From: KENT Mavis D

Sent: Thu Mar 23 11:21:59 2006

To: 'Sarah Prowell'

Cc: 'John Cushing'; 'Chaput, Kenneth G'; Chris Kimmel

Subject: RE: TSA May Diffusion Bag Test Sampling

Importance: Normal

I agree with your proposed second round of diffusion bag sampling.

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

-----Original Message-----

From: Sarah Prowell [mailto:sprowell@ix.netcom.com]

Sent: Thursday, March 23, 2006 9:59 AM

To: KENT Mavis D

Cc: 'John Cushing'; 'Chaput, Kenneth G'; Chris Kimmel

Subject: RE: TSA May Diffusion Bag Test Sampling

Hello Mavis,

We’ve received the analytical results for TSA diffusion bag testing that was performed in February 2006 and are forwarding those results, for your update (see table attached). While most February test well results were favorable for ongoing diffusion bag sampling, a few locations showed some discrepancy.

The data show that for 12 of the 15 wells tested, there was either:

(1) Close correlation between diffusion bag and conventional sample concentrations, or

(2) Higher TCE concentrations for the diffusion bag sample than the traditional samples.

We view these results as favorable for using diffusion bag sampling methods in the future. However, for BOP-22ds, BOP-60ds, and D-17dg, the February diffusion bag sample results were lower than traditional purge samples by a larger margin than anticipated. We would like to look at test results for these wells again in May, along with sample test results for each of the other 12 wells, for a complete second data set.

We would install bags in the same wells as for February, using the same methodology and depth settings. Consistent with the February round, we would install the bags approximately 2 weeks before sampling. Then in May (concurrent with the TSA quarterly sampling round), we would retrieve and collect the diffusion bag sample, followed immediately by conventional purge sampling, as was done for February. The samples would then be analyzed for VOCs with the quarterly round.

Could you let us know if this second round of test sampling would be acceptable to DEQ? If approved, we’ll then order the sampling bags and coordinate for the Cascade/Boeing installation and sampling schedule.

Thanks for your review.

Sincerely, Sarah Prowell