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ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K.Heran,R.E.H.S. Carl Bor man,R.E.H.S. <br /> �- 304 East Weber Avenue, Third Floor g <br /> Director Mike Huggins,R.E.H.S.,R.D.I. <br /> Al OIsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> • c.• �r Program Manager (Telephone: (209) g g 468-3420 Margaret La orio,R.E.H.S. <br /> 9 t1F ORa P <br /> Laurie A.Cotulla,R.E.H.S. Fax: (209)464.01.38 Robert McClellon,R.E.H.S. <br /> Program Manager Mark Barcellos,R.E.H.S. <br /> Mike Wallace Mr. Jeffery Setness B <br /> City of Stockton Redevelopment 2453 Grand Canal, 2 d Fl <br /> 305 North El Dorado, Suite 200 Stockton, CA 95207-8259 <br /> Stockton., CA 95202 <br /> RE: Chase Chevrolet Facility <br /> 423 Madison,Stockton,CA <br /> WORKPLAN:Remedial Action Additional Site Assessment Work Plan <br /> DATED: May ,2003 PREPARED BY:Advanced GeoEnvironmental Inc. <br /> APPROVED ■ with Conditions (see below) <br /> DISAPPROVED <br /> ADDENDUM 0 Submit by: <br /> ADEQUATE AND NECESSARY ELEMENTS OF THE WORKPLAN (H&S <br /> 25299.37,subd.(c)(3).): <br /> 1) Install a ground water extraction system using existing well EW-1. The extracted <br /> groundwater will be treated with a 1,000 pound granulated active carbon (GAC)vessel and <br /> store in a 750-gallon holding tank,and discharge to City of Stockton sewer system under <br /> permit when the contamination concentrations is treated to below acceptable limits. <br /> 2) Install one down-gradient deep monitoring well screened at approximately 50 to 55 feet <br /> below surface grade (bsg) to define the vertical extent of the groundwater contamination. <br /> COMMENTS AND CONDITIONS: <br /> 1) Provide contingency plan to install additional GAC unit(s) if the 1,000-pound GAC vessel is <br /> insufficient in removing the contamination to acceptable levels for disposal to city sewer. <br /> 2) Install the deep down-gradient monitoring well by July 25,2003. Submit all appropriate <br /> permits and fee before scheduling work with E HD. - <br /> REASONS FOR DISAPPROVAL OF THE WORKPLAN (H&S 25299.37,subd.(C)(3).): <br /> 1) Use of a closed-loop air stripper in addition to the GAC for extracted groundwater <br /> treatment is not approved at this time. It is unknown if air stripper is an effective treatment <br /> technology against petroleum hydrocarbons at low concentrations. If AGE wishes to pursue• <br /> the use of air-stripper as pre-treatment before GAC,please provide cost benefit analysis <br /> between air-stripper and GAC versus GAC alone,demonstrate effectiveness of air-stripper <br /> in removing individual contaminants at this site,and any additional cost that may accompany <br /> with the use of the air-stripper. <br /> DATED :J n PJL IT Z06? BY �•�� <br /> Cc: CRWQCB, Central Valley Region—James L.L. Barton <br /> Fax: Advanced GeoEnvironm.ental,Inc.-Paul Dotson <br />