croix Watershed Management Plan PROBLEM DEFINITIONS 3.4.1 Impaired Waterbodies USVI DPNR is responsible for implementing and enforcing territorial water quality standards and pollution control laws under the federal Clean Water Act. To meets these goals, DPNR administers two water quality monitoring programs, the coastal water quality monitoring program and the beach water quality program. The coastal water quality monitoring program is the primary mechanism for monitoring the U.S. Virgin Islands coastal water quality. In this program, delineated waterbodies referred to as assessment units (AUs) are sampled for a variety of water quality indicators on a quarterly basis. In the beach water quality monitoring program, designated beaches throughout the territory are sampled for water quality indicators on a weekly basis. Due to the ephemeral nature of guts, water quality monitoring programs focus on coastal waters and beaches. Data collected by these programs is used to protect public health and provide notification of beach closures. The data also determines effluent permit limits and develops waterbody impairment listings for the 303(d) list. This list is used to establish priorities for the implementation of water quality improvement measures including the development of TMDLs. According to the current U.S. Virgin Islands water quality standards, the waters of the U.S. Virgin Islands exist in one of four classes: I, A, B, and C. Standards as defined in the 2020 Integrated Water Quality Monitoring and Assessment Report can be found in Table 11. • Class I waters include either inland surface waters or inland groundwaters are therefore excluded from the water quality monitoring program at this time. • Class A waters (or Outstanding National Resource Waters) are marine and coastal water with exceptional recreational, environmental, or ecological significance to be preserved. They are designated for maintenance and propagation of desirable species of aquatic life (including threatened, endangered, and indigenous species), for primary contact recreation, and for use as potable water sources. • Class B waters encompass all marine and coastal waters not classified as Class A or Class C. As with Class A waters, they are designated for maintenance and propagation of desirable species of aquatic life, for primary contact recreation, and for use as potable water sources. • Class C waters are those waters which are located in industrial harbors and ports. They have less stringent water quality standards for certain parameters and are designated for the maintenance and propagation of desirable species of aquatic life, primary contact recreation, industrial water supplies, shipping, navigation, and for use as potable water sources for those waters being used currently or that could be used in the future as potable water sources. Diamond Watershed Problem Definitions 61 | P a g e Diamond, St. Croix Watershed Management Plan Table 11. Water Quality and Assessment Criteria (USVI DPNR, 2020). Parameter Source Data Type Assessment Method Enterococcus Ambient, Beach The 30-day geometric mean for enterococcus shall not exceed 30 colony-forming units/100 mL and no more than 10 percent of the samples collected in the same 30 days shall exceed 110 colony- forming units/100 mL. Turbidity Ambient, Beach A maximum nephelometric turbidity unit reading of three (3) shall be permissible, and secchi disk reading of minimum of 1 meter. Clarity Ambient, Beach *For areas where coral reef ecosystems are located, a maximum nephelometric turbidity unit reading of one (1) shall be permissible, and secchi disk reading of minimum of 1 meter. Total Phosphorus Ambient Shall not exceed 50 μg/l pH Ambient Class A, B: Range shall not be outside 7.0 to 8.3 standard units Class C: Range shall not be outside 6.7 to 8.5 standard units Dissolved Oxygen Ambient Class A, B: Shall be no less than 5.5 mg/L Class C: Shall be no less than 5.0 mg/L Temperature Ambient Shall not exceed 32 degrees Celsius at any time, nor as a result of waste discharge to be greater than 1.0°C above natural conditions. *For areas where coral reef ecosystems are located, shall not exceed 25-29°C at any time, nor as a result of waste discharge to be greater than 1.0°C above natural. *Areas that contain coral reef ecosystems are determined based on Benthic Habitat Mapping in Puerto Rico and the U.S. Virgin Islands (NCCOS, 2002) The Diamond watershed includes three (3) assessment units (AUs), with representative data taken from one water quality monitoring station (Figure 36). All three AUs are classified as Class B, with two not monitored, and one with Impairments for chronic toxicity, pH, dissolved oxygen, and turbidity (Table 12). All the impairments are classified as “Low Priority” for TMDL development. Diamond Watershed Problem Definitions 62 | P a g e Diamond, St. Croix Watershed Management Plan Figure 36. Assessment units and water quality monitoring stations in the watershed. Diamond Watershed Problem Definitions 63 | P a g e Diamond, St. Croix Watershed Management Plan Table 12. Assessment units (AUs) with 303(d) listing in the watershed (USVI DPNR, 2020). AU ID AU Name Associated Monitoring Stations Priority Class Impairment Years Impaired TMDL Completion VI-STC- 73 Diamond Nearshore Currently no monitoring stations Low B None N/A N/A VI-STC- 74 Enfield Green Beach/VIRIL Outfall Currently no monitoring stations Low B None N/A N/A VI-STC- 75 Diamond subwatershed, offshore STC-24B Low B pH 2020 2029 VI-STC- 75 Diamond subwatershed, offshore STC-24B Low B Chronic Toxicity 2010, 2014, 2020 2029 VI-STC- 75 Diamond subwatershed, offshore STC-24B Low B Dissolved Oxygen 2010, 2014, 2016, 2018 2029 VI-STC- 75 Diamond subwatershed, offshore STC-24B Low B Turbidity 2020 2029 Diamond Watershed Problem Definitions 64 | P a g e Diamond, St. Croix Watershed Management Plan 3.4.2 Stormwater 3.4.2.1 Lack of Management Practices Stormwater BMPs improve the water quality of stormwater runoff both by removing pollutants through filtering or settling, and by controlling both the volume and rate of flow of runoff entering guts and coastal waters. As detailed in Section 3.5.2., the watershed has only two existing stormwater practices. The majority of the watershed is presently untreated. As land development continues in the USVI, stormwater management practices will play an important role in reducing flooding and improving water quality by infiltrating a greater amount of water into the groundwater, and detaining stormwater to reduce peak discharge rates, more nearly approximating the pre-developed hydrograph. 3.4.2.2 Deteriorated & Absent Stormwater Conveyance Failure to manage stormwater runoff from roads, most notably unpaved roads, is one of the primary land based sources of pollution in the USVI (U.S. Virgin Islands, 2020). There are 45.2 miles of roads in the Diamond watershed (Figure 38). To minimize surface water contamination and reduce flooding, roadway stormwater infrastructure such as culverts, swales, and surface crossings are utilized to intercept flows and convey water. Many of the roads of St. Croix either do not have adequate infrastructure or the existing infrastructure is not functioning properly (i.e., clogged or damaged). This can result in ponding and flooding within and along the roadway and can result in erosion in other areas due to the increased water volume and velocity of the stormwater (Figure 38). This presents both a public safety hazard and maintenance burden. Figure 37. Road erosion (left) and clogged stormwater infrastructure (right). Diamond Watershed Problem Definitions 65 | P a g e Diamond, St. Croix Watershed Management Plan Many of the stormwater drainage structures needed maintenance as of June 2021 field observations. Some structures needed structural repairs while many were obstructed and/or plugged with sediment, debris, and trash. Field crews in June 2021 encountered several DPW crews clearing and cleaning guts near structures. However, there is a need for a structured program that ensures routine and post-storm event maintenance, as local property owners often indicated that maintenance was an issue. Regularly scheduled maintenance would help alleviate some of the localized flooding problems by removing obstructions from the guts and roadway swales. One way of assessing adequate drainage infrastructure in the watershed is to determine how far road segments are from drainage structures. Of the 45.2 miles of roads in the Diamond watershed, only 7.1 miles (approximately 15.7%) are within 50 feet of a drainage structure (Figure 38). This indicates that in these locations, stormwater must travel overland for long distances prior to accessing a drainage relief structure, often resulting in large volumes of concentrated stormwater flow. Figure 38. Roads and transportation network in the Diamond watershed. Diamond Watershed Problem Definitions 66 | P a g e Diamond, St. Croix Watershed Management Plan 3.4.3 Wastewater Wastewater including leaking, broken, or disconnected wastewater and septic system pipes also pose a significant threat to the watershed. In the watershed, wastewater pipes are often outdated and infrequently maintained. Consequently, illicit discharges from leaking, broken, or disconnected sewer or damaged or malfunctioning septic systems may run-off into the region’s stormwater system, leading to increased pollution and contamination. Wastewater can pose human health risks and contains high bacteria and nutrient loads. Wastewater treatment for the USVI is provided by either the public wastewater treatment system or by private on-site septic systems (OSDS). Septic system use can be constrained by a number of factors, including poor suitability of soils for conventional systems. A study of OSDS applicability in the Virgin Islands found that much of land area on the USVI is unsuitable for septic soil absorption systems, including conventional and some alternatives (The Cadmus Group, 2011). Of the three islands studied, St. Croix had the greatest area served by sanitary sewers, with some opportunities for alternative systems such as sand filters and wetland treatment systems. Figure 39 shows the percentage of housing units in the Diamond watershed with a septic tank or cesspool as well as the sanitary sewer system. According to the VIWMA, the agency provides wastewater services including collection, pumping, treatment, and disposal to an estimated 60% of the Virgin Islands residents (VIWMA, 2021). The agency and system are funded in part by an annual wastewater user fee of $110.77 per equivalent residential unit that support the operations, maintenance, and capital investment plan (RAND, 2020). The current sewer system in the USVI consists of eight wastewater treatment plants, 31 pump stations, and hundreds of miles of buried wastewater lines. More than 4.5 million gallons of wastewater are collected daily (VIWMA, n.d.). Of the eight plants run by the agency, five are on St. Thomas, one is located on St. Croix, and the remaining two are on St. John. Figure 39 shows the sewer system in the Diamond watershed. The system includes combined sewer where wastewater and rainwater are collected together. Since many of the wastewater lines are located along the intermittent waterways (guts) that carry stormwater runoff, they may be subject to possible overflows (SSOs) that can result in untreated sewage being introduced into stormwater flows. No data for SSOs is currently available at the time of this report development. Possible illicit discharges due to failing or misconnected infrastructure was a major issue identified by field crews. Illicit discharges can contribute both pollutants and bacteria to surface waters and the storm drain system through leaking pipes, illegal connections, and unexpected overflows during storm events and pose a public health risk. Field crews observed leaking sewer lines during field visits on the island, suggesting that illicit discharges may be a significant issue in the territory. Diamond Watershed Problem Definitions 67 | P a g e Diamond, St. Croix Watershed Management Plan Figure 39. Sanitary sewer system and percent of housing units by estate with septic tanks or cesspools in the Diamond watershed (Sources: 2010 U.S. Census data, VIWMA). Diamond Watershed Problem Definitions 68 | P a g e Diamond, St. Croix Watershed Management Plan 3.4.4 Point Source Pollution In addition to the infrastructure system and associated pollutants that are introduced due to age or failure, other pollutant sources include permitted industrial and municipal discharges. The National Pollutant Discharge Elimination System (NPDES) program requires stormwater discharges from certain municipal separate storm sewer systems (MS4s), industrial activities, and construction sites to be permitted. USVI DPNR is the delegated authority to implement the NPDES Program, and it does so through its own Territorial Pollutant Discharge Elimination System (TPDES) Program. The program issues regulatory permits associated with the management of stormwater discharges from construction activities and industrial facilities. TPDES permits have terms no longer than five years and permittees that wish to continue discharging must apply for permit renewal at least 180 days prior to the expiration date of their permit. If the permitting authority has a complete application but does not reissue the permit prior to the expiration date, the existing permit is "administratively” continued. As of the writing of this report, no TPDES permits are active in the Diamond watershed. 3.4.5 Solid Waste Management The Virgin Islands Waste Management Authority (VIWMA) is responsible for all waste disposal in the territory. The organization has made efforts to start and sustain various recycling and composting efforts, but the organization is historically underfunded and markets for recycled materials are difficult to access. 3.4.5.1 Improper Waste Disposal Through field observations, it was observed that solid waste such as trash and debris is abundant alongside roadways and at dumpster sites around waste bins. This is most often caused by improper household waste disposal (Figure 40). Signs directing the proper disposal of waste are abundant throughout the island but are often ignored. Dumpster sites often overflow with waste, leading to a significant amount of garbage accumulating adjacent to the dumpsters. Figure 40. Example of illegal dumping Diamond Watershed Problem Definitions 69 | P a g e Diamond, St. Croix Watershed Management Plan Improper solid waste management presents risks to public and environmental health and reduces aesthetics. It can increase the risk of disease, water and air pollution, leachate, trash odors, and scavenger animals. When improperly contained and managed, trash, especially plastic waste, can also become floatable debris, which is an issue of international concern. Trash can also enter and clog stormwater systems, limiting the infrastructure’s functionality within the watershed and causing localized flooding. 3.4.5.2 Hazardous Waste In contrast to non-hazardous waste, hazardous waste is directly harmful to human health and the environment. Household hazardous waste may include cleaning supplies, furniture polish, fertilizers, motor oil, paint supplies, nail polish remover, lighter fluid, and other chemicals. Industrial sites often produce hazardous waste as well. In the Hovensa watershed, shipyards, manufacturing companies, boat repair, and automobile shops may use hazardous waste such as grease and gasoline toxic to the stormwater system, and improper handling and storage of these wastes can pose a significant risk to human health and wildlife habitat. Although they were not the focus of field assessments, solid waste management and hazardous waste management sites were documented when observed. No hazardous waste sites were identified in the Diamond watershed. 3.4.5.3 Damaged & Abandoned Vehicles During field visits, an accident was observed where potentially hazardous fluids were leaking from the damaged vehicle (Figure 41). Although emergency services were on the scene of the accident, no spill response measures were applied to these leaking fluids. The fluids were draining towards stormwater infrastructure that is directly connected to the ocean. Another issue of concern is the abundance of abandoned vehicles. Options for disposing of these vehicles are limited and require both time and, in some cases, a fee. The Office of the Administrator launched an Abandoned Vehicle Taskforce in 2019 to mark and dispose of abandoned vehicles and as of May 2019, approximately 45 abandoned vehicles were removed on St. Croix. Although abandoned vehicles are subject to a minimum $1,000 fine (Figure 41), these fines are rarely enforced. Figure 41. Warning sign about abandoned vehicles (left) and damaged vehicle (right). Diamond Watershed Problem Definitions 70 | P a g e Diamond, St. Croix Watershed Management Plan 3.4.6 Other Issues of Concern 3.4.6.1 Sea Level Rise Climate changed influenced sea level rise is an issue of concern for the USVI. Due to the melting of polar ice caps and thermal expansion of ocean waters, sea level rise poses a significant risk to the island in the forms of shoreland erosion, infrastructure degradation, and the contamination of groundwater aquifers, wetlands and estuaries. Data provided by the Sea Level Rise and Coastal Flood Hazard Scenarios and Tools Interagency Task Force suggests that sea level rise proximal to St. Croix will be about 3.34 ft by 2100, with a high estimate of 6.76 ft and a low estimate of 1.17 ft (Sweet et al., 2022). This is of notable concern as many of the critical harbors and bays surrounding St. Croix are within a few feet of sea level. Interactive sea level rise projection maps can be found here: https://sealevel.nasa.gov/task-force-scenario-tool. Figure 42. Coastal erosion due to sea level rise threatens stability of homes near the coast. Diamond Watershed Problem Definitions 71 | P a g e Diamond, St. Croix Watershed Management Plan 3.4.6.2 Mangrove Health Mangroves provide important coastal protections from storm surges, store and filter stormwater, and provide wildlife habitat. Mangroves are threatened by development pressures, pollution especially from marine debris and from polluted stormwater, and climate change impacts including sea level rise. 3.4.6.3 Coral Health Coral reefs provide coastal protection from storm surges and damage, aquatic habitat for critical local food sources and biodiversity, and economic contributions through are a draw for tourism and recreation. On an economic scale, the total value of the USVI coral reefs is an estimated $187 million (Brander & Van Beukering, 2013). The island’s coral reefs are at risk due to climate change driven temperature increases, increased hurricane storm intensity, ocean acidification, bleaching, reduction in reef predators and herbivores, pollution from human activity and increased sedimentation from land-based development. Stony coral tissue loss disease (SCTLD) is another threat to coral reefs, and this often-fatal disease has been detected in spread throughout the USVI. 3.4.6.4 Air Pollution Although air quality in the USVI is generally good, air quality can be degraded by Saharan dust events, industrial pollutants, and vehicle emissions. Dust from storms occurring in Africa can be transported by prevailing winds from the North African desert over the Atlantic Ocean and to the USVI. These dust events can cause issues for people with respiratory conditions (Platenburg, 2018). St. Croix is heavily reliant on passenger vehicles and public transportation is not well utilized, there are vehicle emissions especially concentrated in the urban areas of the island that can cause reductions in air quality (Shirley et al., 2012). Figure 43. Mangroves provide critical habitats and hydrologic functions to the islands of USVI. Diamond Watershed Problem Definitions 72 | P a g e Diamond, St. Croix Watershed Management Plan 3.4.6.5 Sargassum Since 2011, sargassum seaweed has periodically washed ashore in large quantities. Prior to this time, only small amounts of the seaweed would wash ashore. As it decomposes near shore, it can kill seagrass through shading and deoxygenation, prevent turtle nesting, and smother coral. Sargassum also creates hydrogen sulfide, a foul smelling and toxic gas that can irritate lungs and eyes. It also poses a significant economic issue for the region both in a reduction in tourism and in the cost to remove and dispose of the seaweed as it washes up on beaches. Figure 44. Sargassum build up on a beach in USVI. 3.4.6.6 Marinas Marinas can be a source of pollutants due to dumping from boats or leaking pumping stations. This direct discharge of fuel or sewage can result in bacteria and toxic pollutants in near shore waters that can affect important coastal habitat. There are four marinas on the island of St. Croix, but none of them are within the Diamond watershed. Diamond Watershed Data Collection 73 | P a g e Diamond, St. Croix Watershed Management Plan DATA COLLECTION 3.5.1 Stormwater Infrastructure Mapping An inventory of stormwater infrastructure was conducted and evaluated as part of field investigations for this Plan. Prior to this, very limited digitized stormwater infrastructure data existed for St. Croix. No publicly available centralized GIS repository of stormwater infrastructure currently exists for the territory. This lack of infrastructure data presents a several of challenges to watershed planners. Without knowing what stormwater infrastructure is present, determining hydraulic flow paths through watersheds can often be unclear, in turn making it difficult to accurately delineate contributing drainage areas of existing or proposed stormwater treatment practices. Furthermore, a lack of data on the condition and effectiveness of existing infrastructure makes planning for regular maintenance, repairs, or upgrades inefficient. Accurately mapping the existing infrastructure is critical to understanding the connectedness of these systems to plan for future stormwater upgrades to improve resiliency. Stormwater best management practices (BMPs) improve water quality both by removing pollutants through filtration, infiltration, or settling, and by reducing the volume and velocity of runoff entering guts and coastal waters. As land development continues in the USVI and precipitation patterns are impacted by climate change, stormwater management practices will play an even more important role in reducing flooding, protecting water quality and marine ecosystem health, reducing peak discharge rates, and more nearly approximating the hydrology of undeveloped lands. Figure 45. Examples of stormwater infrastructure in the Diamond watershed. Diamond Watershed Data Collection 74 | P a g e Diamond, St. Croix Watershed Management Plan The infrastructure mapping effort for this Plan was split into field and desktop phases. Field data was collected with handheld GNSS equipment (primarily a Trimble TSC7) using the mobile data collection app ArcGIS Collector. Most field data was collected from March to early May 2021. Photo attachments were included for all data points if feasible. Notes were added about each feature such as the number and direction of pipe connections, condition, if maintenance was needed, and size if possible. The desktop mapping stage focused on quality control and completeness of the map data. Pipe connections were drawn where field notes described, cross culverts were completed with inlet/outlet pairs, and additional infrastructure visible from satellite imagery or