From: KENT Mavis D

Sent: Mon Sep 11 16:46:04 2006

To: 'Sarah Prowell'; 'Chris Kimmel'

Subject: TSA Aquifer Remedial Action Annual Performance Evaluation Report

Importance: Normal

I have reviewed the 4/1/05 to 3/31/06 Annual Performance Evaluation Report and have forwarded comments via email which we have discussed and acted upon. I think that sections 5.4 and 5.5 should be modified to provide some clarification, and the footnote on Table A-1 potentially corrected. This could be done and new pages inserted into the document without having to re-issue the whole document. Otherwise, you have provided the needed clarifications.

There needs to be more detail presented in Sections 5.4 and 5.5 to fully lay out the steps from reduced monitoring, to removal from the monitoring program or pilot shutdown, to recommendations to decommission wells. These two sections don't fully describe all of the criteria that we have been discussing in our emails the past couple of months.

Here, I think, are the sources of my confusion:

·  The second bullet in Chris Kimmel's email of July 11, 2006, says that well decommissioning will be proposed if wells have been removed from the performance monitoring program…if they meet the established criteria in Section 5.4. Section 5.4 only lists two criteria for modifications in the number of wells (without specifically saying removal from the monitoring program; which I think is a good descriptive term) including if a well is far from the plume with no detects since 1997 (this seems to be two criteria lumped together) or the well duplicates other well data. Chris' email says well removal criteria includes non-detect for 2 or more years, not non-detect since 1997.

·  Pilot shutdown may be discussed in an earlier performance report, but I think it would be helpful to discuss this more fully in one of Sections 5.4 or 5.5 particularly since having gone through a pilot shutdown is a criteria for deciding to recommend decommissioning. The concept of well shutdown not adversely affecting hydraulic control should be added to this discussion.

·  The criteria for well decommissioning are tied to the 5 ug/l cleanup level for either pilot shutdown wells or wells removed from the monitoring program. Chris' other July 11 email response indicates that a well would not be proposed for decommissioning if the concentration of TCE is at or above 5 ug/l but the two criteria in Section 5.5 don't say this.

·  There are two sentences in Section 5.5 regarding land development; these should be combined at the end of the section and stated more simply as Chris has suggested that wells can also be evaluated for decommissioning in the face of potential land development. Are the criteria that these wells must meet those for pilot shutdown and/or removal from the monitoring program, or the criteria for considering well decommissioning? That is, be able to be shut down or removed or more or less two years of stable concentrations below the cleanup criterion for TCE have ensued after pilot shutdown or removal from the monitoring program?

I think the shutdown and decommisioning will be easier to decide upon if these two sections are revised to be more complete and clearer. Let me know your thoughts then I can prepare a letter responding to the performance report.

Mavis D. Kent

Cleanup & Emergency Response Section

DEQ Northwest Region - East Side Office

1550 NW Eastman Parkway, Suite 290

Gresham, Oregon 97030

503-667-8414 X55008

503-674-5148 Fax

kent.mavis.d@deq.state.or.us