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Monitoring TDG for Compliance with WA Water Quality Standards

Monitoring TDG for Compliance with WA Water Quality Standards. Susan Braley Washington State Department of Ecology. Monitoring Requirements for Fish Spill.

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Monitoring TDG for Compliance with WA Water Quality Standards

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  1. Monitoring TDG for Compliance with WA Water Quality Standards Susan Braley Washington State Department of Ecology

  2. Monitoring Requirementsfor Fish Spill • TDG must not exceed an average of one hundred fifteen percent as measured in the forebays of the next downstream dams and must not exceed an average of one hundred twenty percent as measured in the tailraces of each dam (these averages are measured as an average of the twelve highestconsecutivehourly readings in any one day, relative to atmospheric pressure).

  3. Intent of averaging consecutive hourly TDG values • 1997 Rule • “12 highest hourly readings” • 2003 Rule Revision • Ecology added “consecutive” to the language. • More biologically relevant because it tracks exposure duration rather than intermittent exposure. • Latest rule revision became effective February, 2008.

  4. Interpreting this change in rule • Ecology memo April 2, 2008 attempted to clarify the application. • Use a rolling average of hourly TDG values • Define “day” as 1am to 12am • Each measure should be averaged with previous 11 hours • Report the highest average for the calendar day

  5. Problems noted with this Interpretation • Grant and Douglas PUDs noted concerns with applying this change • Spills commonly occur during late evening to early morning. • Ecology’s definition of “day” can split data from the critical period. • Can cause “double counting” of exceedances (High TDG values carried over to next calendar day). • Concerns about how this affects compliance (# of violations?)

  6. May 19th highest value May 18th highest value

  7. Agreed upon goals for TDG monitoring • Monitoring should be done from a biological perspective. • Keep “consecutive” • Ecology should clarify how data will be used to assess compliance • What does an “episode” mean? • Episodes vs. hourly exceedance • “Day” must be defined

  8. Next Steps • 2009 TDG spill season reporting • Operators can continue to report data as they have in the past. • Note when “double-counting” may be occurring • Ecology will continue discussions with PUDs on revisions to methodology for measuring TDG • Certainty for future compliance

  9. For Further Information • Contacts • Susan Braley • 360-407-6414 • susan.braley@ecy.wa.gov • Chad Brown • 360-407-6000 • chad.brown@ecy.wa.gov

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