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California Regional Water Quality Control Board <br /> Central Valley Region ; <br /> Robert Schneider,Chair e.ay <br /> Alan C.Lloyd,Ph.D. Arnold Schwarzenegger <br /> Secretary for 11020 Sun Center Drive#200 Rancho Cordova,CA 95670-6114 Governor <br /> Environmental (916)464-3291•Fax(916)464-4704 <br /> Protection http://w%vw.swrcb.ca.gov/rwgcb5 <br /> 22 February 2005 <br /> RD ECOV E <br /> F.rf,3 2 3 2005 <br /> Mr. Darin Rouse Mr. Phil Johnson <br /> Chevron Products Company Sims-Group Management ENVIF,CNMENT HEALTI1 <br /> P.O. Box 6004 374 Lincoln Center NE VVIIPSERVICES <br /> San Ramon, CA 94583 Stockton, CA 95207 <br /> REVIEW, CHEVRON#9-6171, 6633 PACIFICA VENUE, STOCKTON, SAN JOAQUIN COUNTY <br /> I reviewed the Fourth Quarter 2004 Groundwater Monitoring Report (Report);submitted on behalf of <br /> Chevron Product Company(Chevron) by Secor International Inc. (Secor). The Report states that <br /> petroleum hydrocarbon contamination was detected in the six of 14 monitoring wells. Downgradient <br /> monitoring wells MW-12 through MW-14, as well as onsite monitoring wells MW-8 through MW-10, <br /> were "not sampled due to insufficient water". MW-4 was also not sampled due to being"Inaccessible— <br /> buried under landscaping". Total Petroleum Hydrocarbons as Gasoline (TPH-g) ranged from 330 to <br /> 6,400 µg/L, Benzene was up to 0.5 µg/L, and Methyl tert Butyl Ether(MtBE) was <2 µg/L. The Report <br /> states that a site conceptual model will be submitted during the first quarter of 2005. <br /> Comments: <br /> 1. The monitoring well data does not show adequate delineation of the vertical and lateral extent of <br /> petroleum hydrocarbon contamination in groundwater. As a result, Secor is conducting an <br /> independent evaluation of Lincoln Center's monitoring well data and groundwater model to develop a <br /> site conceptual model for Chevron's site. This new model will be used to confirm or dispute Lincoln <br /> Center's groundwater model, which shows that the Chevron petroleum hydrocarbon groundwater <br /> plume is being captured and treated by Lincoln Center's groundwater pump and treatment system. It <br /> is my understanding that Lincoln Center samples Chevron's monitoring wells quarterly for <br /> chlorinated solvents; that the Lincoln Center groundwater extraction and air stripper treatment system <br /> is using a granulated activated carbon polish for petroleum hydrocarbons in their influent water,but <br /> that the two sites do not share their data. I strongly suggest that you coordinate groundwater <br /> monitoring with Lincoln Center and share monitoring results with each other, in order to provide a <br /> comprehensive overview of the two commingled groundwater plumes, Lincoln Center's PCE and <br /> Chevron's petroleum hydrocarbon. <br /> California Environmental Protection Agency <br /> ca Recycled Paper <br />