SITE INFORMATION AND CORRESPONDENCE

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Chevron/UPRR - 3 - 12 June 2007 TAOC Tracy Pump Station HT-IRA Regional Water Board response: Several small soil stockpiles including some containing petroleum-affected soil will be distributed across the site prior to final grading and paving. According to the various investigations, separate phase product has not been observed in the soil stockpiles. Additional clarification and/or investigation of the stockpiles is not warranted. 3. Regional Water Board comment: A well survey should be conducted to obtain information of groundwater production wells used for municipal, domestic, agricultural, industrial, and/or other uses on or within 2,000 feet of the property. Geomatrix comments: "A well survey is currently in progress and will be submitted under separate cover." Regional Water Board response: Concur. 1. OEHHA HHRA comment. ..."Geomatrix used silica-gel cleanup of groundwater samples before analysis to eliminate biodegradable products..." Geomatrix comments/clarification: "Silica gel cleanup was only performed on samples analyzed for TPH (EPA Method 8015). The use of silica gel on TPH analyses will not affect the results of the existing risk assessment." And, ..."TPH measurements were not considered constituents of potential concern (COPC) because the current practice in the State of California is to evaluate these mixtures based on the aggregate toxicity of key individual chemicals in the mixture, such as BTEX or PAHs." Regional Water Board response: No comment. 2. OEHHA HHRA comment: Exposure point concentrations. "Geomatrix probably calculated the exposure, risk, and hazard from inhalation of particulates based on the first data set (no explanation was found in the text). This approach assumed no soil disturbance despite the fact that soil disturbance and placement of deeper soil on the surface is expected to occur during construction activities."