A grassy meadow covers the Midway Landfill, next to the I-5 freeway southbound lanes between Seattle and Tacoma.
And, with plenty of cooperation among public agencies.
We’re working to do exactly that with Sound Transit, the Washington State Department of Transportation (WSDOT), and Seattle Public Utilities (SPU).
The site: a former landfill
The City of Seattle’s 60-acre Midway Landfill site adjoins the west side of I-5 in Kent. The landfill closed in 1983. Under our oversight, and review by the U.S. Environmental Protection Agency, SPU:
- Covered the landfill with an engineered, multilayered waterproof cap and a top layer of grass.
- Installed a gas extraction system to control methane generated by material in the landfill.
- Controlled surface water.
- Fenced the landfill to limit access to the site.
These protective elements have been in place since 1992. SPU continues to monitor groundwater quality and landfill gas at the site, under a legal agreement with us, last updated in 2006.
Transportation projects
Sound Transit will build light rail on the landfill's east side,
along I-5's southbound lanes.
The combined project will involve excavating some of the landfilled municipal waste, and will affect the landfill cap, the gas collection system, and surface water monitoring network. Because of this, we’re requiring:
- Transfer of excavated municipal waste to an authorized landfill.
- Restoration of disturbed portions of the landfill cap and other infrastructure.
- Documentation of all required work for our review and approval.
Some of the site’s land ownership will change. Sound Transit will acquire part of a strip — for the light rail tracks — that now belongs to WSDOT and will assume responsibility for maintaining that portion of the landfill cap. Seattle will continue to operate surface water controls, the gas extraction system, and the ongoing monitoring program.
Plans and agreement available
- Consent Decree Amendment: update to our existing legal agreement with SPU.
- Prospective Purchaser Consent Decree: new legal agreement between us and Sound Transit.
- Cleanup Action Plan Amendment: describes actions we will require to maintain the integrity of the site’s protective elements during and after the proposed construction.
- Public Participation Plan: explains how people can participate in the cleanup process.
Comments invited; public meeting planned
Looking south across the Midway Landfill where it adjoins I-5.
- 7 p.m. to 9 p.m. Feb. 11, 2020
- Des Moines Elementary School, 23801 16th Ave. S.
- Interpreter services will be available in Spanish, Korean, and Somali.
We’ll review and respond to all comments received. We expect the new plans and agreements to be in place by mid-2020.