From: KENT Mavis D
Sent: Tue Dec 18 12:44:38 2007
To: 'Sarah Prowell'
Cc: Chris Kimmel ; CKoltermann258@comcast.net
Subject: RE: Proposed TSA Monitoring and Operational Modifications
Importance: Normal
I have reviewed the proposed monitoring and operational modifications presented in the email below. The following are my responses:
1. Upper TSA add BOP-21(ds) to annual sampling/semiannual water level monitoring: agreed.
2. Upper TSA: previously agreed to diffusion bag sampling in wells BOP-22(ds) and EW-22(ds), and well integrity evaluation for BOP-22(ds).
3. Lower TSA discontinue monitoring D-16(dg), D-18(dg), RPW-1(dg), RPW-2(dg) and EMC-2(dg): RPW-2(dg) is not non-detect as the email below states. I agree with discontinue monitoring of all wells except for RPW-2(dg) since it is within a linear area of detectable concentrations even though it is below the MCL.
4. Lower TSA continue monitoring EMC-2 and D-16(dg) in conjunction with PWB pumping events per the PWB contingency pumping plan.
Note: DEQ and PWB met last week to discuss general wellfield issues and sites. One item noted by PWB is that future pumping years will be similar to 2007 where pumping will begin at a lower level sooner in the year and pumping may continue longer. This is related to work they are doing to release Bull Run water for protection of fish in streams. This may mean that the level of monitoring for pumping events will increase with the anticipated future length of pumping events.
5. Lower TSA discontinue monitoring MW-16(dg): agreed.
6. Lower TSA pilot shut down extraction wells EW-11 and EW-12: agreed but will the monitoring remain quarterly?
7. Lower TSA pulse pump EW-18: agreed, but the map should have a new category for every two months monitoring for wells EW-18 and MW-14R(ds), which are now marked quarterly and annually, respectively.
Please revise Figure 2, and provide a new copy of the figure with a cover sheet detailing the final agreed upon modifications so that I can put a copy of the final modifications in the file.
Let me know if you want to discuss any of my responses. I am in the office today and tomorrow, then out until 12/26.
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: Wednesday, December 12, 2007 5:33 PM
To: KENT Mavis D
Cc: Chris Kimmel ; CKoltermann258@comcast.net
Subject: Proposed TSA Monitoring and Operational Modifications
Mavis,
We would like to propose the following TSA remedy operational and monitoring modifications, for your review. The proposed actions are also shown in Figures 1 and 2 (attached), along with the August 2007 TCE concentration contours, for reference. Chris Koltermann, Pegasus Geoscience, performed groundwater particle track modeling for our use in evaluating the proposed operational changes, so we are forwarding those results as well (Figures 3 and 4, attached). Modeling results show particle tracks in the Lower TSA with and without proposed operational changes.
For the Upper TSA, we propose to add monitoring well BOP-21(ds) to the routine TSA remedy annual sampling and semiannual water level monitoring schedule. This well was voluntarily sampled in August 2007 and is shown in Figure 1, attached. It will provide delineation of the eastern perimeter of the Upper TSA plume and will support groundwater elevation contouring.
Per your prior email request, we are also summarizing the previously approved actions of EW-22 temporary shutdown and vertical profile diffusion bag sampling in Upper TSA wells BOP-22(ds) and EW-22(ds)this month. EW-22 has been shut down and the diffusion bags have been deployed for December sample collection, with resumed EW-22 operation scheduled for late December.
An evaluation of the BOP-22(ds)well integrity is also being performed by Landau, per Chris Kimmel’s December 5 email to you. This work will assist with the source evaluation of TCE detections in BOP-22(ds).
For the Lower TSA, the August 2007 TCE data show significant plume shrinkage in the area of new Lower TSA extraction well EW-23. The plume has retracted further south, and now reflects a relatively narrow east-west configuration. TCE concentrations declined in most of the Lower TSA wells in August 2007, compared with the August 2006-February 2007 results contoured in the annual report.
As a result, we propose to discontinue remedy monitoring of wells D‑16(dg), D‑18(dg), RPW-1(dg), RPW-2(dg), and EMC-2(dg), which are located far north of the retracting Lower TSA plume. These wells are non-detectable for TCE and duplicate “sentinel” monitoring wells BOP‑22(dg), BOP-43(dg), BOP-20(dg), BOP-44(dg), and PWB-1(lst), which will remain on the monitoring schedule. EMC-2 and D-16(dg) will continue to be monitored solely for PWB pumping events, as outlined in the 2007 Monitoring and Contingency Plan for PWB Pumping Events (June 12, 2007; Appendix A of the 2007 TSA Annual Report).
Also, we propose to discontinue monitoring in well MW-16(dg)(formerly EW-4), since this well is duplicative of nearby wells MW-25(dg) and EW‑5(MW-24(dg)). TCE concentrations have remained consistently below the MCL in this well since November 2002.
In response to ongoing plume shrinkage to the east, we also propose to pilot shut down Lower TSA extraction well EW-11. As shown by groundwater particle track modeling (Figures 3 and 4), EW-15 extraction is drawing the plume inward, while EW-11 pumping shows only limited hydraulic affect. EW-11 is now located outside the plume, with TCE concentrations remaining below the MCL since February 2007.
EW-12 is also proposed for pilot shutdown, to minimize hydraulic interference with EW-1 and EW-23 pumping. Groundwater modeling results show this location is no longer needed for plume capture and extraction removal, given EW-23’s operation (Figures 3 and 4). TCE was detected at 5.5 micrograms/liter in August 2007, near the MCL.
TCE concentrations declined to 23 micrograms/liter in Lower TSA well MW-14R(ds) in August 2007. Groundwater modeling shows this area is captured and remediated primarily by EW-2 and EW-14 pumping, with only limited remediation by EW-18. However, to seek potential restoration improvement in the vicinity of MW-14R(ds), we propose to pulse pump EW‑18 on two-months-off, two-months-on cycles. A sample will be collected from MW-14R(ds) and from EW-18 before the end of each two-month operational cycle to evaluate TCE concentration changes. Higher TCE concentrations during pump off cycles and lower concentrations during pump on cycles may indicate that residual TCE is present in areas that remain unsaturated during continual remedy pumping. In this case, resumed on-cycle operation is designed to remove the TCE.
We seek your approval to implement the above monitoring and operational modifications to assist with Upper TSA plume characterization and ongoing Lower TSA plume shrinkage.
Sincerely, -Sarah
(p.s. I will mail full size copies of the 11 x 17 figures to you.)
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