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Californi,- 'Ptegional Water Quality Cor*rol Board <br /> Central Valley Region <br /> Karl E.Longley,ScD,P.E.,Chair ' <br /> Linda S.Adams OfficeArnold <br /> Sacramento Main Oce <br /> Secretaryfor Schwarzenegger <br /> Environments! 11020 Sun Center Drive 4200,Rancho Cordova,California 9567461 14 Governor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> http://www.waterboards.cca.gov/centralvalley II <br /> 22 April 2008 ltl7Ls��ll���l <br /> Gonzales Trucking APR 2 3 2008 <br /> c/o Ms. Vickie Mello ElVV!RWPM11•s IC. KEALTH <br /> 24774 Ullrey Avenue PEJ91,417;'S I:,V1;E, <br /> Escalon, CA 95320 <br /> DOCUMENT REVIEW, TONY GONZALES TRUCKING, 1855 JACKSON AVENUE, <br /> ESCALON, SAN JOAQUIN COUNTY(LUSTIS NO. 390220) <br /> I reviewed the 16 April 2008 Groundwater Quality Confirmation and Soil Gas Investigation <br /> (Report) submitted on your behalf by Ground Zero Analysis, Inc. (GZA). The Report describes <br /> the advancement of one boring (enclosed Figure 2) to collect a grab groundwater sample <br /> downgradient (based on regional groundwater flow direction) of the former underground <br /> storage tanks (USTs). The purpose of the confirmation sampling was to validate the results of <br /> a July 2007 soil contaminant leaching SESOIL modeling report, which predicted that there <br /> would be no detectable petroleum hydrocarbon impacts to groundwater. Also, six soil vapor <br /> probes were advanced to approximately 5 feet depth near the USTs and the residence to <br /> assess potential vapor intrusion threats. Vapor samples were analyzed at the site, using a <br /> mobile lab to provide real-time soil vapor probe leak detection and soil gas data. <br /> The Report states that no petroleum hydrocarbons were detected in the SB-4 grab <br /> groundwater sample (dissolved lead was present at 2.2 micrograms per Liter, or ug/L) <br /> collected on 15 January 2008; therefore, the SESOIL model was validated. <br /> On 29 February 2008, the soil gas samples were analyzed at the site by TEG Northern <br /> California. Regional Board staff were present during a portion of the sampling event. <br /> Vapor leaks were not detected in the sampling equipment. Maximum soil gas concentrations <br /> Were-benzene, 0:D50-ug/L; toluene, 0.43-uglL;"and xyienes, 0.32 ug/L. The-benzene results <br /> exceeded the TIER 1 screening levels (California Human Health Screening Levels and San <br /> Francisco Bay Regional Board Environmental Screening Levels). GZA then conducted a <br /> TIER 2 Risk Assessment for benzene, using a Johnson and Ettinger (J&E) Model. The Report <br /> states the J&E Model benzene risk results were as follows: <br /> • <10-7 for cancer risk (10-6 is typically considered acceptable), <br /> • the maximum individual non-cancer hazard risk (hazard quotient) of 2.8x104, and <br /> • a combined hazard quotient of <10-2 (<1 is typically considered acceptable). <br /> The Report recommends site closure. <br /> California Environmental Protection Agency <br /> 01 Recycled Paper <br />