July 25, 2002

EPA turns up the heat with temperature rules

  • Rules seek to protect fish from industrial warm water discharges
    MCS Environmental

    Photos courtesy of MCS Environmental
    The EPA temperature criteria are intended to meet the thermal requirements of native salmonids.

    With the recent listings of several species of Northwest salmonids under the Endangered Species Act, federal, state and local agencies and the tribes have enacted programs to reverse habitat degradation potentially threatening these stocks.

    Although many factors have contributed to the decline of Northwest salmonid populations, elevated water temperatures attributable to development in watersheds historically supporting salmon runs is believed to be a major contributor.

    In October 2001, Region 10 of the U.S. Environmental Protection Agency (EPA) released its first public review draft guidance for developing water quality standards for temperature intended to protect native salmonids in the Pacific Northwest.

    The draft temperature guidance was prompted, in part, by proposed revisions to Oregon’s temperature standard that were submitted to the EPA for approval. During the review process, the EPA, the National Marine Fisheries Service, other agencies and the tribes raised concerns that the standards would not protect all life stages of threatened and endangered salmonids. To address these concerns, the EPA initiated a project to develop temperature criteria that would be fully protective of native Northwest salmonids.

    The basic goals for the temperature criteria guidance are to:

    • Meet the biological requirements of native salmon species for survival and recovery pursuant to the Endangered Species Act.

    • Provide for the restoration and maintenance of surface water temperature to support and protect native salmonids pursuant to the Clean Water Act.

    • Meet the salmon rebuilding needs of federal trust responsibilities with treaty tribes.

    • Recognize the natural temperature potential and limitations of water bodies.

    • Allow effective incorporation by states and tribes in water quality standards programs.

    The draft temperature guidance proposes a four-part approach for state and tribal temperature water quality standards to support native Pacific Northwest salmon:

    1. Development and adoption of thermal potential numeric criteria.

    2. Adoption of “interim” species life-stage numeric criteria.

    3. Adoption of a temperature management plan provision.

    4. Adoption of provisions to protect existing cold-water areas.

    The first approach entails estimating the thermal potential of a specific water body and adopting numeric temperature criteria based on that potential. The EPA believes that the most appropriate geographic area to assess thermal potential is the sub-basin scale. The thermal potential numeric criteria would define the maximum allowable temperatures for critical seasons (e.g. summer).

    The proposed criteria are also intended to restore water temperatures that will be protective of native salmonids.

    Thermal potential is defined as the estimated temperature regime after all reversible man-made sources of heat are removed. According to the EPA, the closer the thermal potential numeric criteria are to the historic thermal regime (i.e., prior to Euro-American settlement), the higher degree of confidence that the thermal potential numeric criteria will support salmonid uses.

    As an alternative to adopting thermal potential values as numeric criteria in a water quality standard, the EPA is also considering the option of having thermal potential values be expressed as part of a total maximum daily load (TMDL).

    The second approach involves developing “interim” species-life-stage numeric criteria for waters designated as supporting various life stages of salmon. These criteria would be effective for all waters until such time thermal potential numeric criteria are adopted to replace species-life-stage numeric criteria.

    Under the third approach, the EPA recommends that states and tribes adopt provisions in their water quality standards allowing National Pollutant Discharge Elimination System (NPDES) sources to comply with water quality-based effluent limits derived from species-life-stage numeric criteria through a temperature management plan.

    The temperature management plans would mandate that no source discharge contribute to incipient lethal temperatures (77° F) in a water body (including within the mixing zone) and that discharges cannot contribute to salmonids migration blockage temperatures (70° F) in more than a quarter of the receiving water. If, after implementation of all feasible methods, a discharge (end-of-pipe) exceeds the species-life-stage numeric criteria, then the source must compensate for the excess thermal load through mitigation elsewhere in the sub-basin.

