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�1�A��TH SEP <br /> K <br /> vlRpNMENrf A COUNTY Unit Supe"iIss E H. <br /> SAID JOAQVI S. <br /> Carl Borgman, R 17.I. <br /> ,a�.�.N. � venue,Third Floor Mlke xuggins,R.E.H.S•' x,s. <br /> eber A La VJ�lson,R•�• <br /> 1_6 ' °c Heran,R.E.H.s, 304 East W 5202-2'708 Doug4as <br /> Donna K. California g ono,R. •11.5. <br /> Stockton, Margaret Lag <br /> :{ Director 2ag� 469-3420 R01)c,t McClellon,R.1 -11.5. <br /> Al Olsen,R.E.YLS. Tele 110ne: � S. <br /> - p R.E.". <br /> - prog�an:Manager 2D9 464-013$ Mark garcellos, <br /> • c4�:j o o.9�� Laurie A.COtulla,R.�-H•S. <br /> Fax: (� ) <br /> program Manager <br /> DEC 2 3 7.003 <br /> LIZ SEWELL <br /> CONOCOPHILLIPS <br /> 76 BROADWAY <br /> SACRAMENTO CA 95818 <br /> RE: 76 Service Station No. 11193 <br /> 3202 West Hammer Lane <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 (Secor). 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 MW-12) will be advanced to 30 bgs using 8-inch diameter hallow-stem auger <br /> drilling equipment, and soil samples will be collected at 5-foot intervals for lithological <br /> description from ground surface to the total completion depth in each of the borings for the <br /> OS and groundwater monitoring wells. At least three selected soil samples will be <br /> analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethyl <br /> benzene, total xylenes (BTEX), and methyl tertiary-butyl ether (MTBE). In addition to <br /> these analyses, EHD requests that soil samples be analyzed for tertiary butyl alcohol <br /> (TBA), di-isopropyl ether (DIPE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl <br /> ether (TAME), 1,2-dichloroethane (1,2-DCA), 1,2-dibromoethane (EDB), and total <br /> petroleum hydrocarbons as diesel (TPHd). 1,2-DCA should be reported at <br /> 0.5 micrograms per liter (pg/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 borings <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 />