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California- Regional Water Quality Co- `rol Board �'° <br /> Central Valley Region ' <br /> t <br /> Karl E.Longley,ScD,P.E.,Chair y,�'`` <br /> Linda S.Adams Arnold <br /> Secretaryfor Sacramento Main Office <br /> 11020 Sun Center Drive#200.Rancho Cordova;California 95670-6114 Schwovernegger <br /> EnvironmentallPhone(9]6)464-3291 •PAX(916)464- 4 Governor <br /> Protection (� <br /> htip://www.waterboards.ca.gov/central �WF[0 <br /> 13 December 2007 DEC 197 2007 <br /> Gonzales Trucking ENVIRONMENT HEALTH <br /> c/o Ms. Vickie Mello PERMIT/SERVICES <br /> 24774 Ullrey Avenue <br /> Escalon, CA 95320 <br /> DOCUMENT REVIEW, TONY GONZALES TRUCKING, 1855 JACKSON AVENUE, <br /> ESCALON, SAN JOAQUIN COUNTY (LUSTIS NO. 390220) <br /> 1 reviewed the 17 September 2007 Workplan for Groundwater and Soil Gas Investigation <br /> (Workplan) submitted on your behalf by Ground Zero Analysis, Inc. (GZA) in response to my <br /> 22 August 2007 letter. The Workplan proposes advancing one confirmation soil boring to <br /> collect a grab groundwater sample downgradient (based on regional groundwater flow <br /> direction) of the former underground storage tanks and near soil boring S13-4 (enclosed Figure <br /> 3), to validate the results of a July 2007 SESOIL modeling report for soil contaminant leaching, <br /> which predicted no petroleum hydrocarbon impacts to groundwater. Also, three soil vapor <br /> probes will be advanced to approximately 5 feet depth near the residence to assess potential <br /> vapor intrusion threats, using a mobile lab to provide real-time soil vapor probe leak detection <br /> and soil gas data. <br /> The Workplan Figure 2 (enclosed) shows in cross section that the soil contamination occurs <br /> between 14 feet and 44 feet below ground surface (bgs), while depth to groundwater in 2002 <br /> was 60 feet bgs. Maximum soil concentrations (soil boring S13-1) in November 2000 were <br /> Total Petroleum Hydrocarbons as gasoline, 31,000 milligrams per kilogram (mg/kg); benzene, <br /> 70 mg/kg; toluene, 900 mg/kg; ethylbenzene, 800 mg/kg; xylenes, 3,800 mg/kg; and total lead, <br /> 38 mg/kg. Site lithology consisted of interbedded clays, silts and sands to 60 feet bgs, the <br /> total depth investigated. <br /> Comments: <br /> The Workplan is appropriate and necessary to validate the SESOIL modeling prediction that <br /> groundwater has not been impacted and to evaluate threats from soil gas intrusion, and is <br /> approved with the following conditions: <br /> 1) Please include at least three (3) additional soil gas sample locations at the former tank <br /> pits. This additional data would provide results necessary to evaluate threats to future <br /> land use or expansion of the existing residence. Provide a letter revision to the <br /> Workplan by 4 January 2008 consisting of text describing, and a figure showing, a <br /> minimum of three additional soil gas survey locations. <br /> 2) The Workplan states benzene, toluene, ethylbenzene, and xylenes (BTEX) will be <br /> analyzed by USEPA Method 8021, while fuel oxygenates (MtBE, etc.) and lead <br /> scavengers will use USEPA Method 8260. USEPA Method 8260B provides results for <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />