Department of
Environmental Quality

DEQ's water quality criteria may not always reflect the toxicity of a pollutant in a specific water body. They represent only a limited number of the natural and humanmade chemicals that exist in the environment that may pose a threat to designated or existing beneficial uses. Therefore, it may be prudent in some water bodies to develop new water quality criteria or modify existing criteria through site-specific analyses that will effectively protect designated and existing beneficial uses.

Site-specific criteria are allowed by regulation and are subject to EPA review and approval. As with all water quality criteria, site-specific criteria must be based on sound scientific principles in order to protect the designated use.

The following are acceptable conditions for developing site-specific criteria:

• Resident species of a water body are more or less sensitive than those species used to develop a water quality criterion.
• Biological availability and/or toxicity of a pollutant have been 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., hardness, temperature, or pH).
• Seasonal changes to the physicochemical characteristics of a water body affect the biological availability and/or toxicity of a pollutant (seasonally dependent site-specific criteria).
• Existing ambient water quality is not protected with statewide water quality criteria.
• Other factors or combinations of factors that may warrant modifications to the criteria.

DEQ's procedures to derive site-specific criteria can be found in Idaho's Water Quality Standards (IDAPA 58.01.02, Section 275.01(h)).

Some site-specific criteria have been established for specific Idaho water bodies to reflect local environmental conditions.

South Fork Coeur d'Alene River Subbasin

Site-specific criteria have been established for cadmium, lead, and zinc in the South Fork Coeur d'Alene River (SFCDA) subbasin. The SFCDA site-specific criteria were developed using EPA's "resident species" approach that involved testing the toxicity of cadmium, lead, and zinc in actual site water near the headwaters of the SFCDA (upstream of pollution from mining activities) using native species that occur in the subbasin. The studies included toxicity tests with 14 species, including westslope cutthroat trout, shorthead sculpin, mayflies, stoneflies, caddisflies, other insects, and snails.

The following DEQ technical documents describe the criteria derivation for cadmium, lead, and zinc and an evaluation of whether criteria developed for cadmium, lead, and zinc using species and water from the headwater reaches of the SFCDA watershed are appropriate to apply to the lower SFCDA and tributaries.

• Application of Site-specific Water Quality Criteria Developed in Headwater Reaches to Downstream Waters (December 2002)
• Derivation of Acute and Chronic Criteria for Lead and Zinc (May 2002)
• Comparisons of Cadmium Criteria to the Results Toxicity Testing with Species Resident to the South Fork Coeur d'Alene River (February 2003)

Boise River

Site-specific criteria have been established for copper and lead in the Boise River. The Boise River site-specific criteria were developed using EPA's “water-effect ratio” (WER) approach that involved comparing the relative toxicity of copper and lead in river water and in lab water that was intended to represent the typical lab waters used by EPA to develop national criteria guidance. The WER studies used standard aquatic test organisms (fathead minnows and the water flea Ceriodaphnia dubia) in side-by-side comparisons in actual site (river) water and lab water. The following document describes this project in detail.

• Boise City Water-Effect Ratio Project (August 2002)

Snake River

On November 14, 2003, Idaho adopted a site-specific temperature criterion to protect fall Chinook spawning in the reach of the Snake River from Hells Canyon Dam to the Salmon River. That criterion is a maximum weekly maximum temperature of 13°C, based on EPA’s Region 10 recommendation to protect salmonid spawning, and applies from October 23 through April 15 of each year. EPA, after consultation with NOAA Fisheries, approved this criterion on July 20, 2004. 

In 2011, DEQ initiated rulemaking to revise Idaho’s Water Quality Standards to modify the existing site-specific temperature criterion. The rule, which was approved by the Board of Environmental Quality and adopted by the Idaho Legislature, established a site-specific criterion of maximum weekly maximum temperature of 14.5°C from October 23rd through November 6th and a maximum weekly maximum temperature of 13°C from November 7th through April 15th.

Selenium Site-Specific Criterion Proposal for Streams Draining the Smoky Canyon Mine

On January 30, 2012, Simplot Corporation delivered to DEQ for the agency’s consideration a proposal for a site-specific selenium criterion and supporting technical documents. The proposal is for a fish egg/ovary criterion, with translation to wholebody tissue selenium and water selenium concentrations as well, and would apply to certain streams draining Simplot’s Smoky Canyon Mine in southeast Idaho.

• Cover Letter from Alan L. Prouty, Vice President, Environmental and Regulatory Affairs, J.R. Simplot Company, to DEQ, January 30, 2012
• Proposed Site-Specific Selenium Criterion, Sage and Crow Creeks, Idaho
• Technical Support Document: Proposed Site-Specific Selenium Criterion, Sage and Crow Creeks, Idaho
• Appendix A - Summary of Exposure Conditions
• Appendix B - Summary of Biological Populations and Communities
• Appendix C - Analysis and Interpretation of Trout Standing Crop and Habitat Relations
• Appendix D - Brown Trout - Laboratory Reproduction Studies
• Appendix E - Yellowstone Cutthroat Trout - Adult Laboratory Reproduction Studies
• Appendix F - Yellowstone Cutthroat Trout - Early Life Stage Laboratory Studies
• Appendix G - Responses to Workgroup Comments on the Draft Interpretative Report

DEQ is reviewing the proposal and its supporting documents. When that is done, DEQ will make a decision to either proceed with rulemaking to adopt the selenium site-specific criterion as proposed, modify the proposal and then proceed, or request further information from Simplot before proceeding. DEQ anticipates reaching this decision within a couple of months of receiving the proposal.

If DEQ proceeds with rulemaking, at least one negotiated rulemaking meeting will be held. This meeting will be announced in Idaho’s Administrative Bulletin will be open to the public. Based on the negotiations, DEQ could publish a proposed rule and take formal public comment or end the process.

The opportunities for public comment during rulemaking include the following steps:

• Negotiated rulemaking meeting
• Written public comments during the public comment period as announced in the Administrative Bulletin
• Board of Environmental Quality rule review meeting
• Before the legislative germane committees

All final water quality rules must be submitted to EPA for approval. Only with EPA approval would the site-specific criterion become be effective for purposes such as 303(d) listing decisions, TMDLs, or NPDES permitting under the Clean Water Act.

Each state step—initiation of negotiated rulemaking, proposed rule, pending rule, and final rule—is published in the Idaho Administrative Bulletin. DEQ also tracks the process on its website. Check back for further developments.