LiDAR topography was added. Finally, during field visits in June 2021, additional verification was performed on previously mapped infrastructure. A limited amount of new data was collected during these visits as well, particularly around potential BMP sites. Figure 46. Inspection of existing stormwater infrastructure during field assessments (above) and an example of the maps produced (below). Diamond Watershed Data Collection 75 | P a g e Diamond, St. Croix Watershed Management Plan This dataset is the most complete and accurate mapping of the stormwater infrastructure within the watershed. However, no mapping of this scale can capture all infrastructure. There are many private areas that were unable to be accessed in the field. It is also expected that there is some infrastructure that has become buried with sediment over time and is unable to be identified. Additionally, as-built plans were unavailable for much of Diamond watershed, so in areas where field investigations were unable to be completed or where pipe connections were unclear, this data was unable to be captured. Additional steps to clarify connections or identify additional infrastructure such as feeding cameras through the stormlines or utilizing a pipe locator were not within the scope of this project. Cross culverts and surface crossing comprised the majority of stormwater infrastructure assets mapped in the Diamond watershed. These surface crossings, which are common throughout St. Croix, are depressed areas in roads, often near intersections, that allow stormwater to pass over the road. Several of the neighborhoods mapped in Diamond have these surface crossings as the only significant stormwater conveyance method. The recently developed Louis E. Brown Apartments, just north of Route 66 along the eastern boundary of the watershed, contain a number of stormwater ponds and associated conveyance systems. This apartment complex likely contains several unmapped assets and would benefit from digitization of any available as-built plans. In total, 129 point, 53 line, and 2 polygon features were mapped within the watershed for a total of 182 features. A breakdown of the number of features identified by infrastructure type are included in Table 13 below. Table 13. Summary of infrastructure data collected by type in the watershed. Feature Type Infrastructure Type Quantity Point Features Catchbasin 11 Culvert inlet 40 Culvert outlet 35 Information point 6 Outfall 1 Sanitary manhole 3 Surface crossings 33 Line Features Storm line 37 Paved swale 3 Swale 11 Polygon Features Stormwater treatment practice 2 Total 182 Diamond Watershed Data Collection 76 | P a g e Diamond, St. Croix Watershed Management Plan 3.5.2 Existing Stormwater BMPs Stormwater best management practices (BMPs) improve water quality both by removing pollutants through filtration, infiltration, or settling, and by reducing the volume and velocity of runoff entering guts and coastal waters. As land development continues in the USVI and precipitation patterns are impacted by climate change, stormwater management practices will play an even more important role in reducing flooding, protecting water quality and marine ecosystem health, reducing peak discharge rates, and more nearly approximating the hydrology of undeveloped lands. Understanding where current BMPs exist is critical to properly allocate stormwater resources across the watershed. For example, if a neighborhood or region within a watershed is already being treated by a current BMP practice, a new BMP may be better served elsewhere within the watershed. The existing BMPs will also play a significant role in the hydrologic and water quality modeling completed for this project since these BMPs reduce pollutants and stormwater volume and velocity entering guts and coastal regions. Like much of the watershed’s stormwater infrastructure, BMPs were previously scarcely mapped, and BMP locations were generally unknown. Existing BMPs in the watershed were identified using a combination of field observations, site plans, Hexagon imagery, and LiDAR topography data and digitized into a GIS database. This identification process focused on the identification of structural BMPs, such as bioretention cells, infiltration basins, treatment wetlands and wet ponds. Non-structural practices, such as disconnections to filter strips and vegetated buffers as well as reforestation efforts could not be feasibly identified. It is possible that some existing BMPs remain unidentified due to a lack of access to private property, lack of comprehensive site plans, or small size rendering them undetectable in the available data sources. In total, two infiltration basins were identified as shown in Figure 47 and described in Table 14 below. Drainage areas for each existing BMP were delineated utilizing one-foot contours derived from LiDAR elevation data and mapped infrastructure. These drainage areas are shown in Figure 47 below in yellow. In general, the drainage areas for the existing BMPs were fairly small. Table 14. Summary table of existing BMPs identified in the watershed. Map ID BMP Type BMP Description 1 Basin Surface basin with minimal infiltration. 2 Basin Surface basin with minimal infiltration. 3.5.3 Updates to Existing Data DPNR-provided watershed boundaries and FEMA-provided gut layers for the watershed was revised utilizing newly available data including LiDAR-derived elevation data (USGS, 2018), Hexagon imagery (0.15m, 2019), and stormwater infrastructure mapped as a part of this project. Mapped infrastructure such as surface crossings, culverts, and stormwater pipes as well as assumed flow confinement from roadways and buildings were also considered during drainage area delineation. This new data allowed for a better understanding of topography and drainage patterns including the impacts of previously unmapped stormwater infrastructure. For the Diamond watershed, the updates to the watershed boundary resulted in a net watershed area change of 1.1 acres (0.04% of the watershed). Diamond Watershed Data Collection 77 | P a g e Diamond, St. Croix Watershed Management Plan Figure 47. Existing BMPs identified within the Diamond watershed. Diamond Watershed Data Collection 78 | P a g e Diamond, St. Croix Watershed Management Plan 3.5.4 UAS Data Collection Land cover data (see Section 3.3.2) was created using 2019 Hexagon imagery as the primary source. However, in the last three years there may have been significant changes in land cover that could impact stormwater flows including the construction of new commercial or residential developments or clearing of forested areas. To understand potential development changes, an unmanned aircraft system (UAS) was flow over key areas in March 2022 to capture up to date very high-resolution imagery (≤5 cm). The areas of suspected change were identified based on information regarding current and recent known development and shared with DPNR. DPNR stakeholders reviewed the proposed areas and recommended several additional areas to collect data to ensure that any known areas of change were covered by these UAS flights. Where possible, given Federal Aviation Administration (FAA) flight height restrictions around airports, a fixed wing WingtraOne Gen II UAS was utilized (Figure 49). Where flight height restrictions prevented the use of the Wingtra UAS, a DJI Phantom quadcopter UAS was utilized. The collected data was used to assess the level of development change in the watershed and update the land cover data used to model the selected stormwater management practice concept designs (see Section 3.7.4). In addition, topographic information derived using photogrammetry was generated for areas flown with the Wingtra UAS. This data will be provided to DPNR for use in other projects. In this watershed, data was collected for approximately 125 acres. Figure 48. WingtraOne Gen II UAS utilized to collect data in the study watersheds. Diamond Watershed Water Quality Monitoring of Guts 79 | P a g e Diamond, St. Croix Watershed Management Plan WATER QUALITY MONITORING OF GUTS 3.6.1 Monitoring Overview Efficient management and monitoring of natural resources requires informative data derived from areas of interest. The guts of St. Croix are the primary source and conveyance system of fresh water on the island. Likewise, they are also the main conduit through which chemical pollutants and sediment from the watersheds of St. Croix reach the ocean (Platenburg, 2006). Despite their importance, the guts of St. Croix have not been monitored with consistency and their terrestrial sources of pollutants are not well understood. The guts on the island are ephemeral, only flowing following rainfall, and this makes sampling of the guts very challenging. This study represents the most widespread and comprehensive sampling of guts in the USVI. This monitoring effort also serves as a pilot project and the lessons learned during this effort can be used to guide future monitoring and can also be used to identify pollutant sources and guide efforts to improve water quality. In this study, synoptic sampling of major guts during storm events was conducted to establish a baseline of water quality data and to assist in the prioritization of sub-watersheds for further assessment. Synoptic sampling is a form of water quality sampling in which surface water is collected from many sites across a watershed in a short period of time. It is a common method for exploring the relationships between land- use and water quality, providing a brief “snapshot” of stream (or gut) health (Wayland et. al, 2003). The sampling completed under the scope of this WMP consisted of four main components: 1. Rainfall monitoring 2. Grab sampling 3. Flow measurements 4. Sediment sampling Each of these four elements is described in detail below. The locations for these monitoring points are shown in Figure 50. Diamond Watershed Water Quality Monitoring of Guts 80 | P a g e Diamond, St. Croix Watershed Management Plan Figure 49. Grab sampling, sediment sampling, and water logging locations. Diamond Watershed Water Quality Monitoring of Guts 81 | P a g e Diamond, St. Croix Watershed Management Plan 3.6.2 Rainfall Monitoring Given the ephemeral nature of the guts on St. Croix, the focus of the monitoring effort was on sampling during and following and storm events, understanding rainfall patterns, and collecting rainfall data. This crucial component of the study is greatly influenced by rainfall patterns, which vary across the island of St. Croix. The different geographic regions are referred to as microclimates and they experience unique patterns of rainfall intensity or duration (Bowden, 2021). In this study, rainfall was monitored with two RG3 HOBO Data Logging Rain Gauges, a widely used tipping bucket rain gauge (Figure 50). The deployment locations of these rain gauges were selected to ensure that spatial variability in precipitation across the watersheds of St. Croix were accounted for. This was determined to be adequate for the purposes of this study as data will be supplemented with existing active weather stations managed by the CoCoRaHS network and Water Resources Research Institute (WRRI) at the University of the Virgin Islands (UVI) (Figure 51). Figure 50. JS rain gauge (left) and HQ rain gauge (right). Diamond Watershed Water Quality Monitoring of Guts 82 | P a g e Diamond, St. Croix Watershed Management Plan Figure 51. Rain gauge locations on St. Croix. Diamond Watershed Water Quality Monitoring of Guts 83 | P a g e Diamond, St. Croix Watershed Management Plan 3.6.3 Grab Sampling Grab sampling, that is, samples taken at a discrete point in time, was attempted during storm events exceeding 0.25 inches of rain in a quarter hour from four gut sampling locations across the Diamond watershed (Figure 52). The four sampling locations were selected to characterize critical portions of the main guts within the watershed. Grab samples were analyzed for a number of pollutants that are indicative of gut health. The specific pollutants monitored and their impact on gut health is summarized in Table 15. For sampling locations where no flow was observed during two qualifying storm events, this lack of flow was recorded. The lack of flow was confirmed either by visual observation or by the installed HOBO water level loggers. This lack of gut flow was an important finding as it indicated that characteristics of the upstream drainage area caused the lack of gut flow at this rainfall threshold. There are several watershed- specific characteristics that are likely to result in this observation including but not limited to: 1. Soil composition in the watershed allows for infiltration of rainfall at least up to the observed rainfall threshold, taking into account antecedent soil moisture. 2. Significant storage upstream of the monitoring point such that enough detention is taking place to eliminate flow at this location. Storage could include natural depressions and manmade ponding areas. 3. Alteration of natural drainage patterns to the extent that enough drainage is directed away and disconnected from the gut that the contributing area is effectively much smaller than it would be otherwise. This could include inadvertent rerouting of stormwater down driveways and along roadways or intentional collection of stormwater via infrastructure and discharge to the bay or downstream of the monitoring point in the gut. For these monitoring locations without flow, an assessment was made of the contributing drainage area to determine the probable cause of this observation. The assessment focused on mapped soils, topography, and mapped stormwater infrastructure. A summary of this analysis is provided for each monitoring location without measurable flow. Figure 52. Grab sample collection from sampling sites Dia02 (left) and Dia01 (right). Diamond Watershed Water Quality Monitoring of Guts 84 | P a g e Diamond, St. Croix Watershed Management Plan Table 15. Water quality monitoring parameters measured via grab sampling. Water Quality Class Water Quality Parameters Description Nutrients Total Phosphorus (TP) & Total Kjeldahl Nitrogen (TKN) TP and TKN are two of the most frequently monitored elements in water quality studies throughout the United States due to their role in promoting eutrophication (Bowman, 1982). TP and TKN are commonly derived from agricultural runoff during and following major storm events. Other sources include human and animal waste, septic systems, and fertilized lawns Bacteria Escherichia coli (E. coli), & Enterococci E. coli and enterococci are two forms of fecal coliform bacteria derived from the digestive tract of humans and other warm-blooded animals. The presence of these fecal coliform bacteria in water is a strong indication of recent sewage or animal waste contamination. Sediment & Organic Matter Total suspended solids (TSS) TSS is a measurement of the total waterborne material that exceeds 2 microns in size, primarily comprised of mineral and organic matter. Minerals and organic matter play an important role in the transportation of nutrients and contaminants in water. TSS is often derived from erosion, which can be exacerbated by impervious surfaces, poor agricultural practices, and other forms of human activity. Volatile Organic Compounds (VOCs) Acetone, Carbon Disulfide, Dichloromethane, Trichloroethylene, & Tetrachloroethylene VOCs are chemicals that have the ability to both dissolve in water and vaporize into the air. VOCs have notable adverse effects on human health and are dangerous to the environment. Common sources of VOCs include industrial spills and leaks as well as the dumping of household cleaning products. Inorganic Contaminants Orthophosphate, Nitrate, Nitrite, Bromide, Sulfate, Fluoride, & Chlorine. Inorganic contaminants in water can range across a variety of chemicals from a variety of different sources. In this study we focus on inorganic contaminants primarily derived from the production of fertilizers and drinking water. Total petroleum hydrocarbons (TPHs) Automotive Gasoline, Fuel Oils, Benzene, Toluene, & Naphthalene TPHs are a family of chemicals derived from crude oil. The presence of oil in guts has detrimental effects on human, aquatic, and environmental health. In this study, we measure the most common chemicals within the TPH family. Heavy Metals Lead, Cadmium, Arsenic, Mercury, Chromium, & Copper Heavy metals, while usually present in only trace amounts, can be incredibly toxic and cause severe issues for human, aquatic, and environmental health. Heavy metals occur naturally in rocks, however excess heavy metal concentrations found in water is usually the byproduct of anthropogenic activity. Diamond Watershed Water Quality Monitoring of Guts 85 | P a g e Diamond, St. Croix Watershed Management Plan 3.6.4 Flow Measurements Gut discharge (i.e., flow) is a key parameter in understanding gut hydrology and water quality. In this study, gut discharge was monitored at one location – Dia02 - as shown in Figure 53. Discharge was measured using Onset HOBO U20 Water Level Loggers (Figure 53). Pressure measurements derived from the logger during storm events were converted to discharge measurements by correcting for changes in barometric pressure in the air and using of Manning’s equation to determine channel roughness. To use Manning’s equation, channel geometry, slope, and friction coefficient for each of the flow measurement locations were determined. Channel geometry was determined by direct measurements in the field. Channel slope was determined by taking the slope of LIDAR-derived elevation data 10m above and below the deployment location. In the case where channel became subterranean within 10m of the gauge downstream, the slope was measured from the point of subterranean entrance and a point 20m upstream. Friction coefficient was determined by channel material. Full details of sampling method can be found in Appendix B2. Figure 53. Field crew member setting up an Onset HOBO U20 Water Level Logger at gauge station Dia02 (left). Water sheet flowing through the concrete structure at Dia02(right). Diamond Watershed Water Quality Monitoring of Guts 86 | P a g e Diamond, St. Croix Watershed Management Plan 3.6.5 Sediment Sampling Sediments deposited in guts were collected and analyzed for grain size and contaminants. Sediment sampling occurred once at all grab sampling locations (see Figure 50) unless it was infeasible because 1) there is no sediment to sample, a possibility in some concrete channels, or 2) the sampling personnel were unable to safely access the channel. Some of the drainage ways at the point of sampling are concrete lined while others are not lined and over natural ground. Upon arrival at the site, the sampling site was photographed. A measuring tape was stretched across the drainage way and photographed to document the various sediment deposition types across the channel. Probes were made at each variation of sediment type (i.e., gravel, fines, mixed sediment) and depths of loose or lightly compacted sediment were measured at each point and recorded. A small diameter metal rod was used to estimate deposition depth. The rod was driven in with the rubber mallet and when resistance changed, a core was taken to resistance or 2 inches below that depth where a notable resistance change was noted. The 4 inch plexiglass core was cut into lengths 6 inches longer than the estimated deposited soil depths. The rubber mallet was used to drive the core to the depth of the estimated deposition. Once the core was completely in, a thin metal sheet (approximately 6 inches in width) was placed beneath the core by excavating adjacent to the core to clear an area to slide it beneath. The core with the metal sheet on the bottom was lifted vertically and placed upright. The depths of the various visible layers were measured with a metered tape adjacent to the core. Once measured and photographed, the core was dumped into a labeled sample bag. This was repeated at each identified soil type change. Once all samples were collected, a subsample of each sample was taken into the compositing container and well mixed and apportioned into the appropriate laboratory provided sample bottles. Samples were taken to Ocean Systems Laboratory for grain size analysis according to ASTM Standards. The complete methods used for the collection of deposited sediment from each of these environments can be found in Appendix B2. Field photos can be found in Figure 54. Figure 54. A sediment core being collected from the Dia02 gut channel (left). The depth of the sediment core verified with measuring tape (center). A cross-section across the Dia02 gut channel measured to collect a scrape sample (right). Diamond Watershed Water Quality Monitoring of Guts 87 | P a g e Diamond, St. Croix Watershed Management Plan 3.6.6 Results & Discussion 3.6.6.1 Rainfall & Flow Measurements In the USVI, rainfall can be unpredictable and occur over a small geographic area and have varying intensity over a very short period of time. This makes it challenging to correlate rainfall data collected in rain gauges, even when gauges are distributed across the island, to in-gut flow. As such, the flow measurements shown below often do not coincide with the rainfall data over time. In some cases, the rainfall may occur at the rain gauge after the flow is observed in the gut because of the path of the storm event over the island. It would be challenging to accurately pair these measurements as even a rain gauge positioned at each monitoring location may not capture the rainfall that produced the stormwater flowing through the gut when an isolated high intensity storm occurs upstream of the gut location. This is a limitation of the study design but also highlights the difficulty of monitoring both flow and rainfall in the USVI. The water level logger located at the Dia02 monitoring site captured the first qualifying storm event on December 12th, 2021. The peak rainfall intensity of 0.28 inches per 0.25 hours was reached at the IKINGS181 rain gauge, located northeast of the Dia02 monitoring location, between 12:00 pm and 12:15 pm. Active stormwater flow into the gut channel began logging shortly after this rainfall intensity was achieved (Figure 55). A total rainfall accumulation of 0.61 inches was logged at this rain gauge. The peak flow rate (5.1 cfs) of the storm event occurred 2:00 and 3:00 am on December 13th, 2021, after the total 0.61 inches of rainfall had accumulated. A total of 24,377 cubic feet of stormwater discharge flowed through the Dia02 location for the duration of the storm event. Diamond Watershed Water Quality Monitoring of Guts 88 | P a g e Diamond, St. Croix Watershed Management Plan Figure 55. A hydrograph displaying flow at the Dia02 gut monitoring site (5.1 cfs) in red and the corresponding rainfall accumulation for the storm event (0.61 in.) in blue that occurred on December 12th, 2021. Diamond Watershed Water Quality Monitoring of Guts 89 | P a g e Diamond, St. Croix Watershed Management Plan The second qualifying storm event of the monitoring period occurred on February 4th, 2022. The peak rainfall rate of 0.25 inches per 0.25 hours was reached at the IKINGS181 rain gauge between 1:00 pm and 2:00 pm with a total rainfall accumulation of 0.55 inches for the duration of the event. Similar to the previous event, active stormwater flow into the gut channel began logging shortly after this rainfall intensity was achieved and reached peak flow (17.9 cfs) within an hour of the peak rainfall intensity (Figure 56). A total of 26,054 cubic feet of stormwater discharge flowed through the Dia02 location for the duration of the