Laserfiche WebLink
Lee Higgins -2- 16 February 2011 I <br /> i <br /> Chevron, Tracy Byron Road <br /> • Area 4 - analytical results for samples from boring SB-43, drilled south of prior borings, , <br /> were ND for TPH as crude oil (TPHc); benzene at concentrations 0.003 and 0.0007 <br /> milligrams per kilogram (mg/kg) in soil respectively, at depths of 6 and 19 feet below <br /> ground surface (bgs), do not exceed environmental screening levels. Analysis for the <br /> SB-43 groundwater sample was ND for TPH as diesel (TPHd) and benzene, toluene, <br /> ethylbenzene, and xylenes (BTEX) compounds. Soil and groundwater has been I <br /> adequately delineated and additional characterization is not needed. <br /> • Area 7 - the analytical results for samples from boring SB-45 located south and <br /> upgradient of this area, reported TPHc at 4.5 mg/kg for a sample from a depth of six <br /> feet bgs and ND for the sample from a depth of 17 feet bgs. Analytical results for all <br /> other TPH compounds in soil were ND. Analysis for the groundwater sample was ND I <br /> for TPHd and the BTEX compounds. Soil and groundwater has been adequately <br /> delineated and additional characterization is not needed. <br /> • The twelve areas of crude oil affected soil identified at the Site have been delineated , <br /> with the vertical extent defined at depths of approximately 20 to 25 feet bgs. Additional <br /> characterization is not needed. I <br /> • The lateral and vertical extent of crude oil affected groundwater has been delineated <br /> and additional characterization is not needed. <br /> • A human health screening evaluation is recommended. <br /> Based on our review, Central Valley Water Board staff has the following comments: I <br /> • The lateral and vertical extent of crude oil affected soil and groundwater has been I <br /> adequately delineated and additional characterization is not needed. <br /> • A human health screening evaluation may be completed for the project. The potential <br /> risk for the TPH crude oil compounds associated with each affected area should be <br /> I addressed separately. A risk screening determination should be completed for each of <br /> the affected areas. <br /> By 1 June 2011, please submit the human health screening evaluation for the project Site. <br /> If you have any questions or comments, please contact Dean Hubbard at (559) 445-5179. I <br /> i� <br /> SHELTON R. GRAY C. DEAN HUBBARD <br /> Senior Engineering Geologist Engineering Geologist <br /> P.G. No. 6357 <br /> cc: Michael Infurna, San Joaquin County EHD, Stockton <br /> Michael Hurd, SAIC, Oakland I <br />