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• • E...B.BROWN JP. <br /> .-a .. <br /> MINEW Rooewucz <br /> Water Boards °""`",- <br /> Central Valley Regional Water Quality Control BoarRECEIVED a <br /> LTJ <br /> 11 February 2014 FEB 12 2014 <br /> ENVIRONMENTAL HEALTH <br /> PERMIT/SERVICES <br /> Mr. Brian Duggan <br /> Environmental Manager <br /> Crop Production Services, Inc. <br /> 3005 Rocky Mountain Ave. <br /> Loveland, Colorado 80538-9001 <br /> CONDITIONAL CONCURRENCE WITH REVISED SITE INVESTIGATION WORKPLAN, <br /> CPS STOCKTON, 1905 N. BROADWAY, SAN JOAQUIN COUNTY <br /> Crop Production Services (CPS) operates an agricultural chemical formulation and distribution <br /> business at its Stockton facility. Historical operators have polluted soil and groundwater with <br /> 1,2-dichloropropane (1,2-DCP), 1,2,3-trichloropropane (1,2,3-TCP), nitrate, ammonium, and <br /> other chemicals. Site investigations have identified soil source areas of 1,2-DCP and 1,2,3- <br /> TCP. In a 29 April 2013 letter, California Regional Water Quality Control Board, Central Valley <br /> Region (Central Valley Water Board) staff requested a feasibility study to identify treatment <br /> strategies to clean soil and groundwater. In a 23 July 2013 meeting with CPS, Central Valley <br /> Water Board staff agreed that CPS needs to assess aquifer properties at the site before it can <br /> prepare a meaningful feasibility study. Central Valley Water Board staff also requested that CPS <br /> determine if the volatile compounds 1,2-DCP and 1,2,3-TCP in the subsurface are a health <br /> hazard to adjacent residents or on-site workers. <br /> Central Valley Water Board staff has reviewed the 19 November 2013 Revised Site <br /> Investigation Work Plan (Work Plan) prepared by Rubik Environmental, which proposes aquifer <br /> drawdown tests, soil vapor analyses, and soil properties analyses to obtain the data to satisfy <br /> the feasibility study data gaps and assess human health exposure. Central Valley Water Board <br /> staff conditionally concur with the Work Plan. <br /> Aquifer Parameters <br /> Step draw-down pumping tests are proposed at five A-zone monitoring wells, which are about <br /> 50 feet below ground surface (bgs), and at three B-zone monitoring wells, which are about 100 <br /> feet bgs. These selected test wells are located adjacent to areas of subsurface contamination. <br /> In addition, slug tests are proposed at three upgradient A-zone wells, in order to assess the <br /> ability of the formation to receive injectants. <br /> The existing monitoring well network is proposed to serve as observation wells during the pump <br /> tests. The distance from observation wells to pumping wells within the same aquifer range from <br /> 50 feet to 160 feet. The pumped water is proposed to be contained in 5,000 gallon polyethylene <br /> tanks that will be strategically staged on-site, characterized, and disposed of by CPS waste <br /> management personnel. Based on pump tests done in 2001, the A-zone wells are expected to <br /> produce about 1,000 gallons of water each during the step draw-down test, and the B-zone <br /> wells are expected to produce about 3,000 gallons each. <br /> KARL E. LONOLEV SCD, P.E., CHAIR I PAMELA C. CREEDON P.E., SCEE, EXECUTIVE OFFICER <br /> 11020 Sun Center UrIve e200,Rancho Cordova,CA 95670 1 www.waterboartla.ca.govtcentralvalley <br /> 1I KkCY1LtU vaPex <br />