New rules took effect Sunday for managing stormwater runoff in dozens of New Hampshire towns.
The Environmental Protection Agency permit for small municipal stormwater systems will last until 2023.
New Hampshire is currently one of four states that has the EPA manage its stormwater permits, though legislators plan to study letting the state take that over.
The EPA says stormwater is the top cause of poor water quality in the Granite State.
Its new permit tells about 60 towns how to manage their storm drains, sewers, outfalls and other systems to prevent water pollution.
Officials say the new permit requires the same basic controls, but gives towns more flexibility to use local knowledge in prioritizing stormwater projects.
Towns will have a year to update their practices.