storm event. While the two monitored storm events (>0.50 inches) occurred two months apart, they both demonstrated how quickly a large volume of stormwater runoff flowed into the gut channel at this location directly after rainfall began. Land characteristics such as high impervious cover, soils with high runoff potential, and the average slope within the Dia02 watershed are likely to be prevailing factors in the frequency and volume of stormwater draining to this location. Extended monitoring coupled with a drainage area study of the Dia02 location can provide additional context on the hydrologic performance of this particular portion of the gut channel. Figure 56. A hydrograph displaying flow at the Dia02 gut monitoring site (18 cfs) in red and the corresponding rain accumulation for the storm event (0.55 in.) in blue that occurred on February 4th, 2022. Diamond Watershed Water Quality Monitoring of Guts 90 | P a g e Diamond, St. Croix Watershed Management Plan 3.6.6.2 Water Quality Data Water quality results for the two grab samples at each sampling location, Dia01 and Dia02, could not be compared to each other as they are representative of a discrete point in time during two different storm events. However, the collective set of preliminary results was compared to various water quality standards established by the EPA and the USVI DPNR to determine which pollutants are of concern and will likely require extended monitoring in the Diamond watershed guts if detected at acute concentrations in this preliminary monitoring study. The water quality standards used for comparison were based on the assumption that the two grab samples each taken from Dia01 and Dia02 were entirely comprised of freshwater. The Amended 2019 USVI Water Quality Standards for inland freshwater were used to determine pollutant exceedances. Within the 2019 USVI Water Quality Standards, if there was no inland freshwater standard defined for a measured parameter, the standard for the receiving water body of the Diamond watershed – Class B coastal waters – was used alternatively. If there was no comparable standard provided in the 2019 USVI Water Quality Standards, the EPA National Primary and Secondary Drinking Water Regulations (NPDWRs and NSDWRs) were used to understand the magnitude of particular pollutant concentrations such as copper, bromide, fluoride, and sulfate in the grab samples. Within the EPA NPDWRs and NSDWRs, it is understood that these regulations are for human consumption of water and therefore are highly stringent compared to regulations for non-potable freshwater. However, for grab sample water quality results that exceed the EPA NPDWRs and NSDWRs, they will be acknowledged for being held to these higher standards due to the standard for non-potable gut discharge being undefined. The two grab samples taken at Dia01 and Dia02 did not exceed the EPA drinking water quality standards for sulfate (Table 16 and Table 17). The bromide concentration in the second grab sample taken at Dia01 exceeded the EPA primary drinking water quality standards by 60% (Table 16). While more restrictive, the EPA standard for bromide concentrations was used for preliminary comparison as there was no standard defined for USVI waters. There are no federal regulations or advisories for the concentration of petroleum range organics or acetone in water to protect human health. Raw data results for these two parameters are presented in Table 16 and Table 17 but could not be applied to any established standard from the EPA or USVI DPNR. However, specific pollutants within the class of TPHs that are measures of petroleum constituents, including benzene, naphthalene, and toluene were not detected in either sets of grab samples. The primary pollutants of concern based upon exceedances of the Amended 2019 USVI Water Quality standards in the two grab samples were: 1. E. coli 2. Enterococci 3. Sediment 4. Total Nitrogen (TN) 5. Total Phosphorus (TP) 6. Copper (Heavy Metal) E. coli and Enterococci: The acute concentration of fecal coliform bacteria, specifically E. coli and enterococci, in all grab samples in Dia01 and Dia02 indicates that there were significant amounts of sewage and/or animal waste contaminating the monitored portions of the Diamond guts. The water quality standards used to measure the magnitude of fecal coliform bacteria is based on consistent sampling over a 30-day period which is not representative of the sampling conditions of this study (Table 16 and Table 17). However, this standard provides context that an essential, long-term water quality goal is to prioritize the prevention of human or animal fecal matter entering waterways at any time. Consistent sampling of gut flow in all rain events within a 30-day period is needed to confirm whether this acute water quality exceedance is consistent over a longer duration. Diamond Watershed Water Quality Monitoring of Guts 91 | P a g e Diamond, St. Croix Watershed Management Plan Sediment: The USVI DPNR’s standard for turbidity (<3.0 NTU) was exceeded in all grab samples. As there was no empirical standard for turbidity of TSS provided for inland freshwater, this value is the standard for the receiving waters of the Diamond guts, Class B coastal waters. All turbidity results exceeded this standard by at least 160% (Table 16 and Table 17). These results indicate there is a high concentration of mineral and organic matter that may be sourced from the erosion of impervious surfaces, agricultural fields, or other land uses. Additional study on the land use acreages of this site’s drainage area can determine the hierarchy of sources contributing to this exceedance of sediment in the Diamond gut channels. TP and TN: The USVI DPNR’s standards for TP (<0.05 mg/L) and TN (<0.207 mg/L) were exceeded in all grab samples. As there was no empirical standard for TP and TN provided for inland freshwater, both values are standards for the receiving waters of the Diamond gut, Class B coastal waters. All TP results were in exceedance of the receiving coastal water standard by at least 45%. The TN standard is based on consistent sampling of coastal waters over a three-year period which is not representative of the sampling conditions of this study (Table 16 and Table 17). While the TN results are not directly comparable to this standard due to the limited sampling conditions of this preliminary study, it provides the basis to extend monitoring of this location, when possible, to focus on the dynamics of TN (and TP) over a longer temporal scale to determine how this gut is performing in its nutrient dynamics. Extended monitoring could also be advanced to determine loading values of TN and TP along the Diamond gut channels to determine the source and magnitude of these nutrients in this watershed. Copper: As there was no empirical standard for acute copper concentrations provided for inland freshwater at Dia01 and Dia02, standards for its receiving waters, Class B coastal waters, were used for comparison. The USVI DPNR’s standard for acute copper concentrations in Class B coastal waters (<4.8 ug/L) were exceeded in both grab samples at Dia01 and Dia02 by at least 60%. Copper is typically found in natural surface waters at low concentrations, however acute concentrations of this metal can have adverse effects on aquatic life by inhibiting their survival, growth, reproduction, and more (Kapustka et al., 2004). Continued monitoring of the Dia01 and Dia02 is recommended to determine the source of acute copper concentrations and if they are consistently exceeding the water quality standard for Diamond’s receiving coastal waters as was demonstrated in the preliminary results. Diamond Watershed Water Quality Monitoring of Guts 92 | P a g e Diamond, St. Croix Watershed Management Plan Table 16. Water quality monitoring parameters measured via grab sampling at Dia01 on February 4th and 5th, 2022. Red cells demonstrate a water quality exceedance of the Amended 2019 USVI Water Quality Standards for inland freshwater. Yellow cells demonstrate a water quality exceedance of the EPA NSDWRs. Water Quality Class Water Quality Parameter Dia01 (02/04/22) Dia01 (02/05/22) 2019 USVI Water Quality Standard EPA National Primary Drinking Water Regulations (NPDWRs) EPA National Secondary Drinking Water Regulations (NSDWRs) Inland Freshwater pH 9.41 6.94 Between 7.0-8.3A N/A N/A Salinity (psu) 0.05 0.34 <0.50 psu N/A N/A Temperature (°C) 23.64 22.70 <32°C N/A N/A Dissolved Oxygen (mg/L) 8.68 3.95 >5.50 mg/L N/A N/A Sediment Turbidity (NTUs) 169.00 28.60 >3.0 NTUB N/A N/A Total Suspended Solids (mg/L) 138.60 11.10 None from wastewater sources which will cause disposition or be deleterious for the designated uses shall be present in any waters. N/A N/A Bacteria E. Coli Positive Positive Negative N/A N/A Enterococci Positive Positive Negative N/A N/A Enterococci MPN per 100 mL 4,374 10,112 <30 CFU/100 mLC <110 CFU/100mLD N/A N/A Total Petroleum Hydrocarbons (TPHs) Petroleum Range Organics (mg/L) Undetected Undetected - - - Benzene (ug/L) Undetected Undetected N/A N/A N/A Naphthalene (ug/L) Undetected Undetected N/A N/A N/A Toluene (ug/L) Undetected Undetected N/A N/A N/A Heavy Metals Arsenic (ug/L) Undetected Undetected <340 ug/L (acute), <150 ug/L (chronic) N/A N/A Cadmium (ug/L) Undetected Undetected <1.8 ug/L (acute), <0.72 ug/L (chronic) N/A N/A Diamond Watershed Water Quality Monitoring of Guts 93 | P a g e Diamond, St. Croix Watershed Management Plan Water Quality Class Water Quality Parameter Dia01 (02/04/22) Dia01 (02/05/22) 2019 USVI Water Quality Standard EPA National Primary Drinking Water Regulations (NPDWRs) EPA National Secondary Drinking Water Regulations (NSDWRs) Chromium (ug/L) 8.1 Undetected <16 ug/L (acute)E, <11 ug/L (chronic)E N/A N/A Copper (ug/L) 15.0 9.0 <4.8 ug/L (acute) A, <3.1 ug/L (chronic) A N/A N/A Lead (ug/L) Undetected Undetected <65 ug/L (acute), <2.5 ug/L (chronic) N/A N/A Mercury (ug/L) Undetected Undetected N/A N/A N/A Volatile Organic Compounds (VOCs) Acetone (ug/L) Undetected Undetected - - - Carbon Disulfide (ug/L) Undetected Undetected N/A N/A N/A Methylene Chloride (ug/L) Undetected Undetected N/A N/A N/A Tetrachloroethane (ug/L) Undetected Undetected N/A N/A N/A Trichloroethene (ug/L) Undetected Undetected N/A N/A N/A Inorganic Pollutants Bromide (mg/L) Undetected 0.19 N/A <0.1 mg/LC N/A Chloride (mg/L) 5.0 69.2 <860 mg/L (acute)E, <230 mg/L (chronic)E N/A N/A Fluoride (mg/L) 0.016 0.25 N/A N/A <2.0 mg/L Sulfate (mg/L) 3.9 55.8 N/A N/A <250 mg/L Nutrients Total Nitrogen – Kjeldahl (mg/L) 1.6 1.4 <0.207 mg/LF N/A N/A Total Phosphorus (mg/L) 0.54 0.15 <0.05 mg/LB N/A N/A A When discharging to class B coastal waters. B In marine or coastal waters. C 30-day geometric mean. D No more than 10% of the samples collected in the same 30 days. E Human health for the consumption of water + organisms. F In more than 10% of samples over a three-year period in estuarine, marine, and coastal waters. Diamond Watershed Water Quality Monitoring of Guts 94 | P a g e Diamond, St. Croix Watershed Management Plan Table 17. Water quality monitoring parameters measured via grab sampling at Dia02 on December 12th, 2021, and February 4th, 2022. Red cells demonstrate a water quality exceedance of the Amended 2019 USVI Water Quality Standards for inland freshwater. Water Quality Class Water Quality Parameter Dia02 (12/12/21) Dia02 (02/04/22) 2019 USVI Water Quality Standard EPA National Primary Drinking Water Regulations (NPDWRs) EPA National Secondary Drinking Water Regulations (NSDWRs) Inland Freshwater pH 7.10 8.80 Between 7.0-8.3A N/A N/A Salinity (psu) 0.16 0.08 <0.50 psu N/A N/A Temperature (°C) 27.30 23.59 <32°C N/A N/A Dissolved Oxygen (mg/L) - 8.84 >5.50 mg/L N/A N/A Sediment Turbidity (NTUs) 34.40 48.20 >3.0 NTUB N/A N/A Total Suspended Solids (mg/L) 24.00 41.50 None from wastewater sources which will cause disposition or be deleterious for the designated uses shall be present in any waters. N/A N/A Bacteria E. Coli Positive Positive Negative N/A N/A Enterococci Positive Positive Negative N/A N/A Enterococci MPN per 100 mL 10,112 10,112 <30 CFU/100 mLC <110 CFU/100mLD N/A N/A Total Petroleum Hydrocarbons (TPHs) Petroleum Range Organics (mg/L) 1.1 1.3 - - - Benzene (ug/L) Undetected Undetected N/A N/A N/A Naphthalene (ug/L) Undetected Undetected N/A N/A N/A Toluene (ug/L) Undetected Undetected N/A N/A N/A Heavy Metals Arsenic (ug/L) Undetected Undetected <340 ug/L (acute), <150 ug/L (chronic) N/A N/A Cadmium (ug/L) Undetected Undetected <1.8 ug/L (acute), <0.72 ug/L (chronic) N/A N/A Diamond Watershed Water Quality Monitoring of Guts 95 | P a g e Diamond, St. Croix Watershed Management Plan Water Quality Class Water Quality Parameter Dia02 (12/12/21) Dia02 (02/04/22) 2019 USVI Water Quality Standard EPA National Primary Drinking Water Regulations (NPDWRs) EPA National Secondary Drinking Water Regulations (NSDWRs) Chromium (ug/L) 2.6 5.1 <16 ug/L (acute)E, <11 ug/L (chronic)E N/A N/A Copper (ug/L) 9.1 9.3 <4.8 ug/L (acute) A, <3.1 ug/L (chronic) A N/A N/A Lead (ug/L) Undetected Undetected <65 ug/L (acute), <2.5 ug/L (chronic) N/A N/A Mercury (ug/L) Undetected Undetected N/A N/A N/A Volatile Organic Compounds (VOCs) Acetone (ug/L) 5.3 Undetected - - - Carbon Disulfide (ug/L) Undetected Undetected N/A N/A N/A Methylene Chloride (ug/L) Undetected Undetected N/A N/A N/A Tetrachloroethane (ug/L) Undetected Undetected N/A N/A N/A Trichloroethene (ug/L) Undetected Undetected N/A N/A N/A Inorganic Pollutants Bromide (mg/L) Undetected Undetected N/A <0.1 mg/LC N/A Chloride (mg/L) 17.0 10.8 <860 mg/L (acute)E, <230 mg/L (chronic)E N/A N/A Fluoride (mg/L) 0.11 0.057 N/A N/A <2.0 mg/L Sulfate (mg/L) 9.7 10.8 N/A N/A <250 mg/L Nutrients Total Nitrogen – Kjeldahl (mg/L) 0.58 0.51 <0.207 mg/LF N/A N/A Total Phosphorus (mg/L) 0.081 0.086 <0.05 mg/LB N/A N/A A When discharging to class B coastal waters. B In marine or coastal waters. C 30-day geometric mean. D No more than 10% of the samples collected in the same 30 days. E Human health for the consumption of water + organisms. F In more than 10% of samples over a three-year period in estuarine, marine, and coastal waters. Diamond Watershed Water Quality Monitoring of Guts 96 | P a g e Diamond, St. Croix Watershed Management Plan 3.6.6.3 “No Flow” Analysis Two out of the four water quality monitoring locations, Dia03 and Dia04, within the Diamond watershed did not receive any measurable gut flow during at least two qualifying storm events at each site (Table 18). Visual inspection by field crew members at Dia03 and Dia04 confirmed that there was no active stormwater flow in the guts to collect grab samples for water quality analysis (Figure 57). Table 18. An overview of the dates on which qualifying storm events and grab sampling attempted occurred at Dia03 and Dia04. Site Location First Rain Event Date Second Rain Event Date Dia03 12/12/2021 1/14/2022 Dia04 12/12/2021 1/14/2022 Subsequently, a “no flow” desktop analysis was conducted to determine what environmental factors contributed to the lack of flow including the average slope, soil type, land cover within the Dia03 and Dia04 drainage areas, and the presence of stormwater infrastructure to divert runoff away from the gut channel. Figure 58 provides a map of where the two monitoring sites are located along the gut channels and their delineated drainage areas within the Diamond watershed. Figure 57. No storm flow was observed at Dia03 (left) and Dia04 (right) monitoring locations. Diamond Watershed Water Quality Monitoring of Guts 97 | P a g e Diamond, St. Croix Watershed Management Plan Figure 58. Two of the four monitoring locations within the Diamond watershed were confirmed to have no gut flow during at least two qualifying storm events in December 2021 and January 2022 (red). Each drainage area is delineated in blue. Diamond Watershed Water Quality Monitoring of Guts 98 | P a g e Diamond, St. Croix Watershed Management Plan The desktop analysis demonstrated that the most salient factor likely contributing to the absence of flow at these two monitoring locations was a high green space composition in the Dia03 and Dia04 drainage areas (Figure 59). This finding was expected as previous research has shown that healthy vegetated areas have a significant capacity to absorb and slow stormwater flows. Both drainage areas were largely comprised of green space (>90%) and had less than 15% of their respective land covers comprised of impervious surfaces. The average slope and soil type within each drainage area was also calculated to determine if there were overlapping factors contributing to these land cover findings. There is no existing stormwater infrastructure within the Dia03 and Dia04 drainage areas to divert flow away from gut channels, so this factor was not applicable to the analysis. Figure 59. The land cover composition of the Dia03 and Dia04 drainage areas is predominately green space. In addition to the land cover composition, the average slope within each watershed was calculated. A slope threshold of 5% or below was established as an indicator of limited conveyance of stormwater runoff into gut channels. Surfaces above this average slope value get increasingly steep and subsequently increase stormwater velocity. Surfaces at or below a 5% slope are fairly flat and limit the volume of stormwater runoff that can sheet flow into the guts. Results indicated that the Dia03 and Dia04 had a slope of 8.2% and 9.7% respectively (Figure 60). These results exceed the low slope threshold and therefore likely do not impact the lack of flow at these two sites. Diamond Watershed Water Quality Monitoring of Guts 99 | P a g e Diamond, St. Croix Watershed Management Plan Figure 60. The average slope of the Dia03 and Dia04 drainage areas within the Diamond watershed. The soil composition was calculated and categorized into four Hydrological Soil Groups (HSGs) for the Dia03 and Dia04 drainage areas. Soils within the HSG A and B groups are defined as having a “low to moderately low runoff potential when thoroughly wet” whereas HSG C and D soils have a higher runoff potential when saturated. Both drainage areas did not have any mapped A or B soils and are entirely comprised of soils with high runoff potential (HSG C and D; Figure 61). However, the large magnitude of green space absorbing rainfall, coupled with the trends of limited rainfall and antecedent dry conditions in the watershed, were identified as the factors that likely influenced the lack of flow at these sites. Figure 61. The soil composition within the Dia03 and Dia04 drainage areas. Diamond Watershed Water Quality Monitoring of Guts 100 | P a g e Diamond, St. Croix Watershed Management Plan 3.6.6.4 Sediment Sampling Sediment sampling occurred once at the Dia01, Dia02, Dia03, and Dia04 monitoring sites on November 17th and 18th of 2021. The composited sediment was analyzed for grain size distribution and composition. Grain sizes were separated into seven categories: • <63 microns (clay particles and very fine to coarse silt) • 63-125 microns (very fine sand) • 125-250 microns (very fine to fine sand) • 250-500 microns (medium sand) • 500-2,000 microns (coarse to very coarse sand) • 2,000-4,000 microns (very fine pebbles) • >4,000 microns (fine to very coarse pebbles, cobbles, and boulders) These grains often wash into gut channels from both impervious and pervious surfaces in the contributing drainage areas of the gut channels. Developed surfaces including roadways, sidewalks, rooftops, and active construction sites within commercial, industrial, and residential regions and even undeveloped, vegetated surfaces can be eroded by stormwater runoff. Traveling at fast enough velocities, stormwater runoff is highly effective at displacing sediment at various sizes, from fine clay particles all the way to boulders, and depositing them along gut channels. The individual sediment grains each have the surface area that provides space for pollutants to chemically or physically bind onto the sediment. If high volumes of sediment are washed into waterways during storm events, it is likely that the sediment is carrying additional pollutants with it. The combined surface areas from the individual grains provides the capacity to carry potentially high pollutant loads of nutrients, oils, and metals, and therefore sediment can be considered a separate pollutant category for this reason. Additionally, too much sediment can simply clog stormwater infrastructure and natural waterways to the extent that it can alter the original drainage paths and cause ponding, puddling, and even flooding issues. Identifying solutions to limit or prevent sediment pollution into natural waterways will subsequently aid in limiting other pollutants from entering waterways and reducing the chance of ponding and flooding events. At Dia01, one sample was scraped from the bottom of the concrete culvert. During field collection, the material was described as a loamy and gravelly soil that was gray-brown in color and contained organic material (Munsell Notation = 10YR 6/3, wet). Results from the grain size analysis demonstrated that the Dia01 sample was largely comprised of sediment between 500 and 4,000 microns in size (46%). This indicates that almost half of the sample was comprised of coarse sand and very fine pebbles. Approximately 42% of the sediment was comprised of pebbles and cobbles larger than 4,000 microns in size. Only 12% of the sample was comprised of fine sand, silt, and clay particles smaller than 500 microns in size (Figure 62). Diamond Watershed Water Quality Monitoring of Guts 101 | P a g e Diamond, St. Croix Watershed Management Plan Figure 62. The percent composition of the seven grain size categories within the Dia01 sediment sample. Diamond Watershed Water Quality Monitoring of Guts 102 | P a g e Diamond, St. Croix Watershed Management Plan At Dia02, a composite sample of one 9.0-inch sediment core from the earthen gut channel and loose sediment scraped from the concrete culvert within the gut was collected. During field collection, the sediment core material was described as a loose, sandy, and gravelly soil that was predominantly brown in color with flecks of gray and white (Munsell Notation = 10YR 6/4, dry). The scraped sediment was described as gray-brown dried algal mats. Results from the grain size analysis demonstrated that the composite sample at Dia02 was largely comprised of sediment larger than 4,000 microns in size (44%). This indicates that most of the sample was comprised of pebbles and cobbles. Approximately 37% of the sediment was comprised of pebbles and cobbles larger than 4,000 microns in size. The remaining 19% of the sample was comprised of fine sand, silt, and clay particles smaller than 500 microns in size (Figure 63). Figure 63. The percent composition of the seven grain size categories within the Dia02 sediment sample. Diamond Watershed Water Quality Monitoring of Guts 103 | P a g e Diamond, St. Croix Watershed Management Plan At Dia03, a composite sample of loose sediment scraped from both the earthen gut channel and the concrete culvert within the gut was collected. During field collection, the scraped material was described as a loose, sandy, and gravelly soil with gray construction gravel (Munsell Notation = 5YR 7/3, wet). Results from the grain size analysis demonstrated that the composite sample at Dia03 was largely comprised of sediment larger than 4,000 microns in size (51%). This indicates that more than half of the sample was comprised of larger sediment such as pebbles and cobbles. Approximately 44% of the sediment was comprised of coarse sand and very fine pebbles between 500 and 4,000 microns in