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1 i These data demonstrate that the petroleum plume at the Site is stable Geomatrix <br />' 3.2.2 me When Estimated i <br /> t T li n WQOs Will Be Achieved <br />' The temporal trends of BTEX and TPHg concentrations in wells MW3-1, MW3-2, and MW3-3 <br /> since 1999 (since groundwater monitoring began at the Site) and in well MW3-6 since 2003 <br />' (since installation in 2003) are shown on Figures 5, 6, and 7 Based on the stable trends <br /> indicated by the site groundwater monitoring data during the period of record, it is anticipated <br /> that the concentrations of BTEX and/or TPHg in the groundwater samples will not increase, <br /> however, it is unlikely that samples from these four wells will achieve all of the WQOs within <br /> the next few years <br />' <br /> 32.3 Verification That There Are No Current or Anticipated Uses of Impaired Water <br /> Within the Timeframe Projected to Meet WQOs <br /> When San Joaquin County began permitting wells in 1972, dunking-water supply wells were <br /> required to be completed with a minimum annular seal of 50 feet Since the late 1980s or early <br />' 1990s, San Joaquin County has required a minimum annular seal of 100 feet for public, <br /> domestic, and industrial supply wells and a minimum annular seal of 50 feet for agricultural <br /> wells according to the Well Construction and Destruction Standards (San Joaquin County, <br /> 1993) At certain locations within San Joaquin County, deeper seals may be required based on <br />' site-specific conditions (SJCPHS, 2003) These San Joaquin County requirements effectively <br /> preclude the use of groundwater from the shallow and intermediate water-beanng zones in the <br />' vicinity of the Site for public, domestic, and industrial supply purposes These requirements <br /> also preclude the use of the groundwater from the shallow zone for agricultural uses <br />' According to the Water Management Plan for the San Joaquin County Flood Control and Water <br /> Conservation District (CDM, 2001), groundwater in the western Stockton area is not used for <br />' domestic or municipal water supply Area groundwater has high chloride concentrations as a <br /> result of sea water intrusion from the Sacramento/San Joaquin River Delta (to the west of the <br />' Site) Poor groundwater quality in western Stockton has resulted in importation of drinking <br /> water from eastern Stockton through the municipal water distribution system The Water <br /> Management Plan indicates that the saline front (based on 300 parts per million of total <br />' dissolved solids concentration) is located east of Interstate 5 and will migrate further east at <br /> approximately 200 feet per year This information indicates that the Site is located within the <br />' area affected by sea water intrusion <br /> • <br />' 1 16MOs16437 OMArchive16437-041 doc 9 <br />