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0 0 <br /> James L. Tjosvold, P.E. <br /> August 19, 1996 <br /> Page 4 <br /> • Source Area 3, former tar pit and tar sump: The total affected depth has been <br /> revised from 13 to 17 ft bgs. The total volume is now 272 cubic yards. <br /> • Source Area 4, fuel tank, oil tank, gas/oil sump: The total affected depth has <br /> been revised from 40 to 25 ft bgs. The total volume is now 3,516 cubic yards. <br /> The total soil volume recommended for treatment has changed from 9,600 to 10,150 <br /> cubic yards. Justification of the affected depths discussed above is described in the <br /> responses to the RWCQB's specific comments 9 through 13. <br /> Comment: <br /> 2. Section 9 of the FS discusses conclusions and recommendations for soil remedial actions to <br /> be taken for the site. The first paragraph concludes human health risks from current exposure <br /> to the site, as determined in the risk assessment, are minimal. Therefore, Remedial <br /> Alternative 5 is proposed to maintaining these acceptable risks associated with soil through <br /> ground covers and other access restrictions and by reducing contaminant migration to <br /> groundwater. Section 9 fails to address the component of Remedial Alternative 5 that will <br /> maintain current exposure conditions at Site Area I, Area IT, and the Hazelton Avenue <br /> Strip. A Deed restriction for property use, maintenance of ground-cover, controls for future <br /> management of site soils, and site access controls should be discussed in detail for these areas. <br /> Response: <br /> 2. A Deed restriction for property use, maintenance of ground cover, controls for <br /> future management of site soils, and site access controls will be discussed in the <br /> combined soil and groundwater FS for Areas I, II, and the Hazelton Avenue Strip. <br /> Comment: <br /> 3. Section 8.1.2 discusses components of alternative 2 (institutional controls)which includes <br /> groundwater monitoring to track groundwater quality over time. Semiannual groundwater <br /> monitoring, as proposed, may or may not be adequate to track conditions of groundwater. <br /> The groundwater monitoring schedule may be revised upon completion of the groundwater <br /> FS and groundwater Remedial Action Plan (RAP) to adequately track conditions of <br /> groundwater. <br /> Response: <br /> 3. PG&E agrees that the groundwater monitoring schedule may be revised during <br /> completion of the combined soil and groundwater FS and RAP to adequately track <br /> groundwater conditions. The assumption on monitoring frequency used in the <br /> OUFS was made for the purpose of costing this alternative. Our experience is that <br /> after several years of quarterly data, annual or semi-annual monitoring is sufficient <br />