SITE INFORMATION AND CORRESPONDENCE

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Messrs Trommer and Lar—m 21 July 2008 Preliminary Five-Year Review Letters Page 2 of 3 Various Sites 4444 Pershing Avenue, N. The CUF recommended that the EHD direct the RP to continue to assess remedial technologies and to implement active remediation to achieve WQ0s in a timely manner. The EHD agrees with this recommendation, but notes that remediation on this site is problematical as a significant mass of sorbed contaminants are in fine-grained soil in the saturated zone. Soil vapor extraction (SVE) was preformed to the limits of the technology; groundwater pump and treat via U.V.B. well extraction, ozone injection and hydrogen peroxide injection has been pilot tested, but yielded unfavorable results. The high arsenic content of groundwater may create a treatment hurdle for extracted groundwater. 632 El Dorado Street, S. The CUF recommended that the EHD consider the site for closure, the EHD agrees that the site appears to be heading toward closure consideration and will be addressing the following issues to achieve that point. Groundwater extraction is still in operation on one well, which will require rebound testing. The potential for vapor intrusion must still be addressed; the EHD anticipates that soil gas samples will be collected for laboratory analysis to obtain data for the evaluation. If the results from these tests are favorable, the EHD believes closure consideration would be in order. 345 Yosemite Street, N. In the 24 June 2008 Preliminary 5-Tear Review Summary Report, the CUF concurred with the EHD that the RP must define the vertical extent of groundwater contamination, further delineate the extent of groundwater contamination toward the northwest and conduct batch extraction to reduce groundwater contamination. The EHD agrees with this recommendation. 15406 Tracy Boulevard The CUF concurs with the EHD directive that the RP define the vertical and down-gradient extents of contamination, and conduct a groundwater-pumping test on MW-4. The EHD concurs with this recommendation. 521 Cherokee Lane, N. The CUF recommended that the EHD direct the RP to assess remedial technologies and implement active remediation to achieve WQ0s in a timely manner. The EHD agrees with this recommendation. A work plan has been approved and permits issued to pilot test SVE and insitu air sparging (IAS). Three additional monitoring wells have been installed down-gradient, offsite, to delineate the lateral extent of impacted groundwater; a report of findings is pending. 850 Milgeo Road The CUF has recommended that the EHD direct the RP to assess remedial techniques that will identify remaining sources of free phase petroleum and recover to the extent feasible. The EHD agrees with this recommendation and 5-Year Review Comment Letter 072108.doc