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Sent By: RWQCB; 2553439; Sep-24-Oq 15:27; Page 2/3 California Regional Water Quality Control Board Central Valley Region Robert Schneider,Chair 9 WInston H.Hickox Grav Davis Secretaryfor Sacramento Main Office Governor Environmental Internet Address: http://www.sxrcb.ca.gov/--rwgcb5 Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 Phone(916)255-3000•FAX(916)255-3164 APPROVED 22 May 2003 Author 2#9S �G Senior Ms. Linda M. Gonsalves Pacific Gas and Electric Company California Gas Transmission 375 North Wiget Lane, Suite 200 Walnut Creek, California 94598-2412 REMEDIAL ACTION DOCUMENT, PACIFIC GAS & ELECTRIC COMPANY, LATHROP DEHYDRATOR STATION, SAN JOAQUIN COUNTY We have reviewed the 6 May 2003 Remedial Action Document(Work Plan)and the 30 April 2003 Q14 Groundwater Monitoring Report(GMR), submitted by CH2M Hill on behalf of the Pacific Gas and Electric Company(PG&E) for the Lathrop Dehydrator Station. The Lathrop Dehydrator Station is at the northwest corner of the intersection of Undine and Willow Glenn Roads about 6 miles northeast of Tracy in San Joaquin County. The GMR contains the groundwater monitoring results for samples collected in January 2003 and reports that monitoring well MW-1,which contained the highest pollutant concentrations in the past, contained 35 µg/1 of benzene, 13,000 µg/1 of total petroleum hydrocarbons in the gasoline range (TPHg), and 23,000 µg/1 of total petroleum hydrocarbons in the diesel range(TPHd). Five of 12 monitoring wells did not contain detectable concentrations of the pollutants. In the Work Plan,PG&E proposes a soil cleanup strategy. PG&E proposes to remove the inactive production equipment and foundation pads, and excavate around the former reboiler, extending the excavation offsite. PG&E proposes to properly abandon monitoring wells MW-1, MW-9 and MW-10 before conducting the excavation work. PG&E also proposes to collect soil confirmation samples from the excavation pit and to use soil cleanup standards of 100 mg/kg for TPHd and 10 mg/kg for TPHg. PG&E contends that soil that meets the TPHg and TPHd cleanup objectives will not contain detectable concentrations of benzene, toluene, ethylbenzene and xylene. The remaining groundwater monitoring wells will continue to be sampled in accordance with Monitoring and Reporting Program No. 5-01-877 and,if necessary, a groundwater cleanup strategy will developed after four quarters of sampling. The Work Plan is acceptable, and PG&E should proceed with its implementation. California Environmental Protection Agency 0 Recycled Paper The energy challenge facing California is real. Every Califomian needs to take immediate action to reduce energy consumption. Fora list of simple ways you can reduce demand and cut your energy costs,see our Web-site at http://www.swrcb.ca.gov/rwgcb5