SITE INFORMATION AND CORRESPONDENCE

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fl N Messrs Trommer and La. son 30 June 2008 Preliminary Five-Year Review Letters Page 3 of 5 Various Sites 715 Hunter Street, N. • The CUF recommended that the EHD direct the RP to assess remedial technologies and implement active remediation to achieve WQOs in a timely 'j manner and to delineate impacted groundwater toward the north. The EHD agrees , noting that DPE has been tested , recommended , and a system has been installed and ready for use for several months. The EHD will direct immediate implementation of the remediation system and delineation of the dissolved plume toward the north . 610 Hunter Street, N . • The CUF has recommended that the EHD direct the RP to assess remedial technologies and conduct focused remediation near monitoring well MW-1 to achieve WQOs more rapidly. The EHD agrees with this recommendation; at the recommendation of the RP's consultant, the EHD has directed preparation of a feasibility study, and work plan if determined to be feasible, for ozone injection. The EHD has also directed that the SVE performance and efficiency be evaluated , which may be useful for intermittent operation . 2650 Monte Diablo Avenue • The CUF has recommended closure consideration for this site; the EHD does not agree with this recommendation at this time. Soil gas samples collected as part of a vapor intrusion evaluation exceeded ESLs. Recently, confirmation borings were advanced on the site to assess residual impacted soil and to recollect a soil gas sample ; the results of the investigation have not been submitted to the EHD. If favorable results are obtained the site may be ready for closure consideration . 639 Clay Street, W . • The CUF has concurred with the EHD directive that the ozone injection system should be expanded to achieve WQOs more rapidly. 4511 Pacific Avenue • The CUF has recommended that the EHD direct the RP to shut down the SVE system , conduct confirmation sampling to document adequate remediation , and maximizing the GWE system as necessary to achieve WQOs in a timely manner. The EHD agrees with these recommendations. The SVE system operation has ceased and confirmation soil samples have been collected, analyzed and reported . The GWE system has not been in operation since April 2006 , but the EHD will address this issue . The results of the confirmation sampling showed some deep soil samples exceed the ESLs , however the soil gas, groundwater and most soil sample data were favorable ; the EHD will review these results in more detail and issue directives to address the concerns raised by these results. 2553 Toste Road • The CUF has recommended that the EHD direct the RP to assess the effectiveness of the current groundwater treatment system and maximize the 5-Year Review Comment Letter 063008 .doe