size. Only 5% of the sample was comprised of fine sand, silt, and clay particles smaller than 500 microns in size (Figure 64). Figure 64. The percent composition of the seven grain size categories within the Dia03 sediment sample. Diamond Watershed Water Quality Monitoring of Guts 104 | P a g e Diamond, St. Croix Watershed Management Plan At Dia04, a composite sample of loose sediment scraped from both the earthen gut channel and the concrete culvert within the gut was collected. During field collection, the scraped material was described as a brown, loamy, and gravelly soil with organic material (Munsell Notation = 10YR 6/2, wet). Results from the grain size analysis demonstrated that the composite sample at Dia04 was largely comprised of sediment between 500 and 4,000 microns in size (50%). This indicates that half of the sample was comprised of coarse sand and very fine pebbles. Approximately 46% of the sediment was comprised of pebbles and cobbles larger than 4,000 microns in size. Only 4% of the sample was comprised of fine sand, silt, and clay particles smaller than 500 microns in size (Figure 65). Figure 65. The percent composition of the seven grain size categories within the Dia04 sediment sample. Overall findings from the grain size analysis at Dia01, Dia02, Dia03, and Dia04 demonstrated that the sediment sample composition was moderately equal between medium and larger sized sediment ranging from coarse sand to gravel pieces and larger cobbles. Fine particles such as silt and clay were consistently a small fraction of all four sediment samples. While extended monitoring can provide context of the prominent sediment types introduced into the gut channel over a longer temporal scale and through seasonal variation, the form of discrete sampling in this study provides a basis to identify the source of sediment influxes and to develop solutions to limit these influxes, particularly coarse sand and construction gravel, into surface waters that bind to and carry pollutants throughout the Diamond gut channels. Limiting these influxes can aid in reducing the formation of algal mats observed in the gut channels. Diamond Watershed Identification and Ranking of Stormwater BMPs 105 | P a g e Diamond, St. Croix Watershed Management Plan IDENTIFICATION AND RANKING OF STORMWATER BMPS 3.7.1 Identification of Potential BMP Project Sites 3.7.1.1 Desktop Assessment A desktop assessment was completed and 23 sites for potential stormwater management and flooding mitigation best management practices (BMPs) were identified. This process involved a thorough review of GIS resources and associated attribute data. Data included, but was not limited to, stormwater infrastructure data collected during this project, soils classifications, parcel data, topography, and guts. Assessments also considered areas of concern identified by project stakeholders and collected during and following public meeting input. This data was used to identify and map areas of water quality and flooding concern as well as areas where opportunities for potential BMP implementation were located. A point location was created for each identified site or area for assessment in the field (Figure 67). Also identified were 22 locations at which the mapped guts intersected roads. These points were identified as easy-access locations to assess bank erosion and the general health of the guts. Guts were easily visible from the road in certain locations, but thick vegetation or other obstacles limited the capacity to perform gut assessments at many locations as well. Shown on the maps below are desktop- identified potential BMP points as well as road/gut intersection points. Figure 66. Overview map of desktop identified potential BMPs and road / gut intersections. Diamond Watershed Identification and Ranking of Stormwater BMPs 106 | P a g e Diamond, St. Croix Watershed Management Plan 3.7.1.2 Field Assessments Targeted field assessments were completed in June 2021 and were focused on BMP assessment (Figure 68). These areas were prioritized prior to field work to further focus these efforts. In order to maximize efficiency in the field and better understand site-specific conditions, digital base maps were created. The maps show guts, watersheds, and stormwater infrastructure. This information was used in the field to assess potential feasibility issues for proposed practices and to better identify preliminary BMP locations. The base layers were pre-loaded into a project-specific mobile app that was customized for this project using the Fulcrum platform (Figure 67). The app was also pre-loaded with the 23-point locations identified during the desktop assessment. These points allowed for easy site location and data collection in the field. Figure 67. Fulcrum app interface used for field assessments. Diamond Watershed Identification and Ranking of Stormwater BMPs 107 | P a g e Diamond, St. Croix Watershed Management Plan At each site, the customized mobile data collection app was used to collect information including site suitability, photographic documentation, proposed BMP practice, hydrologic connectivity, operations and maintenance issues, follow-up notes, and other pertinent data. All collected data was securely uploaded to the Cloud for later use. Of the 23 initial desktop-identified potential BMP locations, four were visited and assessed in the field. These are shown in Figure 69 below in orange. Additionally, during the course of field investigations, five new BMP locations were identified in the field. These are shown in Figure 69 below in purple. Road/gut intersections were assessed in the field if they were reasonably accessible during the priority BMP assessments. The nine assessed intersections are shown below in Figure 69 in green. Of these road / gut intersections, three were selected as sites appropriate for a BMP and were added to the list of potential projects. Figure 68. Field assessments were completed across the watershed Diamond Watershed Identification and Ranking of Stormwater BMPs 108 | P a g e Diamond, St. Croix Watershed Management Plan Figure 69. Overview of map of potential BMP locations and road / gut intersections assessed in the field including new field identified locations. Diamond Watershed Identification and Ranking of Stormwater BMPs 109 | P a g e Diamond, St. Croix Watershed Management Plan 3.7.2 Preliminary Ranking of BMP Project Sites A total of 31 sites for potential stormwater best management practices (BMPs) were identified in the Diamond Watershed. To help determine which practices would be most effective and feasible, a preliminary prioritization process was applied to the list of potential sites. The goal of this preliminary ranking was to assess each identified project for its associated benefits and feasibility issues and narrow down a large list of projects to a more manageable list of 10 projects that will be impactful in terms of water quality benefits and quantity. This process is important because both time and resources are limited and can only be allocated to a limited number of practices at one time. However, this is not to imply that other projects from the list are not important. Once the feasible top 10 projects are implemented, the next highest ranked projects should be further assessed and moved forward to additional design and eventually implementation. The preliminary ranking considered the following factors, scoring on qualitative scales: 1) Impervious cover managed: If a large percentage of the estimated drainage area was impervious surface, a “High” rank was applied. Some small practices, for example parking lot treatment systems, may have had a small total area of impervious cover within their drainage areas but received a “High” rank as the impervious cover represented a high percentage of the drainage area. 2) Drainage area size: Practices that would treat large areas, relative to the other proposed practices within the watershed, received “High” scores. This included practices that would treat guts directly as guts often drained larger areas. 3) Potential water quality benefits: Ranking for this metric considered nearby land use and existing known water quality issues (for example, documented turbid runoff or road erosion). Nearby industrial, commercial, or high-density residential land use were generally considered to pose greater water quality risks than lower density development. If an area lacked existing stormwater treatment features, the potential water quality benefits were considered greater than if the proposed practice would retrofit or supplement existing stormwater features. 4) Potential for flood mitigation: If the proposed practice would help store and slow a large quantity of runoff during storm events, a “High” score was assigned. Practices located upstream of high- density development areas were generally considered to have higher potential flood mitigation benefit as they directly impacted the communities downstream. 5) Difficulty of design/construction: The available space, scale of project, and density of surrounding development were all considered for this metric. Proposed BMPs that would require potentially complicated overflow and routing systems to tie with existing infrastructure were considered higher difficulty and thus scored lower. These types of complications were often linked to concerns with construction access, land ownership, topography, and other similar limiting factors. 6) Site of particular concern?: This metric was either “Yes” or “No”. If a site had documented water quality, erosion, or flooding concerns based on local knowledge or field investigation, it was marked “Yes”. Diamond Watershed Identification and Ranking of Stormwater BMPs 110 | P a g e Diamond, St. Croix Watershed Management Plan Table 19. BMP preliminary ranking metric scores. Metric Ranking Option Scores Impervious cover managed Low 1 Medium 2 High 3 Drainage area size Small 1 Medium 2 Large 3 Potential water quality benefits Low 1 Medium 2 High 3 Potential flood mitigation Low 1 Medium 2 High 3 Difficulty of design/construction Low 1 Medium 2 Complex 3 Site of particular concern? No 0 Yes 1 The sum of the numeric qualitative rankings represented each BMP’s preliminary prioritization score. A maximum score of 16 was possible for each assessed BMP, and the closest to that score, the higher the rank. Of the 31 ranked sites, one site received a score of 15, one site received a score of 12, and seven sites received a score of 11, making up the top 9 BMPs. Three sites scored 10 where the expert opinion determined which site should qualify as a top 10 BMP. The ranking determined that these sites are capable of treating a large amount of impervious surfaces, improving water quality, and reducing flood potential within the watershed. Additionally, the chosen BMP locations have minimal known barriers to implementation. The 10 highest ranking proposed BMPs were reviewed by project stakeholders at DPNR to ensure there was not any site-specific information that the project team were unaware of were that would impact implementation. Following this review, these 10 projects were advanced to the next round of prioritization, the final ranking. Complete preliminary ranking information and the point locations of these 54 projects are included in Appendix B3. A 1-page BMP summary sheet has also been created for reach of the 10 highest ranking proposed BMPs which can be found in Appendix B3. Diamond Watershed Identification and Ranking of Stormwater BMPs 111 | P a g e Diamond, St. Croix Watershed Management Plan Figure 70. Map of proposed BMP points and preliminary ranking results. Diamond Watershed Identification and Ranking of Stormwater BMPs 112 | P a g e Diamond, St. Croix Watershed Management Plan Table 20. Summary table of preliminary BMP ranking results. ID Number Description Final Score 20* Gut is actively head cutting. Open area is a good opportunity for a gut restoration/stabilization project. Gabion check dams with long basins with gabions between. Infiltration trench upstream of head cut. 15 29* Provide storage in gut. Stabilize erosion. 12 4* Potential to create a surface basin to provide flood storage for large drainage swale. 11 17* Retrofit existing BMP; add additional drainage from gut and expand basin. 11 23* Potential to create a surface basin to provide flood storage for gut. 11 24* Provide storage in gut. 11 26* Provide storage in gut. 11 27* Provide storage in gut. 11 31* Potential to manage drainage from road including swales and another large inlet pipe. 11 9* Potential to expand surface basin to provide flood storage for gut and install gabions. 10 21 Potential for surface feature in green space. Potential to redirect grass swale across the road to collect additional drainage. 10 30 Pave road and stabilize erosion. 10 1 Possible turnout here to diffuse runoff 9 2 Potential for surface basin in greenspace. 9 10 Potential for surface basin in greenspace. 9 11 Potential for surface basin in greenspace. 9 15 Potential for surface basin in greenspace. 9 16 Retrofit existing BMP; add additional drainage from gut and expand basin 9 18 Retrofit existing BMP; expand basin 9 22 Potential for a surface feature along road. The remainder of the green space is elevated. Grass swales on other side of road. Potential to integrate into a combined practice 9 28 Potential for surface feature in green space. 9 3 Potential for surface basin after swale. 8 5 Retrofit existing BMP 8 6 Retrofit existing BMP 8 7 Retrofit existing BMP 8 12 Existing pond to be improved 8 13 Road paving poor - repave and provide surface crossings and turnouts. 8 19 Potential for surface basin in greenspace. 8 25 Potential to provide additional gut storage via a surface basin, but gut is in good condition, and this is a low priority. 8 8 Collect facility entrance, main road, and side road and manage in surface basin. 7 14 Sunken road; unpaved; needs surface crossing, surface stabilization. 7 *Top 10 sites. Diamond Watershed Identification and Ranking of Stormwater BMPs 113 | P a g e Diamond, St. Croix Watershed Management Plan 3.7.3 Final Ranking of BMP Project Sites 3.7.3.1 Methods & Materials Once the 10 highest ranking proposed BMPs were determined, a more comprehensive rating methodology was utilized to establish a final ranking of the top 10 BMPs. The ranking is designed to account for the highest priorities that should be pursued for concept and final design implementation described in Table 21 below. The Ranking accounts for twenty factors, including both qualitative and quantitative metrics. There are 15 quantitative factors. Quantitative factors were scored on a range of one to five using Jenks Natural Breaks Classification, a classification method designed to find natural groupings in the data to group similar values together. Classes in Jenks Natural Breaks Classification are divided where there are relatively large differences in the data values. Only values of the top 10 BMPs within the watershed were factored into the classification. Scores associated with pollutant load reductions and hydrologic properties were based on the water quality modeling and hydrologic/hydraulic modeling described in the following section. There are five qualitative categories: community input, severity of water quality discharge violations, feasibility concerns, ancillary benefits, and expert opinion. Each of these categories have a unique scoring and classification system individualized to each qualitative variable being scored. All scores are summed, yielding a final score for each BMP. The BMPs are then ranked from highest score (rank 1) to lowest score (rank 10). Table 21. Metrics included in the final ranking and their respective score ranges. Metric Description Scoring Impervious Surfaces The total area of impervious surface in each identified Drainage Area (m2) Given a score 1-5 determined by Jenks Natural Breaks Classification. Development Potential The percentage of area at risk of development by 2050 within each identified drainage area as defined by the future land use model. Given a score 1-5 determined by Jenks Natural Breaks Classification. Industrial Zoning The percentage of industrial zoning designations within each drainage area Given a score 1-5 determined by Jenks Natural Breaks Classification. Public Zoning The percentage of public zoning designations within each drainage area Given a score 1-5 determined by Jenks Natural Breaks Classification. Riparian Forest Cover The percentage forested area within 100 ft of a gut within each drainage area Given a score 1-5 determined by Jenks Natural Breaks Classification. Gut Density The gut density in each drainage area (m/m2) Given a score 1-5 determined by Jenks Natural Breaks Classification. Outfall Density The infrastructure density in each drainage area (m/m2) Given a score 1-5 determined by Jenks Natural Breaks Classification. Flooding Severity The percentage of 100-year floodplain zones as defined by FEMA within each drainage area Given a score 1-5 determined by Jenks Natural Breaks Classification. Diamond Watershed Identification and Ranking of Stormwater BMPs 114 | P a g e Diamond, St. Croix Watershed Management Plan Metric Description Scoring Bank Erosion Severity Number of locations identified as Medium to High erosion severity in each drainage area during field assessments. Given a score 1-5 determined by Jenks Natural Breaks Classification. Road Gut Crossings Count of road/gut crossings in each drainage area Given a score 1-5 determined by Jenks Natural Breaks Classification. Community Input Whether or not there is voiced community concern within the drainage area. Given a score 1 or 5 determined by if there was a voiced community concern within the BMP’s drainage area Total Nitrogen Total Nitrogen (TN) Given a score 1-5 determined by Jenks Natural Breaks Classification Total Phosphorus Total Phosphorous (TP) Given a score 1-5 determined by Jenks Natural Breaks Classification Total Suspended Solids Total Suspended Solids (TSS) Given a score 1-5 determined by Jenks Natural Breaks Classification Fecal Coliform Reductions Fecal Coliform Reductions (lbs/year) Given a score 1-5 determined by Jenks Natural Breaks Classification BMP Storage Volume The amount of water the bmp would be sized to hold (ft3) Given a score 1-5 determined by Jenks Natural Breaks Classification Severity of Water Quality Violations in Discharge Ranked based on the severity of water quality violations in BMP discharge points as defined by … Ranked from 1-5: 1 – Not of Concern 3 – Low Concern 4 – Moderate Concern 5 – High Concern Feasibility Concerns? What is the magnitude of feasibility concerns in putting a BMP at the location? BMP feasibility concerns may include, but are not limited to ownership, space, high cost, lack of public support, etc. Ranked from 0-30: 0 – High Concern 15 – Moderate Concern 30 – Minimal Concern Ancillary Benefits Any significant benefits of BMP outside of metrics in ranking? Benefits may include aesthetics, educational, healthy vegetation, etc. Ranked from 1-5: 1 – None 3 – Some 5 - Many Expert Opinion How highly regarded is the site by experts in the field? Ranked from 0-30: 0 – Recommended Lowly 15 – Recommended Moderately 30 – Recommended Highly Diamond Watershed Identification and Ranking of Stormwater BMPs 115 | P a g e Diamond, St. Croix Watershed Management Plan 3.7.3.2 Final Ranking Results The final ranking of BMP project sites can be found below in Table 14. Scores of the top 10 BMPs ranged with BMP Numbers 20 and 29 receiving the two highest scores in the final ranking. Figure 71 displays the spatial distribution of the final scores and each BMP’s associated drainage area. The top 10 ranked sites are spatially distributed across the watershed, covering a total drainage area of 2,377.2 acres (81.3% of the watershed area). Consequently, the selected BMPs can treat a variety of regions and neighborhoods throughout Diamond Watershed. The ranking determined these sites are capable of treating large impervious areas, improving water quality, and reducing flood potential within the watershed. Additionally, the chosen BMP locations have minimal known barriers to implementation. The top two ranked BMPs, 20 and 29, were furthered progressed towards 30% concept design development. Table 22. Top 10 recommended BMPs in the Diamond watershed. BMP ID Rank BMP Description Drainage Area (Acres) Impervious Area (Acres) Storage Volume (ft3) Total Nitrogen Removed (lb/year) Total Phosphorus Removed (lb/year) Total Suspended Solids Removed (lb/year) 20* 1 Basin, Stabilization, Floodplain / gut restoration 541.95 24.89 378,375 30 9 10,835 29* 2 Basin 610.24 33.81 735,492 18 5 6,263 27 3 Basin 269.46 23.64 587,968 73 22 26,033 23 4 Basin 2,264.85 188.12 1,223,568 303 89 107,765 26 5 Basin 2,287.14 191.24 1,983,541 8 2 2,744 4 6 Basin 77.78 21.22 104,834 41 11 14,744 9 7 Basin 464.65 11.40 334,996 86 26 30,133 24 8 Basin 462.96 6.85 585,753 79 24 27,762 17 9 Basin 11.61 4.49 57,217 8 2 2,868 31 10 Basin 9.00 2.66 55,813 5 1 1,810 * Selected 30% design site. Diamond Watershed Identification and Ranking of Stormwater BMPs 116 | P a g e Diamond, St. Croix Watershed Management Plan Figure 71. Depiction of the relative ranking of each BMP and the associated BMP drainage area. Note that some drainage areas overlap. Diamond Watershed Identification and Ranking of Stormwater BMPs 117 | P a g e Diamond, St. Croix Watershed Management Plan 3.7.4 30% Design Sites 3.7.4.1 Infiltration Chambers (BMP 20) This 30% design features 680 ADS-Stormtech MC-4500 infiltration chambers beneath greenspace at the Lorraine apartment complex in Estate Plessen (Figure 72). This site was originally scoped as a potential surface basin opportunity, but the design later evolved to subsurface chambers to maintain the existing greenspace. Two guts flow through the site and converge near the proposed chamber system. A weir constructed within the gut directs flow from both guts into the chamber system. The chamber system is designed to infiltrate runoff from the 1” rain event and provide detention benefits to the watershed. Two rows of the chamber system are designed with water-tight pipe, allowing the storage and reuse of stormwater for irrigation on-site. Site constraints include existing underground utility infrastructure. The complete 30% design plans can be found in Appendix B4. A map of the drainage area for this proposed system can be found below in Figure 73. Figure 72. Example photo of subsurface infiltration chambers (above) and greenspace at the Lorraine apartment complex (below). Diamond Watershed Identification and Ranking of Stormwater BMPs 118 | P a g e Diamond, St. Croix Watershed Management Plan Figure 73. Drainage area to proposed BMP 20. Diamond Watershed Identification and Ranking of Stormwater BMPs 119 | P a g e Diamond, St. Croix Watershed Management Plan 3.7.4.2 Gut Restoration (BMP 29) This 30% design features restoration of an eroding gut in Plessen Estate (Figure 74). Originally scoped as a potential detention basin opportunity, this design focuses on restoration of the gut, while the proposed chamber system at the Lorraine Apartments (BMP 20) provides detention to the same gut just upstream. This design proposes several gabion check dams across the gut to slow flow during rain events, additional gabions or stone keyed into the toe of each bank where incising is occurring, grading to lessen the slopes of each bank, and establishing a 15' vegetative buffer where space exists. Site constraints include adjacent development and septic infrastructure along the gut. The complete 30% design plans can be found in Appendix B4. A map of the drainage area for this proposed system can be found below in Figure 75. Figure 74. Existing conditions of proposed BMP 29 site location. The photo above is of the existing culvert underneath the road. Diamond Watershed Identification and Ranking of Stormwater BMPs 120 | P a g e Diamond, St. Croix Watershed Management Plan Figure 75. Drainage area to BMP 29. Diamond Watershed Watershed Modeling 121 | P a g e Diamond, St. Croix Watershed Management Plan WATERSHED MODELING 3.8.1 Modeling Overview Hydrologic and hydraulic (H&H) modeling, as well as water quality modeling were completed on both the watershed scale and individual BMP scale to assess four primary scenarios: 1. Existing watershed conditions: Assess watershed-scale water quality and hydrology taking existing BMPs into account. 