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California&gional Water Quality Coi#1 Board <br /> l \- Central Valley Region ` } <br /> vKarl E. Longley,ScD, P.E.,Chair <br /> Linda S.Adams SacrameArnold <br /> Serremryfor Drive <br /> n Main Cordova, <br /> Schwarzenegger <br /> E",a onmental 11020 Sun Center Drive)200.Rancho Cordova,California 956"IP6114 Governor <br /> Protection Phone(916)464-3291 •FAX(91�6)464-46I45 <br /> http//www.waterboards.ca.gov/ d pllust❑Ir�C� OED <br /> 6 February 2008 FEB 0 7x2008 <br /> Mr. Gil Moore ENVIRONMENT HEALTH <br /> New West Petroleum, Inc. PERMTSERVICES <br /> 1831 16`h Street <br /> Sacramento, CA 95814 <br /> DOCUMENT REVIEW, NEW WEST PETROLEUM #1003 (SHELL BRANDED), <br /> 6437 BANNER STREET, LODI, SAN JOAQUIN COUNTY(CAO R-5-2007-0709) <br /> I reviewed the Problem Assessment Report (PAR), submitted 1 February 2008 by your <br /> consultant Closure Solutions, Inc. (CSI) in response to the Regional Board Cleanup and <br /> Abatement Order No. R5-2007-0709 (CAO). The PAR states it uses the 16 April 2004 <br /> Regional Board guidance, Tri-Regional Board Staff Recommendations For Preliminary <br /> Investigations and Evaluation of Underground Tank Sites, Appendix A — Reports. <br /> The PAR includes the following: <br /> • Review of the previously submitted Risk Assessment and Site Conceptual Model <br /> (enclosed Figure 2), <br /> • Provides the summaries of prior investigations for petroleum hydrocarbon <br /> contamination in soil and groundwater, <br /> • Evaluates the performance of the currently active interim remediation (groundwater <br /> pump and treatment, or GWP&T system), <br /> • Provides estimates of remaining mass of methyl tert-butyl ether (MTBE), the primary <br /> constituent of concern, in soil and groundwater. <br /> The maximum groundwater concentration for MTBE in October 2007 was 3,300 micrograms <br /> per Liter (ug/L) in onsite extraction well EW-4. The current known extent of the groundwater <br /> plume is shown in enclosed Figures 10 and 11. Plan view orientation of the PAR geologic <br /> cross section is indicated in enclosed Figure 4, while soil lithology is shown in enclosed <br /> geologic cross section Figure 5. Soils consist of sands, silts and clays. Groundwater flow <br /> direction is towards the southeast. <br /> In soil, the estimated remaining mass of MTBE is 563.4 pounds; however the PAR states the <br /> soil mass is conservatively estimated using the maximum distance between soil sample <br /> locations, and may be"...significantly lower...". The remaining MTBE mass in groundwater is <br /> estimated at 21.5 pounds in the A-zone and B-zone of the aquifer. <br /> Due to the effectiveness of the interim remediation, the PAR recommends expanding the <br /> interim GWP&T system from the current onsite source area, by adding an offsite GWP&T <br /> California Environmental Protection Agency <br /> ea Recncled Paper <br />