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�i <br />r <br />California Regional Water Quality <br />Central Valley Region <br />Alan C. Lloyd, Ph.D. <br />Agency Secretary <br />17 February 2006 <br />Robert Schneider, Chair <br />0 <br />Control Board <br />Sacramento Main office <br />it <br />C t Drive #200 Rancho Cordova, California 95670.6114 <br />Arnold <br />Schwarzenegger <br />4/ Governor <br />11020 Sun ene, <br />Phone (9 16) 464-3291 • FAX (916) 464-4645 F I•-F� <br />hanI/www.waterboards.ca.gov/centralvalley U <br />Mr. Michael McAnulty <br />Atlantic Richfield Company <br />6 Centerpointe Drive <br />La Palma, CA 90623 <br />ENVIRONlNENT HEALTH <br />PERMIT/SERVICES <br />EXTRACTION WELL CONCURRENCE AND REQ DOR OWN T ONISTOCKTON, <br />INVESTIGATION, APPLIED AEROSPACE STRUCTURES <br />SAN JOAQUIN COUNTY <br />In our 8 February 2006 letter, staff of the Central Valley Regional used extraction <br />ter Qx alit onontrol well Board On 10 <br />(Regional Water Board) conditionally approved the location p p the consultant for <br />February 2006 Regional Board Staff conversed with Mr. Fred Kinser of Parsons, of that conversation, Staff believes that <br />Applied Aerospace Structures Corporation (A a rdesult one ofd pression should capture any <br />and theexpecte <br />the proposed location of GW -7 is appropriate, <br />further trichloroethylene releases from the AASC site. <br />However, Regional Board Staff do not believe the extent of the TCE f TCEplume <br />each of sown gradienmontof M events <br />15 <br />has been defined. MW -15 has contained approximately 5 ug/l o <br />since August 2004, and monitoring well MW -5/5R has containedup <br />of the existing groundwater extraction <br />/I of TCE seasonally since <br />November 1998. Both of these wells are outside the capture <br />and treatment system, therefore it is possible that a TCE plume has migrate t fro know_ <br />distanced an If TCE iom <br />MW -15. AASC needs to define the extent of the TCE plume do g <br />detected down gradient of MW -15, another monitoring well may be required. <br />By 24 March 2006, please submit a work plan to accomplish the required tasks. If you have any <br />questions regarding this investigation, you may contact me at (916) 464-4677 or by email at <br />gdiuthni waterboards.ca.gov. <br />�= <br />GERALD J. DJUTH, P.E., C.E.G. <br />Associate Engineering Geologist <br />cc: Ms. Margaret Lagorio, San Joaquin County <br />Public <br />Health Servicut es, <br />Stockton <br />Mr. Fred Kintzer, Parsons Engineering <br />California Environmental Protection Agency <br />01 Recycled Paper <br />