2. Existing watershed conditions with future development: Assess watershed-scale water quality and hydrology taking existing BMPs into account through future predicted land cover scenarios in the years 2030, 2050, 2080, and 2100. 3. Proposed watershed conditions: Assess watershed-scale water quality and hydrology taking any existing BMPs into account and the proposed Top 10 ranked BMPs. 4. Proposed watershed conditions with future development: Assess watershed-scale water quality and hydrology taking existing BMPs into account and the proposed Top 10 ranked BMPs through future predicted land cover scenarios (2030, 2050, 2080, and 2100). Limited technical information regarding modeling methodologies is included in this section to improve readability and allow for more discussion of modeling results. Complete modeling methodology and complete modeling results are included as Appendix B5 and B6. Water quality modeling was completed using the Watershed Treatment Model (WTM), a spreadsheet- based tool developed by the Center for Watershed Protection that calculates total nitrogen (TN), total phosphorus (TP), total suspended solid (TSS), and fecal coliform (FC) loads based on several drainage area sources including land use, soil type, sewage use and disposal, stream channel erosion and nutrient concentration, and marina characteristics. H&H modeling was completed using HydroCAD, a software most commonly used to model stormwater runoff and design stormwater management systems. Models were developed in HydroCAD to estimate peak flow rates and model volumes, as well as to assess the peak flow rate reduction benefits of existing and proposed BMPs. Diamond Watershed Watershed Modeling 122 | P a g e Diamond, St. Croix Watershed Management Plan Peak flow is measured in cubic feet per second (cfs) and is indicative of how quickly water flows through a watershed. High peak flows are problematic because they exacerbate erosion and flooding as stormwater flows in fast-moving, concentrated channels down a slope. Generally, watersheds or drainage areas with a high peak flow are likely to have had land cover and/or land use changes occur, altering the natural state. Land cover is a key determinant of peak flow, although underlying soil conditions, topography, and drainage area also can play significant roles. The implementation of stormwater BMPs can reduce peak flow and delay the timing of thee until peak flow, which more closely mimics an undeveloped watershed (Figure 76). Figure 76. Illustrative hydrographs demonstrating the peak flow reduction value of implementing BMPs. Data and information inputs to the H&H models were: • Drainage areas for existing and proposed best management practices (source: delineated in GIS utilizing topography, imagery, mapped stormwater infrastructure, and limited field verification), • Time of concentration, defined as the time required for a drop of water to travel from the most hydrologically remote place in a drainage area to the point of collection (source: digitized in GIS as the longest flow length), • Hydrologic soil group (HSG) (source: National Resource Conservation Service (NRCS) soil data), • Existing and future land use (source: developed for this project as described in Sections 3.3.2 and 3.3.6), and • Rainfall depth and distribution (source: NOAA Atlas 14 Point Precipitation Frequency Estimates, and a Type II storm distribution is used in accordance with the Soil Conservation Service (SCS) 24- hour Rainfall Distribution). Additional details about HydroCAD modeling methodologies can be found in Appendix B5. Diamond Watershed Watershed Modeling 123 | P a g e Diamond, St. Croix Watershed Management Plan 3.8.2 Existing Conditions The watershed contains two existing BMPs that were identified during this project (see Section 3.5.2 for more discussion on the identification and location of these practices). The capacity of these BMPs to reduce peak flow and treat water quality were included into the modelling of existing conditions. 3.8.2.1 H&H Modeling of Existing Conditions Land use and soils data for each existing BMP drainage area and the greater watershed was imported into HydroCAD as a subcatchment node. Each land use was assigned a Curve Number (CN) according to the land cover and underlying soil type. Time of concentration was calculated for each subcatchment by the watershed lag method. BMPs were represented as pond nodes and routed to the watershed outlet by reach nodes describing paths along major guts. The SCS TR-20 runoff method was used to generate a total runoff hydrograph for each study watershed subcatchment and each BMP subcatchment. Runoff volume was calculated separately for each CN, which was then summed to calculate the total runoff from each subcatchment node. This approach preserves the runoff volume from each subarea within the subcatchment node and thus is called the flow-weighted or “Weighted-Q” method. Storage volume measured to first overflow outlet of each BMP was defined in HydroCAD using GIS measurement tools, existing stormwater infrastructure, and elevation contour layers. Table 23 below describes each of the practices, the storage volume associated with the practice, and the assumptions that were incorporated into the water quality and hydrologic modeling scenarios. Taken together, the existing stormwater BMPs capture 4.32 acres of impervious cover. Table 23. Storage volume and assumptions of existing BMPs. Existing ID BMP Type Storage Volume (cf) BMP Description and Assumptions 1 Basin 20,975 Volume measured to berm. Overflow at SW edge of berm to existing roadside swale Square concrete riser from Jeff's photos. Outlet pipe discharges to roadside swale - diameter unknown. Surface areas estimated from contours. No available site plans. 0.21 in/hour infiltration rate from SSURGO. 2 Basin 6,840 Volume measured to 98.5' at outlet of West Basin. Double 24" pipes connect with West Basin - diameters estimated from Jeff's photos. Surface areas estimated from contours. No available site plans. 0.21 in/hour infiltration rate from SSURGO. Without the inclusion of the existing BMPs, peak flow during a 1-year storm event at the outlet of the watershed is 2,176 cfs. Peak flow during a 1-year storm event with the existing BMPs is 2,178 cfs. There is no peak discharge reduction that can be attributed to the existing BMPs. Diamond Watershed Watershed Modeling 124 | P a g e Diamond, St. Croix Watershed Management Plan 3.8.2.2 Water Quality Modeling of Existing Conditions The existing loads, summarized by major land use category are presented in Table 24. In this watershed, urban land has the highest estimated loads for TN and channel erosion contributes the highest loads for TP. TSS loads were dominated by channel erosion, which was estimated from the length of guts in the watershed. Channel erosion represents about 83% of the total sediment load from the watershed, representing a high level of channel erosion. The estimated contribution from all sewage sources— sanitary sewer overflows (SSOs), illicit discharges, and septic systems—represented the majority of the fecal coliform loading, while runoff originated primarily from the “Urban Land” category. Table 24. Existing pollutant loads to surface waters in the watershed. Land Use TN (lbs/year) TP (lbs/year) TSS (lbs/year) Fecal Coliform (billion/year) Urban Land 6,814 1,295 349,027 274,066 Active Construction 17 3 11,713 0 Channel Erosion 3,363 1,345 2,690,400 0 Forest 3,976 318 159,038 19,085 Rural Land 245 37 5,316 2,073 Point Sources 0 0 0 0 Onsite Sewage 3,747 624 24,978 53,143 SSOs and Illicit Discharges 1,485 248 9,900 1,123,654 Open Water 9 0 107 0 Total 19,655 3,872 3,250,478 1,472,021 Diamond Watershed Watershed Modeling 125 | P a g e Diamond, St. Croix Watershed Management Plan 3.8.3 Existing Conditions with Future Development The five existing BMPs were modeled to assess the existing watershed-scale conditions along with the future predicted land cover scenarios in order to determine the impacts of increased development without the construction of any additional stormwater BMPs. The models were created to assess each of the four future land cover scenarios: 2030, 2050, 2080, and 2100. A summary of the land cover changes from the present condition to these future conditions are summarized in Table 25 below. Over the projected time periods, changes are minimal but in general green space decreases while impervious cover and bare soil increase. Note that land cover information for 2019 differs slightly in the future land cover modeling because the data had to be aggregated to grid cell format to be compared with the future land cover projections that were developed using this grid cell format Table 25. Future Land cover summary table. Land Cover Category Acres 2019 2030 2050 2080 2100 Bare Soil 118.1 119.45 119.89 126.63 133.15 Green Space 2,537.3 2,534.15 2,511.53 2457.21 2,412.94 Impervious Cover 265.63 267.45 289.63 337.2 374.96 Water 1.56 1.56 1.56 1.56 1.56 3.8.3.1 H&H Modeling of Existing Conditions with Future Development Over time, as projected impervious cover increases and green space decreases, the watershed-scale peak flow rate increases. By 2100, peak flow from the watershed will be 2,296 cfs. This is a 5% increase in flow from 2019. This trend can be observed in Figure 77 below. Figure 77. Relationship between watershed scale peak flow (blue) and the predicted impervious cover (red) over time. Diamond Watershed Watershed Modeling 126 | P a g e Diamond, St. Croix Watershed Management Plan 3.8.3.2 Water Quality Modeling of Existing Conditions with Future Development The water quality modeling results for the projected future land cover mirror the results observed in the hydrologic modeling (Figure 77). Over time, as impervious cover increases and green space decreases, each of the four pollutants of concern that were modeled increase (Figure 78). Figure 78. Relationship between watershed-scale pollutant loading for TN (yellow), TSS (blue), TP (green), and Fecal Coliform (orange) and the predicted impervious cover increase (red) over time. Diamond Watershed Watershed Modeling 127 | P a g e Diamond, St. Croix Watershed Management Plan 3.8.4 Top 10 Proposed BMPs The top 10 proposed BMPs identified in Section 3.7 were modeled to ensure that they are adequately sized and to assess their impact on watershed-scale peak discharge reduction. A summary of the model assumptions and storage volumes of proposed BMPs can be found in Table 26. Table 26. Model assumptions and storage volumes of proposed BMPs. Proposed ID BMP Type Storage Volume (cf) Total Area (Acres) Impervious Area (Acres) 9 Basin 334,996 464.72 11.40 27 Basin 587,968 269.52 23.64 29 In-Gut Storage 735,492 59.32 6.27 31* Basin 55,813 9.00 2.66 4 Basin 104,834 77.78 21.22 24 Basin 585,753 463.01 6.85 23 Basin 1,223,568 910.70 119.31 17 Basin 57,217 11.62 4.49 20 Subsurface Chambers 378,375 77.30 13.49 26 Basin 1,983,541 22.33 3.13 *It was assumed that all BMPs were sized for detention of a 1-year event, 2.7 in/hour infiltration rate from SSURGO which the exception of BMP 31 which was sized for 1 in/hour. Each BMP is represented in HydroCAD by a Pond node with storage and outlets. Flow-through structures are modeled as nodes with insignificant storage, which provide velocity information used to size the structures. The storage volume for each BMP was defined in HydroCAD, using the available surface area at each site as the primary constraint. A series of outlets were defined for each BMP, typically with a smaller, low-flow orifice located at the bottom of the pond or structure, a larger overflow orifice one to three feet from the bottom, usually in the form of a riser, and a long overflow emergency spillway weir three to four feet from the bottom (Figure 79). Each proposed BMP node is designed to maximize peak discharge reduction benefits during the 1-year rain event within the available space. For sites where space constraints preclude the storage volume from providing the necessary volume for detention of the 1-year rain event, the BMP is sized for the “water quality volume” (WQv) storm event, which typically transports the majority of stormwater pollutants. See Appendix B5 for further discussion of the water quality volume. Any flow that exceeds the storage capacity of the BMP nodes is automatically routed to the next downstream node which is either a reach node, another BMP node, or directly to the watershed outlet. All flow is routed to a single node representing the watershed outlet, where flows are summed into a hydrograph. Diamond Watershed Watershed Modeling 128 | P a g e Diamond, St. Croix Watershed Management Plan Figure 79. Dry detention basin design. Graphic adapted from the 2017 Vermont Stormwater Management Manual Rule and Design Guidance (Vermont ANR, 2017). 3.8.4.1 H&H Modeling of Proposed BMPs Using current land-use conditions, it was determined that the 10 proposed BMPs reduced the modeled peak flow by 76% at the Diamond watershed outlet during the 1-year storm event, from 2,178 cfs to 513 cfs (Figure 81). This is a substantial reduction in peak flow and would likely lead to profound reductions in erosion and flooding. Figure 80. Peak flow was reduced at the watershed outlet from 2,178 cfs with existing BMPs to 513 cfs with addition of the Top 10 proposed BMPs. Diamond Watershed Watershed Modeling 129 | P a g e Diamond, St. Croix Watershed Management Plan 3.8.4.2 Water Quality Modeling of Proposed BMPs The pollutant load reductions from BMPs proposed in the watershed can be found in Table 27. In the model the proposed practices are effective at reducing pollutants associated with sediment and erosion (TN, TP, & TSS), however are not effective at treating pollution associated with wastewater (Fecal Coliform). It is important to note that of the pollutants in the WTM, fecal coliform is the most difficult to characterize. Research has shown that stormwater treatment practices such as the one’s proposed can be effective at treating fecal coliform from surface water, so it is feasible that this potential reduction was not capture in the model (Mallin, 2016). Table 27. Estimated pollutant and runoff reduction benefits of each proposed retrofit. Proposed Practice ID TN (lbs/year) TP (lbs/year) TSS (lbs/year) Fecal Coliform (billion/year) 9 86 26 30,133 0 27 73 22 26,033 0 29 18 5 6,263 0 31 5 1 1,810 0 4 41 11 14,744 0 24 79 24 27,762 0 23 303 89 107,765 0 17 8 2 2,868 0 20 30 9 10,835 0 26 8 2 2,744 0 Total 650 191 230,958 0 As previously noted, the WTM includes several different sources of pollutant loading for the watershed as a whole, including: The total load reduction from surface runoff loads (from urban, rural, and forest land) ranges from 0% (for fecal coliform) to 45% for TSS, but the reduction as a percentage of total watershed loads is lower, ranging from 0% for fecal coliform to 7% for TSS (Table 28 and Figure 81). Some estimated sources, especially from sewage discharges, channel erosion and point sources, are not directly addressed by the proposed retrofits. • Surface Runoff (Urban, Rural, and Forest), • Point Sources, • Active Construction, • Onsite Sewage, • Channel Erosion, • SSOs and Illicit Discharges, and • Open Water. Diamond Watershed Watershed Modeling 130 | P a g e Diamond, St. Croix Watershed Management Plan Table 28. Estimated pollutant loads in the watershed for the existing conditions and with reductions associated with the Top 10 proposed BMPs. Time Frame TN (lbs/year) TP (lbs/year) TSS (lbs/year) Fecal Coliform (billion/year) Existing Conditions 19,655 3,872 3,250,478 1,472,021 Existing Conditions with Top 10 Proposed BMPs 19,005 3,680 3,019,521 1,472,021 Total Reduction 650 191 230,958 0 Figure 81. Pollutant load reductions attributable to the Top 10 BMPs for the Surface Runoff category (blue) and for all modeled watershed sources (orange). Diamond Watershed Watershed Modeling 131 | P a g e Diamond, St. Croix Watershed Management Plan 3.8.5 Proposed Conditions with Future Development The hydrologic and water quality benefits of the proposed Top 10 BMPs were then assessed in comparison to the future land cover predictions for the watershed. 3.8.5.1 Hydrologic Modeling Results of Proposed Conditions with Future Development With the combination of proposed BMPs and forecasted new development in the watershed, peak flow is anticipated to increase between 2030 and 2100 (Figure 83). However, even with the increased impervious cover, the peak flow in 2100 is still predicted to be lower than the existing conditions when the peak flow reductions associated with the Top 10 BMPs are included. 3.8.5.2 Water Quality Modeling Results of Proposed Conditions with Future Development The predicted future development in the watershed results in increased pollutant loads between 2030 and 2100 (Figure 83). The increase in development is well correlated to increased pollutant loads. The pollutant load reductions associated with implementation of the Top 10 BMPs reduces these loads. However, over time and with increased development, the benefits of these BMPs are diminished and, in some cases in the future conditions, pollutant loads exceed existing conditions. This highlights the need for continued efforts to mitigate the impacts of development so that watershed conditions improve over time. Figure 82. Relationship between watershed peak flow for the existing conditions (light blue) and proposed conditions (gray), which includes the implementation of the Top 10 BMPs over time. The predicted impervious cover increase (red) over time is also shown. Diamond Watershed Watershed Modeling 132 | P a g e Diamond, St. Croix Watershed Management Plan Figure 83. Relationship over time between watershed scale pollutant loading for the existing conditions (lighter colors) and proposed conditions (darker colors), which includes the implementation of the Top 10 BMPs. Loading is shown for TN (yellow), TSS (blue), TP (green), and Fecal Coliform (orange). The predicted impervious cover increase (red line) over time is also shown. 133 | P a g e Diamond, St. Croix Watershed Management Plan 4 RECOMMENDATIONS & CONCLUSIONS Recommendations & Conclusions Proposed Management Measures 134 | P a g e Diamond, St. Croix Watershed Management Plan PROPOSED MANAGEMENT MEASURES A variety of proposed management measures and specific actions were identified during the development of this Watershed Management Plan. Some of the measures are proposed at an island scale while others apply to specific watersheds. Recommendations were derived from the watershed specific modeling, field assessments, water quality monitoring, community outreach, review of existing research, and discussions with DPNR, DPW, and WMA. Additionally, the “Eight Tools of Watershed Protection” was used by the project team to evaluate the current state of watershed management in the USVI. This audit tool, developed by CWP, identified programmatic strengths and gaps in watershed protection strategies and helped to inform the following watershed planning recommendations. The recommendations detailed below are categorized as recommendations for: 1. Stormwater Management and Non-Stormwater Discharges 2. Watershed Planning 3. Land Use Planning and Resource Protection 4. Site Design Guidelines 5. Solid Waste Management 6. Watershed Stewardship 7. Future Research 4.1.1 Stormwater Management and Non-Stormwater Discharges 4.1.1.1 Stormwater Management Standards and Regulations USVI is not currently regulated by the US EPA under the NPDES Phase II permit for municipal separate storm and sewer systems (MS4 program); however, EPA authorized the USVI TPDES program in 1976. Organization of the TPDES program around the basic NPDES MS4 six minimum measures for stormwater management is recommended to incorporate basic elements of a stormwater management program that are missing in USVI, including post-construction, pollution prevention and good housekeeping, and illicit discharge detection and elimination (IDDE). The USVI does not currently have regulatory criteria for post-construction stormwater management including inspection and maintenance; however, the Horsley Witten Group is in the process of developing a USVI Stormwater Standards and Design Manual that should incorporate specific design criteria, maintenance requirements, and typical plan details necessary for best management practices to meet stormwater standards (USVI, 2020). The updated manual should incorporate green infrastructure (GI) techniques to reduce stormwater runoff to the maximum extent practicable such that there is little to no discharge from the 1-year, 24-hour storm. It is recommended that this manual be adopted and promoted. Recommendations & Conclusions Proposed Management Measures 135 | P a g e Diamond, St. Croix Watershed Management Plan It is also recommended that USVI develop a post-construction stormwater management program with inspection and maintenance checklists and adopt a post-construction stormwater management ordinance for new and redevelopment. Specific references to help develop these standards include: • Managing Stormwater in Your Community: A Guide for Building an Effective Post-Construction Program and the Appendices with Model Post Construction Ordinance • Maryland Model Stormwater Management Ordinance 4.1.1.2 Erosion & Sediment Control (ESC) In the USVI, erosion and sediment control (ESC) is required for all sites (12 V.I.C. § 533, Earth Change Plans) “[b]efore any real property is cleared, graded, filled or otherwise disturbed for any purpose or use.” An earth change permit is provided upon approval of an earth change plan detailing the erosion and sediment control for a development site. A building permit or other permits will not be received until an earth change permit is obtained. It is recommended that requirements be amended to require limits of disturbance to be shown on construction plans and physically marked at the site. Limits of disturbance for existing trees should include the critical root zone also known as the drip line. Construction sites are inspected for compliance with erosion and sediment control requirements by third party inspectors on a weekly basis. The inspectors have national certification – Stormwater Pollution Prevent Plan (SWPPP) Inspector or similar or Professional Engineer (P.E.) or similar. There are erosion and sediment control enforcement mechanisms in place (e.g., fines, stop work orders, etc.). However, several construction sites were observed during field assessments where erosion control measures such as silt fences were not properly installed. This is an issue of concern as these unstable construction areas, even in temporary, can contribute significant sediment loads to surface waters if not properly managed. It should be determined whether these noncompliant sites were either: • Not inspected, • Were inspected but no