Draft Ambient Water Quality Criteria Recommendations for Lakes and Reservoirs: U.S. Environmental Protection Agency Federal Register Notice Addressing Numeric Nutrient Criteria Development

The United States Environmental Protection Agency (“EPA”) announced in the Federal Register publication of a document titled:

“Draft Ambient Water Quality Criteria Recommendations for Lakes and Reservoirs of the Conterminous United States Information Supporting  the Development of Numeric Nutrient Criteria”.

The EPA states that it will be accepting comments for a 60 day period.

 Water Quality Criteria (“WQC”) are ambient water quality conditions deemed protective for the use established for a water body. States are required to adopt WQC to protect designated uses pursuant to Section 303 of the Clean Water Act. The WQC must specify maximum concentrations of pollutants that may be present in the water without impairing its suitability for certain uses. However, they can assume three forms. They may include:

1. Numerical terms reflecting maximum concentration of a particular pollutant in the receiving water;
2. Bioassay or biomonitoring results which reflect mortality rates of certain waterborne organisms relative to the concentrations of particular pollutants; or
3. Terms narrative in nature.

Clean Water Act National Pollution Discharge Elimination System permits must incorporate the limitations necessary to ensure the maintenance of the water quality standards applicable to the water body receiving the wastewater.

The scientific basis or rationale for a particular WQC is obviously important. The WQC represents a judgment as to what levels, concentrations, or conditions can support a desired use for a water body. An indication of the importance of the WQC is the Clean Water Act’s requirement that the EPA periodically issued new or revised WQC. States can develop their own WQC if justified by technical data. EPA also undertakes this task pursuant to Section 304(d) of the Clean Water Act. EPA WQC are frequently used by the states in establishing or revising their water quality standards.

The phrase “nutrients” refers to nitrogen and phosphorus.

EPA has for a number of years been considering strategies to develop nutrient WQC for lakes and reservoirs. EPA issued guidance in 2013 referencing a combined criterion approach. This approach was not limited to numeric phosphorus and nitrogen limits. States could potentially include biological, physical, and chemical parameters.

The draft numeric document EPA published in the May 22nd Federal Register references national criteria recommendations which are described as models for total nitrogen and total phosphorus concentrations in lakes and reservoirs. The designated uses for which they are intended to protect are stated to include:

• Aquatic life
• Recreation
• Drinking Water Source Protection

The draft WQC are stated to be based on stressor-response models. They link pollution stressors (i.e., nitrogen, phosphorus) to responses associated with protection of designated uses.

EPA states they would replace previously recommended ambient nutrient criteria for lakes and reservoirs.

A copy of the Federal Register’s Notice can be downloaded here.