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1
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2
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- 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.
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3
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4
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5
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6
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7
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8
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9
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- How did spill in 2006 compare to past years?
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10
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11
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12
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- 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
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13
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14
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15
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16
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17
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- Are we asking for additional spill???
- No – based on preliminary analysis
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18
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19
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- 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.
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20
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- 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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