October 17, 2019


Water Classification Program
38 MRS § 464-470

The state has established a water quality classification system to monitor and protect water quality. All of Maine’s water bodies are divided into categories:

  • rivers, streams, and small ponds
  • ponds with more than ten acres of surface area
  • coastal and tidal waters
  • groundwater

Within each category, waters are assigned a class rating of AA (best), A, B, and C. These ratings are then used to determine limits on licensed discharges of pollutants.

Additionally, an “Anti-Degradation Policy” provision is intended to prevent further decline of Maine’s waters. According the the policy, no license may be granted which authorizes additional discharges into a water body that doesn’t currently meet the minimum standards of its classification.

Read the Statute