SITE INFORMATION AND CORRESPONDENCE

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ENVIRONMENTAL HEALTH DEPARTMENT SAN JOAQUIN COUNTY 'Con, Unit Supervisors Q. t; Donna K.Heran,R.E.H.S. "- Director 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S. Al Olsen,R.E.H.S. Stockton, California 95202-2705 Mike Huggins,R.E.H.S.,R.D.t. • c P • Program Manager Douglas W.Wilson,R.E.H.S. er FO,Rag Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. Laurie A.Cotulla,R.E.H.S. Program Manager Fax: (209) 464-0138 Robert McClellon,R.E.H.S. Mark Barcellos,R.E.H.S. MS SANDI SARALE APR 15 2m P O BOX 6066 STOCKTON CA 95206 RE: SARALE FARMS Site Code: 0850 16500 CLIFTON COURT RD STOCKTON CA 95206 San Joaquin County Environmental Health Department (EHD) has received and reviewed Additional Site Assessment Work Plan Addendum (AWPA); dated 11 January 2005, prepared by Advanced GeoEnviron mental, Inc. (AGE) for the above-referenced site. The AWPA describes the general status of the site investigation of the unauthorized release of fuel hydrocarbons from the former underground storage tank (UST) system, and proposes a scope of work to complete the site investigation. In the AWPA, AGE proposes to advance five paired cone penetration testing (CPT) borings to a target depth of 100 feet below surface grade (bsg) to better characterize the hydrogeologic setting and to assess the vertical and lateral extent of impacted soil and groundwater. In Additional Site Assessment Work Plan (AWP), dated 07 October 2004, AGE had proposed total depths for CPT borings at 50 feet bsg. AGE increased the proposed total depth due to the presence of 1,2-dichloroethane (1,2-DCA). EHD finds the proposed actions necessary and adequate to continue the site characterization and approves the proposed CPT investigation to delineate the vertical and lateral extent of impacted media and to expand the hydrogeological model; however, EHD approves the originally proposed total depth of investigation of 50 feet bsg rather than the more recently proposed total depth of 100 feet bsg. EHD notes that the 1,2-DCA is presumed to be a dissolved constituent of gasoline, not a free phase dense, nonaqueous phase liquid (DNAPL) that can sink through the soil and water column to greater depths than gasoline components. If during the course of the investigation field evidence indicates contaminants have migrated to and beyond the approved total depth, the borings can be advanced to greater depth based on that field evidence and good professional judgment.