SITE INFORMATION AND CORRESPONDENCE_FILE 1

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San Joaquin County DIRECTOR Donna Her an, RENS Environmental Health Department �0. _�. _• .CO ASSISTANT DIRECTOR ti. 600 East Main Street Laurie Cotulla, REHS :X Stockton , California 95202-3029 PROGRAM COORDINATORS Mike Huggins, REHS, RDI 6 , -� P • Margaret Lagorio, REHS q FoRa� Website: www.sigov, orglehd Robert McClellon, REHS Phone: (209) 468-3420 Jeff Carruesco, REHS, RDI Fax: (209) 464-0138 Kasey Foley, REHS December 23 , 2008 Floyd Barnes 9477 Fountain Valley Stockton, CA 95209 Subject : Barnes Trucking SITE CODE : 2506 1817 Fresno Avenue Stockton, CA 95206 The San Joaquin County Environmental Health Department (SJC/EHD ) has reviewed "Offsite Groundwater Investigation Report" (Report) dated November 12, 2008 , submitted on your behalf by Clearwater Group (Clearwater) and has the following comments . The Report presents the data obtained from an investigation conducted in June 2008 , offsite and down-gradient from your contaminated underground storage tank (UST) site . The investigation consisted of the advancement of two direct push soil borings ; two grab groundwater samples were collected from each boring location and submitted for laboratory analysis. Analytical results from B- 13 , the more northern boring location , were reported as non-detect. Analytical results from B- 11 , the boring located most directly down-gradient from onsite groundwater monitoring well MW-513 were reported at concentrations similar to but slightly lower than those reported in offsite groundwater monitoring well MW-7. In the Report Clearwater recommends the installation of five additional groundwater monitoring wells. The EHD does not agree with this recommendation . Additional wells located on the same north/south transect with MW-7 and MW-8 would be redundant . To be truly down-gradient, any additional wells would need to be installed east of the fire station building . However, the contaminant concentrations in wells MW-7 and MW-8 are stable and declining ; per current Regional Water Quality Control Board guidelines , the concentrations in MW-8 are low enough to provide definition of the plume southeast of MW-5B. In Work Plan and Remedial Action Plan dated May 21 , 2004 Clearwater stated " . . .the contaminant plume is stable and delineated". While the groundwater dewatering activities that occurred in October 2006 may have impacted the concentrations of the contamination temporarily in MW-513 , they do not appear to have moved the core of the plume. As previously noted , concentrations in SBA 1 were lower than those in MW-7. The EHD approves the installation of one additional groundwater monitoring well only, at the location indicated on Figure 6 as MW- 10. This location will confirm the lateral , cross-gradient extent of the contamination reported in MW-5B . Clearwater suggested that if the soil and groundwater in the wells they proposed to install was not impacted (specifically stated as : "below closure levels"), they would convert the new wells to oxygen infusion wells. The EHD does not agree that remediation wells need to be installed in non-impacted areas of the site.