Montana's Clean Water Act Information Center

FREQUENTLY ASKED QUESTIONS

Refer to the Instructions for complete information.

Total Daily Maximum Daily Load (TMDL) is a tool for implementing water quality standards and is based on the relationship between pollutant sources and water quality conditions. A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. It allocates pollutant loadings among point and non-point sources and is most often expressed as a mass per unit loading of the pollutant, e.g., tons/year of sediment.

All waters in the state that have been defined as an assessment unit (AU) are entered into the state’s assessment database (ADB) and can be queried through the CWAIC web application. While DEQ’s Water Quality Planning Bureau has not defined AU’s for all waterbodies in the state, the waterbodies that have been defined and assigned an AU ID appear in the CWAIC application regardless of their level of beneficial use support. Every AU has a “listing category” assigned which is related to the level of use support and type of impairment, if one or more is identified (refer to FAQ “What is a Water Quality Category?”).

Under the Federal Clean Water Act, all surface waters are designated with specific beneficial uses (e.g., livestock and irrigation, drinking water, recreation, fish and aquatic life, etc.) and assigned to a “use class.” Water quality standards are established to protect these beneficial uses. Each “use class” has associated standards for how clean the water must be to support associated use. These standards are used as a measuring stick to indicate if waters are meeting or not meeting water quality goals. Montana’s water quality use classes and associated beneficial uses may be found in ARM 17.30.6.

The designated beneficial uses for each class in the system are as follows:
A-CLOSED – Waters are suitable for drinking, culinary and food processing purposes after simple disinfection and are also suitable for swimming, recreation, and growth and propagation of fishes and associated aquatic life (although access restrictions to protect public health may limit actual use).
A-1 – Waters are suitable for drinking, culinary, and food processing purposes after conventional treatment for removal of naturally present impurities. Water quality must be suitable for bathing, swimming, and recreation; growth and propagation of salmonid fishes and associated aquatic life, waterfowl, and furbearers; and agricultural and industrial water supply.
B-1 – Waters are suitable for drinking, culinary, and food processing purposes after conventional treatment; bathing, swimming, and recreation; growth and propagation of salmonid fishes and associated aquatic life, waterfowl, and furbearers; and agricultural and industrial water supply.
B-2 – Waters are suitable for drinking, culinary and food processing purposes, after conventional treatment; bathing, swimming and recreation; growth and marginal propagation of salmonid fishes and associated aquatic life, waterfowl and furbearers; and agricultural and industrial water supply.
B-3 – Waters are suitable for drinking, culinary, and food processing purposes after conventional treatment; bathing, swimming, and recreation; growth and propagation of non-salmonid fishes and associated aquatic life, waterfowl, and furbearers; and agricultural and industrial water supply.
C-1 – Waters are suitable for bathing, swimming, and recreation; growth and propagation of salmonid fishes and associated aquatic life, waterfowl and furbearers; and agricultural and industrial water supply.
C-2 – Waters are suitable for bathing, swimming and recreation; growth and marginal propagation of salmonid fishes and associated aquatic life, waterfowl and furbearers; and agricultural and industrial water supply.
C-3 – Waters are suitable for bathing, swimming, and recreation; growth and propagation of non-salmonid fishes and associated aquatic life, waterfowl and furbearers. Naturally marginal for drinking, culinary, and food processing purposes, agriculture and industrial water supply.
I – The State of Montana has a goal to improve these waters to fully support the following uses: drinking, culinary, and food processing purposes after conventional treatment; bathing, swimming, and recreation; growth and propagation of fishes and associated aquatic life, waterfowl, and furbearers; and agricultural and industrial water supply.

Based on its assessment and listing methodology, each state or territory should report to the Environmental Protection Agency the water quality status of all waterbodies within the state’s jurisdiction. Each waterbody is placed in only one unique assessment categories as listed below.

