Idaho Administrative Code
Title IDAPA 58 - Environmental Quality, Department of
Rule 58.01.02 - WATER QUALITY STANDARDS
Section 58.01.02.276 - DISSOLVED OXYGEN STANDARDS FOR WATERS DISCHARGED FROM DAMS, RESERVOIRS, AND HYDROELECTRIC FACILITIES
Current through August 31, 2023
Under the terms specified under this section, waters discharged from dams, reservoirs and hydroelectric facilities shall not be subject to the provisions of Subsection 250.02.a. or 250.02.f.i. (3-31-22)
01. Applicability. Subsections 276.02, 276.03 and 276.04 shall apply to all waters below dams, reservoirs, and hydroelectric facilities as far downstream as the point of measurement as defined in Subsection 276.05. Downstream of that point of measurement, all discharges to the waters shall be subject to the provisions of Subsections 250.02.a. or 250.02.f.i. (3-31-22)
02. Dissolved Oxygen Concentrations Below Existing Facilities. As of the effective date of these regulations, and except as noted in Subsections 276.03 and 276.04, waters below dams, reservoirs, and hydroelectric facilities shall contain the following dissolved oxygen concentrations during the time period indicated:
|
mg/l Dissolved Oxygen |
|||
|
Time Period (annually) |
30-day Mean |
7-Day Mean Minimum |
Instantaneous Minimum |
|
June 15 - Oct 15 |
6.0 |
4.7 |
3.5 |
(3-31-22)
03. Dissolved Oxygen Concentrations for Modifications of Existing Facilities or for New Facilities. Modifications of existing facilities or new facilities are subject to the provisions of Subsection 276.02 unless the state has documented the existence of significant fish spawning areas below the facility. If such areas exist, then waters below those facilities shall contain the dissolved oxygen concentrations shown in Subsection 276.02 during the modified time periods indicated for each species below:
|
Fish Species |
Time Period (annually) |
|
Cutthroat trout |
July 1 - Oct 15 |
|
Kokanee and Chinook Salmon |
June 15 - Aug 1 |
|
Bull Trout |
June 15 - Sept 1 |
(3-31-22)
04. Dissolved Oxygen Concentrations Below American Falls Dam. All waters below American Falls Dam shall contain the following dissolved oxygen concentrations during the time period indicated:
|
mg/l Dissolved Oxygen |
|||
|
Time Period (annually) |
30-Day Mean |
7-Day Mean Minimum |
Instantaneous Minimum |
|
May 15 - Oct 15 |
5.5 |
4.7 |
3.5 |
(3-31-22)
05. Point of Measurement. For the purpose of determining compliance with Subsections 276.02, 276.03 and 276.04, the dissolved oxygen shall be measured at a single location in the river downstream from the hydroelectric facilities. Such location shall be as close to the facilities as practical to obtain a representative measurement, but in all cases shall be sufficient distance downstream to allow thorough mixing of reaerated waters, spilled by-pass waters, and other waters that have passed through the facility. (3-31-22)
06. Instantaneous Minimum. Any measurement of dissolved oxygen below the applicable instantaneous minimum will be considered a violation unless that measurement is followed by two (2) consecutive measurements at or above the instantaneous minimum and taken within twenty (20) minutes of the initial measurement (at ten (10) minute intervals). (3-31-22)
07. Procedures and Conditions for Variances. The Board may grant a variance, on an individual basis, to the dissolved oxygen standards, the applicable dates of compliance, or both, as listed in Subsections 276.02, 276.03, or 276.04 only if: (3-31-22)
