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08/24 '98 20:37 ID:LANIERFftX4500 FAX: SDMS Document 115558 August 24, 1998 Ms. Caroline Kwan U.S. Environmental Protection Agency Region II Emergency Remedial Response Division 290 Broadway, 20* Floor New York, KY 10007-1866 RE: Island Chemical Site St. Croix, U.S. Virgin Islands Clarirications 10 Supplemcntnl Remedinl Investigation dated August 12,1998 Dear Ms. Kwan; On August 20, 1998, a conference call was held between the U.S. Environmental Protection Agency (EPA), CDM Federal Programs Corporation (CDM Federal), Berlex Laboratories, Inc. (Berlex), and McLaren/Hart, Inc. (McLaren/Hart) to discuss comments on the Supplemental Remedial Investigation (Phase IV Rl) letter submitted on August 12, 1998. The purpose of this letter is to summarize and address the concems raised during the conference call, and to serve as an amendment to the August 12* correspondence. Screening Criterion The screening criterion for the delineation of horizontal and groundwater will be 80 Mg^. As an example, if chloroform is detected at location GWPP-29A, and at a depth of 70 feet below ground screening point will be positioned laterally from this point, to accessibility. Groundwater samples will be collected at the same inten bgs, b this case), at the interval above the exceedance (i.e., 60 feet the exceedance (i.e., 80 and 90 feet bgs). This is one potential scena during the investigation. Additional screening locations and appropriate of samples will be detennined, in consultation with EPA and CDM analytical results. It is McLaren/Hart's understanding that if chloroform below 80 /ig/1 at any interval (e.g., 78 ;/g/l), additional delineation wi Packer Testmg bgl), McLaren/Hart understands that there may be uncenainties involved with groundwater samples collected above and below the packer in produci that there is a hydraulic connection between the overburden and bedroqk will be substantiated with additional hydrogeologic data. G;V.STAFF\NEICHL\i»ItndSph»»«4\rcvi«ion.wptl 25 Independence Boulevard, Warren, New Jersey 07059 (908) 647-8111 FAX (908) 647-8162 vei[tica] chloroform impacts to at a concentration of 85 ^g/l surface (bgs), then another vertical the extent feasible based on al as the exceedance (70 feet , and at two intervals below io that could be encountered depth intervals for collection Federal, after evaluating the is detected at a concentration not be required. interpreting the results from ion well P-1. If it is believed zones, then this connection 302355P ' ii^otafi 08/24 '98 20:37 ID:LANIERFAX4500 FAX: PAGE Ms. Caroline Kwan August 24. 1998 Pa^e2 Automatic Groundwater Elevation Measurements Telog* automatic water level monitoring devices will be installed in the following wells: • ejdsting deep monitoring wells MW-7, MW-8, and MW-9, • production wells P-1 and P-2, and • newly-installed deep monitoring wells MW-12 and MW-14. Multiple activities at the well locations will be coordinated, to the extent practicable, to allow for a maximum time interval for collection of water levels (i.e., ^/ill attempt to complete packer testing at P-1 shortly after mobilization to the site so that the Telog* can be installed immediately afterwards). Investigation Derived Waste (IDW) As stated in the August 12* correspondence, the existing drums of IDW at the site (Phase III work) has been tested, as appropriate, for determination of an appropriate means of disposal. The non- hazardous drums of soil, mud, and water will be emptied and spread over the area ofthe site from which they were generated. The drums of w^ter that were characterized as RCRA-hazardous (based on the analytical results) will be separated into two categories, decontamination fluids and AST development/purge water, and resampled (one composite sample from each category). IDW generated during the Phase IV RI work will be segregated by matrix (i.e., mud, soil, water) and staged for sampling at the end ofthe investigation. A composite sample will be collected irom each matrix and analyzed onsite for the Target Site Compounds (chloroform, toluene, ethylbenzene, xylenes, acetone, and methylene chloride). The total concentration of each compound will be divided by 5 and compared to the Toxicity Characteristic Leaching Procedure (TCLP) regulatory level for the specific compound. If the concentration of each compound is below the TCLP level, the IDW will be considered non-hazardous and treated in the same manner as the Phase III material. If the concentration of any ofthe compounds is above the TCLP level, the material will be segregated for further characterization. Based on a review of this letter, McLaren/Hart would like to request written notification ofthe approval the Phase IV Rl activities scoped for the Island Chemical Site, If you have any additional questions or concerns, please feel free to contact either of us at (908) 647-8111. Very truly yours. M ^ c v m o - o ^ v-Atin(4_ ;_ Perry l ^ i r \ ^ J ? Norma Eichlin Principal Environmental Scientist Senior Engineer ENVIRONMeNTAL ENQINEERING CORPORATION 3 0 2 3 5 5Q