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ENVIRONMENTAL HEALTHDEPARTMENT <br /> Donna K Henn,R.E.H.S. SAN JOAQUIN COUNTY Unit Supervisors <br /> Director 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S. <br /> A]Olsen,R.E.H.S. Stockton, California -95202-2708 Mike Huggins,R-E.H.S.,R.D.I. <br /> Program Manager Telephone: (209) 468-3420 Douglas W.Wilson,R.E.H.S. <br /> ri <br /> Laue AL Cotulla,R.E.H.S. Margaret Lagorio,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Robert McClellan,R-E.H.S. <br /> Mark Barcellos,R.E.H.S. <br /> DARIN ROUSE SEP 0 3 2003 <br /> EXXOMMBIL REFINING AND SUPPLY COMPANY <br /> PO BOX 4032 <br /> CONCORD CA 94524-4032 <br /> RE: Former Exxon Retail Site 7-3942 SITE CODE: 2231 <br /> 4444 North Pershing Avenue <br /> Stockton, CA <br /> San Joaquin county Environmental Health Department (EHD) is the lead agency providing the <br /> oversight of the investigation and cleanup of releases from underground storage tanks <br /> (UST) within San Joaquin County. EHD has a Contract with California State Water <br /> Resources control Board (SWRCB) to conduct an UST corrective action program. <br /> EHD has completed reviewing the Feasibility Study and Work Plan for well installation <br /> submittal prepared by ETIC on behalf of Eoconmobil and has the following comments: <br /> 1. The deep monitoring well (MK) proposed off site to define the vertical extent <br /> of soil and groundwater contamination in the down gradient flow direction is <br /> approved in concept. Please submit a well permit application, a work Plan <br /> (w?), and an $89.00 fee for EHD review and permit issuance. When the permit <br /> is issued, well installation can begin. <br /> 2. MWS SW-1 and SW-2 are in the area of the unauthorized release on site. They <br /> have well screens from 40-45 feet bgs and have evidenced ground water <br /> contamination approximately 20 feet below the current static water table. <br /> These Mws have been recently added to the sampling schedule and should remain <br /> on a quarterly monitoring and sampling schedule. To define the vertical extent <br /> of contamination in the source area, a deep ground water investigation is <br /> required to define the limits of contamination. <br /> 3. The adsorbed or dissolved contaminant masses for soil or ground water have not <br /> been estimated. When the vertical limits in soil and ground water <br /> contamination have been defined, you are required to calculate and report <br /> these contaminant masses. To date, only remediation system removal mass has <br /> been reported, but the estimated residual =as has not. <br /> 4. Due to the apparently large contaminant mass caused by the unauthorized <br /> release and the high contaminant concentrations. in ground water, EHD cannot <br /> approve passive remediation, or natural attenuation, as the remedial choice <br /> for corrective action at this site. Passive natural attenuation will not <br /> restore groundwater quality in a reasonable amount of time. Therefore, = I <br /> recommends an active remedial technology for corrective action. EHD recomminds <br /> a pilot study be conducted to evaluate low-flow rate ozone sparging at this <br /> site. The study should also evaluate contaminant migration and/or destruction <br /> and any modification of ground water flow direction as a result of the ozone <br /> sparing. <br /> If you have any further questions regarding this matter, please contact Harlin Knoll at <br /> (209) 468-3442. <br /> Donna Heran, HERS, Director <br /> Environmental Health Division <br /> Harlin Knoll, Senior RZHS Nuel 0. Henderson rr "�j Z�� <br /> LOP/Site Mitigation unit IV LOP/Site Mitigati <br /> CC: /CI -James L. L. Barton <br /> VETIC-Ted Moise SE 11 M]",L <br /> ljBank of Stockton-Rick Correia Lf L) <br /> Brooke Burkie <br />