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Messrs Trommer and La, P)n 30 June 2008 Preliminary Five-Year Review Letters Page 2 of 5 Various Sites 1 justifications for these proposals. The EHD will direct rebound testing with evaluation of the sustainability of significant vapor concentrations a test objective; the EHD will also direct a work plan for confirmation borings to evaluate effectiveness of the previous SVE/IAS operation and identify locations where additional SVE wells may be beneficial . The EHD will also direct a vapor intrusion evaluation for the site . 2315 EI Dorado Street, N . • The CUF recommended that the EHD direct the RP to continue to operate the groundwater remediation system and maximize it as necessary to achieve WQOs in a timely manner. The EHD agrees with this recommendation . Dual phase extraction has been employed on the site; a letter will be issued to revaluate the DPE operation and recommend appropriate modifications, if needed , to maximize contaminant mass recovery. 6230 Pacific Avenue • The CUF recommended that the EHD direct the RP to assess an alternative groundwater treatment technology that will achieve WQOs more rapidly and cost effectively; the EHD agrees with this recommendation . A meeting was held with the RP in January 2008 to discuss various proposals to maximize the cost effectiveness of the remediation effort in view of the diminishing CUF monies available for this site. The proposals presented to the EHD were given as options with estimated cost and effect on the depletion date of CUF monies; technical justifications were not provided , nor were any professional recommendations. The EHD has issued a directive to submit a feasibility study if an appropriate technology can be employed , with technical and cost effectiveness evaluations. The EHD also noted the need for additional plume delineation . 517 Fremont Street, E. • The CUF recommended that the EHD direct the RP to assess remedial technologies and implement active remediation to achieve WQOs in a timely manner. The EHD agrees with this recommendation . Remediation wells have recently been installed and a pilot test proposed . The EHD will direct prompt performance of the pilot test. 420 Yosemite Avenue, W. • The CUF has recommended that the RP reduce monitoring frequency and that the EHD direct the RP to add additional remedial technology to achieve WQOs more rapidly, also the CUF noted that the plume was poorly defined toward the northwest. The EHD agrees with these recommendations. By letter dated 26 September 2007, the EHD approved a reduction of sampling frequency for selected wells and directed differentiation of total petroleum hydrocarbons quantified as gasoline (TPHg ) from tetrachloroethylene (PCE) by EPA Method 8260B . A GWE system operated from January 2002 to September 2007; a work plan has been submitted for installation and utilization of two additional GWE wells ; the EHD will review the work plan and comment as appropriate. The EHD will issue a directive to complete the plume delineation toward the northwest and has issued a directive to perform a vapor intrusion evaluation . 5-Year Review Comment Letter 063008.doc