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ENVIRONMENTAL HEALTH DEPARTMENT <br /> 4a�+1` SAN JOAQUIN COUNTY <br /> — s4 <br /> Donna K Heran,R E H 5 Unit Supervisors <br /> ` Director 304 East Weber Avenue, Third Floor Carl Borgman,R E H S <br /> AI Olsen,RX H S Stockton, California 95202-2708 Mike Huggins,R E H S ,R D I <br /> P• <br /> Program Manager Douglas W Wilson,R E H S <br /> �cf�aa� Laurie Cotulla,R E N S Telephone (209) 468-3420 Margaret Lagorto,R E H S <br /> Program Manager Fax (209) 464-0138 Robert McClelion,R E H S <br /> Mark Barcellos,R E H S <br /> LIZ SEWELL DEC 2 3 2003 <br /> CONOCOPHILLIPS <br /> 76 BROADWAY C (OPY <br /> SACRAMENTO CA 95818 <br /> RE 76 Service Station No 11193 <br /> 3202 West Hammer Lane ��-�- 2 b 20�3 <br /> Stockton, CA <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Revised <br /> Interim Remedial Action Plan and Work Plan for Ozone Sparge Well Installation and <br /> Additional Off-Site Assessment, dated 15 September 2003, which was submitted on your <br /> behalf by Secor International Incorporated (Seeor) An ozone sparging (OS) system will <br /> be installed using ten OS wells (OS-1 through OS-10), completed at a depth of 30 feet <br /> below ground surface (bgs) In addition, two shallow groundwater-monitoring wells <br /> (MW-11, and MWA 2)will be advanced to 30 bgs using 8-inch diameter hollow-stem auger <br /> drilling equipment, and soil samples will be collected at 5-foot intervals for iithological <br /> description from ground surface to the total completion depth in each of the bonngs for the <br /> OS and groundwater monitonng wells At least three selected sod samples will be <br /> analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethyl <br /> benzene, total xylenes (BTEX), and methyl ternary-butyl ether ((FERE). In addition to <br /> these analyses, EHD requests that soil samples be analyzed for tertiary butyl alcohol <br /> (y,8A ,^ di-isopropyl ether (PJFtEy, ethyl tertiary butyl ether (Ep'BEY. tertiary amyl methyl <br /> ether (TAME}', 1,2-dichloroethane (ta-DGAc), 1,2-dibrornoethane (EDB), and total <br /> petroleurirl hydrocarbons as diesel (TPHd), 1,2-DSA should be reported at <br /> 0 5 micrograms per liter (Mg/L,), if possible, in future groundwater samples collected at this <br /> site <br /> EHD approves the work plan as submitted for Installation of an OS system to replace the <br /> Interim groundwater batch-extraction migration control program, and installation of two <br /> monitoring wells down gradient of MW-6 to further define the dissolved petroleum <br /> hydrocarbon contamination EHD recommends continuous coring of the bonngs <br /> advanced for installation of the groundwater monitoring wells to better characterize the <br /> sand occurrences and to ensure that the monitoring objectives are met. A deeper well <br /> may be necessary adjacent to or down gradient of MW-6, based on collected data <br /> Further investigation of contamination in groundwater will be necessary to assess the <br /> vertical extent of impacted groundwater at this site Please submit a work plan to address <br /> • vertical extent of contamination at this site by 4 June 2004 <br />