Iowa Thermal Discharges regulations & environmental compliance analysis

Iowa Thermal Discharges: What you need to know

Governing Law and Regulations

Surface water quality criteria: Iowa Administrative Code (IAC) 567-61.2(455B) to 567.61.3(455B)

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Water temperature quality standards: IAC 567-61.2(455B)

National Pollutant Discharge Elimination System (NPDES) permits: IAC 567-64.7(455B)

Disposal of pollutants into wells: IAC 567-62.9(455B)

Regulatory Agencies

Iowa Department of Natural Resources (DNR) Environmental Protection Division Water Quality Bureau

U.S. Environmental Protection Agency (EPA) Region 7

See ADDRESSES & CONTACTS for addresses and telephone numbers.

See national section for basic information and federal regulations.

Comparison: State vs. Federal

Rules. Iowa has more specific requirements than the federal requirements for regulating water temperatures under its water quality standards and discharge permit programs.

Administration and enforcement. DNR's Water Quality Bureau administers and enforces the state's water quality program, including thermal discharge requirements.

State Requirements


IAC 567-61.2(455B)

Iowa provides water temperature standards as minimum conditions of water quality and also provides a set of standards based on usage. As a general rule, water temperatures may not exceed 32°C (89.6°F). Heat of an artificial origin cannot be added to the surface water in excess of the amount that would raise the temperature of the water beyond the mixing zone more than 3°C (37.4°F) above natural conditions. Iowa requires that the normal daily and seasonal temperature variations of a surface water existing before the addition of heat must be maintained.

It is the policy of the state of Iowa that existing surface water uses and the level of water quality ...

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