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locked. Well purge water is stored on.siie in labeled, closed top 55-gallon steel drums until the purge water is disposed by the City of Tracy. 8.0 Chemical Analysis---Groundwater Monitoring Well Samples Four groundwater sample�Nere�halyzed at Ki- nalytical .LLC, a State-certified analytical laboratory in Davis, Califor.nfa. -All samples(vill be ested for the following; Total Petroleum hydrocarbons as Gasoline(TPHG) and Diesel.(TP14D), 'Benzene (B), Toluene (T), Elhylbenzene (E),Xylene (X), Volatile Organic Compounds(VOC), :Methyl-tart-butyl-ether(MTBE), and fuel oxygenates tert-Amyl-1vlethyl-Ether, Ethyl-tent-Butyl-Ether, Di-Isopropyl Ether and tert-Butyl Alcohol, 1,2-Dichloroethane (1,2-DCA), and Ethanol (Eth) and Methanol (Meth) using EPA Methods 3510/8015, 8020 and 8260/82608. The analyses were performed and a "normal" ten- day turnaround(see Table 4). 9.0 Subsurface Conditions 9.1 Brief Conceptual Site Model,and Subsurface Conditions The project site is located in central Tracy, near the northwestern edge of the San Joaquin Valley (see Figure 1). Holocene aIluviall fan and fluvial deposits eroded and dissected by streams draining from the nearby Coast Range Hills to the northwest underlie the area. Surficial soils in the region are mapped by the U. S. Department. of Agriculture as Capay-Stomar-Zacharias, moderately well drained and moderately fine textured with gravel forming on alluvial fans, interfan basins and stream terraces. Historic urban development and railroad use have greatly altered or removed these surflcial native soils on and around the project site vicinity. Large surface impoundments used for railroad.oil use were used very near the site. The underlying alluvium may generally consist of weakly consolidated and irregularly interbedded sand, silt and clay deposits. These subsurface strata may show variable lateral and vertical continuity and extent(Page, 1986; Bertoldi,e€al., 1991). Shallow aquifers contained in.the alluvium occur under the site area and groundwater may occur within the upper '10 to 20 feet, Very large groundwater aquifers under]le the 'Tracy region at depth and these aquifers produce very large quantities of agricultural and municipal drinking water. Regional groundwater flow in the large deeper aquifers is estimated as northerly. The largest nearby surface water body, Paine Slough occurs about three miles northeast of the site. A City of Tracy municipal water well occurs about 1000 feet north of the project site. 9.2 Subsurface Conditions Six GeoProbe (13-7 through 13-12)borings and four borings converted to monitoring wells (MW- S, MW-2, MW-3 and MW-4) were advanced on the site. The borings revealed silty and sandy sediments that are Locally complexly interbedded. Sandy silt, clayey silt and clay occur to depths of about 10 feet. These strata are underlain. by clayey sand, silty sand and sand to depths of about 20 feet. interbedded sandy and silty sediments underlie the sandy strata to depths of 25 feet. A sandy silt to sandy clay stratum occurs from roughly 25 to 30 feet, that in turn is Fare 6 of 14