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San Joaquin County <br /> a u i <br /> DIRECTOR <br /> Environmental <br /> Environmental Health Department Donna Heran,REHS <br /> 'O� 600 East Main Street <br /> 2 y� PROGRAM COORDINATORS <br /> Stockton, California 95202-3029 RobertMcClellon,REHS <br /> _ Jeff Carruesco,REHS,RDI <br /> Kasey Foley, REHS <br /> r..�,rP • Website: wwwsjgov.org/ehd <br /> j 9�iFOR� Phone: (209) 468-3420 <br /> 1 Fax: (209)464-0138 l <br /> April 20, 2010 <br /> Mr. Terry Tarditi <br /> 11396 N. Hwy 99 Frontage Rd. <br /> Lodi, CA 95240 <br /> Subject: T & T Trucking, Inc. LOP Case #: 390882 <br /> 11396 N. Hwy 99 Frontage Rd. APN: 059-260-10 <br /> { Lodi, CA 95240 Global ID#: T06077708 <br /> f <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Quarterly <br /> Report — Fourth Quarter 2009 and Geotracker groundwater sample data submitted by your <br /> consultant, Advanced GeoEnvironmental Inc., and has the following comment. <br /> Recommendations included in the report, stated that quarterly monitoring .and sampling of <br /> monitoring well MW-1 should continue, :MW-1 should temporarily be hooked up to the existing <br /> soil vapor extraction system still active at the site, and that submittal of the required work plan <br /> to install additional monitoring wells should be delayed until conditions at the site warrant the <br /> need. <br /> F <br /> Currently 'MW-1 is the only,one of four monitoring wells that has a deeper screened interval, 70 <br /> feet to 90 feet below grade ('bgs). The depth to first groundwater at the site has steadily <br /> declined since MW-2 through MW-4 (screened 60' to 80' bgs) were installed in 1998. Until just <br /> recently, only MW-1 has contained enough groundwater to be sampled since June 2008. <br /> Six groundwater sampling events have been conducted for MWA and one groundwater <br /> sampling,event was conducted for MW-2 through MW-4 on March 23, 2010. Groundwater <br /> samples from all the monitoring wells and the domestic (drinking) water well for this event were <br /> non-detect for all dissolved petroleum hydrocarbon concentrations. .Based on this trend, your <br /> consultant has determined that the contaminant core area of the groundwater plume has been <br /> 1 significantly remediated and that temporarily extracting residual soil vapor from MWA area <br /> could help reduce the concentrations of the residual contaminant mass in the vadose <br /> (unsaturated) soil. The EHD concurs with the recommendation and considers the proposal as <br /> adequate and necessary [H&S 25296.10(c)(3)]. - <br /> The recommendation to delay the submittal of the work plan for additional monitoring wells is <br /> approved: As an alternative, the EHD will require.a work plan for confirmation .soil sample <br /> collection and soil gas sample collection for the soil vapor intrusion health risk assessment <br /> j required for site closure consideration. <br /> Your consultant is to determine if soil vapor concentrations extracted from MWA's new hook up <br /> to the soil vapor extraction system are significant enough to warrant additional remediation. If <br /> the soil vapor system is to remain online to treat the vapor, then the work plan for confirmation <br /> soil sample collection and soil gas sample collection may be delayed. <br />