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Mr.Thomas Bouhs .2- 16 March 2005 Ms.Kitty Walker proposed soil vapor monitoring points with an identifier that has not already been used for sample identification. 4. We do not concur with the monitoring schedule provided on Page 8 of the Work Plan. The scheduled monitoring does not propose sampling until six months after the startup of the SVE system and proposes to eliminate a sampling point after one round of non- detectable results. This is not sufficient. Increased monitoring is needed for the first three months of operation. After the initial rounds of sampling from the soil vapor monitoring points, the L&M OYI may propose performance based monitoring or a set time schedule. 5. The Work Plan needs to include monitoring for methane and polynuclear aromatic hydrocarbons. _ G. The L&M OU needs to provide a discussion of the.proposed teak test during sample collection, which is mentioned on page 8. 7, The locations of the five proposed soil vapor monitoring points are not sufficient to determine the radius of influence for the SVE system. At least one soil vapor monitoring point is needed to the west of the furthest SVE well to determine lateral radius of influence. A soil vapor monitoring point also is needed south of the screened portion of "ASVE•6." Furthermore,all of the monitoring points are proposed to a total depth of five feet below ground surface. Based on the depth of the SVE wells,about nine feet below ground surface, the L&M OU needs at least one location with multiple depth monitoring points to evaluate the effectiveness of the system at capturing vapors at and below the depth of the SVE well_ 8. Proposed SV-1 appears to be lncated to evaluate the influence from SVE-1,which is not consistent with the remaining four proposed soil vapor monitoring points,which are evaluating the"ASVE"wells, The L&M OU needs to include a discussion of each of the proposed soil vapor monitoring points with the rationale for their locations. 9. As shown on Figure 3 of the Work Plan,there is a large area between the dual phase extraction system west to the screened areas of ASVE-3 and ASVE-4. The L&M OU needs to discuss how it wi it determine the effects of the SVE system in this area. 10. Regional Board staff concurs with moving proposed soil vapor monitoring points under the apartment buildings,as requested in DTSC's attached memorandum, to accommodate data needs for the completion of a human health risk assessment. 11. Regional Board staff does not concur with drilling soil vapor monitoring point borings deeper than the proposed total depth of the proposed soil vapor monitoring point to collect additional data for the human health risk assessment, as commented on in the attached DTSC memorandum. For the data needed from deeper depths,the L&M OU