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' • •nnedy/Jenks Consultants The Tulare formation is exposed in the Coast Range foothills along the western margin of the basin and dips eastward toward the axis of the valley. It consists of semi-consolidated, poorly sorted, discontinuous deposits of clay, silt, and gravel. The Corcoran clay occurs near the top of ' the Tulare Formation and confines the underlying fresh water deposits. The eastern limit of the Corcoran clay is near the eastern boundary of the basin. The Tulare formation is moderately permeable, with most of the larger agricultural, municipal and industrial extractions coming from below the Corcoran clay. Wells completed in this zone produce up to 3,000 gallons per minute. ' Small domestic wells often obtain their supply from above the Corcoran clay. However, groundwater above the Corcoran clay is often of poor quality. The total thickness of the Tulare ' Formation is approximately 1,400 feet. (DWR, 2003) 3.1.4 Reclamation Area Groundwater Quality ' Kennedy/Jenks gathered available water quality data for wells that are screened down to maximum depths of about 200 feet bgs in the vicinity of the Musco Site and the potential ' reclamation area. The depth of 200 feet is believed to be the top of the Corcoran clay and wells with perforated intervals above it are considered representative of monitoring groundwater in the Upper Tulare Formation groundwater. Data sources include historical data from Site 300, City of Tracy, Tracy Municipal Airport, and Tracy Defense Depot. Data were also obtained from ' regional studies performed near Jepsen Webb Ranch and Valley View Thoroughbred Farm as well as other private wells. ' Concentrations of TDS, the most abundant of all the water quality parameters were plotted on a regional map (Figure 3) to allow comparisons on a regional scale. Concentration data were taken from documents in USGS archives, DWR archives, City of Tracy water studies, and others research papers. The TDS contours for the deep water-bearing zone are distinguished from those for the shallow water-bearing zone by the different colors for the isoconcentration lines. ' Based on the isoconcentration contours shown on Figure 3, TDS concentrations are generally lowest in the Site 300 area within the shallow water-bearing zone to the southeast, and in the ' southern portion of the City of Tracy within the deeper water-bearing zone. Concentrations in the Site 300 area range between 432 and 585 mg/l, and in the south Tracy area they range from 464 to 610 mg/I. ' TDS concentrations are highest in two particular regions as well as within the deep water- bearing zone. One region is located at the base of the Diablo Range and the other is located north of the City of Tracy. The concentrations at the base of the Diablo Range range between ' 1,700 and 2,800 mg/I. North of the City of Tracy, a TDS concentration of 2,545 mg/I was measured. As suggested by the isoconcentration contours, groundwater beneath an elongated area near the California aqueduct and the Delta Mendota Canal exhibits higher TDS ' concentrations (i.e., 1,860 mg/I, 2,110 mg/I and 2,800 mg/1) and therefore has lower groundwater quality than that outside of this area. ' 3.2 Reclamation Area Characterization Characterization activities were conducted to collect data to evaluate groundwater quality in the ' potential reclamation area. Both Kennedy/Jenks and Kleinfelder, Inc. (Kleinfelder) have Reclamation Report, Page 7 ' Musco Family Olive Company 9 4sWwpda nq&,OV0201 Wmol�,t8.12W.doc