SITE INFORMATION AND CORRESPONDENCE

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45 East Harding Page 2 Pacific Environmental also stated that "Groundwater Monitoring Wells MW-10, MW-11, MW-14 and MW-2R all reported non-detectable concentrations of petroleum hydrocarbons in groundwater prior to the well screens becoming submerged. Please note that when water was at 56.68 feet bgs (October 1992) in MW11, whereby there was less than 20 feet of screen within the water column, that the highest concentrations of petroleum hydrocarbons were detected, with up to 6,000 ppb TPH-gas and 1,300 ppb benzene. As the water continued to rise there was a significant reduction in the concentrations of petroleum hydrocarbons which were evidenced. It is true that the last sample collected from MW11 before the well screen was submerged, when water was at 43.68 feet bgs (April 1995) did not detect petroleum hydrocarbons; however, the following sample collected when water was at 42.74 feet bgs (July 1995) did detect 67 ppb TPH- gasoline. PHS/EHD does not agree with the Pacific Environmental conclusion that the groundwater sampling results are representative of site conditions. Also, the wells which were installed in 1989 which are properly screened for current water levels have been destroyed to accommodate the development of the site. One well, MW8 was destroyed despite PHS/EHD's protest that it was not within the proposed developments footprint and it provided the downgradient well which could monitor representative groundwater quality. The report failed to include all groundwater and soil sample results, for instance, the results of the September 1988 excavation. Also, statements such as "Benzene with few exceptions has not been detected" are difficult to interpret when the summary tables simply note "ND" rather than the detection limit, since frequently detection limits are elevated during analysis of contaminated samples and often benzene is the only volatile hydrocarbon which apparently is not detected. Remaining soil contamination was detected in SB13 at 25 feet bgs of 10,000 ppm TPH-gasoline, "ND" benzene with an actual detection limit of <.005 ppm, 10 ppm ethylbenzene and 280 ppm xylene. The soil contamination evidenced in the SB13 sample at 50 feet was 0.76 ppm benzene, 0.81 ppm toluene, 0.57 ppm ethylbenzene, 14 ppm xylene and 2,200 ppm TPH-gasoline. Also, the report failed to include the June 1-2, 1995 sample's TCLP, organic carbon and dry bulk density results which ranged from 2.35 to 1.17 g/cm3. Actually, when calculating the estimates of soil contaminants an average soil density of 120 lbs/ft' was used. When calculating the average concentration after soil vapor extraction, the total depth and results of six soil borings were used,comprising fifty-six samples;however,the volume of contaminated soil was subdivided into four distinct volumes.When calculating the average concentration before soil vapor extraction only three borings were used, comprising nine samples. When making comparisons it is essential that averages be weighted equally. The evaluation of the threat that the remaining soil contamination poses to groundwater consisted of the statements that "the remaining elevated concentrations of petroleum hydrocarbons tend to reside in relatively tight soils consisting of sandy to clayey silt or silty sandy clay" and that "there is little potential for future impact to groundwater. While this type of evaluation may be sufficient when little if any soil contamination remains, it is not sufficient when TPH-gas concentrations as high as 10,000 ppm remain and when TCLP analysis has indicated that the remaining soil contaminants have significant leaching potentials. Also, PHS/EHD has indicated in previous correspondence that the results of soil analysis may not be used to solely determine the potential threat which the remaining soil contamination poses.