Section 58.01.02.250 - SURFACE WATER QUALITY CRITERIA FOR AQUATIC LIFE USE DESIGNATIONS01.General Criteria. The following criteria apply to all aquatic life use designations. Surface waters are not to vary from the following characteristics due to human activities: a. Hydrogen Ion Concentration (pH) values within the range of six point five (6.5) to nine point zero (9.0);b. The total concentration of dissolved gas not exceeding one hundred and ten percent (110%) of saturation at atmospheric pressure at the point of sample collection;02.Cold Water. Waters designated for cold water aquatic life are not to vary from the following characteristics due to human activities:a. Dissolved Oxygen Concentrations exceeding six (6) mg/l at all times. In lakes and reservoirs this standard does not apply to: i. The bottom twenty percent (20%) of water depth in natural lakes and reservoirs where depths are thirty-five (35) meters or less.ii. The bottom seven (7) meters of water depth in natural lakes and reservoirs where depths are greater than thirty-five (35) meters.iii. Those waters of the hypolimnion in stratified lakes and reservoirs.b. Water temperatures of twenty-two (22) degrees C or less with a maximum daily average of no greater than nineteen (19) degrees C.c. Temperature in lakes shall have no measurable change from natural background conditions. Reservoirs with mean detention times of greater than fifteen (15) days are considered lakes for this purpose.d. Ammonia. The following criteria are not to be exceeded dependent upon the temperature, T (degrees C), and pH of the water body:i. Acute Criterion (Criterion Maximum Concentration (CMC)). The one (1) hour average concentration of total ammonia nitrogen (in mg N/L) is not to exceed, more than once every three (3) years, the value calculated using the following equation: Click here to view image
ii. Chronic Criterion (Criterion Continuous Concentration (CCC)). (1) The thirty (30) day average concentration of total ammonia nitrogen (in mg N/L) is not to exceed, more than once every three (3) years, the value calculated using the following equations: (2) The highest four-day (4) average within the thirty-day (30) period should not exceed two point five (2.5) times the CCC.(3) Because the Department presumes that many waters in the state may have both spring-spawning and fall-spawning species of fish present, early life stages of fish may be present throughout much of the year. Accordingly, the Department will apply the CCC for when fish early life stages are present at all times of the year unless: (a) Time frames during the year are identified when early life stages are unlikely to be present, and(b) The Department is provided all readily available information supporting this finding such as the fish species distributions, spawning periods, nursery periods, and the duration of early life stages found in the water body; and(c) The Department determines early life stages are likely absent.e. Turbidity, below any applicable mixing zone set by the Department, shall not exceed background turbidity by more than fifty (50) NTU instantaneously or more than twenty-five (25) NTU for more than ten (10) consecutive days.f. Salmonid Spawning. The Department shall determine spawning periods on a waterbody specific basis taking into account knowledge of local fisheries biologists, published literature, records of the Idaho Department of Fish and Game, and other appropriate records of spawning and incubation, as further described in the current version of the "Water Body Assessment Guidance" published by the Idaho Department of Environmental Quality. Waters designated for salmonid spawning, in areas used for spawning and during the time spawning and incubation occurs, are not to vary from the following characteristics due to human activities:i. Dissolved Oxygen. (1) Intergravel Dissolved Oxygen. (a) One (1) day minimum of not less than five point zero (5.0) mg/l.(b) Seven (7) day average mean of not less than six point zero (6.0) mg/l.(2) Water-Column Dissolved Oxygen. (a) One (1) day minimum of not less than six point zero (6.0) mg/l or ninety percent (90%) of saturation, whichever is greater.ii. Water temperatures of thirteen (13) degrees C or less with a maximum daily average no greater than nine (9) degrees C.g. Bull Trout Temperature Criteria. Water temperatures for the waters identified under Subsection 250.02.g.i. shall not exceed thirteen degrees Celsius (13C) maximum weekly maximum temperature (MWMT) during June, July and August for juvenile bull trout rearing, and nine degrees Celsius (9C) daily average during September and October for bull trout spawning. For the purposes of measuring these criteria, the values shall be generated from a recording device with a minimum of six (6) evenly spaced measurements in a twenty-four (24) hour period. The MWMT is the mean of daily maximum water temperatures measured over the annual warmest consecutive seven (7) day period occurring during a given year. i. The bull trout temperature criteria shall apply to all tributary waters, not including fifth order main stem rivers, located within areas above fourteen hundred (1400) meters elevation south of the Salmon River basin-Clearwater River basin divide, and above six hundred (600) meters elevation north of the Salmon River basin-Clearwater River basin divide, in the fifty-nine (59) Key Watersheds listed in Table 6, Appendix F of Governor Batt's State of Idaho Bull Trout Conservation Plan, 1996, or as designated under Sections 110 through 160 of this rule. Note: Idaho first adopted bull trout temperature criteria in 1998. These criteria were revised in 2001 (docket 58-0102-0002) and submitted to EPA for approval in 2003. On September 7, 2021, EPA approved the new and revised Idaho bull trout spawning and rearing criteria. However, the 1997 federally promulgated temperature criterion of 10°C for 7-day average maximum daily temperatures from June through September continues to be effective for CWA purposes for waters specified in the federal rule until EPA withdraws the federal rule (40 CFR 131.33). For waters where both the Idaho bull trout spawning and rearing criteria and the 1997 federally promulgated criterion are effective, the more stringent criteria will be the applicable criterion. For more information, go to: https://www.deq.idaho .gov/epa-actions-on-proposed-standards/ |
