SITE INFORMATION AND CORRESPONDENCE

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Chevron/UPRR - 2 - • 16 January 2007 Review - TAOC Tracy Pum otation HHRA Site Conceptual Model - Groundwater Pathways; Item #3, page 3 ...it is understood that the site groundwater will not be used as a source of drinking water ...the locations of the nearest public wells are not provided nor discussion about the potential for public wells contamination due to this site groundwater is provided. A well search was not completed. City of Tracy Municipal Code prohibits the installation, development, and use of shallow groundwater for domestic use (for conditions unrelated to OVP leaks) within the Tracy City limits. A well survey is recommended. Groundwater Pathways; Item #3, paragraph 2, pages 3 and 4 Considering that ...the future construction worker might be exposed to chemicals in ground water through direct contact (dermal), and inhalation of vapors while working in trenches...the future commercial worker might be exposed by inhalation of indoor and ambient air vapors originating from ground water, too..."and "...an addendum (to the HHRH) addressing all potential groundwater pathways should be prepared after on-site groundwater data is collected. Alternatively, Geomatrix may collect soil-gas samples or use the NAPL version of the US EPA Johnson and Ettinger model-based spreadsheet. Geomatrix may collect soil-gas samples for analyses if necessary or use the NAPL version of the Johnson & Ettinger model-based spread sheet to evaluate/determine the potential exposure to inhalation of indoor/ambient air vapors originating from groundwater as suggested by OEHHA. The evaluation could clarify or reduce/eliminate uncertainties associated with potential commercial/industrial worker exposure to petroleum vapors in groundwater as discussed by OEHHA. Future Land Use; Item #4, page 4 Even though the site is currently zoned for medium density residential (MDR)...the risk assessment does not consider on-site residents...and ...HHRA conclusions may be different under a residential land use scenario. The companies may file a land use covenant with the property title documenting the environmental conditions at the site. Or, if in the future the land use was changed to residential, an updated HHRA would be needed to reflect a residential-use scenario. Ambient Air Modeling, Item #8, page 8 ...review of Table 1 demonstrates that indeno(1,2,3-cd)pyrene exceeds its Csar at one sampling point only (soil mound sample GMX-11)... and that ...RWQCB should make a decision about the need of delineation and removal or grading of the soil containing indeno(1,2,3-cd)pyrene as a free product. Consistent with our comments above, removal of certain soil piles may reduce/eliminate potential health risk concerns at those locations.