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ia <br /> CALIFORNIA REGIONAATER QUALITY CONTROL BOARD CaIIEPA <br /> CENTRAL VALLEY REGION <br /> Sacr Roumento, Road, Suite 0 Sacramento, CA 95827-3098 <br /> Phone(916)255-3000 <br /> FAX(916)255-3015 -1 scp 2q M 10: els Pete Wilson,Governor <br /> 25 September 1997 <br /> Mr. Nick Nickerson <br /> Unocal <br /> 2000 Crow Canyon Place, Suite 470 <br /> San Ramon, CA 94583-0973 <br /> CONDITIONAL APPROVAL OFREVISED COMPLETIONSCHEDULE AND WORKPLAN, <br /> FORMER PUREGROIBREA,STOCKTON,SAN JOAQUIN COUNTY <br /> I am in receipt of the 21 August 1997 Revised Completion Schedule and the 10 September 1997 <br /> Workplan for Investigation of Agricultural Chemicals in Soil for the former PureGroBrea Ag facility at <br /> 1905 North Broadway, Stockton. The documents are approved with the following conditions: <br /> 1. The schedule does not contain a task for final definition of the groundwater plume. If the <br /> September 1997 sampling event shows that well MW-9 contains 1,2-DCP,then Unocal will be <br /> required to submit a workplan to define the extent of the plume. <br /> 2. Unocal has indicated that it would prefer to have the human health risk assessment reviewed by the <br /> Department of Toxic Substances Control (DTSC)rather than by the Office of Environmental Health <br /> Hazard Assessment (OEHHA). This is acceptable as long as Unocal signs a contract with DTSC <br /> before the 20 December 1997 due date for submittal of the risk assessment workplan. If the DTSC <br /> contract is not in place at that time, staff will submit the risk assessment workplan to OEHHA for <br /> review under an existing contract. <br /> 3. All soil samples are to be analyzed for nitrate and total Kjeldahl nitrogen. In addition, soil samples <br /> from the four borings around the old tank farm (NSB 1-4) are to be analyzed for volatile organic <br /> chemicals including 1,2,3-trichloropropane. <br /> Based on Unocal's schedule,the report containing the results of the on-site soil characterization is to be <br /> submitted by 1 November 1997 and the human health risk assessment workplan by 20 December 1997. <br /> If you have any questions, I can be reached at(916) 255-3078. <br /> WENDY WYELS <br /> Site Cleanup Unit <br /> cc: Mr. Mike Infurna, San Joaquin County Environmental Health Department, Stockton <br /> Mr. Eric Chase, Sierra Pacific Groundwater Consultants, El Dorado Hills <br /> Ms. Nancy Bishop, Western Farm Service, Lafayette <br /> Mr. Jan Wagoner, Unocal, West Sacramento <br />