Laserfiche WebLink
Mr. Ken Price - 2 - 30 July 2004 <br /> Former Occidental Chemical Corporation, Lathrop <br /> • Notification and implementation of the contingency plan if chemical concentrations are detected in <br /> groundwater samples from one or more contingency monitoring well(s). Proposed trigger levels for <br /> the contingency well(s) include California Maximum Contaminant Levels for DBCP at 0.2 <br /> micrograms per liter, µg/1, and EDB at 0.05 µg/1 and the preliminary California Department of <br /> Health Services criteria for sulfolane at 57 µg/1; <br /> • Re-evaluation of the Remedial Pumping Optimization Program at the end of the two-year cycled <br /> pumping; and <br /> • Semiannual reporting of Site sampling activities and results, data evaluation, and recommendations. <br /> Due to workload constraints, we apologize for the delay in providing review comments on the <br /> Workplan. Our comments on the Workplan are as follows: <br /> 1. We concur with the operation of the groundwater remedial system on a six-month cycled pumping <br /> schedule (i.e. six months on and six months off) for a one-year period following 6 months <br /> suspension of active pumping for collection of additional hydrogeologic and water quality data. <br /> Prior to implementing the proposed second year six-month cycled pumping schedule, Regional <br /> Board concurrence is required. Upon completion of the first 6 months pumping cycle, please submit <br /> the results and data evaluation, including whether the hydraulic capture was maintained and if <br /> cleanup of the remaining plume can be accomplished in a reasonable time under this pumping <br /> regime. <br /> 2. After completion of a six-month cycled pumping for one-year, active groundwater pumping and <br /> treatment should be continued until Regional Board review of the results and data evaluation <br /> discussed in comment number 1 is completed. <br /> 3. Please note that the well installation and destruction must be conducted in accordance with the San <br /> Joaquin County Environmental Health Division requirements and appropriate permits must be <br /> obtained. <br /> 4. Please provide a schedule, including a start date for implementation of the Workplan. We look <br /> forward to reviewing the results and recommendations. Please contact Ms. Cori Condon at <br /> (916) 364-4619 if you have any questions or concerns. <br /> Sudhakar Talanki, PE. <br /> Water Resources Control Engineer <br /> cc: Mr. Paul Horton, The Source Group, Pleasant Hill <br /> Mr. Harlin Knoll, San Joaquin County Environmental Health Division, Stockton <br /> Mr. Tom Prevost, CRA, Stockton <br />