Category Description
1 - All applicable beneficial uses have been assessed and all uses are determined to be fully supported.
2,2A - Available data and/or information indicate that some, but not all of the beneficial uses are supported.
3 - Insufficient or no data available to determine whether or not any designated use is attained.
4A - All TMDLs required to rectify all identified threats or impairments have been completed and approved.
4B - Other pollution control requirements [see 40 CFR 130.7(b) (1)(iii)] are in place, are expected to address all waterbody-pollutant combinations, and attain all water quality standards in a reasonable period of time. These control requirements act in lieu of a TMDL, thus no actual TMDLs are required.
4C - Identified threats or impairments result from pollution categories such as dewatering or habitat modification thus a TMDL is not required.
5 - One or more applicable beneficial uses are impaired or threatened and a TMDL is required.
5,2B or 5,5N -  Available data and/or information indicate that a water quality standard is not met due to an apparent natural source in the absence of any identified man-made sources.

When a water body does not meet, or is not expected to meet, the state’s water quality standards after full implementation of technology-based controls, it is considered impaired. Waters are placed on the 303(d) list when it is determined they need a TMDL or the TMDL has not yet been approved by the Environmental Protection Agency. The list includes waters that fail to meet any one of their applicable criteria (i.e., narrative, numeric, chemical, physical, or biological). Neither the cause of impairment nor its solution need to be determined for a water to be listed. By definition, the 303(d) list contains only those waters that are in category 5 (refer to FAQ “What is a Water Quality Category?”).

Section 303(d) of the Federal Clean Water Act, and Title 40 part 130 of the Code of Federal Regulations requires each state to develop a list of waters that do not meet water quality standards (i.e., which do not fully support their beneficial uses). The 303(d) list is a subset of all impaired waters listed in the comprehensive 305(b) water quality report. Waterbodies on the 303(d) list have at least one impairment caused by a pollutant (not pollution) and are without a TMDL completed and approved by the Environmental Protection Agency (EPA). In addition, these waters are not expected to meet water quality standards even after technology-based controls for point sources or other control requirements have been used, such as Best Management Practices (BMPs) for nonpoint sources. Currently, states are required to submit their 303(d) lists to EPA every even-numbered year (biennial reporting beginning in 1992).

TPA refers to a TMDL Planning Area. Montana uses a watershed-based approach to developing TMDLs. A watershed is a geographic area drained by a river or stream. It can be as large as the Mississippi River Basin or as small as the Roe River watershed, a 53-foot-long river near Great Falls. A watershed-based approach assumes that water quality restoration and protection are best addressed through integrated efforts within a defined geographic area. DEQ has divided the state into 91 TPAs to facilitate development of TMDL/water quality restoration plans. Note: TPAs are only provided as a search filter criteria in the most recent reporting cycle on the CWAIC site. Also, TPA boundaries may change if deemed advantageous for developing TMDL’s.

Previously, both the 305(b) and the 303(d) reports were submitted separately and often in different years. Beginning with the 2002 reporting year the Environmental Protection Agency (EPA) requested that states combine these two federal reports in to the Integrated Report. Montana’s first Integrated Report was submitted to EPA in 2004.

Pollution is the man-made or man-induced alteration of the chemical, physical, biological, and radiological integrity of water that has a harmful effect on any living thing that drinks or uses or lives in it. For example, a man-made physical alteration would be a dam or an altered riparian forest. A pollutant is any substance that is introduced into a water resource, naturally or by human activities, that adversely affects the water quality for a specific use. Common water pollutants include pesticides, lead, arsenic, polychlorinated biphenyls (PCBs), and any materials found in industrial, municipal, or agricultural waste discharged into the waterbody.

Section 305(b) of the Federal Clean Water Act (as last reauthorized by the Water Quality Act of 1987) requires each state to submit a report to the Environmental Protection Agency every two years describing the status and trends of its waters. The document, which is commonly referred to as the 305(b) Report, includes an assessment of existing water quality in Montana and an overview of past and proposed water pollution abatement efforts.