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Project No. 014-13157 Page No. 2 composite sample S26, S27, S28, S29. Although the concentrations of arsenic and cobalt exceeded the ESLs and USEPA RSLs, the concentrations are within background levels' for naturally occurring arsenic and cobalt (28 mg/kg and 22 mg/kg, respectively) in soil in California. Formaldehyde does not appear to be present at the site over a large area as evidenced by the fact that only two (2) samples (B1 at 10 feet bgs and composite sample S26, S27, S28, and S29) contained concentrations of formaldehyde above the MDL of 0.60 mg/kg. Formaldehyde is not usually present in soil because it volatilizes upon contact with soil. According to the Formaldehyde Counci12, Formaldehyde does not accumulate in the environment either, because it is broken down within a few hours by sunlight or by bacteria present in soil or water. Based on the low concentrations detected in soil and the fact that the concentrations do not exceed the established regulatory screening level (USEPA RSL), it does not appear that formaldehyde poses a significant risk to the environment in the areas sampled. Elevated concentrations of TPH-d and TPH-mo appeared to be localized in the soil/debris mounds and former wood and metal debris area along the west central portion of the subject site. The only composite sample (S26, S27, S28, and S29) concentrations that exceeded the ESLs for TPH-d and TPH-mo were located near the western property line (see Figure 2). Although TPH-d and TPH-mo were detected in discrete soil sample S-29A, the concentrations were well below those of the soil sample that composed the composite sample S26, S27, S28. Thus, it appears that the elevated concentrations of TPH-d and TPH-mo were localized in the area of composite sample S26, S27, S28. Krazan recommended that additional soil samples be completed in this area to determine the vertical extent of TPH-d and TPH-mo impacted soil. However, the client stated that they did not want to conduct additional soil sampling, but instead indicated their desire to move forward with a limited excavation remedial approach in the area of composite sample S26, S27, S28. Client-Directed Scope On January 17, 2014, the client requested that Krazan prepare a workplan to address the hydrocarbon- impacted soil. PROPOSED LIMITED EXCAVATION ACTIVITIES The objective of this project is to conduct limited excavation activities that result in removal of the hydrocarbon-impacted soil in the area of previous composite sample S26, S27, S28. ' Diamond, David, et. Al. 2009, Analysis of Background Distribution of Metals in Soil at Lawrence Berkeley National Laboratory, June 2002, Revised April 2009. 2 Formaldehyde Council, Formaldehyde: Facts and Background Information, November 2007, http:/ / formaldehydefacts.ore_base/pdf/ fact_sheets/11_01_07-FormadehydeFactsandBackgroundInformation.pdf KRAZAN & ASSOCIATES, INC. With Offices Serving the Western United States 014-13157 2014-3-28 WP for Excavation_Wilson Way Stockton FINAL