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Meeting Minutes 3130100 Page 3 of 7 3. Nestle Groundwater Investigation and Cleanup Actions Jean Moran presented a brief oven�iew of hydrogeology, and then summarized the extent of WE contamination in the groundwater and the cleanup actions performed to date This item is summarized below and in the attached slides Hydrogeology in the Ripon area is characterized by four laterall,,-continuous sands and/or gravels designated as the B-, A-, C-, and D-aquifer zones The B- aquifer zone includes the water table and extends from approximately 25 to 70 feet bgs The A-aquifer zone is encountered at depths of aper oaunately 85 to 120 feet bgs The C-aquifer zone, which is sometimes subdr�ided into the Cl- and C2-aquifer zones, is encountered between 140 to 200 feet bas The D- aquifer zone generally occurs below a depth of 220 feet The depth to groundwater is approximately 25 feet beneath the former Nestle site Groundwater generally flows northward in each aquifer zone. but flow directions vary locally under the influence of pumping munimpal`industnal supply wells and recharge from municipal/industnal lagoons located near the Stanislaus Raver © Groundwater contamination was discovered in 1986 and investi2ation/cleanup actions have been ongoing since that time A total of 54 wells have been installed to monitor plume migration and assess cleanup efforts The current groundwater monitoring program also includes periodic sampling of municipal, domestic, and industrial supply wells Two wells (E-I1 and E-2) are currently used to extract and treat contaminated groundwater • Former supply well N-1, located near the Nestle water tower. N'�as initially used to extract/treat groundwater from 1986 to 1996 A total of 2.124 lbs. of TCE were removed by well N-1 In 1996 well N-1 was replaced by A-zone extraction well E-11 A total of 1,149 lbs of TCE has been extracted from E-I1 New extraction well E-2, located southwest of the former Nestle site (near the intersection of Stockton Avenue and Fourth Street), came on-line in October 1999 This well is screened in the B- and A-aquifer zones and currently extracts 70 gpm of groundwater The initial influent concentration of TCE was 45 µg/1 on 1014199 and is currently 150 µg/1 o In August 1999,Nestle began a potassium permanganate pilot test Approximately 7,200 gallons of potassium permanganate were infected into the A-aquifer zone source area Permanganate destroys TCE and its daughter P1UUUL U) UkU l lYl,t-LVL' alld Vlliyl C111101ide L111VLLS11 uAtuau%jil xit,, stzocluometric reaction for TCE is