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M ` Pacific Pride-South El Dorado Street Page 2 3147 South EI Dorado Street March 26, 2008 Stockton, California 95206 depths as great as 100 feet bsg. Please submit a work plan to the EHD by June 19, 2008, that will address the lateral extent of the dissolved petroleum hydrocarbon plume southeast of MW-9A in the shallow zone (approximately 35 to 45 feet bsg). Although the SCM provided much information about your site, there was no mention concerning the high concentrations of total petroleum hydrocarbons quantified as kerosene (TPH-k) detected in groundwater collected from MW- 1 and MW-7 and the abrupt disappearance of this chemical of concern. In addition to detecting TPH-k at low concentrations in groundwater samples collected from MW-2, MW-3 , MW-4, and MW-5, TPH-k was also detected in soil samples collected from MW-1 , MW-5, and MW-B. Please provide the EHD an explanation why TPH-k is no longer being detected in groundwater collected at your site. AGE has recommended that a soil vapor extraction pilot study be performed to determine if this remedial method may decrease the concentrations of petroleum hydrocarbons present in soil and groundwater. The EHD approves this pilot test. Please submit a work plan to the EHD by June 19, 2008, that will address performing a soil vapor extraction pilot test at your site. Continue to collect groundwater samples quarterly from MW- 1 , MW-7, MW-8A, MW-9A, and MW- IOA, MW- IOB, and MW-IOC; and continue to analyze for total petroleum hydrocarbons quantified as diesel (TPH-d) in groundwater samples collected quarterly from MW-1 and MW-7. Semi -annually collect groundwater samples from MW-5 and MW-8B. Annually, during the first quarter of each year, collect groundwater samples from MW- 1 , MW-2, and MW-4 through MW- 12 and include TPH-d and TPH-k in the analytical list at this time. Ethyl tertiary-butyl ether (ETBE), di-isopropyl ether (DIPE), 1 ,2-dibromoethane (EDB), and tertiary-butyl alcohol may be removed from the analytical list since these compounds have not been detected in groundwater samples collected quarterly since 2004. If any analytes are detected in samples collected on a non-quarterly basis, the well should be sampled the following quarter(s) until concentrations return to non-detect (i.e. MW-6). Collect groundwater samples from MW-6 during the next monitoring event and analyze the groundwater for MTBE and TAME. If you have any questions, please contact Vicki McCartney, Senior Registered Environmental Health Specialist, at (209) 468-9852 or by email at vmccartney@sjcehd.com. Sincerely,Le C Victoria L. McCartney, RENS Nuel . Henderson, Jr. , PG Senior Registered Environmental Health Specialist Engineering Geologist c : Mr. Timothy J. Cuellar, Advanced GeoEnvironmental, Inc., 837 Shaw Road, Stockton, California 95215 Mr. James L .L. Barton, PG, California Regional Water Quality Control Board Central Valley Region, 11020 Sun Center Drive, Suite 200 , Rancho Cordova, California 95670