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ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Donna K.Heran,R.E.H.S. Unit Supervisors <br /> to: XDirector 304 East Weber Avenue, Third Floor Carl Borgnan,AE.H.s. <br /> Al Olsen,R.E.H.S• SCOC1Cton, California 95202-2708 Mike Huggins,R.E.H.S.,R.D.I. <br /> oQLi..o.... Program Manager Telephone: {209}468-3420 Douglas W.Wilson,R.E.H.S. <br /> Laurie A.Cotulla,R.E.H.S. Margaret Lagorio,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Robert McClellon,R.E.H.S. <br /> Mark Barce±los,R.E.H.S. <br /> JUN 2 3 2CQS <br /> KYLE CHRISTIE ROSE V RODGERS TRUST ETAL <br /> ATLANTIC RICHFIELD COMPANY BILL & LORRAINE HALVORSON <br /> 6 CENTERPOINTE DRIVE LPR6-161 10040 DAVIS ROAD <br /> LA PALMA CA 90623-1066 STOCKTON CA 95209 <br /> RE: FORMER ARCO STATION NO. 2168 Site Code: 1056 <br /> 441 W. CHARTER WAY <br /> STOCKTON, CA 95202 <br /> San Joaquin County Environmental Health Department p rtment (SJC/EHD) has received <br /> and reviewed Workplan for the Abandonment of a Groundwater Monitoring Well, ' <br /> Installation of an Interim SOY Vapor Extraction / Air Sparge Groundwater <br /> Treatment System, and Installation of Groundwater Monitoring� t9 Wells {WP}, dated <br /> d <br /> 10 July 2005. In addition, SJC/EHD discussed several questions regarding the WP <br /> with your consultant, Mr. Vernon Elarth of URS- Corporation, via telephone on 20 <br /> June and 21 June 2005. <br /> URS has proposed in the WP to: <br /> • Destroy monitoring well MW-4 by pressure grouting the well and then <br /> overdrilling the upper 5 feet of the former well with 10-inch augers and <br /> r` grouting with portland cement with a 5% bentonite mixture; <br /> • Install a soil vapor extraction (SVE) system and in-situ air sparge (IAS) <br /> system and 21 nested SVE/IAS wells; and <br /> • Install three shallow, down- ra ' <br /> dlent monitoring w ". <br /> g g ells to monitor the effects C <br /> of the SVE/IAS system. <br /> SJC/EHD cannot approve pressure grouting as the method of well destruction for <br /> monitoring wells set in contaminated areas_ URS agreed during the 20 June 2005 <br /> 1 <br /> � conversation"to destroy MW-4 by over-drilling its entire length and backfilling with <br /> the portland cement grout. SJCIEHD approves over-drilling well destruction <br /> method for MW-4. <br /> i <br /> o , <br /> As there has been no pilot or feasibility tests, SJC/EHD was concerned with <br /> the <br /> IAS design with sparge points set approximately 15 feet below the groundwater <br /> table in silt just above a sand interval. IAS has not been 'previously shown to be <br /> { , effective for this site and it is not certain that most of <br /> the sparged air will penetrate <br /> C <br />