Site-Specific Surface Water Quality Criteria

01. Procedures for Establishing Site-specific Water Quality Criteria. The water quality criteria adopted in these standards may not always reflect the toxicity of a pollutant in a specific water body. These criteria also represent a limited number of the natural and human-made chemicals that exist in the environment which may pose a threat to designated or existing beneficial uses. Thus, it may be possible in some water bodies to develop new water quality criteria or modify existing criteria through site-specific analyses which will effectively protect designated and existing beneficial uses. (3-31-22) a. The following are acceptable conditions for developing site-specific criteria: (3-31-22) i. Resident species of a water body are more or less sensitive than those species used to develop a water quality criterion. (3-31-22) (1) Natural adaptive processes have enabled a viable, balanced aquatic community to exist in waters where natural background levels of a pollutant exceed the water quality criterion (i.e., resident species have evolved a greater resistance to higher concentrations of a pollutant). (3-31-22) (2) The composition of aquatic species in a water body is different from those used to derive a water quality criterion (i.e., more or less sensitive species to a pollutant are present or representative of a water body than have been used to derive a criterion). (3-31-22) ii. Biological availability and/or toxicity of a pollutant may be altered due to differences between the physicochemical characteristics of the water in a water body and the laboratory water used in developing a water quality criterion (e.g., alkalinity, hardness, pH, salinity, total organic carbon, suspended solids, turbidity, natural complexing, fate and transport water, or temperature). (3-31-22) iii. The affect of seasonality on the physicochemical characteristics of a water body and subsequent effects on biological availability and/or toxicity of a pollutant may justify seasonally dependent site-specific criteria. (3-31-22) iv. Water quality criteria may be derived to protect and maintain existing ambient water quality. (3-31-22) v. Other factors or combinations of factors that upon review of the Department may warrant modifications to the criteria. (3-31-22) b. Any person may develop site-specific criteria in accordance with these rules. To insure that the approach to be used in developing site-specific criteria is scientifically valid, the Department shall be involved early in the planning of any site-specific analyses so that an agreement can be reached concerning the availability of existing data, additional data needs, methods to be used in generating new data, testing procedures to be used, schedules to be followed and quality control and assurance provisions to be used. (3-31-22) c. Site-specific criteria shall not impair designated or existing beneficial uses year-round (or seasonally for seasonal dependent criteria) and shall prevent acute and chronic toxicity outside of approved mixing zones. If site-specific criteria are seasonally dependent, the period when the criteria apply shall be clearly identified. (3-31-22) d. Site-specific criteria, if appropriate, shall include both chronic and acute concentrations to more accurately reflect the different tolerances of resident species to the inherent variability between concentrations and IDAHO ADMINISTRATIVE CODE IDAPA 58.01.02 Department of Environmental Quality Water Quality Standards Section 275 Page 168 toxicological characteristics of a pollutant. (3-31-22) e. Site-specific criteria shall be clearly identified as maximum (not to be exceeded) or average values. If a criterion represents an average value, the averaging period shall be specified. The conditions, if any, when the criteria apply shall be clearly stated (e.g., specific levels of hardness, pH, water temperature, or bioavailability). Specific sampling requirements (location, frequency, etc.), if any, shall also be specified. (3-31-22) f. A site may be limited to the specific area affected by a point or nonpoint source of pollution or, if appropriate, an expanded geographical area (e.g., ecoregion, river basin, sub-basin, etc.). For a number of different water bodies to be designated as one site, their respective aquatic communities cannot vary substantially in sensitivity to a pollutant. Site boundaries shall be geographically defined. (3-31-22) g. Proposed site-specific water quality criteria must be approved by the Board in accordance with the Idaho Administrative Procedure Act. The Department of Environmental Quality shall determine whether to approve a request for site-specific criteria in accordance with this section and within twenty-eight (28) days after receipt of the request, and will introduce acceptable site-specific criteria for rule-making. (3-31-22) h. The following are acceptable procedures for developing site-specific criteria for aquatic life protection. (3-31-22) i. Site-specific analyses for the development of new water quality criteria shall be conducted in a manner which is scientifically justifiable and consistent with the assumptions and rationale in “Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses,” EPA 1985. This document is available for review at the Idaho Department of Environmental Quality or may be obtained from EPA or the U.S. Government Printing Office. (3-31-22) ii. Site-specific analyses for the modification of existing water quality criteria shall be conducted in accordance with one of the following procedures, as described in the “Water Quality Standards Handbook,” EPA 1983. This document is available for review at the Idaho Department of Environmental Quality or may be obtained from EPA or the U.S. Government Printing Office. (3-31-22) (1) Recalculation Procedure. This procedure is used to account for differences in sensitivity to a pollutant between resident species and those species used in deriving the criterion. Bioassays in laboratory water may be required for untested resident species. (3-31-22) (2) Indicator Species Procedure. This procedure is used to account for differences in biological availability and/or toxicity of a chemical between the physicochemical characteristics of the water in a water body and the laboratory water used in developing criteria. Bioassays in site water are required using resident species or acceptable nonresident species. (3-31-22) (3) Resident Species Procedure. This procedure is used to account for differences in both resident species sensitivity and biological availability and/or toxicity of a pollutant. Bioassays in site water using resident species are required. (3-31-22) (4) Water effects ratios as defined by EPA guidance documents. (3-31-22) (5) Other scientifically defensible procedures such as relevant aquatic field studies, laboratory tests, biological translators, fate and distribution models, risk analyses or available scientific literature. (3-31-22) (a) Deviations from the above described EPA procedures shall have justifications which are adequately documented and based on sound scientific rationale. (3-31-22) (b) The data, testing procedures and application factors used to develop site-specific criteria shall reflect the nature of the pollutant (e.g., persistency, bioaccumulation potential, avoidance or attraction responses in fish, etc.), the designated and existing beneficial uses, and the most sensitive resident species of a water body. (3-31-22) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.02 Department of Environmental Quality Water Quality Standards Section 276 Page 169 02. Water Quality Criteria for Specific Waters. Standards provided in Sections 276 through 298 for specific waters will supersede Sections 210, 250, 251, 252, and 253 when the application of the standards contained in both sections would present a conflict. (3-31-22) 276. DISSOLVED OXYGEN STANDARDS FOR WATERS DISCHARGED FROM DAMS, RESERVOIRS, AND HYDROELECTRIC FACILITIES. 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: (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: (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: (3-31-22) 05. Point of Measurement. For the purpose of determining compliance with Subsections 276.02, 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 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 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 IDAHO ADMINISTRATIVE CODE IDAPA 58.01.02 Department of Environmental Quality Water Quality Standards Section 278 Page 170 276.03 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) 277. (RESERVED)