Mill Creek stormwater pond retrofit project

Project will help clean the water in Mill Creek by upgrading the stormwater pond in the Kings Park neighborhood, so it can catch and treat more stormwater runoff before it flows into the creek.

Construction will begin on August 31, 2026

Project overview

King County is making improvements to a stormwater pond near Mill Creek, at S 298th St and 33rd Ave S in south King County, to enhance water quality and reduce pollutants in the wetland that flows to Mill Creek. Improvements to the stormwater pond, built in the 1970s, are critical because most of the stormwater from the neighborhood is running directly into the adjacent wetland.

Improvements will redirect pipes into the stormwater pond which allows pollutants time to settle to the bottom of the pond that are removed by King County maintenance crews. Establishing new native plants and trees in the stormwater pond also helps to filter out pollutants.

The improvements will reduce the flow of stormwater to the wetland during high rainstorms. The community can expect to see standing water in the stormwater pond on a permanent basis.

A small-scale aerial map shows a dense residential area west of Auburn, King County. A red box indicates the

Location of the Mill Creek stormwater pond, at S 298th St and 33rd Ave S. - open an Acrobat PDF version

Project goals and benefits

Improve function of the pond by directing stormwater into the pond.
Increase the size of the pond.
Improve water quality treatment.
Reduce pollutants discharging into the wetland that flows to Mill Creek.

What is stormwater runoff?

Stormwater runoff is the rain that falls on the streets, sidewalks, rooftops, and driveways and flows into the drains along your neighborhood streets. The rainwater picks up and mixes with oil, metals, fertilizers, pesticides, animal waste, soil, soaps, and other pollutants. In many areas this polluted stormwater runs directly into streams, lakes, and wetlands in your neighborhood.

Polluted stormwater can harm or kills fish and other wildlife that use these waterways. Poorly managed stormwater can cause flooding. Stormwater facilities, like this pond, help reduce flooding, erosion, and improve water quality.

How you can help

Everyone can take small steps to help improve the water quality within the wetlands and streams in their community. Check out these ideas:

Report drainage issues to King County
Keep the green spaces in your community waste free
Place grass clippings in the yard waste bins
Help keep the storm drains clean by removing leaves
Pick up dog waste and dispose of in the garbage
Take your car to a commercial car wash
Keep your tires properly inflated

An empty, grassy open space that is a stormwater pond. The stormwater pond has tall, bright green grasses and weeds, with a few small yellow wildflowers. Residential houses and chain-link fences surround the pond in the background. — Mill Creek Pond, looking west.

A chain-link fence in front of a grassy open space that is a stormwater pond. Residential homes and large trees are behind the stormwater pond. — Mill Creek Pond looking north.

Construction schedule

Construction starts: August 31, 2026

Construction ends: October 14, 2026

During this time, construction will take place Monday through Friday from 7 am to 6 pm.

During construction you can expect:

One lane reduction on South 29th Street and 33rd Avenue South. See map below for details.
Parking restrictions around the pond during construction. See the map below for details.
Increased truck and foot traffic near the pond.
Noise from construction equipment during work hours.

An aerial map of construction work around the southwest corner of S 298th Street and 33rd Ave S. There is a fence around the construction zone area and no parking outlined in red along S 298th St and 33rd Ave S adjacent to the construction zone. Reduced lanes are outlined in dashed lines S 298th Street and 33rd Ave S near the construction zone.

After construction you can expect:

A deeper pond that is wet year-round.
Changing water levels of up to 2 feet during the rainy season.
Removal of the weeds and cedar tree.
New native shrubs and trees planted in and around the pond.
New sign for the pond.
New sidewalk and asphalt road around the pond.
King County staff on site to monitor and maintain the new vegetation.

Project funding

This project is funded by:

Surface Water Management Fees
Washington State Department of Ecology – Stormwater Grant Program

Language assistance

English

Interpretation and translation services are available to you at no cost. If you need them, please contact us at moshoemaker@kingcounty.gov or 206-263-0697.

Español

Hay servicios de interpretación y traducción a su disposición sin costo alguno. Si los necesita, póngase en contacto con nosotros mandando un correo electrónico a moshoemaker@kingcounty.gov o llamando a 206-263-0697.

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Русский

Услуги устного и письменного перевода доступны вам бесплатно. Если они вам нужны, свяжитесь с нами по адресу moshoemaker@kingcounty.gov или по телефону 206-263-0697.

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