compliance issues were recorded indicating a misunderstanding of ESC standards by inspectors, or • ESC noncompliance was noted by inspectors and was not fixed on site. o If following initial observations of noncompliance, the site was still not meeting ESC standards this could indicate that either the site was not reinspected to ensure compliance or enforcement mechanisms were levied but did not result in ESC compliance. It is recommended that a review of noncompliant construction sites be completed to determine the reasons for ESC violations and determine the appropriate steps that need to be taken to address these violations. This could include formal training for inspectors, training for contractors, increased enforcement of fines or stop work orders, increased frequency of inspection, or other measures as determined by this assessment. Currently, the 2002 Virgin Islands Environmental Protection Handbook is being updated, and it is recommended that the USVI finalize and adopt the revised Environmental Protection Handbook. The Handbook should illustrate proper stormwater practice design, installation, and maintenance procedures, as well as construction phase stormwater practices that reduce runoff volumes and prevent or decrease the discharge of pollutants in stormwater. Recommendations & Conclusions Proposed Management Measures 136 | P a g e Diamond, St. Croix Watershed Management Plan 4.1.1.3 Demonstration Projects The implementation of GI demonstration projects on public properties is also recommended. Demonstration of GI practices should be promoted during restoration activities that address drainage improvements to existing conditions, including public projects such as road repairs, facility renovations, and other capital improvements. Parks, schools, and other public spaces should also be inventoried and opportunities for GI identified. One opportunity is to publicly showcase GI stormwater practices installed at the 64 West Center located on UVI’s St. Croix campus. The stormwater practices at this facility include permeable pavements, vegetated bio-swales, and underground detention storage (Rain TanksTM) for landscape irrigation and to supplement water supplies for water closets, urinals, and cooling towers. In addition to the water quality benefits of these practices, educational materials and signs should be distributed and installed in conjunction with these demonstration projects. Increasing the public’s understanding of the importance of managing land based sources of pollution can encourage support of additional and larger stormwater best management practices (BMPs), some of which could be located on private property with participating private landowners. It can also encourage the adoption and construction of smaller scale residential stormwater BMPs. 4.1.1.4 Implementation of Identified BMPs One of the outcomes of this plan was the identification of stormwater and flooding BMPs including 10 high priority sites within each watershed. From the 10 high priority sites per watershed, 30% concept design plans were developed for two priority ranked sites. These concept design plans can be found in Appendix B4. To address the water quality and flooding problems derived from stormwater, the final design and implementation of the two 30% conceptual designs per watershed should be of high priority. Also of importance, further design development and implementation should be pursued for the remaining eight high priority potential BMP sites per watershed. A map and tabulated summary of the 10 high priority sites per watershed can be found in the watershed-specific appendices and sections of this report. The full list of identified BMPs should also be further investigated in the long term. 4.1.1.5 Illicit Discharge & Wastewater Management The USVI does not currently have an Illicit Discharge Detection and Elimination (IDDE) program. Dry- weather flows discharging from storm drainage systems can contribute significant pollutant loadings to receiving waters. Illicit dry weather flows originate from many sources. The most important sources typically include sanitary wastewater or industrial and commercial pollutant entries, failing septic tank systems, and vehicle maintenance activities. It is recommended that the USVI adopt an IDDE ordinance and develop an effective IDDE program. Technical guidance to assist in the creation of such a program can be found in Illicit Discharge Detection and Elimination: A Guidance Manual for Program Development and Technical Assessments (Brown et al., 2004). 4.1.2 Watershed Planning Watershed planning involves critically analyzing the degree and location of future development and associated impervious cover to best account for changes in land use and its effect on water resources. Consequently, watershed planning ranks as perhaps the single most important watershed protection tool. One of the goals of watershed planning is to shift development toward areas that can better support a Recommendations & Conclusions Proposed Management Measures 137 | P a g e Diamond, St. Croix Watershed Management Plan particular type of land use and/or density. The goal of watershed planning is to apply land use planning techniques to redirect development, preserve sensitive areas, and maintain or reduce the impervious cover within a given watershed. 4.1.2.1 Comprehensive Water and Land Use Plan A primary recommendation to is to adopt an updated comprehensive water and land use plan. A proposed comprehensive planning effort for land and water resources was started in 2004 but never adopted. A new Comprehensive Land and Water Use plan was proposed in 2020 and is currently in the RFP process. Associated with the plan adoption are two additional recommendations. First, ensure that the proposed Comprehensive Land and Water Use Plan accounts for impacts of future land use on water resources, including identifying land use planning techniques that promote land development patterns that reduce overall impervious cover, and limit the scale of development and land disturbance in the most sensitive or high-quality watersheds. Second, ensure that current zoning is evaluated and revised to be consistent with overall plan goals. 4.1.2.2 Planning Tools and Conservation Easements Another recommendation is to assess a larger suite of land use planning tools to see if additional techniques may be appropriate. Currently DPNR does permit conservation easements and land acquisition programs as techniques to manage land use and impervious cover, but does not actively facilitate, support, or encourage them. We recommend that DPNR consider promoting the use of easements by gathering informational materials together for applicants and providing these materials and training to DPNR review staff on how to inform and facilitate this existing policy opportunity. In addition, there are other tools such as promoting infill/redevelopment, transfer of development rights (TDRs), and overlay zoning that may also provide additional protections. 4.1.2.3 Zoning and Subdivision Code Revisions Another recommendation is to revise the Zoning and Subdivision Code, which currently has an exemption for subdivisions creating less than four lots so that they do not come to DPNR for review. There is also a policy of "family subdivisions" not being required to pave their roads. This means that development can occur with little or no erosion and sediment controls in place, and that the road system can act as both a source of sediment and a conduit for stormwater runoff. A thorough review of the Code may reveal other specific code changes that could ensure that most developments are required to meet minimum standards. 4.1.2.4 Coastal Zone Tier Revisions The management of major developments in the coastal zone uses a tiered system as was discussed in previously. It has been suggested that a shift from the two-tier system to a watershed approach will make plan reviews more thorough and provide more protections to upland sites currently considered Tier 2. While removing the boundary between Tiers 1 and 2 would provide a more comprehensive review process for permit applications for major developments, it would also have a major impact on the review process and require additional permit staff. Since this change would require revamping the current process and coordination through several departments, a stepped process may work best. Potential steps in the process include: Recommendations & Conclusions Proposed Management Measures 138 | P a g e Diamond, St. Croix Watershed Management Plan 1. Adopt a comprehensive plan to address water resources. 2. Revise the current Earth Change law to provide to provide additional protections and stringent application conditions to areas near guts and on steep slopes in the Tier 2 zone, similar to the more stringent Tier 1. 3. Increase plan review fees and fines to fund additional staffing and required training. 4. Identify some sample development projects in the Tier 2 zone that can be test subjects for a more extensive review similar to Tier 1 projects. These pilot projects could be selected by some combination of project size and distance from or impact on significant environmental resources. 5. Redefine coastal setback limits in the codes and comprehensive plan. 4.1.3 Land Use Planning and Resource Protection The green spaces, guts, wetlands, and coastal buffers of St. Thomas provide critical hydrologic functions, offer unique habitats, and support human and environmental health. Conserving and restoring these spaces are of the utmost importance when it comes to maintaining and improving the health of the watersheds of St. Thomas. Land conservation as a watershed protection tool involves making careful choices about the mix of natural habitats and cultural areas that must be conserved to sustain the integrity of its aquatic and terrestrial ecosystems while maintaining desired human uses. The land conservation areas to protect can include: • Critical habitats for plant and animal communities, • Aquatic corridors along streams and shorelines, • Hydrologic reserve areas that sustain a stream’s hydrologic regime, • Water hazards that pose a risk of potential pollution spills, • Cultural and historical areas that are important to a sense of place. The USVI currently uses multiple land conservation tools to protect valued resources. These include participating in the National Flood Insurance Program and mapping their floodplains, as well as having code language (29 V.I.C. § 280-288 and 29 V.I.C. § 950 – 964) to preserve cultural or historical areas. 4.1.3.1 Agriculture Preservation Future food security needs should be protected by more actively encouraging agriculture preservation. The Virginia Office of Farmland Preservation has developed tools that provide examples of methods for agricultural preservation, including agricultural and forest districts that protect working farm and forestland, and land use assessment based on current use value of a property and not at its fair market value when determining local property taxes. 4.1.3.2 Develop a Steep Slope Ordinance Steep slopes are not currently protected in the USVI, but when these areas are disturbed and developed, they can become major sources of land based sources of pollution. These areas are already of interest for DPNR. We recommend the adoption of steep slope legislation to protect hilltops and prevent erosion, potentially with varying levels of requirements based on slope percentage. Some communities regulate slopes starting at 15%, which ties in with U.S. Department of Agriculture soil survey slope classifications. Others start at 25%, another soil survey threshold and a clear benchmark for land-use limitations. While the development of this ordinance would require a thorough literature review to determine appropriate Recommendations & Conclusions Proposed Management Measures 139 | P a g e Diamond, St. Croix Watershed Management Plan standards, specific guidance, and examples to help the USVI with development of steep slope regulations include: • WeConservePA Steep Slope Guide • Example steep slope regulations in Appendix B from Town of Boone, North Carolina Unified Development Ordinance that separates slopes based on conditions • Peoria, Arizona steep slopes zoning overlay district (pg. 5-19) • Verona, NY Steep Slope Ordinance • Vancouver, Canada Slope Hazard Development Permit Area 4.1.3.3 Forest Conservation and Tree Removal Fee Trees are important for soil stabilization, reducing stormwater runoff, reducing climate change, shade, aesthetics, and wildlife habitat. Forest conservation is encouraged (12 V.I.C. § 133) in the Community and Heritage Tree Law of the Virgin Islands. The Virgin Islands Tree Board is charge with a mission to protect, manage, remove, and establish trees on public property within the Virgin Islands. It was noted that several parcels of land that were purchased through federal funds from the Forestry Service program have strict mandates and guidelines for conservation: • No heritage tree may be pruned, removed, or damaged in any way unless an Urban Forester, a designated arborist, or the Territorial Forester determines that there is an overriding need for public improvements, or a severe hardship exists for reasonable use of a site. • Any person or entity that violates any provision of this chapter by causing, contributing to, or permitting the injury of, removal, or destruction of a public tree, shrub or a heritage tree is subject to a civil penalty of not less than $100, but not more than $500 for each violation. To discourage removal of trees, a fee for proposed tree removal could be implemented during the application process for a tree removal permit. This fee could act as a source of funding for the permit review office for additional staffing or as funding for heritage tree conservation. The USVI should also consider adopting a tree ordinance and permit requirements for private lands. This ordinance can include measures such as requiring a percentage of a site to be maintained as trees and directing that those trees be located near guts to provide channel protection. This would also help with protecting development from happening near or on top of guts. Example ordinances include: • City of Charlotte, North Carolina tree ordinance • Key West, Florida Tree Protection Ordinance • Gulf Breeze, Florida Tree Protection Ordinance 4.1.3.4 Tree Canopy Goal The VI Tree Board should also consider developing a tree canopy goal using the land cover dataset developed under this WMP and evaluating the current tree canopy extent. The future land cover dataset could be used to determine the estimated tree canopy loss based on previous development patterns. Opportunities can then be analyzed to reduce or limit future tree canopy loss and increase the current canopy level (i.e., plantings in gut buffers, public parks, etc.) to help achieve the tree canopy goal. Tree canopy is also an important part of addressing climate change. 4.1.3.5 Undeveloped Land Protection in Headwaters It is highly recommended that the USVI implement a program to preserve the undeveloped land within the gut headwaters of the St. Thomas watersheds. Using the land cover dataset developed for this WMP, Recommendations & Conclusions Proposed Management Measures 140 | P a g e Diamond, St. Croix Watershed Management Plan maps displaying developed and undeveloped land cover were developed for each of the study watersheds to guide these protection efforts (Figure 84). Protection measures could include conservation easements, purchase of undeveloped areas along gut headwaters, or zoning restrictions. Figure 84. Potential gut headwater protection areas in the Diamond watershed. Recommendations & Conclusions Proposed Management Measures 141 | P a g e Diamond, St. Croix Watershed Management Plan 4.1.3.6 Gut Channel and Buffer Zone Protection Guts in the USVI act as the conveyance system for most stormwater runoff and deserve special protection including riparian buffers. There are protections for guts and drainage channels (29 V.I.C. § 226) in the code. However, it is unclear how strictly this is enforced or how often variances are granted to this requirement. Field observations have found that development may be occurring overtop some guts. It is recommended that gut locations and potential impacts be reviewed during the permit review process and then during the construction inspection phase to afford the necessary protections to these channels. A buffer can be placed along a gut, shoreline, or wetland to physically protect a channel from future disturbance or encroachment. For guts, a network of buffers will act as a right-of-way during floods and sustain the integrity of gut ecosystems and habitats. Buffers can also filter pollutants traveling in stormwater or groundwater and provide wildlife habitat and recreation. Current code language does not allow clearing or construction within 25 feet of the edge or 30 feet of the center of natural watercourses (12 V.I.C. § 123). A natural watercourse is defined as any gut with a reasonably well-defined channel and includes guts with a permanent flow and those that result from the accumulation of water after rainfall, and which regularly flow through channels formed by the force of the water. However, this protection should be expanded to a minimum of 50 feet for all guts, and 100 feet for guts where rare, threatened, or endangered species exist. Exceptional circumstances will include areas with steep slopes or valued wetlands that require additional protections. The DPNR should promote a zoned buffer system that will allow for some uses while supporting channel protection. One proposal would be a system with 30 feet of “natural vegetation” adjacent to the protected water requirements (as is currently in the codes) with an outer additional 20 feet where a greater range of impacts are allowed. The allowable uses might include septic fields (assuming they are vegetated), pathways with permeable surfaces, or other low impact activities. The publication “Better Site Design” (CWP, 1998) provides an example of a three-zone buffer system and suggested allowable uses in the buffer zones. The development of a gut restoration program should also be a high priority and include riparian buffer assessment and reforestation to ensure buffers are vegetated primarily with high quality native vegetation instead of possible invasive species. The program should identify and prioritize the list of guts for restoration based on the larger overall watershed plans to ensure that the most impacted channels are addressed first. 4.1.4 Site Design Guidelines 4.1.4.1 Better Site Designs The Better Site Design (BSD) development code review identified street widths, rights-of-way, and parking lot ratios as meeting BSD standards. These are areas of development that together help reduce the creation of impervious cover. Within the right of way, placing utilities under the pavement allows for the opportunity for stormwater treatment using bioretention or other green stormwater infrastructure. This area can also be planted with large trees to provide shade, capture rainfall, and generally beautify and improve neighborhoods. The review identified other opportunities in the development code to minimize impervious cover in requirements for parking lots and driveways. USVI parking ratios meet better site design standards while other aspects of parking need improvement. Shared parking is allowed as a practice in the USVI and is a Recommendations & Conclusions Proposed Management Measures 142 | P a g e Diamond, St. Croix Watershed Management Plan strategy that reduces the number of parking spaces needed by allowing a parking facility to serve multiple users or destinations. This practice should be encouraged by providing a model shared parking agreement and allowing for reduced parking requirements. To reduce the creation of impervious cover in parking lots consider allowing a percent of commercial parking spaces for compact cars. Compact stalls create up to 30% less impervious cover than standard stalls so can be an important strategy for reducing impervious cover in large parking lots (CWP, 2017). Also, consider designating spillover parking areas for larger parking lots and promoting the use of alternative paving materials in these areas. The University of the Virgin Island’s St. Croix campus at the 64 West Center is a local example of the use of permeable pavements. In addition, the standard parking space stall width should be reduced to nine feet or less. Landscaping requirements should be considered for parking lots that can manage stormwater in best management practices while increasing aesthetics and providing shade. Some options include: bioretention, bio swales, perimeter sand filters, filter strips, and structural soils with trees. The analysis revealed several opportunities for code revisions regarding driveways. Consider allowing for the use of alternative driveway surfaces, two-track design, and shared driveways that connect two or more homes together. A two-track driveway has two strips of paving corresponding to wheel tracks with a vegetated area in between. In addition, the minimum width for a one-lane driveway should be defined in the code. Another recommendation to consider in residential areas is to allow parking lanes to also serve as traffic lanes in higher density developments. Also, in residential areas consider allowing the use of alternate pedestrian networks (e.g., paved trails through common areas, walkways and bike trails connecting streets) to be substituted for sidewalks. The USVI allows for the creation of open space developments and does not require extra steps for development review. Consider allowing for flexible site design criteria for development that utilize open space or cluster design options. This will allow for a more unified open space rather than leftover bits of unusable property. One of the goals of open space development is to protect natural lands. Regulatory changes to consider meeting this goal include requiring a percentage of open space to be left in its natural condition, consolidating into larger units, and defining allowable and unallowable uses in the open space. 4.1.5 Solid Waste Management Illegal dumping and trash were identified as a major environmental concern. Trash and debris are abundant alongside roadways and dumpster sites, most often caused by improper household waste disposal. Although bins are provided for waste disposal, they are sometimes located in areas where runoff from leaky dumpsters drains to the guts and sensitive mangrove areas. 4.1.5.1 Reduce Waste and Encourage Reuse The most important and impactful strategy to reduce the negative impacts of solid waste is to have residents and visitors complete a lifestyle change where a focus on reducing waste and reusing items is the new normal. A territory wide campaign to emphasize reuse and source reduction to reduce reliance on disposal infrastructure for solid waste is critical. Options for reuse and composting are not readily available in USVI, forcing residents to put these items into the waste stream. Strategies for reducing waste include: Recommendations & Conclusions Proposed Management Measures 143 | P a g e Diamond, St. Croix Watershed Management Plan • Develop an incentive program and/ or an ordinance to prevent the use of Styrofoam and plastic single use food and beverage packaging for “to go” items, • Encourage residents to select products with minimal packaging, utilize reusable bags, decline plastic straws, and use refillable water bottles, • Install public water refill stations in public areas, • Encourage and provide educational materials on how to compost food scraps at a residential scale, • Explore the feasibility of encouraging and / or incentivizing a commercial or other large scale composting facility where food scraps could be collected and processed, • Sponsor or encourage repair and repurposing of items that would otherwise enter the waste stream, and • Publicize the Caribbean Green Technology Center’s Trash to Treasure Guide and other similar reuse guides. 