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EPA Finalizes Ambient Water Quality Criteria for Nutrients in Lakes and Reservoirs with Negligible Revisions

August 18, 2021

EPA released its final ambient water quality criteria (AWQC) to address nutrients in lakes and reservoirs on August 13. This publication finalizes the Agency’s 2020 proposed rulemaking that moves towards a national stressor-response modelling framework approach that allows states the ability to input local or regional limnological data to derive more specific numeric nutrient values. EPA is publishing its recommended criterion model approach as Clean Water Act Section 304(a) criteria and not as technical guidance – a significant aspect of the proposal that NACWA objected to.

States and authorized tribes can choose to adopt EPA’s recommended numeric nutrient criteria and incorporate them into water quality standards. However, if states and authorized tribes choose not to use the recommended models to adopt new or revised nutrient criteria, they must provide justification to EPA during the triennial review process. This administrative hurdle could hamper state efforts with existing nutrient criteria or those that have EPA-approved nutrient reduction implementation plans.

EPA's final recommendations replace the 2000 and 2001 ecoregional criteria – an improvement towards identifying endpoints associated with specific uses, related response variables to those endpoints, and inclusion of a duration component. The recommended AWQC identify total nitrogen and total phosphorus concentrations to protect aquatic life, recreation, and drinking water designated uses.

The Agency has published a fact sheet and a technical support page that offers Nutrient Scientific Technical Exchange Partnership and Support (N-STEPS) as part of an online compendium of resources to help states and stakeholders.

NACWA submitted substantial comments to the Agency last year with serious concerns with the approach the Agency is taking with its recommended ambient water quality criteria for nutrients in lakes and reservoirs. Members are encouraged to review this concise document highlighting the Agency’s specific responses to our comments or EPA’s complete response to comments here.

While NACWA is still reviewing the final rulemaking and the implications to POTWs, if members have heard from state regulatory agencies on future adoption or implementation plans, please let us know. NACWA is planning to reach out to EPA to discuss the recommendations and response to comments and will keep members apprised of this conversation and any outcomes.

If members have questions, please contact Emily Remmel, NACWA’s Regulatory Affairs Director, for more information.

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