The Nickel Report

A new decision curtails agency discretion to approve total maximum daily loads for impaired waterbodies and sets a precedent that may lead to more stringent National Pollution Discharge Elimination System (NPDES) permit limits.

Total maximum daily loads (TMDLs) have been described as “pollution budgets” for impaired waterbodies. A permitting authority developing a TMDL typically considers all known sources of the pollutant at issue (including contributions from point and non-point sources) as well as the relevant characteristics of the waterbody (such as flow rates) and determines how much pollutant the waterbody can receive without exceeding applicable water quality standards. Once a TMDL is adopted for a specific pollutant that is adversely affecting a waterbody, the permitting authority (either a delegated state or EPA) will use the TMDL to derive NPDES permit limits for facilities that are sources of the pollutant.