Impact/Purpose:

In 1998, as part of the Clean Water Action Plan, EPA initiated a program to develop and implement ecoregional based numeric nutrient program (see ). Nutrient criteria are numerical values for both causative (phosphorus and nitrogen) and response (chlorophyll a and turbidity) variables associated with the prevention and assessment of culturally eutrophic conditions. EPA proposes to develop criteria specific to ecoregions and water-body types (lakes and reservoirs; rivers and streams; estuaries). In 2000, U.S. EPA published Arecommended ambient water quality criteria@ in ecoregions and water body types in specific areas of the country. States and tribes are expected to adopt or revise these Aecoregional nutrient criteria@ published in 2000 and 2001 into water quality standards by 2004. The Aecoregional nutrient criteria@ are to be used as starting points to identify more precise numeric levels for nutrients needed to protect aquatic life, recreational, aesthetics or other uses on a site-specific or subregion-specific basis. Ultimately, nutrient criteria will be implemented by state water quality programs through development of state water quality standards, setting limits for discharge permits, and in determining total maximum daily loads (TM

Description:

A major goal of the numeric nutrient criteria program is to develop waterbody-type technical guidance manuals for assessing trophic state. EPA has published guidance for lakes and for rivers. EPA Region 1 is publishing New England-specific guidance in 2001 for lakes, ponds and reservoirs (called a ARegional Implementation Manual@). The overall approach is to collect nutrient-related data to distinguish regional natural background levels of enrichment from over- enrichment caused by pollution. The criteria will be determined based on a synthesis of existing (post B 1990) representative data relating nitrogen (N) and phosphorus (P) concentrations or loadings, with important eutrophication endpoints, such as chlorophyll-a concentration or secchi disk depth. Criteria will be developed based on an evaluation of the distribution of the data, comparison to reference water bodies, and to waterbodies whose designated uses are impaired. To that end, we have issued a cooperative agreement to the New England Interstate Water Pollution Control Commission (NEIWPCC) to work with a Regional Technical Assistance Group (RTAG) composed primarily of state representatives and help gather ambient nutrient related data from lakes, river and estuaries. NEIWPCC has hired an consulting firm, ENSR, to compile and analyze data. The data will be analyzed using approaches suggested in the technical guidance manuals, and other approaches suggested by the RTAG members. RTAG members will review work products from ENSR and NEIWPC

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