EPA ID# WAD980639462
EPA Region 10
King County

9th Congressional District

Other Names: Kent-Highlands Disposal Site, Military Road Landfill, City of Seattle, Kent Highlands Disposal Site
Last Update: April, 2010

Hide details for Site DescriptionSite Description

The Seattle Municipal Landfill (Kent Highlands) site is located in the city of Kent, Washington, approximately 14 miles south of Seattle. From 1968 to 1986, the City of Seattle leased the site and disposed of refuse on about 60 acres of a 90-acre ravine located on a hillside above the Green River. In addition to municipal wastes, the landfill accepted paint residues, industrial sludge, and other industrial wastes. In 1984, contaminants reached monitoring wells, and leachate (contaminated liquids) was leaking from the eastern side of the landfill. The leachate mixed with storm water runoff was collected in a pond, which discharged into a sanitary sewer system permit by the city of Kent.

Site Responsibility: This site is being addressed through state and municipal actions.

NPL Listing HistoryDates
Proposed Date:06/24/1988
Removed Date:
Withdrawal Date:
Final Date:08/30/1990
Deleted Date:

Hide details for Threats and ContaminantsThreats and Contaminants

Media Affected: Groundwater
Landfill gas contains volatile organic compounds (VOCs) including toluene, xylene, vinyl chloride, and trichloroethylene (TCE). Groundwater is contaminated with VOCs and heavy metals.

The landfill is located within the City of Kent. The surrounding area is a mix of urban residential areas and commercial areas. Three public water supply wells are located within three miles of the landfill. People could become exposed to contaminants through ingestion of or direct contact with contaminated groundwater and lechate, or through inhalation of landfill gas.

Hide details for Cleanup ProgressCleanup Progress

The landfill was closed in 1986. Measures to contain contamination on landfill property were completed in July 1995. Ongoing monitoring is being performed to assess the effectiveness of the containment measures. The cleanup actions are being overseen by the Washington Department of Ecology (Ecology).

A recent review of monitoring data by Ecology indicates gas is being controlled as required. Landfill leachate is sent to a publicly-owned water-treatment works; leachate characteristics are within permit limits.

Ground water monitoring indicates that vinyl chloride and manganese exceed standards established for the landfill in selected compliance monitoring wells. The levels of vinyl chloride and manganese do not constitute an emergency condition.

Surface water discharge to the Green River may need some additional treatment measures to bring the water quality into full compliance with state standards. Specifically, the dissolved oxygen concentration in the water may need to be increased and the ammonia concentration decreased. These are not emergency conditions.

Ecology is discussing actions to address these conditions with the City of Seattle.

Hide details for Regional ContactsRegional Contacts

SITE MANAGER(S):Mark Adams (state)
PHONE NUMBER:425-649-7107

Tim Brincefield (EPA contact)
COMMUNITY INVOLVEMENT COORDINATOR:Jusitne Asohmbom (Washington Department of Ecology)
PHONE NUMBER:425-649-7135
Information pertaining to this site is housed at the following location(s):
King County Library System
Kent Library
232 South Fourth Street
Kent, WA 98032