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SDMS Document 115584 iYl 5 Harding Lawson Associates M a y 15, 1996 • ' '^ 35241.2.1 , j Ms. Sherrel D. Henry United States Environmental Protection Agency Section II Emergency and Remedial Response Division 290 Broadway New York, New York 10007-1866 Additional Requested Information Proposed Site Activities Phase II Remedial Investigation Work Plan Island Chemical Company, St. Croix, U.S. Virgin Islands Dear Ms. Henry: Harding Lawson Associates (HLA) is submitting this letter, on behalf of Island Chemical Company (ICC), to provide additional information related to proposed site activities as requested in your correspondence dated April 18, 1996 and May 2, 1996. In January 1995, one boring (SBBl) was installed in the AST area (Area B) to investigate soil quality in the area. Volatile organic compounds were detected in soil samples collected from boring SBBl. A soil sampling program will be conducted to investigate the lateral and vertical extent of impact to soil near boring SBBl in the AST area. The surficial extent of impact in Ai'ea 13 will be evaluated by collecting and analyzing 12 surface soil samples as pj'oposed in Figure 1. Surface soil samples will be collected using decontaminated stainless steel hand augers. Samples will be collected from the 18- to 24-inch interval below ground surface. Samples will be placed directly into laboratory-prepared sample containers. Additional sample volume will be collected into resealable plastic bags and screened in the field using a PID according to procedures described in the previously approved FSP (HLA,8/94). The vertical extent of impact in Area B will be evaluated by collecting and analyzing selected soil samples from four borings (Figure 1). Up to two additional borings may be installed based on photoionization detector (PID) results and observations from the surface and subsurface sairrpling. Proposed locations for the four borings are presented in Figure 1. Continuous split spoon samples will be collected from the stirface to the water table at each boring location. Samples wih be placed directly into laboratory-prepared sanrple containers. Additioiral sample volume will be collected into resealable plastic bags and screened in the field using a PID accordiirg to procedures described in the previously approved FSP. Procedures for sample handling, management, and shipping are described in the FSP and QAPP (HLA, 8/94). Two samples will be analyzed from each boring, one from directly above the water table and one from the interval with the highest PID reading. Soil sanrples will be analyzed for target compound hst (TCL) volatile organic compounds (VOCs). The surface soil sample or soil boring with the highest VOC concentrations, based on solely on PID readings, will be asstimed to correspond to the most highly concentrated source of groundwater contamination, if any, in subsurface .soils. Unle.ss diis area coincides with the location of MW-1, ICC proposes to install a second monitoring well in this area. Consequently, either MW-1 or the new monitoring well (MW-6), if installed, will provide water quality information direcUy beneath the area of highest soil contamination. This should adecjuately characterize the iriagnitude of contamination associated with the AST area. If this concentration is shown to be below levels that would pose a threat to huirran health or the environment, fui'tlier delineation of chemicals in grouirdwater in this E n ^ i ^ n ^ i l i l d ' ' ^ 0 ' ^ ^ ^ '^^'^'^^-'''^Washington Park. 14 Washington Road, Princeton Junction, NJ 08550 609,/93e-0700 Fax 609/936-i020 Environmental Services ,-i ,',i,/.,>;,;;,i^v,.f';/,i,-,;/;i;.-i,,>,„7„i,vi . C'iti,.:r.\i,.iii<ii..i.:c 305310 Ms. Henry USEPA May 15 1996 Harding Lawson Associates With EPA approval, planned monitoring well MW-2 was not completed during the January 1995 field program. As discussed with EPA, an area of low permeability was encountered above the water table in SBCl. The possibility that well installation might provide a conduit for contaminants to reach groundwater was a concern at the time. However, analytical results of soil samples collected from SBCl indicated that soils above the water table in this area were not contairrinated. Therefore, MW-2 will be installed in Area C, as specified in the Phase I Work Plan. This well will be used to evaluate groimdwater at the center of the site and to provide additional water level control data. The well(s) will be installed and developed as described in the FSP. Development water will be placed in 55-gallon drums and staged onsite pending disposal. Groundwater samples collected from the proposed monitoring well (MW-2 ) will be analyzed for l^CL VOCs, TCL SVOCs, TCL Pesticides, TCL PCBs, Pyridine, and TAL Inorganics (total and dissolved). Groundwater samples collected from the proposed monitoring well(MW-6), if installed, will be analyzed for TCL VOCs. The location and elevation of MW-2 and MW-6 (if iirstalled) will be sinveyed as specified in the Phase I Work Plan. The horizontal position will be surveyed with respect to the Puerto Rican/Virgin Islands plane coordinate system (North American Datum of 1983, or NAD 8,3) and existing monitoring wells to the nearest tenth of a foot. The well locatioir will be converted from plane coordinates to latitude and longitude. The conversion shall be performed to an accuracy of one hundredth of a second of latitude and longitude. The vertical position of each well will be surveyed with respect to Mean Sea Level (MSL) to the nearest hundredth of a foot. Well elevations to be surveyed include the top of inner casing, top of outer casing, and adjacent ground surface. The location of the inner casing elevation measurement will be permanently marked for future water level measurements. Upon receipt of the analytical data, a data summary report will be prepared and forwarded to the EPA. Please call either of the undersigned if you have any questions. Yours very truly, HARDING LAWSON ASSOCIATES John S. Virgie,/.G. Senior Geologist Edward A. Nemecek, R.G., CPG Principal Hydrogeologist Regional Geosciences Manager EAN\JSV\]sv \WORK\29872\01\epa2ltr.doc This document was prepared for the sole use of the ICC and the regulatory agencies involved with the project, the only intended beneficiaries of our work. No other parties should rely on the information contained herein without the prior written consent of HLA. 305311 o cn OJ M to