South Park Landfill

Updated February 2020

City of Seattle begins work on Interim Action

The City of Seattle is in the preliminary engineering phase for an interim action on their property, approved in January 2016. This partial cleanup is designed to reduce the chance of human contact with contaminants, control landfill gas, and further reduce stormwater and groundwater contamination at the site. For complete details, see the Interim Action Workplan in the 2016 Agreed Order Amendment.
 
This interim action is very similar to the one completed by South Park Property Development (SPPD) in 2015 (see Previous Cleanup section below). 

To view site reports and fact sheets, click on the "View Electronic Documents" link to the right.
 
Why this cleanup matters 
 
The landfill and its associated contamination (including methane) could pose risks to human health and the environment in surrounding areas. This site is also part of Ecology’s Lower Duwamish Waterway source control efforts, because it is located near the Lower Duwamish Waterway (LDW) Superfund Site. 

The US Environmental Protection Agency (EPA) put the lower 5 miles of the Duwamish River on its Superfund National Priorities List in 2001. EPA leads cleanup of the river sediments. The sediments contain a wide range of contaminants due to decades of industrial activity and urban runoff. 

Ecology is leading efforts to control sources of contamination from the land area surrounding the LDW. Contaminants in the soil and groundwater around the river can find their way into the river through storm runoff and other pathways. The long‐term goal is to reduce recontamination of the sediments and restore water quality in the river. For more information, visit our Source Control page.

Site location

The former South Park Landfill is a 40-acre area located in the South Park neighborhood along the 8100 & 8200 blocks of Second Avenue South in Seattle's South Park neighborhood. It is located about 1,600 feet southwest of the Lower Duwamish Waterway. 

The site is bordered to the north by Seattle Public Utilities’ South Transfer Station (across South Kenyon Street), to the west by Occidental Avenue South, to the south by South Sullivan Street, and to the east by Highway 99 and Fifth Avenue South. It is surrounded to the south and east by the residential neighborhood of South Park.

The Lower Duwamish Waterway drainage basin is divided into source control areas. This site is located within the 1st Ave S Storm Drain (river mile 2.1) source control area along the west bank of the river. Current data indicate the landfill is not affecting the LDW, but monitoring will continue in order to confirm this.

Site history

The property, originally owned by King County, was used as a landfill as early as the 1930s. Open refuse burning was a common practice at the site until 1961. The landfill was closed according to existing laws in 1966, when the City of Seattle built the South Recycling and Disposal Station (SRDS) on the site to ship trash out of the area.
 
In 2013 the City opened its South Transfer Station on the other side of South Kenyon Street, as a replacement for the SRDS. In 2014, a portion of the SRDS was reopened as the South Transfer Station Phase II to accept yard waste.

In 2017 the City plans to redevelop the former SRDS for improved recycling facilities and a place to process material cleaned out from stormwater and sewer lines. More information about their redevelopment plan is available at: http://www.seattle.gov/util/southrecyclingrebuild.
 
Part of the landfill was also used as an auto wrecking yard from the 1950s - 1970s. From 1984 to 1996, King County leased portions of the site for storage, mostly consisting of truck storage.

Several different parties now own the former landfill property:SPPD owns 19.4 acres which is currently used for school bus parking.The City of Seattle owns 11 acres which is used by Seattle Public Utilities to collect yard and household hazardous waste, and for parking and vehicle washing (South Transfer Station Phase II).The northwest portion known as Kenyon Industrial Park is privately owned by Harsch Investment Properties, LLC., with a smaller parcel within this area owned by 7901 2nd Ave S. LLC (7901 Property).


Contamination

The contaminants of potential concern for soil, groundwater and air at the site include:

Soil:

•Arsenic and lead
•Diesel and oil range petroleum hydrocarbons

Groundwater:

•Arsenic, iron, and manganese
•Vinyl chloride
•Benzene and cis-1,2-dichloroethene

Air:

•Landfill gas (methane and carbon dioxide)


Previous cleanup work

Site investigations began in the mid-1980s. In 1999, King County entered into Ecology’s Voluntary Cleanup Program (VCP) to address contamination on the site, some of which had migrated off the landfill properties. King County made progress towards defining the nature and extent of contamination.
 
Recent site investigation and cleanup work is being completed through a formal cleanup process following the Model Toxics Control Act (MTCA) regulations. In 2009, Ecology entered into a legal agreement (Agreed Order) with the City of Seattle and SPPD  for cleanup investigation and evaluation of cleanup options.

Two interim cleanup actions have been approved for the site, one in 2013 by SPPD and another in 2016 by the City of Seattle. Each were implemented as amendments to the 2009 Agreed Order after undergoing public comment.

The two interim actions include the following elements:
Constructing a landfill cap to prevent human contact with the landfill, and keep rain and stormwater from coming into contact with landfill waste;
Installing landfill gas and surface water control systems to control the release of landfill gas emissions from the site and move rainwater away from the site;
Restricting future land use activities to minimize potential exposure to contamination and maintain the effectiveness of cleanup actions;
Establishing groundwater and landfill gas monitoring to evaluate the performance and effectiveness of the interim cleanup actions.

SPPD completed the interim action on their property in early 2015. The City is now starting the second interim action on their property. These actions will not interfere with any reasonable alternatives for final cleanup of the whole South Park Landfill site.

The Model Toxics Control Act (MTCA; Chapter 70.105D RCW is Washington’s environmental cleanup law). It provides requirements for contaminated site cleanup and sets standards that protect human health and the environment. Ecology enacts the MTCA and oversees cleanups. The MTCA site cleanup process is completed in steps (see graphic below) over a variable timeline.