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San Joaquin County �. Environmental Health Department DIRECTOR z 600 East Main Street Donna Heran, REHS Stockton, California 95202-3029 PROGRAM COORDINATORS Robert McClellon,REHS �.. Jeff Carruesco,REHS,RDI Ciq �..•�j�P Website: www.sjgov.org/ehd Kasey Foley, RENS �/FOR Phone: (209)468-3420 Fax: (209) 464-0138 May 27, 2010 Ms. Barbara J. Hyduke Barbara J. Hyduke Trust 3627 Adobe Creek Court Stockton, CA 95219 Subject: Valley Motors LOP Case#: 1166 800 E. Main St. CUF#: 12540 Stockton, CA 95202 Global ID#: T607700430 The San Joaquin County Environmental Health Department (EHD) has reviewed Groundwater Extraction Pilot Test Report (Report) dated February 1, 2010, submitted by Upgradient Environmental Consultants and offers the following comments. The pilot test was approved by the EHD after your consultant concluded that groundwater extraction (GWE) was the most feasible and cost-effective remedial alternative for cleaning up the dissolved petroleum hydrocarbon contamination in the groundwater at this site. Conclusions in the Report stated that although GWE is "somewhat effective" in reducing the gasoline impact to groundwater, it would not be wise to proceed to full-scale remediation because of the threat posed by a potential source of chlorinated hydrocarbons thought to be located to the west (upgradient) of the site. No data was presented to demonstrate that such an upgradient source and plume exist. In addition, the report indicates that the groundwater pump did not remain active for any significant length of time. Conclusions included in the Report suggest that the observed small changes in the contaminant concentrations were positive responses to the very limited intervals that pumping was online and do not reflect any natural variation of concentrations over time and are unaffected by any common sources of measurement error, an inference with which the EHD does not concur. The EHD does not consider the data presented to adequately demonstrate the existence of a dissolved chlorinated hydrocarbon plume unassociated with the site, or that such a plume, if present, would be destabilized by the low pumping rate proposed for this corrective action. At this point, it appears that your options are to: 1. proceed with the GWE and monitor for chlorinated hydrocarbon migration, perhaps with a few additional monitoring wells installed for that purpose; 2. conduct additional assessment, perhaps through grab groundwater sampling; or 3. revise the feasibility study to identify a more cost-effective method by which to remediate the site.