Arkansas Total Maximum Daily Loads (TMDL)

Section 303(d) of the Clean Water Act and 40 C.F.R. § 130.7 require states to develop a list of impaired waters (303(d) list) – waters not meeting water quality standards, 8 CAR Part 21 (Rule 2).

Waterbodies on the 303(d) list are prioritized for corrective action to improve water quality including Total Maximum Daily Load (TMDL) development.

A TMDL is a calculation developed for waters that are not meeting or are at risk of not attaining water quality standards. The TMDL calculates the maximum amount of a pollutant a waterbody can receive and still meet water quality standards.

TMDLs calculate waterbody loads at critical conditions and provide a margin of safety to account for uncertainties. The calculated loads are allocated to point source discharges as a wasteload allocation and to nonpoint sources as a load allocation.