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• Water Quality Antrol Board <br />California RRional <br />Central Valley Y Region <br />Robert Schneider, Chair Arnold <br />Alan C. Lloyd, Ph.D.Schwarzenegger <br />Agency Secretary Sacramento Main Office Governor <br />11020 Sun Center Drive 4200, Rancho Cordova, California 95670 6114 <br />Phone (916) 464-3291 • FAX (916) 464-4645 <br />http://www.waterboards.ca.gov/centralvalley RECO", .ED <br />8 February 2006 <br />3 2,006 <br />ENVIRONMENT HEALTH <br />Mr. Michael McAnulty RERfAIT/SERVICES <br />Atlantic Richfield Company <br />6 Centerpointe Drive <br />La Palma, CA 90623 <br />WORK PLAN FOR EXTRACTION WELL GW -7, APPLIAEROSPACE STRUCTURES <br />CORPORATION, STOCKTON, SAN JOAQUIN <br />Staff of the Central Valley Regional Water Quality Control Board (Regional Water Board) have <br />reviewed the 20 January 2006 Work Plan for Extraction Well GW -7 (Work Plan) for the Applied <br />Aerospace Structures Corporation (BP/AA) site in Stockton, submitted on your behalf by Parsons <br />Engineering Sciences. The work plan proposes to install an additional extraction well because <br />trichloroethylene (TCE) pollution continues to be found in monitoring wells MW -5R and MW -15, <br />which are located outside the capture zone of the existing <br />go MW5 ater R and MW- and treatment system. <br />The new extraction well should extend the capture <br />zonThe Work Plan proposes to construct a 4 -inch diameter PVC extraction well inside a 10 -inch hollow - <br />stem auger boring. The new well would have 15 to hree to four feet of .02 -inch screen. The well gallons per minute (gpm)WThe ould be <br />equipped with a variable speed pump rated to yield <br />discharge water will be routed through the existing groundwater treatment system. <br />The six existing extraction wells are similarly constructed and each produce from about 1.0 to 2.5 gpm, <br />therefore the new well could be expected to produce similar capacity. However, the Work Plan does not <br />provide analysis to indicate the size of the cone of depression expected to result from the new well. If <br />capture of the groundwater at MW -15 is not attained, additional_ extraction wells could be required. <br />BP/AA should provide their rationale or design analysis for placement of the new extraction well. <br />s for <br />he <br />We concur with the Work Plan on the condition haB m/c ontactprovides me atlr design (916) 46446771or byemailat <br />placement of the well. If you have any questions, Yoay <br />gdluth a waterboards.ca.gov. <br />GERALD J. DJUTH, P.E., C.E.G. <br />Associate Engineering Geologist <br />cc: Ms. Margaret Lagorio, San Joaquin County Public Health Services, Stockton <br />Mr. Fred Kintzer, Parsons Engineering Science, Inc., Walnut Creels <br />California Environmental Protection Agency <br />(a Recycled Paper <br />