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California'egional Water Quality Con l Board <br /> i1l�w; Central Valley Region <br /> Karl E.Longley,ScD,P.E.,Chair <br /> Linda S.Adams Arnold <br /> Secretaryfor Sacramento Main Office Schwarzenegger <br /> Environmental 11020 Sun Center Drive 4200,Rancho Cordova,California 95670-6114 Governor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> http://www.waterboards.ca.gov/centralval ley <br /> /O <br /> 22 August 2007 c 11 ( 11 <br /> pV, <br /> Gonzales Trucking AUS DD <br /> c/o Ms. Vickie Mello EN 2 9 X00? <br /> 24774 Ullrey Avenue pER�, �A(r <br /> Escalon, CA 95320 E� ZcES H <br /> DOCUMENT REVIEW, TONY GONZALES TRUCKING, 1855 JACKSON AVENUE, <br /> ESCALON, SAN JOAQUIN COUNTY (LUSTIS NO. 390220) <br /> 1 reviewed the 13 July 2007 Fate and Transport Model Using USEPA SESOIL Model (Report) <br /> submitted on your behalf by Ground Zero Analysis, Inc. (GZA) to the Regional Water Quality <br /> Control Board — Central Valley Region (Regional Board). GZA conducted the SESOIL <br /> modeling of existing soil data at the Site (Attached Figure 1) to determine whether the residual <br /> petroleum hydrocarbons remaining after the 1988 removal of the 500 gallon and 10,000 gallon <br /> diesel; and 1,000-gallon gasoline Underground Storage Tanks (USTs) pose a threat to <br /> groundwater. <br /> The Report states the soil contamination occurs between 14 feet and 44 feet below ground <br /> surface (bgs), while depth to groundwater in 2002 was 60 feet bgs. Maximum soil <br /> concentrations in November 2000 at soil boring SB-1 were Total Petroleum Hydrocarbons as <br /> gasoline, 31,000 milligrams per kilogram (mg/kg); benzene, 70 mg/kg; toluene, 900 mg/kg; <br /> ethylbenzene, 800 mg/kg; xylenes, 3,800 mg/kg; and total lead, 38 mg/kg. Site lithology <br /> consists of interbedded clays, silts and sands to 60 feet bgs, the total depth investigated <br /> (Attached Figure 2). <br /> The SESOIL model soils data allows the use of up to four primary soil type layers, each with <br /> four sub soil type layers. This model used all possible layers and sub layers, and provides the <br /> rationale for each choice of soil type. Layer A (surface to 13 feet bgs) was clay; Layer B (13 to <br /> 33 feet bgs) was sandy clay to sandy clay loam; Layer C (33 to 44 feet bgs) was sandy loam; <br /> and Layer D (44 to 60 feet bgs) was silty loam. The intrinsic permeability range is 1.0 E-7 cm2 <br /> (sand) to 1.0 E-11 cm2 (clay). Climatic data, chemical data, and application data are also <br /> inputs into the SESOIL model. Application data uses the impacted soil column area <br /> (144 square feet) and the total depth modeled (60 feet) with the contaminant distribution to <br /> provide the total mass input (283 kilograms of gasoline). The rationale for the mass loading <br /> per layer was included in the Report. The total mass was modeled conservatively as benzene. <br /> zo!3 ? <br /> The SESOIL output files predict contamination will reach groundwater at year 25 (2003) at a <br /> benzene concentration of 0.00005 micrograms per Liter (ug/L), which is less than the lowest <br /> Water Quality Goal for benzene (0.15 ug/L, OEHHA Public Health Goal). SESOIL predicts <br /> that benzene concentrations in groundwater will continue to decline after year 25. The Report <br /> states that at year 22 (2000), grab groundwater sampling and analysis at the Site did not <br /> detect contaminants. <br /> California Environmental Protection Agency <br /> 0*1 Recycled Paper <br />