ii. No thermal discharges will be permitted to the waters described under Subsection 250.02.g.i. unless socially and economically justified as determined by the Department, and then only if the resultant increase in stream temperature is less than five-tenths degrees Celsius (0.5C).h. Kootenai River sturgeon temperature criteria. Water temperatures within the Kootenai River from Bonners Ferry to Shorty's Island, shall not exceed a seven (7) day moving average of fourteen degrees Celsius (14C) based on daily average water temperatures, during May 1 through July 1.03.Seasonal Cold Water. Between the summer solstice and autumn equinox, waters designated for seasonal cold water aquatic life are not to vary from the following characteristics due to human activities. For the period from autumn equinox to summer solstice the cold water criteria will apply: Note: Idaho first adopted seasonal cold water use and temperature criteria in April 2000 and submitted to EPA on April 26, 2000 (docket 16-0102-9704). In March 2001, Idaho revised its temperature criteria for the seasonal cold water use and submitted to EPA on May 29, 2003 (docket 58-0102-0002). Water quality standards adopted and submitted to EPA after May 30, 2000, are not effective for Clean Water Act (CWA) purposes until EPA approves them (see 40 CFR 131.21). This is known as the Alaska Rule. On June 9, 2020, EPA disapproved the Idaho water quality standards addressing seasonal cold water. The following sections submitted to EPA after May 30, 2000, are not effective for CWA purposes: 140.11, Little Camas Creek Reservoir, Unit SW-7, designation of seasonal cold water aquatic life use, and 250.03.b. published in the current Idaho Administrative Code. The following sections were submitted before May 30, 2000, and remain in effect for CWA purposes despite EPA's disapproval: 250.03.b. and c. as published in the 2000 Idaho Administrative Code and 100.01.c. and 250.03.a. published in the current Idaho Administrative Code. For more information, go to http://www.deq.idaho.gov/epa-actions-on-proposed-standards. |
a. Dissolved Oxygen Concentrations exceeding six (6) mg/l at all times. In lakes and reservoirs this standard does not apply to:i. The bottom twenty percent (20%) of water depth in natural lakes and reservoirs where depths are thirty-five (35) meters or less.ii. The bottom seven (7) meters of water depth in natural lakes and reservoirs where depths are greater than thirty-five (35) meters.iii. Those waters of the hypolimnion in stratified lakes and reservoirs.b. Water temperatures of twenty-six (26) degrees C or less as a daily maximum with a daily average of no greater than twenty-three (23) degrees C.c. Temperature in lakes shall have no measurable change from natural background conditions. Reservoirs with mean detention times of greater than fifteen (15) days are considered lakes for this purpose.d. Ammonia. Concentration of ammonia are not to exceed the criteria defined at Subsection 250.02.d.04.Warm Water. Waters designated for warm water aquatic life are not to vary from the following characteristics due to human activities:a. Dissolved oxygen concentrations exceeding five (5) mg/l at all times. In lakes and reservoirs this standard does not apply to: i. The bottom twenty percent (20%) of the water depth in natural lakes and reservoirs where depths are thirty-five (35) meters or less.ii. The bottom seven (7) meters of water depth in natural lakes and reservoirs where depths are greater than thirty-five (35) meters.iii. Those waters of the hypolimnion in stratified lakes and reservoirs.b. Water temperatures of thirty-three (33) degrees C or less with a maximum daily average not greater than twenty-nine (29) degrees C.c. Temperature in lakes shall have no measurable change from natural background conditions. Reservoirs with mean detention times of greater than fifteen (15) days are considered lakes for this purpose.d. Ammonia. The following criteria are to be met dependent upon the temperature, T (degrees C), and pH of the water body: i. Acute Criterion (Criterion Maximum Concentration (CMC)). The one (1) hour average concentration of total ammonia nitrogen (in mg N/L) is not to exceed, more than once every three (3) years, the value calculated using the following equation: Click here to view image
ii. Chronic Criterion (Criterion Continuous Concentration (CCC)). Concentrations of ammonia are not to exceed the criteria defined at Subsection 250.02.d.ii.05.Modified. Water quality criteria for modified aquatic life will be determined on a case-by-case basis reflecting the chemical, physical, and biological levels necessary to attain the existing aquatic life community. These criteria, when determined, will be adopted into these rules.Idaho Admin. Code r. 58.01.02.250