ACWA Comments on Numeric Nutrient Criteria for Lakes and Reservoirs (LNNC)

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(1) August 20, 2020 ACWA and ASDWA substantive comments on the Draft Ambient Water Quality Criteria Recommendations for Lakes and Reservoirs of the Conterminous United States: Information Supporting the Development of Numeric Nutrient Criteria (Draft LNNC) released in May 2020.

ACWA and ASDWA noted their general support of a stressor/response, risk-based approach to replace the 2000/2001 reference condition approach to numeric nutrient criteria (NNC) development. However, ACWA and ASDWA found it difficult to determine whether the Draft LNNC would more precisely and efficiently derive NNC without further clarity from EPA. ACWA and ASDWA noted states’ concerns about the underlying statistical modeling and application of national-scale models to develop lake-specific criteria for N, P, or Chl a relating to three designated uses with differing assessment endpoints and risk metrics. ACWA and ASDWA’s comments:

• • Requested specific resources from EPA to better understand the proposed models, their applicability, and their strengths and limitations;
  • Requested clarity about state/EPA collaboration to generate state- or lake-specific refined models and resultant criteria;
  • Requested EPA clarify that the finalized LNNC would represent guidance for a NNC methodology provided under CWA 304(a) rather than a set of national criteria;
  • Provided technical comments relating to each applicable designated use and several aspects of the Draft LNNC; and,
  • Noted states’ initial technical questions and concerns.

The original comment period was extended by 30 days to August 20, 2020.

(2) June 26, 2020 ACWA, ASDWA and ECOS comment period extension request (60 days) for the “Draft Ambient Water Quality Criteria Recommendations for Lakes and Reservoirs of the Conterminous United States: Information Supporting the Development of Numeric Nutrient Criteria” (draft LNNC).