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2. 5 Estimates of liquid quantity and composition leaked: ; No estimate of the liquid quantity leaked can be made with existing information. The constituents detected in. the i initial soil samples appear to be derived from diesel. r �- 2. 6 Topography, geology, r a surface water, depth to groundwater: �• The . site is situated on level terrain underlain by flood basin deposits of Pleistocene and Holocene age that are composed of sediments similar to and probably conformable on underlying deposits of alluvium and Tulare formation. The flood-basin deposits are light-to dark brown and grey clay, Silt sand and organic materials with locally high concentrations of salt and alkali.. Stream-channel deposits of sand and gravel are also included (Hotchkiss and Balding, 1971 ) . � This study focuses on the water quality in the "shallow water-bearing zone" of Hotchkiss and Balding ( 1971 ) . ` Groundwater within this zone occurs less than 10 feet below I �• grade over most of the Tracy area. The flood-plain deposits of the shallow water-bearing zone have well developed soil t , profiles and, consequently, poor permeability. The base of F the shallow zone is poorly defined and probably is from 5 to 25 feet below land surface. Based on monitoring data from a nearby facility, groundwater flora in the shallow water-bearing zone beneath the Heim plant is to the north. 5 3.0 FIELD INVESTIGATION ZZ 3.1 Purpose and Scope on January 18, 1990, four soil borings (MWI, SB2, SB3 and SB4) were advanced to depths ranging from 7 to 19.5 feet below grade for the purposes of site characterization and the installation of a groundwater monitoring well. Drilling was conducted- by Osterberg and Stewart under C57 license 446670 using a hollow stem auger drill rig. The boring/well ' locations are shown on Figure 2. Soil boring and well completion data are included on the boring/well logs (Appendix II ) . Soil, samples were collected from boreholes (SB-2, SB-3 and SB-4) near the top of the capillary fringe (@ 8 feet below grade) . A sample collected at a depth of 10 feet below grade in MW-1 was saturated and therefore was not submitted for laboratory analysis. The samples were analyzed for benzene, toluene, ethylbenzene, xylenes (BTX) # and total petroleum hydrocarbons as diesel (TPH) using EPA a ' 8020 and DOHS methods, respectively. Sample collection was i handled in accordance with WaterWork' s Soil Sampling Protocol (Appendix III ) . B.C. Laboratories, a State r v z J. 0 �.