Alaska Department of Environmental Conservation Division of Water

FAQs about Total Maximum Daily Load (TMDL)

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Just what is a TMDL?

A TMDL identifies the amount of a pollutant that a waterbody can assimilate and maintain compliance with water quality standards. TMDLs include an appropriate margin of safety and identify the level of management needed to reduce pollutant inputs to a level (or “load”) that allows a waterbody to meet its designated uses.
A TMDL is composed of individual wasteload allocations (WLAs) for point sources and load allocations (LAs) for nonpoint sources and background loads. In addition, the TMDL must include a margin of safety (MOS), either implicitly or explicitly, that accounts for the uncertainty in the relationship between pollutant loads and the quality of the receiving waterbody.

What are water quality standards and designated uses?

Water Quality Standards are either numeric or narrative standards used to define the goals for a waterbody by designating its uses, setting criteria to protect those uses, and establishing provisions to protect waterbodies from pollutants. Designated uses specify appropriate water uses to be achieved and protected. Appropriate uses are identified by taking into consideration the use and value of the water body for public water supply, for protection of fish, shellfish, and wildlife, and for recreational, agricultural, industrial, and navigational purposes. In designating uses for a water body, States and Tribes examine the suitability of a water body for the uses based on the physical, chemical, and biological characteristics of the water body, its geographical setting and scenic qualities, and economic considerations.

How are TMDLs implemented?

The mechanisms used to address water quality problems after the TMDL is developed can include a combination of best management practices (BMPs) for nonpoint sources and/or effluent limits and monitoring required through Alaska Pollutant Discharge Elimination System (APDES) permits. Municipalities and other stakeholders have the opportunity to apply for grants to assist in funding projects to help reduce water pollution. Using a TMDL approach for water bodies does not replace existing water quality control programs or standard treatment technologies. It provides a framework for evaluating all possible water quality control efforts and promotes closer coordination of local, state, and federal efforts to better guarantee that we collectively meet water quality goals.

How does a TMDL affect my property?

A TMDL is not designed to act as a permitting tool but rather as a tool for assessing the various sources of pollution associated with a waterbody that cause the waterbody not to meet Alaska Water Quality Standards. Municipal and State zoning and ordinances apply as they would in any other permitting situation. However, permitting requirements and enforcement may be much stricter for properties adjacent to a TMDL waterbody depending on the type, duration, and extent of development to take place. Point source permits must be consistent with approved TMDLs.

How is the local community involved in restoring water quality?

The DEC supports the use of a watershed approach to address nonpoint source pollution. A watershed approach is based on the premise that water quality restoration and protection are best addressed through integrated efforts within a defined geographic area. Municipalities, non-governmental organizations, and other interested partners, have the ability to develop waterbody restoration plans and apply for funding to implement such programs. On an annual basis DEC looks for partners to address restoration plans through the Alaska Clean Water Actions (ACWA) program.

What happens if the TMDL plan doesn’t restore water quality?

If monitoring indicates that water quality standards are not being achieved after a plan is approved, DEC has the ability to conduct a formal evaluation to determine if:

1. The implementation of new and improved management practices are necessary;
2. Water quality is improving but more time is needed to comply with water quality standards; or
3. Revisions to the plan are necessary to meet water quality standards.

DEC recognizes that some water quality problems will not be resolved quickly or inexpensively.

How can the public comment on the TMDL?

Alaska has a 30-day public comment period in which anyone is welcome to comment on the TMDL. During this period, news releases are sent out and the copies of the TMDL and public notice are posted on the DEC’s TMDL website. DEC will respond to comments in a “Response to Comments” document prior to submitting the TMDL to EPA for approval.