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RPR. 8.2005 B:15RM PSENV. SERVICES N0.234 P.2 <br /> r <br /> ,,••�� .-til <br /> Department of Toxic Substances Control <br /> Alan 9.uovyd,Ph-Q. ae00 Cal Center Drive Arnold Schwa¢enegger <br /> Agency Secretary Sacramento,Callfomia 95826.3200 Governor <br /> CaVEPA <br /> April 1, 2005 <br /> Ms. Betsy Brunswick <br /> PG&E Environmental Services <br /> P.O, Box 7640 <br /> San-Francisco, California 94120 — <br /> COMMENTS ON THE WORK PLAN TO ADDRESS GROUNDWATER CONDITIONS <br /> FOR THE FORMER MANUFACTURED GAS PLAN IN STOCKTON, CALIFORNIA <br /> Dear Ms. Brunswick: <br /> The Department of Toxic Substances Control (DTSC) has reviewed the February 2005 <br /> work plan to address groundwater conditions in the vicinity of monitoring well 26R and <br /> to decommission eight monitoring wells. Acenaphtlene concentrations in groundwater <br /> samples collected from MW-26R have increased from 9.6 to 19 micrograms per liter <br /> (ug/L) in 1997 and 1998 to 100 uglL in 2004. The work plan proposes to install an <br /> additional monitoring well approximately 270 feet downgradient of MW-26R. The well <br /> will be in the B zone which is approximately 100 to 113 feet below the ground surface. <br /> The work plan also proposes to decommission eight existing wells. I have enclosed <br /> comments from DTSC Geological Services Unit. These comments should be <br /> addressed in a revised work plan, Once the additional well is installed, PG&E should <br /> provide a report that explains why the increase in concentration trends in MW-26R are <br /> not following the model used in the March 1998 Remedial Action Plan and recommend <br /> actions that need to be taken. <br /> Please submit a revised work plan to DTSC within 30 days from the date of this letter. If <br /> you have any questions, please call me at (916) 255-3585. <br /> Sincerely, <br /> Duane White <br /> Project Manager <br /> Enclosure <br /> ® Pnntetf on Recycled Paper <br />