Total Maximum Daily Loads
EPA's Total Maximum Daily Loads (TMDLs) Web site provides useful guidance information.
A TMDL specifies the maximum amount of a pollutant that a water body can receive and still meet water quality standards, and allocates pollutant loadings among point and nonpoint pollutant sources. Tribes can become involved in establishing TMDLs in three ways. First, tribes can develop EPA-approved water quality standards and develop their own TMDLs affecting the listed waterbodies on the reservation. Second, tribes may provide information and become involved in the TMDL processes and decisions with states affecting shared water bodies. Third, tribes may assist EPA in developing TMDLs for Indian country. The second and third ways are effective options for tribes to become familiar with the TMDL process and help ensure their interests are represented. TMDLs are submitted to EPA for review and approval. If EPA disapproves a TMDL, the Agency must establish TMDL within 30 days of the disapproval. The TMDL program is found in section 303(d) of the CWA and 40 CFR Part 131.
A TMDL is the sum of the allocated pollutant loads and is set at a level necessary to implement the applicable water quality standards; a TMDL includes:
Wasteload allocations from point sources
Load allocations from nonpoint sources and natural background conditions
A TMDL must contain a margin of safety and a consideration of seasonal variations. In addition, EPA encourages authorized tribes and states to identify a monitoring plan and schedule for considering revisions to TMDLs that will be implemented over time.