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Kennedy,Uenks Consultants oldest to youngest) the Tulare Formation, Older Alluvium, Flood Basin Deposits, and Younger Alluvium. The cumulative sediment thickness is up to 3,000 feet (DWR 2006). The Tulare Formation consists of semi-consolidated, discontinuous deposits of clay, silt, and gravel. The widespread Corcoran Clay unit occurs near the top of the Tulare Formation, extending from the foothills eastward to about the San Joaquin River, and acts to confine the deeper aquifers (DWR 2006; DWR 1967). Many large-capacity wells are completed in units below the Corcoran Clay because of the higher yield and quality of the deeper water. Older Alluvium consists of loosely to moderately compacted sand, silt, and gravel, and is widely exposed between the Coast Range and the Delta. It is approximately 150 feet thick. Flood Basin Deposits are present in the northern two-thirds of the subbasin in the Delta region. Composed primarily of silt and clay with occasional gravel interbeds near present waterways, these deposits have a maximum thickness of about 1,400 feet. This unit generally does not yield significant quantities of water and the quality is generally low (DWR 2006; DWR 1967). The Younger Alluvium is less than approximately 100 feet thick and consists of those deposits that are accumulating or would be accumulating under natural conditions. The deposits consist of unconsolidated silt, fine-to medium-grained sand, and gravel. Significant quantities of water can be extracted from the coarser-grained deposits in this unit (DWR 2006). 2.2.5 Regional Groundwater Quality Regional groundwater quality in the vicinity of the facility was assessed through a search of publicly available groundwater data. The search involved querying the California Department of Water Resources (DWR), United States Geological Survey (USGS), and Environmental Protection Agency (EPA) Storet databases, as well as conducting a file review of nearby sites under the oversight of the CRWQCB. The search parameters included the area in Townships 3 and 4 North, Range 5 East from the Mount Diablo Meridian. Figure 3 shows the results of the well search. The time span of the full data set of the most recent total dissolved solids (TDS) or EC results for each well ranges over 60 years from 1949 to 2008. The full data set includes 179 data points and appears to be log-normally distributed. Subsets of the data are also summarized below including only data collected since 1977 (110 data points, unknown distribution) and data collected since 2000 (27 data points, unknown distribution). Summary statistics are listed in Table 2. There does not appear to be a spatial pattern to the TDS values, as shown on Figure 3. Except for the data obtained from the four sites regulated by the CRWQCB, the data summarized in Table 2 and presented in Figure 3 represent groundwater quality in water supply wells. In general, these water supply wells are believed.to be screened at depths below the first- encountered groundwater beneath the facility and the adjacent parcels to the north. The data indicate that over a 60-year period of record, TDS concentrations in regional groundwater exhibit significant spatial variability. The apparent variability is partially attributable to the lack of well depth data. It is hypothesized that some of the supply wells may be screened at depth intervals with higher ambient water quality (i.e., lower TDS concentrations). The variability in TDS concentrations in groundwater may also be attributable to other factors, including the Monitoring Well Installation Work Plan Page 5 Sutter Home Winery, Lodi, California g:Ys-Brwplon*b1 OW865M0 a4 suMe =eM,+ports insW m pinit XLt