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02/10/06 11:09 FAX 209 983 5 AASC U002 California Regional Water Quality Control Board Central Valley Region Robert Schneider Chair Alan C. Lloyd, Ph.D. Arnold Agency Secretary Sacramento Main Office Schwarzenegger 11020 Sun Center Drive 4200, Rancho Cordova, California 95670-61[4 Goverror Phone (916) 464-3291 • FAX (916) 464-4645 http://www-waterboards.ca.gov/ccntralvalley 8 February 2006 Mr. Michael McAnulty Atlantic Richfield Company 6 Centerpointe Drive La Palma, CA 90623 WORK PLAN FOR EXTRACTION WELL GW -7, APPLIED AEROSPACE STRUCTURES CORPORATION, STOCKTON, SAN JOAQUIN COUNTY Staff of the Central Valley Regional Water Quality Control Board (Regional Water Board) have reviewed the 20 January 2006 YYork Plan for Extraction Well GW -7 (Work Plan) for the Applied Aerospace Structures Corporation (BP/AA) site in Stockton, submitted on your behalf by Parsons Engineering Sciences. The work plan proposes to install an additional extraction well because trichloroethylene (TCE) pollution continues to be found in monitoring wells MW -5R and MW -15, which are located outside the capture zone of the existing groundwater extraction and treatment system. The new extraction well should extend the capture zone to MW -5R and MW -15. The Work Plan proposes to construct a 4 -inch diameter PVC extraction well inside a 10 -inch hollow - stem auger boring. The new well would have 15 to 20 feet of 0.02 -inch screen. The well would be equipped with a:variable speed pump rated to yield three to four gallons per minute (gpm). The discharge water will be routed through the existing groundwater treatment system. The six existing' extraction wells are similarly constructed and each produce from about 1.0 to 2.5 gpm, therefore the new well could be expected to produce similar capacity. However, the Work Plan does not provide analysis, to indicate the size of the cone of depression expected to result from the new well. If capture of the groundwater at MW -15 is not attained, additional extraction wells could be required. BP/AA should provide their rationale or design analysis for placement of the new extraction well. We concur with the Work Plan on the condition that BP/AA provides their design analysis for the placement of the well. If you have any questions, you may contact me at (916) 4644677 or -'by at GERALD J. DJtJTH, P.t., C.E.G. Associate Engineering Geologist cc: Ms. Margaet Lagorio, San Joaquin County Public Health Services, Stockton Mr. Fred Kintzer, Parsons Engineering Science, Inc., Walnut Creek California Environmental Protection Agency Cd Recycled Paper