SITE INFORMATION AND CORRESPONDENCE

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i I j Messrs Trommer and LaWn 19 June 2008 Preliminary Five-Year Review Letters Page 2 of 7 Various Sites chromium (CR 16) in a number of the monitoring weals; the CR+6 was not related to the ozone injection of the pilot test. Approval for; ORC has been put on hold pending and evaluation of the effect of ORC injection on aquifer quality. At this time a pilot test for SVE and insitu air sparging and a work plan to install a sentinel well to protect a nearby down-gradient domestic well have been approved. The EHD agrees with the general recommendation to implement active remediation to achieve WQOs in a timely manner. 102 Wilson Way, S. The CUF recommended that the EHD direct the RP to assess alternative groundwater treatment technologies that might achieve WQOs more rapidly; the EHD agrees with this recommendation, but points out that this directive has been issued. The RP has also been under directive to evaluate and reactivate SVE if appropriate; the SVE unit on site has not been utilized since circa 2002. 101 Wilson Way, S. • The CUF recommended that the EHD direct the RP to assess the effectiveness of the current remediation systems and implement other technologies to achieve WQOs in a timely manner. The EHD agrees with this recommendation. A work plan to advance _three soil borings to assess a source area and evaluate SVE effectiveness -has recently been approved by the'l EHD; borings encountering significant soil contamination will be converted to SVE wells and plumbed into the SVE system. 814 Charter Way, E. • The CUF has recommended site. closure consideration. The EHD does agree that this site is close to closure consideration; contaminant concentrations in most monitoring wells have dropped to low or non-detectable concentrations with the exception of monitoring well MW-108. Recent work has provided data to pass the vapor intrusion evaluation and the ESL comparison: Recently grab water samples have been collected to test the consultant's hypothesis that. contaminants have migrated from an adjacent site�(most likely 749 E. Charter Way) to impact MW-8. If the data supports the hypothesis the EHD will direct submittal of a site closure report. 701 Charter Way, E • The CUF agreed with the EHD directive to submit on interim remediation work, plan and continue plume delineation toward the southeast. An interim remediation work plan is in preparation and is expected to be submitted within a week. The EHD agrees with the CUF recommendation. 3931 Newton Road The CUF agreed with the EHD directive to evaluate remedial technologies for the site. 5-Year Review Comment Letter 061908.doc