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Uses and Criteria: Total Dissolved Gas
Part II–Designated Uses and Criteria
Total Dissolved Gas
173-201A-200
Fresh water designated uses and criteria.
Statutory Authority: Chapters 90.48 and 90.54 RCW. 03-14-129 (Order 02-14), §
173-201A-200, filed 7/1/03, effective 8/1/03.
(f) Aquatic life total dissolved gas (TDG) criteria. TDG is measured
in percent saturation. Table 200 (1)(f) lists the maximum TDG criteria for each
of the aquatic life use categories.
Table 200 (1)(f) Aquatic Life Total Dissolved Gas Criteria in Fresh Water
|
Use Category |
Percent Saturation |
| Char Spawning and Rearing |
Total dissolved gas shall not exceed 110 percent of
saturation at any point of sample collection. |
| Core Summer Salmonid Habitat |
Same as above. |
| Salmonid Spawning, Rearing, and Migration |
Same as above. |
| Salmonid Rearing and Migration Only |
Same as above. |
| Non-anadromous Interior Redband Trout |
Same as above. |
| Indigenous Warm Water Species |
Same as above. |
(Note: spawning, rearing and migration read as spawning/rearing on Table
602. The criteria are the same)
- The water quality criteria established in this chapter for TDG shall not
apply when the stream flow exceeds the seven-day, ten-year frequency flood.
- The TDG criteria may be adjusted to aid fish passage over hydroelectric
dams when consistent with a department approved gas abatement plan. This
plan must be accompanied by fisheries management and physical and biological
monitoring plans. The elevated TDG levels are intended to allow increased
fish passage without causing more harm to fish populations than caused by
turbine fish passage. The following special fish passage exemptions for the
Snake and Columbia rivers apply when spilling water at dams is necessary to
aid fish passage:
- 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
highest consecutive hourly readings in any one day, relative to
atmospheric pressure).
- A maximum TDG one hour average of one hundred twenty-five percent
must not be exceeded during spillage for fish passage.
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Last updated October 2007
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