WHAT IS A TMDL?
A Total Maximum Daily Load (TMDL) study helps determine the best way to reduce pollutants and restore water quality. The TMDL establishes the maximum amount of pollutant allowed to enter a waterbody while still meeting water quality standards for that particular pollutant. These pollutant sources may be point-source or non-point sources.
As part of the Clean Water Act, a TMDL is required for all impaired water bodies (CWA Section 303(d)).
A waterbody is listed as impaired when it does not meet the requirements for a healthy water body. These are determined through monitoring assessment by Utah Division of Water Quality who produces an Integrated Report. This report summarizes the overall condition of Utah’s water and provides a list of waterbodies that do not meet water quality standards.
The TMDL identifies all contributing sources of the pollutant and determines the allowable pollutant load from that source. The report takes into account all natural sources and seasonal variations.
The development of a TMDL consists of 5 parts:
- Selection of the pollutant(s) to consider
- Estimation of water’s loading capacity
- Estimate of pollutant loading from all sources
- Analysis of current pollutant load and reduction needs
- Allocation of allowable pollutant load to meet water quality standards
TMDLs are open for public comment before they are finalized.
The first TMDL in Utah was established in the 90's. You can find a list of Utah’s approved and in-progress TMDLs on the Division of Water Quality website, here.