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California�gional Water Quality C rol Board <br /> Central Valley Region ,vtl <br /> Karl E. Longley, ScD, P.E., Chair <br /> Linda S.Adams Arnold <br /> Secretary for 11020 Sun Center Drive#200, Rancho Cordova, California 95670-6114 Schwarzenegger <br /> Environmental Phone (916) 464-3291 • FAX(916)464-4645 Governor <br /> Protection http://www.waterboards.ca.gov/centralvalley <br /> [R�VEU V ED <br /> 23 December 2008 UE-1 2 9 L008 <br /> Ms. Jennifer Sedlachek ENVIRONMENT HEALTH <br /> ExxonMobil Oil Corporation PERMIT/SERVICES <br /> 4096 Piedmont Ave, #194 <br /> Oakland, CA 94520 <br /> DOCUMENT REVIEW, FORMER MOBIL STATION 99CAS (AKA MARLER PROPERTY, <br /> AKA JH GRIFFIN MOBIL SERVICE), 75 EAST ALPINE AVENUE, STOCKTON, <br /> SAN JOAQUIN COUNTY(LUSTIS #390857) <br /> 1 reviewed the Well Installation and Pilot Test Work Plan (Workplan) received 8 December 2008 from <br /> your consultant ETIC Engineering, Inc. (ETIC). The Workplan was submitted in response to my <br /> 25 November 2008 letter (Letter), which included directives to submit either a Feasibility Study (FS) by <br /> 31 May 2009; or if more data were needed, a Workplan for a bench scale test (BST) or a pilot study <br /> (PS) by 31 March 2009. The Letter also requires a report of the four deep and one shallow wells <br /> installation by 31 May 2009. The Workplan proposes a PS for soil vapor extraction (SVE) using four <br /> nested 2" diameter SVE wells (VEW-1 through VEW-4) screened from 19' to 27' and 29' to 33' below <br /> ground surface (bgs); and groundwater extraction (GWE) using two 4" diameter GWE wells (EX-1 and <br /> EX-2) screened from 35' to 48' bgs. The Workplan states that the SVE will target the clay, silt, clayey <br /> sand, and silty sand soils in the former main tank pit, while the GWE will target shallow groundwater in <br /> clay and silt soils. The well EX-1 aquifer pilot test will include a one-day step drawdown test <br /> (increasing from 0.5 gallons per minute every 30 minutes until drawdown is stable or the well is <br /> dewatered); and a one-day constant rate pump test, using EX-2 and MWA through MW-5 as <br /> observation wells. A portable tank will contain extracted water until transport to an approved <br /> ExxonMobil disposal facility. The two-day SVE pilot test will rotate between each of the four nested (8 <br /> total) SVE wells, using the remaining seven SVE wells as observation wells. The Workplan did not <br /> include a detailed schedule for fieldwork, stated that work would commence "...soon...", but did state <br /> the PS report would be submitted within 90 days of completion of the fieldwork. Depth to water was <br /> reported as approximately 37' bgs during the third quarter of 2008 <br /> The Workplan's emphasis on targeting soils with low permeability does not provide me with a degree of <br /> confidence that the PS will be successful, in that SVE and GWE work best in high permeability soils. <br /> However, the Report geologic cross sections do show the existence of permeable sand beds under the <br /> main tank pit below 30' bgs, and from 10' bgs to 45' bgs near MW-5 (10' south of the tank pit). I <br /> suggest that the proposed wells be moved slightly south to intersect the higher permeability soils, to <br /> provide a greater probability for a successful PS. A revised Figure 3 (and additional text/figures if <br /> deemed necessary) showing the new locations of the proposed wells is due 16 January 2009. After <br /> receipt and my review of the submittal, the appropriate final approval will be given. <br /> California Environmental Protection Agency <br /> 0 Recycled Paper <br />