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i.r Additional Soiled Groundwater Investigation Work Plan Raymond Investment Corporation May 19,2006 Page 3 1.r and MW-2 were sampled, and none of the analytical constituents were detected at or above the laboratory reported detection limits in either of the samples. 3.0 ADDITIONAL SOIL AND GROUNDWATER INVESTIGATION PLAN In her letter dated February 22, 2006, Ms. Victoria McCartney directed submission of a work plan addressing the vertical and lateral extents of contamination at the Site. Ms. McCartney specifically requested addressing the limits of contamination in the area where soil borings SB-3 and SB-4 were advanced in May 2004, and recommended installation of two to three monitoring wells to assess the L+ lateral extent of groundwater contamination in this direction. Potential monitor well locations are limited due to a large building located approximately 20 to 30 feet from the area of SB-3 and SB-4 in the down- gradient direction. Consequently, to as ess he lateral extent of groundwater contamination, Condor �.+ proposes to install one monitoring well 1, to a feet from SB-3 and SB-4 (in the location of the center of the suspected contaminant source area), four soil borings, and three down-gradient hydropunch borings located in the sidewalk or street on the other side of the above-mentioned building. The rationale for L, installing only one additional monitoring well at this time is the'uncertainty of the distribution of contamination in the down-gradient area. Results of the samples collected from the proposed well and other proposed borings will assist in effectively locating additional wells, if necessary. If other additional wells were installed in the current work phase prior to evaluating the results from the proposed borings, they might be ineffectively located. A fourth monitoring well, MW-4, will be placed adjacent to, and down-gradient of, the location of soil boring SB-3. As mentioned above, soil boring SB-3 was previously advanced in May 2004 and is the location where hydrocarbon contamination appears to be concentrated based upon previous investigation ..r activities. Monitoring well MW-4 will be advanced to a depth of approximately 45 feet below ground surface (bgs) and constructed with a 20-foot screen interval. The monitor well will be constructed with 4- inch-diameter casing to facilitate possible future remediation activities. 1r To address the vertical extent of contamination between the locations of SB-3 and SB4, one soil boring, SB-7, will be placed between SB-3 and SB4 and advanced to a depth of 70 feet bgs. Soil samples will be collected at 5-foot intervals beginning at a depth of 5 feet bgs. To address the lateral extent of contamination, four additional soil borings, SB-8 through SB-11, will be advanced at locations 20 to 35 feet laterally from SB-7. These four additional soil borings will be advanced to a depth of 35 feet, and soil samples will be collected at 5-foot intervals beginning at a depth of 25 feet bgs. L+ Three hydropunch borings, HP-1 through HP-3, will be advanced in the sidewalk or street on the west side of Grant Street to a depth of approximately 35 feet. No soil samples will be collected from the hydropunch borings. The hydropunch boring locations are approximately 105 feet down gradient of SB-3 tr. and are positioned outside of the building due to structural considerations including interior walls and a basement with very limited access. All of the borings will be advanced to first encountered groundwater, anticipated to be at a depth of approximately 35 feet bgs. Groundwater samples will be collected at the depth of boring termination, if possible, from all eight borings included in this work plan. The proposed boring and well locations are Ld shown on Figure 3, Appendix A. La CONDOR V