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3 35 Groundwater Sampling Monitoring wells MW-1, MW-2, and MW-3, were sampled by Blaine Tech Services on December 19, 1994 following the Wright Groundwater Sampling Protocol (Appendix B) Prior to sampling, the wells were purged of approximately 4 well volumes The groundwater samples were collected using a Teflon bailer cleaned with an industrial-strength detergent and distilled water Each sample was labeled and placed on ice in an insulated container for delivery to a State-certified laboratory, accompanied by chain-of-custody documents Purge water generated during the sampling process was placed in Department of Transportation-approved 55-gallon drums and left onsite pending characterization for disposal 36 Surveying The monitoring wells were surveyed in January 1995 The elevation of each wellhead was surveyed to within 0 01 foot with respect to a known benchmark and Mean Sea Level by a licensed land surveyor The survey data is presented in Appendix C 4.0 SITE CONDITIONS 41 Hydrogeology and Subsurface Conditions In general, the soils encountered in boreholes B-1 through B-7 were relati%ely consistent (Figure 3) The soil underlying the site is a typical valley alluvial deposit consisting of interbedded and intermixed clays, silts, sands and gravels as shown on the Boring logs (Appendix C) A silty clay and sand,, clay occurs from beneath the pavement to a depth of approximately 14 to 16 5 feet bgs An approximately 1 5 to 2 0 foot thick: siltylclavey sand was observed in boreholes B- 2/MW-I - 21MW-1 and B-5 to a depth of approximately 15 5 to 18'_5 feet bgs The siltylcla,,ey sand laver was not obser,,ed in B-6/MW-2, however, a gravelly sand Iaver occurs from a depth of approximately 16 5 to 18 5 feet bgs Below the silty/clayey sand is a silty/sandy clax Iaver extending to the bottom of boreholes B-2/MW-1, B-6/MW-2, and B-7/MW-3 Groundwater was encountered in boreholes B-2/MW-1, B-3, B-5, B-6/MW-2, and B-7/MW-3, at depths ranging from approximately 13 to 14 feet bgs The water-bearing unit at this depth consists of the silty/claye% sand layer observed in boreholes B-2/MW-1 and B-5 Static water levels measured after deNelopment of wells MW-1, MW-2, and MW-3 were approximately 9 to 10 feet below the top of the PVC casing suggesting a semi-confined condition This is an increase of approximately 3 to 4 feet from first encountered water levels Wright prepared a groundwater contour map using groundwater elevation data obtained on December 19, 1994 (Figure 2) The interpreted gradient was approximately 0 003 and flowed in a northerly direction 42 Soil Analytical Results The soil samples were analyzed by Priority Environmental Labs in Milpitas, California, for total petroleum hydrocarbons as gasoline (TPHG) and benzene, toluene, ethvlbenzene and total xylenes (BTEX) by Environmental Protection Agency (EPA) SW-846 Methods 8015/8020 Concentrations of TPHG and BTEX were detected in soil samples from boreholes B-1 and B-2 at a depth of approximately 9 feet bgs All other analytical results for the soil «ere belovy the detection limits Results of all soil sample analyses are summarized in Table 1 The laboratory reports and chain-of-custody documents are included in Appendix D •