SITE INFORMATION AND CORRESPONDENCE

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Messrs Trommer and Lon 16 June 2008 Preliminary Five-Year Review Letters Page 2 of 7 Various Sites wells. The EHD is awaiting the groundwater extraction test report to comment on pump and treat; the absorbent appears to be for free product and has not been approved. 2500 Lodi Avenue, W. • CUF recommended site closure consideration. A DPE test was recently conducted on MW-3; a report of findings is anticipated in the near future with a closure report addressing vapor intrusion potential and comparison to Region II ESLs. 345 Yosemite Street, N • CUF recommended site closure considerati n. The EHD does not agree with this. recommendation at this time for the follow ng reasons. The site has two UARs and separate site codes (503414 and 221 ), but have been worked under one CUF Claim (#12858). The western former u iderground storage tank (UST) site is nearly ready for closure consideration, but recent review shows that the vertical extent of impacted groundwater has not been demonstrated. Also, a sand unit that is a potential contaminant migration pathway was not sampled toward the northwest. The EHD will direct that these data be acquired. The EHD also believes some attempt should be made to reduce the contaminant concentrations more rapidly, perhaps some batch groundwater extraction. • The eastern former UST site (case #503414) is not fully delineated laterally or vertically. Additional monitoring wells to complete the lateral and vertical assessment of the eastern UST is required. Following receipt of the report of monitoring well installations, assuming favorable analytical results, and sufficient quarterly monitoring of the new wells, this case may then be ready for closure J consideration. As with the other case on the site, the EHD also believes some attempt should be made to reduce the contaminant concentrations more rapidly, perhaps some batch groundwater extraction. The RP will be directed to evaluate the potential benefit from some remediation for both cases. 15406 Tracy Blvd. • CUF recommended. consideration for site c osure; the EHD does not agree with this recommendation at this time. Vertical delineation of impacted groundwater is not complete; the onsite domestic well, screened between 76 and 96 feet bsg, is approximately 100.feet from impacted monil oring well MW-4. A work plan will be submitted in the near future to advance twD geoprobe borings downgradient of MW-4 for lateral and vertical delineation and to perform a pumping test on MW-4; the EHD, in consultation with the CVRW CB, believes this work should be completed before.closure consideration. 757 Eleventh Street • CUF recommended. evaluation of remedial technologies and potential for vapor intrusion. The EHD. agrees with these recommendations, but notes that there were two UST systems with releases approximately 300 feet apart. The down- gradient and cross gradient extents of the dissolved plume centered on former 5-Year Review Comment Letter 061608.doe