SITE INFORMATION AND CORRESPONDENCE

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Page 1 of 1 Mike Infurna JEH] From: Nuel Henderson [EH] Sent: Thursday, April 29, 2010 11:44 AM To: Mike Infuma [EH] Cc: 'Carrow,John (PSC)'; 'panderson@pscnow.com' Subject: 1717 Center Street Call Mike, John Carrow and Paul Anderson called me to discuss the site status and next steps, they thought you would participate in the discussion, but were not aware you would be in training this morning.They want to progress toward closure addressing our remaining concerns,which I discussed with them.We also discussed the CUF recommendation for site closure consideration.They are awaiting a comment letter on their CPT investigation report and would like the following discussion items noted in the comment letter: 1) As a worse case scenario, the CPT2 and MW-5A data should be considered to demonstrate one plume of impacted groundwater and its mass, inferred lateral extent, migration direction and degradation rate should be evaluated in terms of its potential threat to groundwater, human health, etc. 2) Mass estimates should be updated for sorbed and dissolved COCs and compared to pre-remediation sorbed and dissolved masses to demonstrate effectiveness of remedial effort; 3) Trend analysis of CDCs concentrations since remediation should be revisited to estimate time required to achieve WQOs from the current residual masses; degradation rates inferred from pre-remediation data can be utilized as a check on the rates inferred for the current masses; 4) Groundwater flow direction through time for the depth intervals of interest should be reevaluated to demonstrate whether or not MW-4 is a true down-gradient well and whether or not the data from PH6 is of potential concern; 5) Shallow soil data will be compared to SFBRWQCB's ESLs. 6) Based on my current concepts about the site data,the recently acquired deep groundwater data from CPT3 does not appear to be related to the subject site, and if PSC also believes this to be the case,they should demonstrate that interpretation from the site data and show that an interpretation that it is related to the subject site is cannot be supported by the data. I informed them that the general points that must be addressed to get a concurrence on a site closure request is to demonstrate extent of plume, a stable and declining extent and mass, lack of threat to human health or sensitive receptors, and an estimate of the time required to achieve WQOs.Although I didn't mention it at the time, the requirements of the Tri-Regional Guidelines Appendix A must also be met. If you have other concerns that I omitted discussing with John and Paul, please communicate those concerns to them,and me,ASAP. Nuel ti 4/30/2010