Help With Ammonia Criteria Implementation: Tools to be Developed for Utilities

Claudio H. Ternieden, Director of Regulatory Affairs at the Water Environment Federation. He can be reached at

Utilities seeking help implementing ammonia criteria revised by the U.S. Environmental Protection Agency (EPA) will have several tools resulting from an experts workshop held last fall that discussed how to help reduce the burden for permittees.

The workshop, which took place in Arlington, Va., from October 28 to 29, was hosted by the Water Environment Federation (WEF; Alexandria, Va.), National Association of Clean Water Agencies (NACWA; Washington, D.C.), and Water Environment Research Foundation (WERF; Alexandria, Va.).

EPA published final national recommended water quality criteria for protection of aquatic life from the toxic effects of ammonia in freshwater in 2013. The criteria reflect new data on sensitive freshwater mussels and snails, incorporate scientific views EPA received on its draft 2009 criteria, and supersede EPA’s previously recommended 1999 ammonia criteria.

Experts from WEF and NACWA as well as WERF subscribers and state water quality professionals led the workshop. EPA technical staff also provided the agency’s perspectives and updates on implementation efforts.

The workshop objectives included the following:

  • Identify what tools and projects are needed to fill the information gaps or respond to the flexibility discussed in EPA’s guidance.
  • Identify data and information gaps needed for implementation of the revised criteria —  what details pertaining to implementation in permits and other flexibilities are known now or that will be needed.
  • Propose a framework and provide clear guidance for implementation — based on a common set of principles.
  • Produce a final report (prepared by WEF, NACWA, and WERF) on the outcome of the workshop to serve as a path to implementation.

Recommendations from the workshop participants are listed in Table 1 (p. xx).

Table 1. Recommendations from workshop participants

  • Decision trees for mussels present/absent determinations and related permitting decisions

  • Role of use attainability analysis and use sub-categorization/tiered aquatic life uses

  • Possible use water-effects ratio for applying the ammonia criteria

  • Better definition of mixing zones policies applicable to ammonia

  • Additional studies on the fate of ammonia in receiving waters

  • Potential use of in-stream studies to evaluate discharger impacts

  • Better understanding and definition of the consequences of pH, temperature, and upstream background concentration specifications

  • Better understanding of the scope of the problem: How many site-specific criteria needed? Is it principally a small plant discharging to small stream and/or arid west problem?

  • Assess water quality standards attainment options: Adaptive/flexible implementation to make significant, step-wise improvements that may fall short of full attainment

  • Determine effective implementation timeframe that accounts for complexity of issues, including relationship to triennial review process

Key elements of the criteria

The 2013 final freshwater aquatic life criteria for ammonia are pH- and temperature-dependent, and expressed as total ammonia nitrogen (TAN). The new criteria more restrictive than the 1999 criteria — see Table 2 (p. xx) for an example.

Table 2. Freshwater aquatic life criteria (20°C, pH 7 s.u.)

Criterion 2013 1999
Acutea 17 mg/L TAN 24 mg/L TAN
Chronic 1.9 mg/L TAN 4.5 mg/L TAN

aSalmonids present.

The criteria and related materials can be found at EPA’s key contact for questions related to ammonia criteria derivation and implementation in NPDES permits is Lisa Huff (

In addition, EPA published several factsheets and support documents related to criteria implementation and derivation of site-specific criteria. The most important documents in addition to the criteria publication (EPA 822-R-13-001) are:

• Revised Deletion Process for the Site-Specific Recalculation Procedure for Aquatic Life Criteria (EPA 823-R-13-001).
• Flexibilities for States Applying EPA’s Ammonia Criteria Recommendations (EPA 820-F-13-001).
• Technical Support Document for Conducting and Reviewing Freshwater Mussel Occurrence Surveys for Development of Site-specific Water Quality Criteria for Ammonia (EPA 800-R-13-003).

The final proceedings for the workshop will be available in mid-February from WEF. WEF, NACWA, and WERF are working with EPA to help implement the recommendations from this workshop.
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