Maine's Water Quality Standards

Introduction

Section 303(c) of the federal Clean Water Act (CWA) as implemented in 40 CFR Part 131 (federal rules, off-site) requires all States to develop and maintain Water Quality Standards. These standards describe the intended uses of a waterbody, for example recreation in and on the water, fishing, and as habitat for aquatic organisms. Standards also include narrative or numeric criteria and an antidegredation policy that ensures that those uses can be achieved.

This page is intended to provide a general listing of Maine's "water quality standards", as this phrase is used by the Maine DEP's water quality and assessment program in considering ambient water quality, as well as the waste discharge licensing program. These standards are one of the principal foundations for the protection of water quality in Maine.

A majority of these standards are also part of the water quality "docket" of standards that is maintained with the U.S. Environmental Protection Agency (USEPA). Changes to docket standards require the approval of the USEPA for purposes of implementation of the federal Clean Water Act. See the Docket Page for more information on docket standards. See also Water Quality Standards, 40 CFR Part 131 (federal rules) (off-site).

Note that a number of other laws administered by the DEP help to maintain, restore and protect water quality in Maine. Some of these laws provide requirements specific to activities in certain locations, such as activities in or close to protected natural resources (see Natural Resources Protection Act). Some provide additional requirements specific to certain types of activity with significant potential impacts, such as mining, activities disturbing one or more acres (Stormwater Management Law. and the large developments regulated under Maine's Site Location Law. The short and basic requirements of the Erosion and Sedimentation Control Law mean that activities that don't otherwise need a permit should still include measures to prevent unreasonable erosion.

According to the federal Clean Water Act, states are required to periodically, but at least once every three years, hold public hearings for the purpose of reviewing water quality standards and, as appropriate, modifying and developing standards. This process is known as the Triennial Review. Maine Statute contains similar language. The DEP conducted its last Triennial Review between January 2020 and December 2021, and initiated a new Triennial Review in March 2024. For further information, please visit the Triennial Review webpage.

Statute (off-site links)

• The following sections are from Article 1, Organization and General Provisions
  • Definitions, 38 MRS 361-A
  • Waiver or modification of protection and improvement laws, 38 MRS 363-D
• The following sections are from Article 1-F, Nonpoint Source Pollution Program
  • Definitions, 38 MRS 410-H
  • Program implementation, 38 MRS 410-I
• The following sections are from Article 3, Pollution Control
  • Conditions of licenses (waste discharge licenses), 38 MRS 414-A
  • Publicly owned treatment works, 38 MRS 414-B
  • Color pollution control, 38 MRS 414-C
  • Certain deposits and discharges prohibited, 38 MRS 417
  • Log driving and storage, 38 MRS 418
  • Protection of the lower Penobscot River, 38 MRS 418-A
  • Prohibition on the use of tributyltin as an antifouling agent, 38 MRS 419-A
  • Goals for dates of removal of transformers containing polychlorinated biphenyls, 38 MRS 419-B
  • Certain deposits and discharges prohibited, 38 MRS 420
  • Discharge of waste from watercraft, 38 MRS 423
  • Discharge of waste from motor vehicles, 38 MRS 423-A
• The following sections are from Article 3, Enforcement
  • Enforcement, 38 MRS 451
  • Time schedule variances, 38 MRS 451-A
• The following sections are from Article 4-A, Water Classification Program
• Classification of Maine waters, 38 MRS 464
• Standards for classification of fresh surface waters, 38 MRS 465
• Standards for classification of lakes and ponds, 38 MRS 465-A
• Standards for classification of estuarine and marine waters, 38 MRS 465-B
• Standards of classification of groundwater, 38 MRS 465-C
• Definitions, 38 MRS 466
• Sustenance fishing designated use, 38 MRS 466-A
• Classification of major river basins, 38 MRS 467
• Classification of minor drainages, 38 MRS 468
• Classification of estuarine and marine waters, 38 MRS 469
• Classification of groundwater, 38 MRS 470
• In-stream flow and water level requirements; rules 38 MRS 470-H
• Approval criteria, 38 MRS 636 (hydropower projects)

Rules (off-site links)

• Administrative Regulation for Hydropower Projects, 06-096 CMR 450 and 06-061 CMR 11
• Regulations Concerning the Use of Aquatic Pesticides, 06-096 CMR 514
• Interim Effluent Limitations and Controls for the Discharge of Mercury, 06-096 CMR 519
• Surface Waters Toxic Control Program, 06-096 CMR 530
• Discontinuance of Wastewater Treatment Lagoons, 06-096 CMR 550
• Combined Sewer Overflow Abatement, 06-096 CMR 570
• Snow Dumps: Best Management Practices for Pollution Prevention, 06-096 CMR 573
• Classification Attainment Evaluation Using Biological Criteria for Rivers and Streams, 06-096 CMR 579
• Regulations Relating to Water Quality Evaluations, 06-096 CMR 581
• Regulations Relating to Temperature, 06-096 CMR 582
• Surface Water Quality Criteria for Toxic Pollutants, 06-096 CMR 584
• Identification of Fish Spawning Areas and Designation of Salmonid Spawning Areas, 06-096 CMR 585
• Rules Pertaining to Discharges to Class A Waters, 06-096 CMR 586
• In-stream Flows and Lake and Pond Water Levels, 06-096 CMR 587

Contact

• Meagan Sims, 207-508-8776

Related on-site links

• Classification Page
• Total Maximum Daily Load (TMDL) Page