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��'�`° <br />Californkeegional Water Quality Coof Board <br />0 ��_ . � <br />Central Valle Region <br />Karl E. Longley, ScD, P.E., Chair Arnold <br />Linda S. Adams 11020 Sun Center Drive #200, Rancho Cordova, California 95670-6114 Schwarzenegger <br />Secretaryfor Phone (916) 464-3291 • FAX (916) 464-4645 Governor <br />Environmental http://www.waterboards.ca.gov/centraivalley <br />Protection <br />28 January 2010 <br />Chris Markowski <br />Project Manager <br />9800 Goethe Road, Box 17 <br />Sacramento, CA 95827 <br />DRAFT WORK PLAN FOR GROUNDWATER MONITORING ARMELL INSTALLATION, <br />Y NATIONAL GUARD, SAN <br />STOCKTON FIELD MAINTENANCE SHOP, CALIFORNIA <br />JOAQUIN COUNTY <br />California Regional Water Quality Control Board, Central Valley Monitoringion eWell Installationntral Valley ter <br />Board) staff has reviewed the Draft Work Plan for Groundwater <br />(Work Plan) received on 10 December 2009. The Work Plan p dposeswater monitoring to n of five (5) <br />new groundwater monitoring wells and four (4) quarte og <br />ss <br />the extent of groundwater contamination originating from former hetdergemediround st rage <br />tanks (USTs) at the Stockton Field Maintenance Shop <br />ons <br />are warranted. Gasoline and diesel leaked from the 007 investigation, <br />by CANGe <br />that underlies much of the FMS site. Based on the <br />the groundwater plume has not migrated off-site.The <br />Central <br />V ll e ey Water Board staff's <br />General and Specific Comments on the document are pe <br />GENERAL COMMENTS <br />1. Central Valley Water Board staff concur with the proposed locations of the five (5) <br />monitoring wells which assume groundwater generally flows northeast beneath the FMS <br />site. If this assumption on the local groundwater flow direction is incorrect, the California <br />Army National Guard (GANG) may need to install additional monitoring wells. <br />2. The Work Plan proposes placement of four monitoring wells around the plume edge. <br />The Work Plan proposes to construct these wells with 30 -foot screens with approximately <br />10 feet above and 20 feet below the top <br />of the <br />water table. sands alle this nd/or gpa�elssed a are thickse <br />may prove to be ideal for the site if a sequence of <br />encountered, Central Valley Water Board believes placement of the screen should be <br />determined based on the actual subsurface materials encountered in each boring. For <br />example, if a potential aquitard is encountered less than 20 feet below the top of the <br />water table, CANG should consider using shorter well screens, so a potential conduit to <br />deeper water -bearing zones is not created. <br />California Environmental Protection Agency <br />zj Recycled Paper <br />