From: KENT Mavis D
Sent: Wed Mar 21 08:27:02 2007
To: 'Sarah Prowell'
Subject: RE: Conversion of TSA EW-4 + EW-5 to Monitor Wells
Importance: Normal
Then if there is a realistic alternative for EW-5 down the road I think we can go ahead with decommisioning EW-4 as an extraction well and put it in the monitoring category, and maintain EW-5 on the pilot shutdown with the expectation that it should come into compliance with the decommissioning criteria eventually. With that I think we can go ahead and let the conveyance lines be decommissioned and continue to watch EW-5.
I think that in this instance there might be more to a consideration of re-activating EW-5 as an extraction well than just two consecutive quarters of MCL exceedance. I haven't fully thought this through but my feeling is that it would have to be paired with an assessment of the overall pumping network and behavior of the plume such that a portion of the plume is migrating beyond its previous limits or there is an area of stagnation that has developed. Perhpas the two consecutive MCL exceedance would trigger a focused evaluation of that area of the plume to determine whether reactivation of EW-5 (along with re-installation of the conveyance lines and pump) would "cure" the problem. I am not sure whether that would strike you as too nebulous but to me the bottom line would be whether there is an issue that has developed and then whether EW-5 could resolve that issue.
I have to attend a meeting at NWR mid morning (I guess you are out of the office then too) then I will be back here all afteroon if you want to discuss.
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: Tuesday, March 20, 2007 7:03 PM
To: KENT Mavis D
Subject: RE: Conversion of TSA EW-4 + EW-5 to Monitor Wells
Mavis, Your comment’s a good one. And the answer is yes, there would be an alternative. It would be to install a replacement EW-5 line for the segment that is to be excavated and demo’d on the Buyer’s property. This replacement line segment would likely be installed under a modification of Cascade’s access agreement(s) with Boyd Coffee, bypassing the North Parcel Buyer’s property altogether, because the retaining wall would be too big a construction obstacle.
So if it was needed, with DEQ’s request, Cascade would approach Boyd Coffee to install a replacement EW-5 conveyance/conduit line segment near the eastern perimeter of the Boyd Coffee property, extending south (parallel to the OPUS Buyer’s property) and then east onto Cascade’s property to tie in with the existing EW-5 line that would be left in place (capped) on Cascade’s property. The electrical control and power lines would need to be repulled and the pump assembly reinstalled.
It might be reasonable to allow more than just two consecutive exceedances of the MCL in EW-5 to prompt this action,….given all that is entailed. Especially given the low extraction rate and mass removal performance of EW-5. But I like your question. It’s on the mark.
Let me know what you think. Thanks. -sp
(FYI, I’ll be out of the office Wed. AM (meeting w/OPUS) and back in around noon, to provide any further clarification. )
From: KENT Mavis D [mailto:KENT.Mavis@deq.state.or.us]
Sent: Tuesday, March 20, 2007 5:51 PM
To: Sarah Prowell
Subject: RE: Conversion of TSA EW-4 + EW-5 to Monitor Wells
Let me ask you this. If we move these two extraction wells to the monitoring well column, and down the road it becomes apparent that we should resume extraction from EW-5, would there be any alternatives for treatment and disposal?
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: Tuesday, March 20, 2007 4:52 PM
To: KENT Mavis D
Subject: Conversion of TSA EW-4 + EW-5 to Monitor Wells
Hello Mavis,
For EW-4, it is clearly and fully compliant with both the TSA extraction well pilot shutdown and decommissioning criteria.
But I jumped the gun on EW-5. It is compliant with the pilot shutdown criteria (TCE not to exceed 5 ug/L on two consecutive sampling events), but has had one quarterly MCL exceedance each year since pilot shutdown,….then declining below the MCL for the remaining 3 quarters (see attached table file). Thus it doesn’t fully meet the numerical criteria for extraction well decommissioning in the June 2006 annual report (as amended Sept. 27, 2006 to incorporate DEQ comments).
The 2006 annual report amended (Sept. 27) extraction well decommissioning criterion is:
“Extraction well decommissioning may be proposed to DEQ if TCE concentrations remain consistently below the MCL in that well for 2-years following pilot shutdown; two consecutive TCE detections at or above the MCL may prompt resumed operation, as described in Section 5.2.1.2. … As a contingency measure, well decommissioning may be evaluated by DEQ on an earlier timeframe should land use development or property uses conflict with one or more wells.”
Because the well conveyance lines do interfere with property development (see figure attached) it’s eligible for DEQ’s decommissioning consideration. Other relevant factors in evaluating its are (1) the very low EW-5 extraction rate (about 5 gpm), (2) the very limited rate of mass removal (give the low extraction rate and low TCE concentrations), (3) that absence of need to operate this well to maintain hydraulic plume control.
If this line of rationale and request for decommissioning the extraction capabilities of the two wells and using them for monitoring makes sense to you, I’ll prepare a formal email request. Thanks. –Sarah
Sarah Prowell, R.G.
Prowell Environmental, Inc.
2216 SW Sunset Blvd.
Portland, OR 97239
Phone: 503/452-0972
Fax: 503/452-1427
Email: sprowell@ix.netcom.com