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Messrs Trommer and Ldrdon `*r 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 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.doc