From: KENT Mavis D

Sent: Thu Mar 26 15:24:50 2009

To: 'Sarah Prowell'

Cc: John Cushing

Subject: Cascade July-Dec 2008 Semiannual Data Report

Importance: Normal

Sarah, I have reviewed the July-Dec 2008 Semiannual Data Report dated February 27, 2009. I have no comments on the content of the report.

The report recommends:

1.  Decommissioning of the on site groundwater treatment system. I assume that in addition to the ongoing bio treatment within and down gradient of Area 1, there is sufficient bio injectant present in groundwater to make operation of the treatment system infeasible with the likelihood of biofouling occurring. So, if groundwater concentrations increased at some point in the future, additional rounds of biotreatment would be conducted. And, if future groundwater extraction and treatment were deemed necessary and feasible, that a portable treatment system could be installed. Therefore, DEQ approves decommissioning of the onsite groundwater treatment system.

2.  Modification of the TGA water quality monitoring schedule. The proposed modifications are to discontinue sampling the influent and effluent of the onsite treatment system (system will be decommissioned), reduce sampling RW-1 and RW-3 from semiannual to annual, and reduce sampling of monitoring wells MW-30i, MW-32s, MW-35s, and MW-42 and 43 from semiannual to annual. I am assuming that the annual sampling would be conducted in August of each year and there would be in effect a semiannual sample for 2009 as follow up to the recent decrease in wells MW-32s and MW-35s of TCE from above the MCL to non detect (below the MCL) in the last round of semiannual sampling, and to the low concentrations of TCE still detected in MW-30i. DEQ agrees to the modifications proposed in Table 4-1.

No other recommendations were identified in this semiannual report.