Total Maximum Daily Load (TMDL) Program

A TMDL, or Total Maximum Daily Load, is a pollution cleanup plan for impaired water bodies, like streams and rivers, that aren't meeting water quality standards. It's essentially a "pollution diet" that defines the maximum amount of a specific pollutant a water body can handle while still meeting its water quality goals.

• Purpose: TMDLs are designed to restore water quality by setting limits on how much pollution a water body can receive.

• Impaired Waters: The Clean Water Act requires states to identify and list impaired waters, which are then considered for TMDL development.

• Pollutant Focus: Each TMDL focuses on a specific pollutant that's causing the impairment, like nutrients, bacteria, or sediment.

• Calculation: The TMDL calculation considers all sources of the pollutant, including point sources (like wastewater treatment plants) and non-point sources (like runoff from agriculture and streets).

• Waste Load Allocation: The portion of the TMDL that applies to point sources, requiring reductions in their pollutant discharges.

• Load Allocation: The portion of the TMDL that addresses non-point sources, such as runoff.

• Margin of Safety (MOS): An extra buffer in the TMDL to account for uncertainties in the calculations.

• TMDL Implementation: Once a TMDL is developed, it's typically adopted as a rule, creating legal obligations for sources to reduce their pollutant loads.

• Implementation Plan: The TMDL process also includes a plan outlining how the load reductions will be achieved, such as through improved wastewater treatment or best management practices.

Find your region to explore Clean Water Act Section 303(d) program resources: https://www.epa.gov/tmdl