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)
a. A written petition requesting a variance
			 is submitted to the Department; (3-31-22)
b. The petition includes documentation of
			 site-specific biological studies which demonstrate that no significant fishery
			 impacts will occur as a result of the variance, if granted; and
			 (3-31-22)
c. The requested variance
			 will not result in departure from the three point five (3.5) mg/l instantaneous
			 minimum dissolved oxygen requirements of this section.
			 (3-31-22)