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KEI-P86-084A-5 October 25, 1988 Page 2 DISCUSSION AND RECOMMENDATIONS A trace of floating product was noted in MW-3 . None of the other wells had any observable free product. Well ME-5 had a strong odor. Wells MW-4, MW-5, MW-6, and MW-7 all also had a sulfurous odor, which field personnel referred to as a "sewer" smell. The analytical results show non-detectable levels of TPH and BTX&E in wells MW-1, MW-2, and MW-7, while MW--4 had 1, 100 ppb of TPH and 75 ppb benzene. The analytical results indicate that the on-site contamination is confined to the northern and eastern part of the site. A water sample from MW-1 was analyzed for total dissolved solids, with a result of 1500 mg/1. KEI recommends the design and implementation of a ground water remediation system at the site. The persistence of elevated levels of benzene in off-site, downgradient wells MW-6 and MW-8 may indicate that the contaminant plume is migrating downgradient (Table 3 and Location Plan) ; however, it may also indicate that the service stations on the northeast and southeast corners of the intersection of Tracy and Grantline also have problems. More wells are necessary to define the problem and verify the various sources of contamination. In addition, KEI recommends the continuation of the current monitoring and sampling program until after additional monitoring wells are installed. ' A copy of this report should be sent to Ms. Laurie ,Cottula of the San Joaquin Local Health District, and to the Regional Water Quality Control Board, Central Valley Region. LIMITATIONS Soil deposits and rock formations may vary .in thickness, lithology, saturation, strength and other properties across any site. In addition, environmental changes, either naturally- occurring or artificially-induced, may cause changes in ground water levels and flow paths, thereby changing the extent and concentration of any contaminants. Our studies assume that the field and laboratory data are reasonably representative of the site as a whole, and assume that subsurface conditions are reasonably conducive to interpolation and extrapolation. The results of this study are based on the data obtained from the field and laboratory investigations. We have analyzed this data using what we believe to be currently applicable engineering techniques and principles in the Northern California ,region. We make no warranty, either expressed or implied, except that our services have been performed in accordance with generally