4.1.5.2 Expand Recycling Program Another option for removing items from the waste stream involves expanding the recycling program. In the USVI, approximately 35% of waste is organic, 21% is paper, 13% is plastic, 11% is classified as “other” (contaminants and hazardous waste), 11% is textiles, 4% is glass, 4% is metals, and 1% is electronics. There are funds to begin a sustainable waste diversion and materials management program to help reduce waste and divert waste from the Bovoni Landfill on St. Thomas and Anguilla Landfill on St. Croix to the Susannaberg Transfer Station. Through the Department of Planning and Natural Resources, VIWMA has been awarded a Solid Waste Supplemental Grant. Waste types to be diverted include green waste, scrap metal, tires and construction and demolition debris. It will also provide the much-needed equipment to divert the waste stream from the landfill (VIWMA, 2021). 4.1.5.3 Improve Waste Bin Sites It is recommended that waste bin sites be evaluated for waste and stormwater runoff management. The waste bin sites are operated by the Virgin Islands Waste Management Authority (VIWMA). Each waste bin site should be evaluated for site specific issues. Additionally, designs for covered bin areas should be explored as stormwater flowing through the full waste bins and draining to surface waters can contain a number of pollutants. If used motor and cooking oil are to be accepted at a bin site, a leak proof and approved container should be supplied. 4.1.5.4 Increase Enforcement of Illegal Dumping Per Title 19: Health, Chapter 56 § 1563, illegal dumping is subject to a fine of $1,000 and/or imprisonment. The items that are not accepted at bin sites should be brought to the most conveniently located landfill where they can be disposed of, often without a fee (depending on the item). However, illegal dumping, particularly at bin sites and along roadways, is widespread. This illegal dumping introduces hazardous and often toxic materials and other pollutants into the environment, decreases aesthetic value, and encourages additional illegal dumping. It is recommended that enforcement of penalties for illegal dumping be enforced whenever possible. Monitoring of bin locations is also recommended via video surveillance. Recommendations & Conclusions Proposed Management Measures 144 | P a g e Diamond, St. Croix Watershed Management Plan 4.1.5.5 Increase Education about Proper Disposal Accessing up to date information regarding proper disposal of items outside of normal household trash can be challenging. It is recommended that a simple web page be developed instructing residents how and where to dispose of items such as tires, batteries, used motor oil, used cooking oil, junk vehicles, appliances, and other waste. The site should be prominent, easy to locate, and easy to navigate. Hours of operation and fees should be clearly stated in these materials. Currently, the VIWMA website has outdated and incomplete information. Pertinent details can be difficult to locate and those that are available online often contradict. This information should also be publicized on social media and via community groups and other community platforms. This recommendation may also help reduce illegal dumping. 4.1.5.6 Mitigate Known Solid Waste and Hazardous Sites Any known areas where solid waste and hazardous waste are improperly disposed of should be addressed to prevent ongoing and future contamination. These include bin sites and known dumping sites. 4.1.6 Research Topics 4.1.6.1 Recycling Market Study The Green Technology Center conducted a market analysis of the waste, and it is estimated that the possible revenue stream from recycling is $6 million, with aluminum cans, plastic bottles, and cardboard being the most potentially profitable waste (Penn, 2021). A study should be completed to assess recycling markets, existing recycling options, and determine the most feasible expansions to the recycling program for the USVI. 4.1.6.2 Coastline Recession Mapping Multidate high resolution aerial imagery including UAS-collected data and historic imagery could be utilized along the coastline to accurately map areas of coastal erosion. These areas could then be targeted for stabilization efforts including the identification of additional stormwater BMPs, the prioritization of currently proposed stormwater BMPs, the planting of coastal vegetation, or the stabilization of eroding slopes. 4.1.6.3 Sargassum Mitigation Influxes of sargassum seaweed has been a recent ongoing issue negatively impacting coastal ecosystems, air quality, and the tourism industry. Removal by heavy equipment can cause compaction, remove coastal sand, exacerbate erosion, and impact native wildlife such as disturbing turtle nesting areas. The problem continues after the sargassum has been removed because it must be safely disposed of to prevent contamination from leachate. Unfortunately, solutions to reduce sargassum accumulation, remove the seaweed without damaging beaches and harming wildlife, and process the collected materials are not well understood. As these unprecedented influxes likely stem from increased temperatures related to climate change and increased nutrient loads from the Amazon River as land is cleared for agricultural purposes (Wang et al., 2019), wholistic solutions to reduce the sargassum influx would require global cooperation. It is recommended that the USVI participate in these global actions to the extent possible and continue to participate in and review research related to sargassum management and take science-based actions to manage the influx while protecting wildlife. Additionally, research related to safely disposing of sargassum and the potential use of the seaweed for biofuel, fertilizer, building materials, or for other applications should be continued. Recommendations & Conclusions Proposed Management Measures 145 | P a g e Diamond, St. Croix Watershed Management Plan 4.1.7 Watershed Stewardship Programs 4.1.7.1 Expand Targeted Residential and Commercial Campaigns Several education and outreach programs are currently targeted to residents and the commercial and industrial sectors. However, additional education and outreach could be expanded in terms of the scope of messages, frequency of publications, and media type (i.e., social media posts, Story Maps, signs, workshops, handouts including the Visioning Document developed in concert with this WMP, and others). Topics of importance include but are not limited to: • Recycling • Reuse • Waste reduction including reusable items like straws, water bottles, shopping bags, and others • Proper waste disposal including hazardous materials, appliances, vehicles, tires, and others • Stabilize exposed soils and install homeowner and small business owner scale stormwater BMPs • Vegetation protection • Gut importance and protection Many of these recommendations are detailed in the Visioning Document and Story Map as well as the short educational videos that were produced to accompany this project. These materials should be used to advance and inform these campaigns. 4.1.7.2 Develop Targeted Educational Campaigns In additional to residential and commercial outreach, targeted campaigns should also be conducted to inform and educate the judiciary and other key decision makers to build awareness for the need to enforce existing regulations and promulgate new ones. In addition, the tourism industry should be engaged to increase stewardship of coastal areas where hotels, marinas, and restaurants are located. 4.1.7.3 Develop Stewardship Programs A lack of gut stewardship programs and pet waste management were concerns identified from the surveys distributed to DPNR staff. It is recommended that water stewardship programs be developed in coordination with existing community groups such as the Coral Bay Community Council, St. Croix Environmental Association, and Virgin Islands Conservation Society. Another resource could be the University of Vermont Volunteer Water Monitoring Network, which developed a guide for developing volunteer water monitoring programs. The Anne Arundel Watershed Stewards Academy builds capacity in Anne Arundel County, Maryland by training Master Watershed Stewards to help neighbors reduce pollution in our local creeks and rivers. These and other resources can help direct the development of similar programs in the USVI. 4.1.7.4 Develop Homeowner’s Guide to Stormwater Management In order to encourage adoption of best practices at a residential scale, it is recommended that a homeowner and small business owner focused manual is developed to guide design and implementation of these stormwater management practices. This guide can serve as a companion to revisions of the Environmental Protection Handbook currently underway. Examples include Vegetation for Erosion Control – A Manual for Residents published by the Coral Bay Community Council, the Homeowner Guide for a More Bay-Friendly Property from the Chesapeake Stormwater Network, and the Vermont Guide to Stormwater Management for Homeowners and Small Businesses published by the Vermont Department of Environmental Conservation. Recommendations & Conclusions Proposed Management Measures 146 | P a g e Diamond, St. Croix Watershed Management Plan 4.1.7.5 Provide Technical and Financial Assistance to Homeowners A homeowner BMP cost-share program could be implemented to provide property owners financial and technical assistance in implementing stormwater BMPs for improving water quality and reducing the amount of stormwater runoff. If for example, a stormwater utility fee program is developed (see funding mechanisms below), the BMPs developed from the cost-share program could help property owners receive a credit or reduction of their stormwater fee. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 147 | P a g e Diamond, St. Croix Watershed Management Plan FINANCIAL AND TECHNICAL ASSISTANCE NEEDS, TIMELINE, AND COSTS The tables below summarize the recommendations outlined in the previous section and identify potential technical assistance and financial needs for each recommendation. The tables also include a column for the potential lead agency in implementing the recommendation from five DPNR operating divisions and three departments that have responsibilities relevant to watershed management. These include: • Division of Coastal Zone Management (CZM) • Division of Comprehensive and Coastal Zone Planning (CCZP) • Division of Environmental Protection (DEP) • Division of Fish and Wildlife (DFW) • Division of Building Permits (DBP) • Department of Public Works (DPW) • Department of Agriculture (DA) • Waste Management Authority (WMA) An implementation timeline by year is included. It is assumed that many of these actions will be ongoing over time and thus span the entire five-year timeline and may continue into the future. A relative cost (low = $, medium = $$, and high = $$$) was assigned for each action. These costs are based on prior projects and general knowledge as true costs are not obtainable due to the ongoing and preliminary planning level stage of these tasks. 148 | P a g e Diamond, St. Croix Watershed Management Plan 4.2.1 Stormwater Management and Non-Stormwater Discharges Table 29. Stormwater Management and Non-Stormwater Discharges: Technical Assistance and Financial Needs summary table. Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Solution 1: Internal Operations Changes Complete the USVI Stormwater Standards and Design Manual and incorporate green infrastructure techniques. DPNR DEP $$ Staff will be required to develop and review the final product. Example designs for stormwater BMPs will need to be developed and reviewed by a professional engineer. Training will be necessary for contractors who install stormwater practices to ensure they understand the new standards and design procedures. Finalize and adopt a revised Environmental Handbook. DPNR DEP $$ Staff will be required to develop and review the final product. The Handbook will need to be distributed to contractors and a final determination on adopting the handbook as a required guidance document will be needed. Adopt an IDDE ordinance and develop an effective IDDE program. DPNR DEP $$$ A legal expert may be necessary to draft the language of the ordinance and ensure the regulatory authority necessary. Consultant to develop a guide or SOP for conducting IDDE in USVI. Training for multiple staff will be required to learn IDDE field testing procedures and remediation measures. Staff will need to complete a baseline survey of existing sewer infrastructure to identify any CSO/SSO problem areas and illegal discharges. A staff member or consultant would be required to develop and maintain a database to track discharges and enforcement decisions to ensure compliance. Test kits and other equipment will need to be purchased for field evaluations. Solution 2: Policy/Program Changes Organize the TPDES program around the basic NPDES MS4 six minimum measures. DPNR DEP $$ A qualified consultant would be required to develop the organizational structure. Reassignment and training of staff will be necessary to realign programs with minimum measures. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 149 | P a g e Diamond, St. Croix Watershed Management Plan Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Require limits of disturbance to be shown on construction plans and physically marked at the site. DPNR CCZP $ A qualified DPNR staff member will need to review site plans to ensure compliance. An alteration of the Earth Change code will need to be enacted to make this a regulation. Implement green infrastructure demonstration projects. DPW $$$ Staff would be required to catalog the type of practice, maintenance schedule, and what equipment is required to maintain the practice (i.e., hand tools or heavy equipment). Staff would be required to write grant applications or reallocate DPNR’s existing funding. Staff time for outreach and education task to target the public and contractors who would be putting the practices. Solution 3: Structural Improvements Final design and implementation of six highest priority BMPs (two per watershed). DPNR $$$ Staff will be required to manage the development of the final 100% design documents for the construction of project. Contractors with the required equipment, materials, and training to design and install the priority BMPs as needed. Further design development and implementation of the remaining 24 high priority BMPs (eight per watershed). DPNR $$$ Staff will be required to develop or commission the preliminary 30% design documents for the construction of project Staff will be required to develop or commission the final 100% design documents for the construction of project Contractors with the required equipment, materials, and training to design and install the priority BMPs as needed. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 150 | P a g e Diamond, St. Croix Watershed Management Plan 4.2.2 Watershed Planning Table 30. Watershed Planning: Technical Assistance and Financial Needs summary table. Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Solution 1: Internal Operations Changes Shift from the two-tier management system in the coastal zone to a watershed approach. DPNR CCM $$$ Hire additional permit staff for potential increase in workload. Development of a guidance document for staff detailing the watershed approach and the changes to current procedures Training for staff on how the watershed approach differs from the tier system and how to address properties that may straddle watershed boundaries. Adopt an updated Comprehensive Land and Water Use Plan and ensure that it accounts for impacts of future land use on water resources. DPNR DEP $$$ Staff will be required to develop and review the final product. Staff will need to guide the plan through the legislative adoption process. Legal expertise will be needed to address any possible conflicts with other codes or policies. Confirm that current zoning is evaluated and revised to be consistent with the overall Comprehensive Land and Water Use Plan goals. DPNR CCZP $ Internal staff review time will be needed to compare current zoning to any proposed changes. Staff time may be required for public hearings as needed to make changes to zoning categories. Legal expertise will be needed to address any possible conflicts with other codes or policies. Solution 2: Policy/Program Changes Review a larger suite of land use planning tools to see if additional techniques may be appropriate. DPNR CCZP $$ Internal staff review time will be needed to identify potential land use tools. Legal expertise will be needed to address any possible conflicts with other codes or policies. Promote the use of conservation easements. DPNR CCZP $$ Gather informational materials together for applicants and provide these materials. Train DPNR review staff on how to inform and facilitate easements. Revise the Zoning and Subdivision Code regarding small subdivisions DPNR CCZP $$$ Legal expertise will be needed to address any possible conflicts with other codes or policies. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 151 | P a g e Diamond, St. Croix Watershed Management Plan 4.2.3 Land Use Planning and Resource Protection Table 31. Land Use Planning and Resource Protection: Technical Assistance and Financial Needs summary table. Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Solution 1: Internal Operations Changes Adopt steep slope legislation to protect hilltops and prevent sediment erosion. DPNR CCZP $$$ Staff will need to review example steep slope legislation and draft ordinance language. The proposed legislation will need to be reviewed to address any possible legal conflicts with other codes or policies. Adopt a tree ordinance and permit requirements for private lands. DPNR DBP $$ The proposed legislation will need to be reviewed to address any possible legal conflicts with other codes or policies. Staff will need to review examples of ordinance language and draft final ordinance language. Training will be required for staff and materials distributed to the public about the new legislation. Implement a fee for proposed tree removal. DPNR CCZP $$ A fee schedule and tracking system for tree removal permit applications will need to be developed. Potential waivers/exemptions will need to be established by staff. Staff would be needed to implement the fee after tree ordinance is adopted. Develop a tree canopy goal. DPNR CCZP $ Staff will need to review existing and projected future canopy coverage. Planting plans will need to be developed to increase tree canopy in areas where it is lacking. Review gut locations and impacts during the permit review process and then during the construction inspection phase to afford the necessary protections to these channels. DPNR DEP $ Training for staff on review process and necessary protections for guts. Accurate mapping of gut locations and existing development will be needed. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 152 | P a g e Diamond, St. Croix Watershed Management Plan Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Solution 2: Policy/Program Changes Expand buffer requirements to a minimum of 50 feet for all guts and 100 feet for guts where rare, threatened, or endangered species exist. DPNR DEP $ Staff time to review information to identify areas with RTE species. A decision will need to be made about existing locations that do not meet new requirements and how to deal with those situations. Legal expertise may be required if a challenge to increases in required buffer widths is expected. Promote a zoned buffer system. DPNR DEP $ There will be a staff time cost for any code change work. Educational materials will be necessary, highlighting the change and allowed uses of the buffer system. Create a gut restoration program. DPNR DEP $$ Staff or consultant for gut corridor assessments and development of appropriate restoration strategies. Equipment needs will include machinery for gut modification, materials for stream restoration structures, invasive species removal and stock of native species for buffer planting. Staff time and funding for education of contractors who would conduct gut restoration projects. Staff time to update the Stormwater Standards and Design Manual? Create a program to preserve the undeveloped land within the gut headwaters. DPNR DEP $$ Staff time will be required to identify areas, contact landowners, and identify applicable properties where conservation easements could be applied. For some parcels, funding and legal guidance will be needed for the purchase of undeveloped areas along gut headwaters so they can be preserved. Staff time would be needed to monitor and administer program. Actively encourage agriculture preservation. DA $ Gather informational materials on preservation options for applicants and provide these materials. Staff time to provide support for those interested in preserving their agricultural properties. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 153 | P a g e Diamond, St. Croix Watershed Management Plan 4.2.4 Site Design Guidelines Table 32. Site Design Guidelines: Technical Assistance and Financial Needs summary table. Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Solution 1: Internal Operations Changes Provide a model shared parking agreement. DPNR CCZP $ Staff will need time and funding to review examples of shared parking agreements and prepare and print handouts to further educate participants. Allow for reduced parking requirements. DPNR CCZP $$ Staff will need time for code review of current parking requirements and analysis of impact of reduced parking requirements. Time for staff with legal expertise for necessary legal changes to update codes. Allow a percent of commercial parking spaces for compact cars. DPNR CCZP $$ Staff time and funding for code change related costs. Designate spillover parking areas for larger parking lots. DPNR CCZP $$ Staff time and funding for code change related costs. Time to conduct and analysis of possible spillover parking areas. Develop landscaping requirements for parking lots. DPNR CCZP $ Staff time and funding for code change related costs. Development of landscaping standards for parking lots. Enact code revisions regarding driveways allowing for the use of alternative driveway surfaces, two- track design, and shared driveways. DPNR CCZP $ Staff will need time for code review, training on alternative driveway options, and code revisions. Promote the use of alternative paving materials. DPNR CCZP $ Contractors with the required equipment, materials, and training to install alternative paving materials are needed. Development of outreach and education materials including locations for demonstration sites. Solution 2: Policy/Program Changes Place utilities under the roadways. DPW $ Staff time to train contractors. Funding for changes to codes and design manual. Need to make decision on how to retroactively address any exiting utilities and track so that when improvements are made to roadway the utilities are placed correctly. