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California ILegional Water Quality Control Board OLCentral Valley Region��� E.�7 1/I "f1 J! E. Longley,Sc D, P.E.,Chairo <br /> Linda S. Adams Arnold <br /> Secreiarjfor Sacramento Main Office Schwarzenegger <br /> Environmental JAM 0255 ler Drive#200,Rancho Cordova,California 956266114 Governor <br /> Protection -1'none(916)464-3291 •FAX(916)464-4645 <br /> hit <br /> waterboards.ca.gov/centralval ley <br /> ENVIRONMENT HE <br /> P <br /> 24 January 2008ERMIT/SERVICES <br /> Ms. Stephanie Frugal Mr. Jay Allen <br /> Chevron Environmental Management Company Stone Brothers Management Company <br /> 6001 Bollinger Canyon Road 1024 W. Robinhood Dr. <br /> San Ramon, CA 94583 Stockton, CA 95207 <br /> DOCUMENT REVIEW, CLEANUP AND ABATEMENT ORDER (CAO) NO. 5-00-0707, <br /> FORMER UNOCAL STATION #5098 AT 5606 PACIFIC AVENUE, AND FORMER <br /> MONTGOMERY WARDS AUTO SERVICE AT 5400 PACIFIC AVENUE, STOCKTON, <br /> SAN JOAQUIN COUNTY <br /> I reviewed the Addendum to Work Plan for Air Sparging/Soil Vapor Extraction Well Installation <br /> (Addendum) received 18 January 2008 from ENSR, the consultant for Chevron Environmental <br /> Management Company (CEMC). The Addendum was submitted in response to my <br /> 21 December 2007 comments letter (Letter) to the 3 December 2007 Workplan for the <br /> redesign of the air sparging/soil vapor extraction (AS/SVE) treatment system. My Letter <br /> comments are reiterated below. <br /> Letter comments: <br /> It is my understanding from previous conversations with ENSR that there is a question <br /> whether the treatment system could adequately affect the groundwater plume to the <br /> north under Robinhood Drive. Please submit a letter addendum to the Workplan, which <br /> provides a detailed explanation of the existing SVE/AS system testing procedures, <br /> compares the testing results to the expected performance specifications for a similar <br /> designed system, and shows that the entire groundwater plume will be addressed by <br /> the proposed upgrades. In other words, the technical justification for replacing all, or a <br /> portion of, the existing system needs to presented in a manner that the State Water <br /> Resources Control Board, Underground Storage Tanks Cleanup Fund and Regional <br /> Board staffs can concur to ENSR's and CEMC's determination that the upgrades are <br /> necessary and appropriate. <br /> The Workplan does not include labeled geologic cross sectional views of the <br /> remediation well construction and the lithological sequence to be remediated. Submit <br /> two geologic cross sections oriented as an 'X" (at right angles), and include the <br /> proposed remediation wells, along with the existing remediation and monitoring wells, <br /> within the lithology of the remediated zones. <br /> Revise the map or plan view to include the lines of above cross sections indicated as <br /> an 'X "on Attachment B Figure 2 (attached). <br /> California Environmental Protection Agency <br /> - Ca Recycled Paper <br />