Summary

Nutrient criteria are part of the technical inner workings of the Clean Water Act. Regulators use water quality criteria to determine allowable pollutant quantities for National Pollutant Discharge Elimination System (NPDES) permits as well as to determine what is considered acceptable in discharges from nonpoint sources. Water quality criteria are also used by regulators to judge if a water body contains too much of a specified pollutant and if it is unable to meet its “designated use” (such as a source for drinking water or a source of recreation such as swimming and fishing) as determined by the Clean Water Act’s Water Quality Standards (WQS) program. The responsibility for much of the WQS program, including water quality criteria and determinations of “designated use” can be delegated to states including state regulatory agencies.

Nutrient criteria can be either narrative or numeric:

Narrative nutrient criteria might be “no phosphorus will be allowed in this stream at levels that will prevent desired levels of flora and fauna.” Narrative criteria preserve regulators ability to make judgment calls, particularly where hard data is not available, too expensive to gather, or simply an unreliable indicator of whether or not the water body in question is meeting its designated use.

Numeric nutrient criteria might read “no phosphorus will be allowed in this stream at levels in excess of 8 parts per million.” While there is no reason that technically sound, practical and fair numeric nutrient criteria can be established and used by states, they are expensive to establish and the science to support their use in different geographic areas is very limited.

Background

Numeric Nutrient Criteria

Recently, the U.S. Environmental Protection Agency (EPA) has directed all regions and states in the United States to begin developing Numeric Nutrient Criteria (NNC) for surface water bodies. NNC implementation could subsequently trigger nonpoint source regulation if the state determines regulation is necessary to meet the NNC.

Florida Numeric Nutrient Criteria

On Jan. 26, 2010, EPA published a Notice of Proposed Rulemaking (NPRM) to establish water quality standards for Florida’s lakes and flowing waters. 75 Fed. Reg. 4174 (Jan. 26, 2010). The NPRM, published in response to a lawsuit against the agency, represents the first time EPA has attempted to displace a state’s efforts to manage nutrient impacts by establishing federal NNC. However, EPA has already asserted that it may establish such criteria for the Chesapeake Bay, and may seek to take similar action in other watersheds.

EPA’s own Science Advisory Board (SAB) has reviewed EPA’s Empirical Approaches for Nutrient Criteria Derivation (draft EPA 2009). In its review of that guidance, the SAB advised EPA that “[n]umeric nutrient criteria developed and implemented without consideration of system specific conditions can lead to management actions that may have negative social and economic and unintended environmental consequences without additional environmental protection.”