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Mr. Eric Jenks -2 - 23 August 2004 <br /> identified in the grab groundwater samples, thus allowing a source area cleanup plan to be developed, <br /> and will document the progress of future remediation activities. <br /> However, the grab groundwater samples show that concentrations of 1,2-DCP vary in groundwater <br /> between 150 ug/l and 1 ug/l from two samples obtained within about 40 feet of each other. The data <br /> obtained from the grab groundwater investigations do not clearly identify specific source areas for <br /> pollutants such as 1,2-DCP and bromacil. This supports JTF's assertion that a monitoring well may not <br /> provide additional insights at the present time. Therefore, JTF may postpone installing operations' area <br /> monitoring wells until source areas are more clearly identified. As described below, Regaional Board <br /> staff are requesting that you submit a source area investigation work plan by 31 December 2004. <br /> Thank you for proposing a deep boring at the downgradient corner of the property. GeoSyntec will <br /> record stratigraphy below the first aquifer, obtain a grab groundwater sample from the next encountered <br /> water bearing zone, and analyze it for volatile organic compounds and other parameters. <br /> The Delineation Report did not contain a location for the upgradient monitoring well or a construction <br /> diagram. JTF needs to submit a workplan to install the upgradient and downgradient monitoring wells <br /> discussed above and a schedule to conduct the work and provide a report of results. <br /> Source Area Investigation <br /> JTF needs to conduct a soil investigation to locate possible soil source areas contributing to the <br /> pollutants found in the perimeter monitoring wells and the grab groundwater samples. Pollutants <br /> consistently found in groundwater at this site are 1,2-DCP and 1,2,3-TCP identified in MW-4, bromacil <br /> in MW-2, MW-3, and MW-4, and dinoseb in MW-3. The monitoring well network suggests that the <br /> former tank farm is a source of nitrate in groundwater as evidenced by the increases of nitrate in MW-5. <br /> Summary <br /> By 1 October 2004, please provide a work plan to install one upgradient and two downgradient <br /> monitoring wells as discussed above, and by 31 December 2004, submit a source are investigation work <br /> plan. Both work plans shall be prepared in general accordance with the attached Items To Be Included In <br /> A Site Assessment Work Plan. <br /> If you have any questions, you may contact me at(916) 464-4680. <br /> Cr �l. <br /> — rAMY TERRELL <br /> Private Sites Cleanup Unit <br /> cc: Ms. Lori Duncan, San Joaquin County Public Health Services, Stockton <br /> Mr. Thomas Slattery, Wilbur-Ellis Company,Fresno <br /> Ms. Carolyn Kneiblher, GeoSyntec Consultants, Walnut Creek <br />