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 154 | P a g e Diamond, St. Croix Watershed Management Plan Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Plant ROW with large trees. DPW $ Staff time to conduct assessment to identify potential tree planting areas. Staff time or funding for contractors for tree planting and maintenance. Reduce the standard parking space stall width to nine feet or less. DPNR CCZP $ Staff time and funding for code change related costs. Allow parking lanes to also serve as traffic lanes in higher density developments. DPNR CCZP $ Staff time and funding for code change related costs. Conduct traffic analysis to identify any potential impacts in any areas where conflicts may arise. Staff time for changing the lane structure. Education/outreach to the public on the changes. Allow the use of alternate pedestrian networks in residential areas. DPNR CCZP $ Staff time and funding for code change related costs. Approve flexible site design criteria for developments that utilize open space or cluster design options. DPNR CCZP $ Staff time and funding for code change related costs. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 155 | P a g e Diamond, St. Croix Watershed Management Plan 4.2.5 Solid Waste Management Table 33. Solid Waste Management: Technical Assistance and Financial Needs summary table. Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Solution 1: Policy/Program Changes Develop an incentive program and/ or an ordinance to prevent the use of Styrofoam and plastic single use food and beverage packaging for “to go” items. WMA $ Staff time and funding for code change related costs. Staff time for education/outreach to the public on the changes. Expand the recycling program. Encourage residents to select products with minimal packaging, utilize reusable bags, decline plastic straws, and use refillable water bottles. WMA $ Staff time and funding for program development related costs including using the results of the recommended research on recycling markets and options. Staff time for education/outreach to the public on the recommendations. Install public water refill stations in public areas. DPW $ Staff time and funding for implementation and to interface with private commercial business owners to install water stations on their properties. Encourage and provide educational materials on how to compost food scraps at a residential scale. WMA $ Staff time to develop and distribute education and outreach to the public on the recommendations. Explore the feasibility of encouraging and / or incentivizing a commercial or other large scale composting facility where food scraps could be collected and processed. WMA $ Staff will need time and funding to host workshops, find a meeting location, prepare a presentation, and prepare and print handouts to further educate participants. Funding for compost bins may be required if the program elects to distribute bins to workshop attendees. Sponsor or encourage repair and repurposing of items that would otherwise enter the waste stream. WMA $ Education/outreach to the public on how to repair and repurpose items. Funding for repair or provide location for a community repair recurring event so community member can meet and fix items. Publicize the Caribbean Green Technology Center’s Trash to Treasure Guide and other similar reuse guides. WMA $ Staff time will be need for education and outreach to the public on reuse guides as they are released. Evaluate waste bin locations and runoff management. WMA $ This process would require staff time to complete a survey or study of current locations and alternative dumpster sites. Educational materials would need to be developed such as signage to indicate any new dumpster locations. In cases where relocation is not possible, design and installation of stormwater BMPs may be necessary to prevent pollution from runoff. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 156 | P a g e Diamond, St. Croix Watershed Management Plan Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Increase enforcement of illegal dumping and install monitoring network. DPNR $$ Additional staff time will be required to pursue enforcement of illegal dumping. Staff time to install and monitor monitoring equipment and funding to purchase and maintain equipment. Mitigate known solid waste and hazardous sites. WMA $$ Inspection and evaluation of identified hazardous waste sites. Develop plans and strategies to remediate known hazardous sites. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 157 | P a g e Diamond, St. Croix Watershed Management Plan 4.2.6 Research Topics Table 34. Research Topics: Technical Assistance and Financial Needs summary table. Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Conduct a recycling market study. DPNR $$ Create collaboration with researchers, most likely those with UVI to initiate and complete study. Determine funding sources for study, potentially NSF grants. Conduct a coastline recession mapping study. DPNR $$ Create collaboration with researchers, most likely those with UVI to initiate and complete study. Determine funding sources for study, potentially NSF grants. Budget for equipment and assessment costs. Conduct a sargassum mitigation study DPNR $$ Create collaboration with researchers, most likely those with UVI to initiate and complete study. Determine funding sources for study, potentially NSF grants. Budget for equipment and assessment costs. Recommendations & Conclusions Financial and Technical Assistance Needs, Timeline, and Costs 158 | P a g e Diamond, St. Croix Watershed Management Plan 4.2.7 Watershed Stewardship Programs Table 35. Watershed Stewardship Programs: Technical Assistance and Financial Needs summary table. Action Lead Implementation Year Relative Cost Technical Assistance Year 1 Year 2 Year 3 Year 4 Year 5 Solution 1: Internal Operations Changes Inform and educate the judiciary and other key decision makers to build awareness for the need to enforce existing regulations and promulgate new ones. DPNR DEP $$ Staff will need time and funding to schedule visits or find a meeting location, prepare a presentation, and prepare and print handouts to further educate participants. Engage the tourism industry in watershed protection education. DPNR DEP $$ Staff will need time and funding to schedule visits or find a meeting location, prepare a presentation, and prepare and print handouts to further educate participants. Develop stream stewardship and pet waste management programs. DPNR DEP $$ Potential to reduce cost for program management by partnering with an existing nonprofit organization to promote the program(s). Funding will be necessary to install dog waste stations at public parks and gathering areas. Staff time will be necessary to maintain waste stations, staff stream cleanup events, and answer questions from the community. Solution 2: Policy/Program Changes Develop a stormwater guide for homeowners. DPNR DEP $$ DPNR staff or consultant will need to modify an existing example guide and then reproduce and distribute guide. Staff time will be required for education and outreach events for the public. Create a homeowner BMP cost-share program. DPNR DEP $$ Funding will need to be identified to assist in cost share. Equipment may need to be purchased based on the BMP proposed. Staff time for education and answering homeowner questions or hiring of a consultant. Staff for tracking implementation and management of program Distribute the Vegetation for Erosion Control – A Manual for Residents. DPNR DEP $ DPNR will need funding to update (as necessary), reproduce, and distribute the existing manual from Coral Bay Community Council. Staff time for education and outreach events for the public. 159 | P a g e Diamond, St. Croix Watershed Management Plan IMPLEMENTATION STRATEGY 4.3.1 Funding Mechanisms Funding is a major factor in the implementation of the identified regulatory recommendations and capacity building. Local governments typically fund the departments and activities such as stormwater programs through a combination of general funds, federal grants and loans, fees/fines/penalties, or a dedicated funding source (user fees). The expectation is that the private sector will help to pay for environmental protection efforts including the proper management of stormwater generated by development and redevelopment activities or provide money to mitigate impacts by supporting offsite stormwater management activities and restoration efforts. 4.3.1.1 USVI Ordinances There are a number of potential funding sources for watershed restoration efforts already in the current USVI codes. While some are already being used to fund programs, it appears that the language in the code provides enough latitude that funds could be used for watershed planning and protection measures with some creative thinking. Table 10 identifies funds currently authorized in the codes that could provide funding for implementation. Table 36 highlights places in the Code that employ enforcement measures in the form of fines that could also potentially be used for watershed implementation. The fines (Table 37) can help to ensure compliance with the code and discourage violation of enacted policies. One thing that was noted by staff is that some of the fines and fees associated with certain programs may be outdated and undervalued. It would be wise to review the current fee structure and make adjustments to better reflect the actual cost for conducting plan reviews and other programs to determine if additional funds can be created to assist in staffing and equipment issues. Another note is that some of the funds have maximum caps that require additional funds be moved to the general fund once the threshold has been reached. A review of those thresholds to increase them and provide more funding to programs that support the goals the fund was originally created to accomplish is recommended. Recommendations & Conclusions Implementation Strategy 160 | P a g e Diamond, St. Croix Watershed Management Plan Table 36. Current Funding Mechanisms Related to Watershed Planning. Code Funding Description 12 V.I.C.§ 81a. Fish and Game Fund Chapter 1 Wildlife. Subchapter VI Wildlife Restoration The proceeds from all firearms licenses, all excise taxes on firearms, parts and ammunition, all fines imposed by the courts for violation of the fish, game or conservation laws, and all monies obtained as described in Chapter 9A, Section 314 of this title, shall be covered into a special fund in the Treasury of the United States Virgin Islands to be designated as the “Fish and Game Fund”. However, if the balance in the Fish and Game Fund equals $250,000, all monies which would otherwise be covered into such Fund shall be deposited in the General Fund. 12 V.I.C § 81d. Fish and Wildlife Restoration Trust Fund Chapter 1 Wildlife. Subchapter VI Wildlife Restoration (1) The funds in the Trust under this section may be used exclusively for fish restoration and management projects pursuant to 12 V.I.C. § 81c. 12 V.I.C. § 711. Virgin Islands Coastal Protection Fund (1) The Virgin Islands Coastal Protection Fund is established to be used by the Department as a revolving fund for carrying out the purposes of this chapter. The fund shall be limited to the sum of one million ($1,000,000) dollars. To this fund shall be credited all license fees, penalties and other fees and charges related to this chapter, including administrative expenses, and costs of removal of discharges of pollution. 33 V.I.C. § 33. Acquisition of certain lands, expenditures Chapter 2A. Territorial Park Trust Fund The Board may authorize expenditures from the Fund for the following purposes: (1) to acquire lands that represent the ecological diversity of the Virgin Islands, including natural features such as rivers, coastal, and geologic systems and other natural areas; (2) to provide for the preservation and conservation of land for recreational, scientific, educational, cultural, and aesthetic purposes; and (3) to acquire additional lands for parks, trails, aesthetic forests, fish and wildlife management areas, scenic rivers, and natural areas for the use and enjoyment of the public. 33 V.I.C. § 3004. Land Bank Fund Subtitle 3 Finance > Chapter 111. Government Fund Monies pertaining to the Land Bank Fund shall be available for purchases, authorized by law, of real property (including improvements thereon) for purposes of public housing, outdoor recreation, conservation, or any other public uses or purposes. Recommendations & Conclusions Implementation Strategy 161 | P a g e Diamond, St. Croix Watershed Management Plan Table 37. Current Fines in USVI Code that Could Fund Watershed Planning. Code Fine Description 12 V.I.C.§ 107. Penalties Chapter 2. Protection of Indigenous, Endangered and Threatened Fish, Wildlife and Plants Any person violating any provision of this chapter shall, upon conviction thereof, be subject to a fine of not less than $100, and not more than $10,000. 12 V.I.C.§ 125. Penalties for violation Chapter 3. Trees and Vegetation Adjacent to Watercourses Whoever violates any provision of this chapter shall be fined not more than $100 or imprisoned not more than 180 days, or both. 12 V.I.C.§ 145. Penalties Chapter 3A. Community and Heritage Tree Law (a) Any person or entity that violates any provision of this chapter by causing, contributing to, or permitting the injury of, removal, or destruction of a public tree, shrub or a heritage tree is subject to a civil penalty of not less than $100, but not more than $500 for each violation. 12 V.I.C.§ 164. Penalties Chapter 5. Water Resources Conservation (a) Any person who willfully violates any of the provisions of this chapter or of the rules and regulations promulgated pursuant thereto shall be fined not more than $500 or imprisoned for not more than 6 months, or both. 12 V.I.C § 536. Inspections and enforcement Chapter 13. Environmental Protection (b) Any person who fails to secure an Earth Change Permit under section 534 of this title, fails to pay the Earth Change Permit fee, or violates any provision of an Earth Change Permit shall be subject to a civil penalty of $200 per day per violation. 12 V.I.C.§ 538. Violations Chapter 13. Environmental Protection (a) Any violation of this chapter shall be deemed a misdemeanor, and the person, partnership, or corporation who is found guilty of such violation shall be subject to a fine not exceeding $5,000- or one-year’s imprisonment for each and every violation. 12 V.I.C § 913. Enforcement, penalties, and judicial review Chapter 21. Virgin Islands Coastal Zone Management (3) In addition to any other penalties provided by law, any person who intentionally and knowingly performs any development in violation of this chapter shall be subject to a civil fine of not less than one thousand dollars nor more than ten thousand dollars per day for each day during which such violation occurs. 29 V.I.C. § 296. Fees and fines for building permits Chapter 5 Building Code Subchapter II. Permits, Appeals, and Fees (b) Fees are payable at the Department of Planning and Natural Resources as follows: (1) A nonrefundable deposit of $40/commercial and $20/residential at the time of filing the application for all permits. (d) The fee for a permit authorizing the demolition of any building or structure or appurtenances connected or attached to such building or structure shall be $50/residential and $100/commercial or two cents per square foot for residential properties and five cents per square foot for commercial properties, whichever is greater. If, however, the demolition of the structure is included as part of the permitted construction phase, then the fee shall be calculated per square-footage cost and added to the building permit fee. (e) The fee for a Certificate of Use and Occupancy shall be $50 for residential premises and $100 for commercial premises. (f) The fee for a permit authorizing the placing, erecting, construction, or affixing of any sign to any post, fence, building, or structure for out-of-doors advertising shall be $50. (g) Any person who fails to secure a permit or certificate under this chapter or regulation, fails to pay the permit or certificate fee, or violates any provision of any permit or certificate issued under this chapter or regulation shall be subject to a civil penalty of $1500 per day per violation Recommendations & Conclusions Implementation Strategy 162 | P a g e Diamond, St. Croix Watershed Management Plan Table 37. Current Fines in USVI Code that Could Fund Watershed Planning. Code Fine Description 12 V.I.C § 913. Enforcement, penalties and judicial review Chapter 21. Virgin Islands Coastal Zone Management 1) Any person who violates any provision of this chapter, or any regulation or order issued hereunder, shall be subject to a civil fine of not to exceed ten thousand ($10,000) dollars. 4.3.1.2 Grant Funding Sources Federal grants provide additional funding sources. Table 38 below provides a summary of grant funding opportunities. Table 38. Grant program funding sources. Program Description Coastal Zone Management Act Section 309 Grants Improvements to state and territory coastal management programs are encouraged through this program. The focus is on nine enhancement areas: wetlands, coastal hazards, public access, marine debris, cumulative and secondary impacts, special area management plans, ocean and Great Lakes resources, energy and government facility siting, and aquaculture. The program was established in 1990 under Section 309 of the Coastal Zone Management Act. Every five years, states and territories review their programs to identify priority needs and opportunities for improvement. The programs then work with NOAA to develop multi- year improvement strategies that focus on one or more of the priority enhancement goals. https://coast.noaa.gov/czm/enhancement/ NFWF Coastal Resilience Fund The NFWF National Coastal Resilience Fund restores, increases and strengthens natural infrastructure — the landscapes that help absorb the impacts of storms and floods — to protect coastal communities while also enhancing habitats for fish and wildlife. In partnership with NOAA. Shell Oil Company, TransRe, and beginning in 2020, the U.S. Environmental Protection Agency and AT&T, NFWF invests in projects that plan for, design, build, and monitor the restoration or expansion of natural features such as coastal marshes and wetlands, dune and beach systems, oyster and coral reefs, forests, coastal rivers, and barrier islands that minimize the impacts of storms and other naturally occurring events on nearby communities. https://www.nfwf.org/programs/national-coastal-resilience-fund?activeTab=tab-3 US Housing and Urban Development Community Development Block Grant (CDBG). This funding can be used for projects under the Infrastructure Repair and Resiliency Program to address issues with solid waste. Recommendations & Conclusions Implementation Strategy 163 | P a g e Diamond, St. Croix Watershed Management Plan 4.3.1.3 Additional Potential Funding Mechanisms Additional potential funding mechanisms that could be considered for implementation in the USVI are provided in Table 39 below. Table 39. Additional potential funding mechanisms. Funding Mechanism Description Public Works Hazard Mitigation and Infrastructure Improvement Funds Ability to incorporate stormwater infrastructure upgrade projects. Can interview Peter from public works to discuss specifics of the program. Fee-in-lieu Programs For sites where stormwater management or impervious cover waivers are proposed, a fee-in-lieu program could be used to fund environmental protection efforts. Stormwater Utility Fee Similar to a water or sewer fee, a stormwater fee is a recurring user fee charged to property owners by a stormwater utility for the service of managing the stormwater runoff and associated pollutants coming from their property. The fee is calculated based on the demands a property places on the drainage system and is administered separately from general tax fund, ensuring sustainable and adequate funding for these public services. Tourism Revenue Sources Work with the Department of Tourism to identify tourism related revenues to conserve and enhance the natural resources that are the foundation of a long-term, robust, and resilient tourism and recreation economy for the Virgin Islands. https://coast.noaa.gov/data/czm/media/usvi-cmp.pdf Recommendations & Conclusions Implementation Strategy 164 | P a g e Diamond, St. Croix Watershed Management Plan 4.3.2 Monitoring Program During the development of this WMP, extensive gut monitoring was carried out in the priority guts within the study watersheds. Several important conclusions were drawn from this initial monitoring. These include: • Monitoring ephemeral guts is challenging given the variable rainfall patterns and recent history of drought and low antecedent moisture conditions. • Rain gauges often did not record the storm events being sampled due to the conditions noted in the first conclusion. • The majority of flowing guts had significant indicators of water quality impairment. As a next step in this baseline data collection, it is recommended that monitoring be completed at other key locations in the watersheds of concern. Monitoring should be carried out over a longer time span with a focus on the rainy season. For guts that have already been monitored, it is recommended that bracket sampling be completed to isolate potential sources of pollutants that are likely from point source locations such as heavy metals. Sources should then be addressed as appropriate for the site-specific conditions. All monitored guts with flow during the study period had exceedingly high sediment and nutrient loads. Similar bracket sampling paired with an assessment of the contributing drainage area for likely significant sources of this land-based pollution is recommended for these sites to identify the largest source of these pollutants. Erosion control and stormwater BMPs are recommended as a priority for these locations. Recommendations & Conclusions Conclusions 165 | P a g e Diamond, St. Croix Watershed Management Plan CONCLUSIONS This Watershed Management Plan is a comprehensive document meant to document watershed-specific conditions related to water quality, flood risk, and resiliency. A monitoring and modeling component helped to understand the importance of land based sources of pollution within the watershed. A review of current policies and procedures provided insight into the current mechanisms for addressing these pollutants and enforcing the aforementioned policies. This allowed the project team to develop a list of actionable, achievable, and informed recommendations to improve water quality, reduce flooding, and increase resiliency in our changing climate. Each watershed is an interconnected, complex, and unique area. One of the most important conclusions from this watershed management planning approach is that the entire watershed, from ridge to reef, needs to be considered. However, as conditions change over time and many of the provided recommendations are implemented, new challenges and opportunities will become more prominent. Additionally, many of these recommendations are complex and expensive and will take many years to properly implement. As such, this Watershed Management Plan should be reassessed and updated on a five-year timeline. 166 | P a g e Diamond, St. Croix Watershed Management Plan 5 REFERENCES References 167 | P a g e Diamond, St. Croix Watershed Management Plan Alderson, D. L., Bunn, B. B., Eisenberg, D. A., Howard, A. 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