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Spill and GBT Meeting with Oregon DEQ

This document discusses the impacts of the GBT (total dissolved gas) in the controlled spill program. It includes an overview of the original criteria, data collection, biological data, risk assessment, and recommendations for future monitoring. The conclusion emphasizes the importance of managing spill levels based on downstream forebay monitor readings.

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Spill and GBT Meeting with Oregon DEQ

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  1. Spill and GBT Meeting with Oregon DEQ December 2006

  2. GBT Impacts in Controlled Spill Program • Original criteria selected in 1995 based on best available knowledge. • Controlled Spill – managed to TDG of 120% tailrace and 115% forebay. • Data collected over full range TDG due to uncontrolled and over-generation spill. • Biological data suggests original assumptions were appropriate.

  3. Separator Sampling

  4. Fish Sampling

  5. Caudal Fin Bubbles

  6. Summary of signs of GBT (1995-2005)

  7. Updated Risk Assessment • Salmonids • Other species

  8. 2006 Spill Implementation • How did spill in 2006 compare to past years?

  9. Forebay Monitors • Recognized as problem in 2000 BIOP • Location of face of project presents issues for representative monitoring due to localized temperature and biological processes • Reviewed data three time periods without spill

  10. 2001

  11. 2005 Spring

  12. Dissolved Oxygen

  13. Are we asking for additional spill??? • No – based on preliminary analysis

  14. Options for Future Monitoring • Establish criteria of 120% anywhere in river. • This will not increase spill levels over what was anticipated in 1995 or 2000 BIOP. • TDG downstream will dissipate as considered when establishing the criteria in 1995. • Easy to manage and most cost effective option. • Consistent with Biological data. • Consider managing for oxygen gas – remove oxygen from equation. New monitors allow for better estimation. Deleterious effects of oxygen not as much of a concern due to metabolism.

  15. Conclusions • The amount of spill varies from project to project; with a few key projects having the greatest limitation on spill (Lower Monumental, The Dalles, Bonneville and Little Goose) based on the downstream forebay monitor readings. • The reason why the spill was significantly less at some projects is most significantly related to the management of spill to downstream forebay TDG levels. • The use of downstream forebay monitors for measuring dissolved gas relative to spill needs to be addressed. Downstream forebay monitors, as presently configured, are not indicative of the readings in a well-mixed water column due to the local influence of temperature, barometric pressure and biological processes. •  In season management of total dissolved gas can include a criteria for 120% anywhere.

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