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.
(d) Aquatic life dissolved oxygen (D.O.) criteria. The D.O. criteria are measured in milligrams per liter (mg/L). Table 200 (1)(d) lists the 1-day minimum D.O. for each of the aquatic life use categories.
Table 200 (1)(d) Aquatic Life Dissolved Oxygen Criteria in Fresh Water
|Lowest 1-Day Minimum|
|Char Spawning and Rearing||9.5 mg/L|
|Core Summer Salmonid Habitat||9.5 mg/L|
|Salmonid Spawning, Rearing, and Migration||8.0 mg/L|
|Salmonid Rearing and Migration Only||6.5 mg/L|
|Non-anadromous Interior Redband Trout||8.0 mg/L|
|Indigenous Warm Water Species||6.5 mg/L|
- When a waterbody's D.O. is lower than the criteria in Table 200 (1)(d) (or within 0.2 mg/L of the criteria) and that condition is due to natural conditions, then human actions considered cumulatively may not cause the D.O. of that water body to decrease more than 0.2 mg/L.
- For lakes, human actions considered cumulatively may not decrease the dissolved oxygen concentration more than 0.2 mg/L below natural conditions.
- Concentrations of D.O. are not to fall below the criteria in the table at a probability frequency of more than once every ten years on average.
- D.O. measurements should be taken to represent the dominant aquatic habitat of the monitoring site. This typically means samples should:
- Be taken from well mixed portions of rivers and streams.
- Not be taken from shallow stagnant backwater areas, within isolated thermal refuges, at the surface, or at the water's edge.
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