    Finally, the EPA recommends that provisions be adopted in water quality standards to protect waters supporting salmonids that are currently colder than the species-life-stage numeric criteria. For those waters where water quality exceeds numeric criteria, provisions would have to be incorporated into water quality standards prohibiting any sources from increasing thermal loads to those waters supporting endangered or threatened salmonids unless the additional thermal load is offset through mitigation elsewhere in the sub-basin.

    Additionally, in its draft temperature guidance, the EPA is also recommending provisions for beneficial use designations for salmonids that would designate a species life stage use for areas where there is reasonable potential for that use to exist. Under this provision, states and tribes would include in their use designations waters that are anticipated to be available for salmonid use due to fish passage improvements in the near term (e.g., removal of dams and other impassable barriers).

    The public comment period for the draft temperature guidance ended on Feb. 22, 2002, resulting in nearly 700 comments from organizations and individuals. Some of the general comments received by the EPA included:

    • The EPA needs a more rigorous demonstration that human-caused elevations of water temperature presents an adverse impact to salmonids.

    • Concern that the EPA has not allowed for sufficient stakeholder input in the development of temperature guidance.

    • Concern that Region 10 cannot develop guidance that differs from the EPA’s national 304(a) criteria.

    • Concern that the guidance is prescriptive and should go through formal rule-making.

    • Concern that the EPA is going beyond its authority under the Clean Water Act.

    One of the specific criticisms of the EPA’s draft temperature guidance is that it does not account for site-specific conditions, failing to differentiate between a small headwater stream that may provide spawning habitat for char or a large river system, such as the Columbia River, that may provide habitat for multiple species and life stages of salmon. Restricting the temperature of all discharges to below 25° C, regardless of the condition of the receiving environment, is perceived as being overly conservative.

    Some of the site-specific factors that need to be considered in adopting and implementing temperature criteria include:

    • The ability of the receiving environment to buffer temperature alterations that may be attributable to thermal discharges.

    • Species presence and habitat use, spatially and temporally, in the area of a discharge.

    • All industrial, municipal, residential and agricultural activities in an area that may contribute to thermal effects in the receiving water.

    Based on the public review comments, the EPA plans to issue a second draft of the guidance this fall for public comment, with the goal of issuing the final guidance in early 2003. The second draft may include a number of revisions, some of which include:

    • Species-life stage numeric criteria will be the focus of the guidance rather than interim criteria.

    • Replace the temperature management plan recommendation with a recommended water quality standard provision to minimize plume impacts when mixing zones are issued.

    • Recommend off-site mitigation requirements for new sources in waters currently colder than the SLS numeric criteria and for existing sources that currently have large mixing zones in temperature-impaired waters.

    What does the proposed temperature guidance mean for industry and municipalities? For facilities currently discharging process waters with temperatures of 77° F or greater into salmon-bearing waters, it may be necessary to invest millions of dollars designing, building, operating and maintaining cooling towers to reduce discharge temperatures below 77° F.

    In heavily industrialized areas with multiple sources of thermal loading, simply cooling discharges may be insufficient to meet criteria. Mitigation may also be required elsewhere in the sub-basin to help achieve temperature criteria. Industries may also have to implement seasonal adjustments to facility operations to account for seasonal variations in river discharge and salmon usage.

    Implementation of temperature criteria will certainly add another layer of complexity to NPDES permitting. It is likely that a number of industries affected by the proposed guidelines will pursue litigation, challenging some or all aspects of the new temperature guidance. Ultimately, the increased costs to industries and municipalities of complying with the new temperature criteria will affect consumers throughout the Northwest.

    For more information on the EPA’s temperature guidance, visit the Region 10 Web site at, following the path “Surface Water Quality Standards/What’s New/11/01/01 Water Quality Temperature Criteria Guidance Project Status.”

    Bob Stuart is an associate fisheries biologist at MCS Environmental Inc., an environmental consulting firm specializing in aquatic and fisheries-related issues.

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