SITE INFORMATION AND CORRESPONDENCE

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• • 2. In an effort to meet the District's schedule, conditional approval to proceed with public notification (to be approved in form by DTSC prior to distribution) and implementation of soil gas sampling activities only is hereby granted. DTSC has determined that revisions to the Revised PEA Workplan do not impact the proposed soil gas investigation activities. Sample collection and analysis shall be completed as specified in the PEA Workplan and in compliance with Advisory - Active Soil Gas Investigations (DTSC, January 28, 2003) guidance, as applicable. 3. Human Health Risk Assessment: A section outlining the methods and assumptions that will be used in the HHRA should be included. A conceptual site model is also required in the PEA WP which specifies chemicals of potential concern (COPC), exposure pathways and receptors. SPECIFIC COMMENTS: 1. Page 2, Section 3.0 Background, second paragraph, second sentence: Reference to "Appendix A, Figure 3" should read "Appendix D, Figure 3" or "Appendix A, Figure 5", verify and correct as appropriate. 2. Page 11, Sub-section 3.2.3 Previous Environmental Investigations, third paragraph, first sentence: Provide approximate depth to which areas will be scraped with a 36-inch wide backhoe. 3. Page 11, Sub-section 3.2.3 Previous Environmental Investigations, third paragraph, second sentence: Verify that archeological fieldwork will not be initiated until results of the PEA investigation have been made available and after consultation with DTSC Project Manager and the District's environmental consultant. 4. Page 14, Table 5 Summary of Sample Analysis, Arsenic: DTSC recommends that "As", the standard recognized chemical symbol for arsenic, be used as the "Sample Acronym' versus the specified "Ar" designation. All instances should be changed as appropriate. 5. Page 14, Table 5 Summary of Sample Analysis, Soil Vapor Samples: DTSC recommends that BTEX, MtBE and naphthalene be included in the suite of compounds for soil gas analysis. In addition, DTSC recommend that EPA Method 8260 analysis be used for soil gas sample analysis, consistent with method identified in Table 6 footnote. All instances should be changed as appropriate. 6. Page 14, Table 5 Summary of Sample Analysis, Asbestos: DTSC has determined that asbestos soil samples will not be required for the subject site. However, the District is responsible for complying with federal, state, and local requirements for mitigation, management or removal of asbestos containing materials (ACM), and is therefore advised to take appropriate actions for the existing structure prior to demolition activities. All references to ACM sampling should be changed as appropriate. 7. Page 14, Table 5 Summary of Sample Analysis, Auto Maintenance: DTSC recommends that a PAH soil sample be collected and analyzed by EPA Method 8310