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ENVIRONMENTAL HEALTH DEPARTMENT PpUIN SAN JOAQUIN COUNTY 2` 2Donna K. Heran, R.E.H.S. Unit Supervisors N Director 304 East Weber Avenue, Third Floor earl Eorgman, R.E.H.S. AI Olsen,. R.E.H.S. Stockton , California 9$202-2708 Mike Huggins, R.E.H.S . , R.D.I. cq C, ",NSP • Program Manager Telephone: (209) 468-3420 Douglas W. Wilson, R.E.H.S . FOR Laurie A. Cotulla, R.E.H.S. Margaret Lagorio, R.E.H.S. Program Manager Fax : (209) 464-0138 Robert McClellon, R.E.H.S. Website: www.sjgov.org/ehd/ Jeff Carruesco, R.EA.S. JAN 0 g 2006 GARY STALLWORTH LEWIS STALLWORTH 602 CALIFORNIA STREET 1107 BURKETTE AVE STOCKTON CA 95202 STOCKTON CA 95205 RE: Stallworth Auto Sales SITE CODE: 2486 602 California Street Stockton CA 95202 San Joaquin County Environmental Health Department (SJC/EHD) has reviewed Additional Site Assessment Work Plan Addendum dated December 28, 2005, submitted on your behalf by Advanced GeoEnvironmental , Inc. (AGE) and has the following comments. The original work plan (dated February 28, 2005) for this phase of work was conditionally approved by SJC/EHD in correspondence dated March 22, 2005 . The conditions were recommendations that a transect of several versus just one offsite geoprobe boring be installed, and that the screen interval for the proposed deep onsite groundwater monitoring wells be limited to five feet in length . In this addendum AGE has included two additional offsite geoprobe borings, stated that they prefer 10-foot rather than 5400t screen intervals for deep monitoring wells, proposed to not complete any soil sampling during the drilling of the boreholes for the deep monitoring wells, and changed the proposed number of deep onsite monitoring wells from two to one for this phase of work. SJC/EHD approves the proposed locations for the additional offsite geoprobe borings . Instead of eliminating the deep onsite well proposed to be set at 200 feet below surface grade (bsg), SJC/EHD directs that the screen interval be changed to cover the sand interval noted on the logs for CPT- 1 , CPT-2 and CPT-3 at approximately 126-130 feet bsg , and in CPT-4 at approximately 128- 137 feet bsg . While the concentrations of contaminants in the grab groundwater sample from this interval were not excessively high, this interval presents a potentially significant migration pathway across the site. The deep well proposed to be screened in the fine-grained sandy silt at approximately 150 feet bsg should also be installed because the concentrations of contaminants in the grab water sample from that interval were excessively high . The screen interval of these wells may be 10 feet if AGE prefers. Determination of the need for additional wells to define the vertical extent of the groundwater contamination in the former tank pit area , and across the site, can be made following receipt of analytical results from these new wells. I