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The Mitigation and Monitoring (M/M) team makes sure that landscapes affected by our construction projects recover. The team makes sure these areas are as good or better than we found them, helping to protect our waters and provide healthy habitat in a growing area.

When sewer construction disturbs a landscape, the M/M team is there to make sure they fully recover afterward. The team uses the latest science and innovates to keep restoration sites on a path to success. Our planners and crews work in a variety of landscapes, from urban parks to shorelines and wetlands.

Learn more about King County WTD’s Mitigation and Monitoring Program and keep up on our restoration work here!

Urban landscapes

Construction may involve parks, roadsides, and developed beach areas. 


King County installed roadside rain gardens as part of the Barton CSO Control Project

King County installed roadside rain gardens as part of the Barton CSO Control Project to capture and clean stormwater that would otherwise go into the sewer system. During heavy rains, this stormwater can fill pipes and cause overflows into Puget Sound at permitted discharge points. The rain gardens were installed to help prevent those combined sewer overflows, or CSOs. 

The M/M team oversees the maintenance of the Barton roadside raingardens to ensure they are properly functioning and capturing polluted stormwater runoff from streets, sidewalks and other impervious surfaces.

Public access areas

If a project must go through wetlands, parks, or natural areas, the M/M Program ensures that paths, trails, and other recreational amenities are not impacted by aggressive or invasive vegetation along pathways to ensure public access is maintained.


A sewer lining project in the Lake Hills Greenbelt required work by a community garden and wetland area.

A sewer lining project in the Lake Hills Greenbelt required work by a community garden and wetland area. Once restored, the M/M team will take over monitoring and maintenance of the restored wetland area.

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Natural areas

King County’s wastewater projects may create natural areas, like the Brightwater North Habitat area. The new Brightwater Treatment Plant included replacement of an auto wrecking yard, factory, and landscaping company with a number of habitat areas. These areas serve as a serene environment where people and dogs can enjoy trails, wildlife, and nature.

The North Habitat includes the Otter Pond Willow Rafts.

The M/M Program oversees the monitoring and maintenance of the North and South Habitat areas, including the Otter Pond Willow Rafts.


Coal Creek

Restoring affected shorelines on creeks, rivers, lakes and marine environments is critical for water quality and wildlife. When the Coal Creek Trunk Sewer was exposed after a flood, WTD carried out an emergency repair project in the creek. Mitigation required bank protection/restoration, and replacing invasive plants with native plants. The M/M Program oversees this area, and will also monitor and maintain parts of the Coal Creek Natural Area affected by sewer construction to replace the sewer pipe.

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For more information about the Mitigation and Monitoring Program, please contact us at: