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ENVIRONMENTAL HEALTH LEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> so�co Unit Supervisors <br /> Q 2� Donna IC Heran,R.E.H.S. <br /> Director D 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S. <br /> Mike Huggins,R.E.H.S.,R.D.I. <br /> .- r,:• Al Olsen,R.E.H.S. $tOC1CLOn, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> • C`q _.r--NSP Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> �!F b Laurie A.Cotulla,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Robert McClellan,R.E.H.S. <br /> CTBarcelllos,R.E.H.S. <br /> M1 2 6 2005 <br /> KYLE CHRISTIE ROSE V RODGERS TRUST ETAL <br /> ATLANTIC RICHFIELD COMPANY BILL & LORRAINE HALVORSON <br /> 6 CENTERPOINT DRIVE LPR6-161 10040 DAVIS ROAD <br /> LA PALMA CA 90623-1066 STOCKTON CA 95209 <br /> San Joaquin County Environmental Health Department (SJC/EHD) has reviewed Work <br /> Plan for the Abandonment of a Groundwater Monitoring Well, Installation of an Interim <br /> Soil Vapor Extraction/Air Sparge Groundwater Treatment System, and Installation of <br /> Groundwater Monitoring Wells—Addendum /I/(Addendum) dated October 20, 2005, <br /> submitted on your behalf by URS Corporation (URS) and has the following comments. <br /> In Addendum III URS proposes to change the construction of the 22 nested soil vapor <br /> extraction/air sparge (SVE/AS) wells, the installation of which was approved by SJC/EHD <br /> in correspondence dated June 23, 2005. The SVE/AS wells are to be constructed as <br /> nested wells in one borehole; the screen intervals of the AS wells will be placed at 36-38 <br /> feet below surface grade (bsg) and those of the SVE wells will be at 15-25 feet bsg, <br /> which means they will be below the groundwater surface. The originally proposed <br /> construction called for the interval between the filter packs of the respective wells to be <br /> filled with bentonite-grout-bentonite. In Addendum III URS requests approval of sealing <br /> the entire seven-foot interval between filter packs with bentonite. SJC/EHD approves this <br /> change in construction with the condition that verification is made that this interval is <br /> completely submerged below groundwater. Bentonite chips desiccate rapidly and are <br /> therefore not an appropriate sealing material in vadose zone soil. <br /> If you have any questions please call Lori Duncan at (209) 468-0337. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> Lori Duncan, Senior REHS Nuel C. Henderson, Jr., PG <br /> LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV <br /> cc: James Barton, PG, CVRWQCB <br /> Vern Elarth, PG, URS <br />