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ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> �Qi���tic G <br /> Donna K Heron,R E H S Una Supervisors <br /> { Director 304 East Weber Avenue, Third Floor Carl SoWan,R E H S <br /> Al Olsen,R.E HS Stockton, California 95202-2708 Mike fluggrns,R E N S, R D I <br /> • ate. P • Pro ,-ant Manager Douglas W Wilson,R E H S <br /> `ret dR�� Laurie A Coluila,R E H S Telephone (209)46$-3420 Margaret Lagona,ILE H S <br /> Program kfeurrrger Fax (209)464-0138 Rotten McClellon,R E H 5 <br /> Mark Barceilos,R E H S <br /> BOB DENINO MAY 0 3 2005 <br /> SOUTHLAND CORPORATION <br /> 10220 SW GREENBURG RD SUITE 270 <br /> PORTLAND OR 97223 <br /> RE 7-Eleven Store No 19976 SITE CODE 1435 <br /> 1399 North Main Street RO 675 <br /> Manteca, CA 95336 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Work Plan <br /> for DZ Sparge Well Installation, dated March 15, 2005, prepared and submitted by Secor <br /> International Incorporated (Secor) on your behalf for the above-referenced site Before <br /> EHD can comment on this work plan, you must first get approval for the proposed <br /> oxygen Injection from the Central Valley Regional Water Quality Control Board <br /> (CVRWQCB) Please contact James Barton, P G at CVRWQCB for information by <br /> . telephone at (916) 464-4615 or by electronic mail at i barton c wateiboards ca gov Also, <br /> EHD would like documentation that groundwater elevation (mounding) is not occurring <br /> when oxygen is infected routinely at this site <br /> By letter dated July 28, 2004, EHD approved a reduction for sampling monitoring wells <br /> MW-4 and MW-4A from quarterly to annually During the December 2004 quarterly <br /> monitoring event, benzene, toluene, ethyl benzene, and total xylenes were detected in the <br /> groundwater sample collected from MW-4A Therefore, you are directed to sample MW- <br /> 4A quarterly instead of annually, and MW-4 semi-annually to monitor the groundwater <br /> plume to the east <br /> Further groundwater and soil Investigation will be necessary to assess the vertical extent <br /> of hydrocarbon contamination in the area between borehole GP-3 and MW-1/MW-IA <br /> Based on the SB-1 boring log, EliD believes that a monitoring well screened between 55 <br /> and 60 feet below Surface grade (bsg) will provide the needed Information In this source <br /> area Also EHD believes a monitoring well is needed to the west of MW-2 to assess <br /> lateral extent of groundwater contamination in this direction Please subinit a work plan <br /> to EHD by June 24, 2005, that addresses vertical and lateral extents of contamination at <br /> this site <br /> Itu <br /> MAY 0 5 2005 !� <br />