Local governments in Western Washington, including Mercer Island, will see changes to what’s required for managing polluted stormwater runoff, the top threat to the water quality of urban-area lakes, rivers and the Puget Sound.

Stormwater is typically rain that runs off rooftops, paved streets, highways and parking lots. Along the way, it can pick up pollution from oil, fertilizers, pesticides, soil, trash and animal waste. Then the water might flow untreated directly into a local stream, bay, lake or waterway.

The Department of Ecology proposes modifications to the August 2012 municipal stormwater permits for Western Washington only, and has made the changes available for public review.

The changes are required due to rulings by the state Pollution Control Hearings Board to resolve appeals of the permits.

Changes include:

• Technical issues around low-impact development;

• Watershed planning;

• Definitions; and

• Western Washington Stormwater Manual.

The proposed modifications, supporting documents, and additional details on how to submit comments are posted on Ecology’s Municipal Stormwater website.

The website has information about public workshops and hearings ahead.

The public comment period ends Oct. 6. Ecology expects to finalize the permits in December 2014.