Section 58.01.02.275 - SITE-SPECIFIC SURFACE WATER QUALITY CRITERIA01.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. a. The following are acceptable conditions for developing site-specific criteria:i. Resident species of a water body are more or less sensitive than those species used to develop a water quality criterion.(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).(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).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).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.iv. Water quality criteria may be derived to protect and maintain existing ambient water quality.v. Other factors or combinations of factors that upon review of the Department may warrant modifications to the criteria.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.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.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 toxicological characteristics of a pollutant.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.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.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.h. The following are acceptable procedures for developing site-specific criteria for aquatic life protection. 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.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.(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.(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) 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.(4) Water effects ratios as defined by EPA guidance documents.(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. (a) Deviations from the above described EPA procedures shall have justifications which are adequately documented and based on sound scientific rationale.(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.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.Idaho Admin. Code r. 58.01.02.275