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DTSC Comments - Monitoring Well Workplan - Neighborhood C&D <br /> August 4, 2008 <br /> Page 2 <br /> SPECIFIC COMMENTS: <br /> 1. Figure 3, Proposed Groundwater Monitoring Well Locations Areas 4 through 6, <br /> Neighborhood C & D: Three monitoring wells (MW) are proposed for in Area 4 and 3 <br /> MWs in Area 5. One MW in each area is proposed along the centerline of the former <br /> pipeline, and two MWs in each area are proposed down gradient of the centerline. <br /> DTSC recommends that at least one down-gradient MW be installed up-gradient of <br /> Areas 4 and 5 and one upgradient of Areas 5 and 6, to identify potential migration <br /> from an off-site source. <br /> 2. Figure 3, Proposed Groundwater Monitoring Well Locations Areas 4 through 6, <br /> Neighborhood C & D: DTSC recommends that a soil gas sample be collected at <br /> 5 feet and 15 feet below ground surface in one of the proposed down gradient wells. <br /> The samples should be analyzed for volatile organic compounds (including <br /> naphthalene). DTSC is concerned that the time between the removal of impacted <br /> soils and the collection of vapor samples as confirmation of source removal, did not <br /> allow sufficient time for vapors to equilibrate in the source area. <br />