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California Rt,.dional Water Quality Conti,.,/Board <br /> Central Valley Region <br /> Karl E.Longley,ScD,P.E.,Chair <br /> Linda S.Adams 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Arnold <br /> Secretary for Phone(916)464-3291 -FAX(916)464-4645 Schwarzenegger <br /> Environmental http:/twww.waterboards.ca.gov/centralvalley Governor <br /> Protection <br /> 10 November 2009 <br /> Ms. Janet Heikeld <br /> ' Olympian a , <br /> 1300 Industrial Road, Ste. 2 <br /> San Carlos, CA 94070 y <br /> DOCUMENTS REVIEW, JIMCO TRUCK PLAZA, 1022 EAST FRONTAGE ROAD(AKA 22502 <br /> SOUTH HIGHWAY 99), RIPON, SAN JOAQUIN COUNTY(REGIONAL BOARD CASE#390718) <br /> I reviewed the Corrective Action Plan (CAP) and the Groundwater Monitoring Report— Third Quarter <br /> 2009 (Semi-annual Report), received 30 June 2009 and 2 November 2009, respectively from your <br /> consultant, Conestoga-Rovers and Associates (CRA), and submitted in response to my letter dated <br /> 8 July 2009. The CAP included a conceptual site model with figures in plan view and cross sections of <br /> the sediments. The figures contain iso-concentration contours of soil and groundwater contamination <br /> that indicate two distinct soil and groundwater contamination plumes, one near the underground <br /> storage tanks (USTs) release and another near an above-ground tanks(AGTs) release documented in <br /> a 19 May 2005 staff memo to file. The CAP contains an evaluation of three remedial alternatives, and <br /> compares the following technologies for predicted feasibility in achieving-cleanup and cost <br /> effectiveness: additional over-excavation of soil to 25' below ground;surface (approximately <br /> 14,000 yds3), in-situ chemical oxidation (ISCO) injections into aquifer (approximately 20,000 ft), and <br /> dual phase groundwater and soil vapor extraction (DPE). The CAP recommends performing ISCO, <br /> after successful completion of a bench scale testing and a pilot study (BST/PS), and that full scale <br /> injections into the aquifer be conducted.quarterly for two years, using 40 new injection/performance <br /> monitoring wells spaced 25' apart and screened from 20`to 30' below ground surface (bgs).-The CAP <br /> states that if ISCO is not effective in a pilot study, then DPE would be the second choice for a second eq <br /> pilot study. The CAP also provides an investigation work plan for installing either eight or nine new 4" <br /> diameter monitoring wells screened from 15' to 35' bgs, to further characterize lateral extent of total <br /> petroleum hydrocarbons as diesel (TPHd) groundwater plume(s). The new wells may also be used to <br /> remove free product(FP) described in the CAP as southeast and east of the USTs and to the <br /> southeast of the AGTs, prior to conducting bench scale testing and.a pilot study for ISCO. The design <br /> and specifications for a proposed FP extraction system will be described in a future remedial work plan. <br /> In contrast to the CAP, the Semi-annual Report states that FP was not present-in any wells on <br /> 28 August 2009. Depth to water in the monitoring wells varied from 25' to 27' bgs. Groundwater flow <br /> direction was towards the southeast at a gradient of 0.0005 ft/ft. Maximum groundwater monitoring <br /> results from monitoring wells near the USTs were TPH as gasoline (TPHg), 530 micrograms per Liter <br /> (ug/L); TPHd, 110,000 ug/L; benzene, 1.2 ug/L; methyl tert-butyl ether(MTBE), 190 ug/L; and tertiary <br /> butyl ether(TBA), 1,200 ug/L. Groundwater monitoring results for MW-6,which is located 80 feet <br /> downgradient of the USTs release and nearer to the existing AGTs located southeast of the USTs, <br /> were TPHg, 170 ug/L and TPHd, 100,000 ug/L. <br /> California Environmental Protection Agency <br /> I <br /> �a Recycled Paper <br />