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S E C 0 R Cleanup Plan . October 27, 2003 Page 3 A summary of water wells within a one-mile radius of the site and their approximate locations are provided as Table 1 and Figure 5, respectively. There are no county or city operated pumping wells ' in the general area. San Joaquin County municipal water supply wells are typically screened in the Lower Tulare Aquifer. ' Groundwater located in the Upper A, A and B zone beneath the site is not used for human consumption due to naturally poor water quality. In a conversation between SECOR and Lee Helms (Helms, Lee. Telephone Interview. 13 May 2003), Mr. Helms indicated a domestic well on his ' property produces water high in total dissolved solids (TDS), and this water is not used for human consumption. 2.2.3 Extraction Wells Affect on Groundwater Flow One onsite groundwater extraction well (WSW-1) and fourteen offsite groundwater extraction wells were identified within a one-mile radius of the site (Table 1 and Figure 5). Based on historical ' groundwater monitoring data, pumping from these wells does not appear to impact groundwater flow. No groundwater injection wells were identified in the vicinity of the site. 2.3 Surface Water The site is located approximately 2'/2 miles west of the San Joaquin River, within the San Joaquin River Basin (Figure 5). The CRWQCB-CVR defines the San Joaquin River basin as the area liedrained by the San Joaquin River, including all watershed tributaries to the San Joaquin River, and the Delta south of the Sacramento River and south of the American River Watershed. Tom Paine Slough and the Paradise Cut are located approximately one mile northeast of the site (USGS, 1998). ' Historical groundwater gradient data suggest that Tom Paine Slough and the Paradise Cut are gaining surface water bodies. ' Three unlined retention ponds are located onsite along the northeastern site boundary. These ponds are used to temporarily store surface water run-off prior to surface discharge. These ponds may also recharge shallow groundwater. ' 2.4 Hydraulic Connection with Aquifers The Upper Tulare Aquifer contains groundwater in unconfined conditions from approximately 5 feet ' bgs to approximately 200 feet bgs. Below this depth, groundwater is confined by the impermeable Corcoran Clay Layer. The unconfined Upper Tulare Aquifer is in hydraulic communication with surface water, reducing water quality in the Upper Tulare Aquifer(USGS, 1998). ' 2.5 Local Land Use ' Land use in the area is primarily agricultural with some industrial. The site is surrounded to the north, west and east by farmland. A card lock facility and an equipment maintenance shop, operated by Woolsey oil, are located just south east of the site. Interstate 5 Is located approximately 400 feet east of the site. • 1 ' I:\Chevron\1001621\REPORTS\2003\2003-Cleanup Plan\Cleanup Plan.doc