South Park Landfill

The South Park Landfill is a closed solid waste landfill located on an approximately 40-acre area between Highway 99 and Highway 509 in Seattle's South Park neighborhood. It is located about 1,600 feet southwest of the Duwamish River. 

The South Park Landfill property was originally owned by King County and 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. During the 1950s – 1970s, part of the landfill was also used as an auto wrecking yard. By 1970, several facilities had been built on top of the former landfill.

The site is divided into the following four areas: 

• CenterPoint South Park (CPSP) Area: This 21-acre area is now owned by CenterPoint South Park LLC. Cleanup work is being done under the 2019 Consent Decree.
• South Transfer Station (STS) Area (formerly referred to as SRDS): This 10.55-acre area is owned by the City of Seattle and is the location of the future STS Phase 2 construction.  The construction will support the City’s solid waste handling and will also address the landfill remedy. Cleanup work is being done under the 2019 Consent Decree, and the construction is part of an Interim Action.
• Kenyon Industrial Park (KIP) Area: This 6.49-acre area is owned by Schnitzer Properties, LLC and is used for a mixture of office and manufacturing/warehouse space. Cleanup work is described in the documents for this comment period.
• 7901 2nd Ave S, LLC (7901) Area: This 0.72-acre area is owned by an organization with the same name and the property is mostly covered by a warehouse. Cleanup work is described in the documents for this comment period.

Given the past and future upgrades to the first two areas of the landfill, these legal agreements and supporting CAPs will ensure that all areas of the landfill are equally protective and have the same standards of maintenance and monitoring.

The legal agreements issued to the PLPs of the Kenyon Industrial Park Area and 7901 2nd Ave. S. require the PLPs to address the following items in their respective Cleanup Action Plans:

• Landfill cap: Install a cap or paved cover over the entire area not covered by a building. The existing pavement on the two properties do not meet the minimum standards for a landfill cap remedy.
• Landfill gas: The landfill is still producing methane in some areas but with no measurable pressure build up. The KIP CAP requires the PLP to install two landfill gas probes on the southern and western edges of the KIP Area to ensure methane is not migrating off-site. The properties will also be required to monitor buildings for methane. The CAPs contain different actions that are triggered when higher levels of methane are detected. 
• Maintenance: The PLPs are required to perform inspections and maintenance to ensure the long-term effectiveness of the remedy.  The KIP PLP is required to inspect and maintain a 30” stormwater pipe that was constructed in an area at the landfill perimeter that was partially backfilled with cement kiln dust. An Environmental Covenant will be placed on the properties to ensure the cleanup actions stay in good condition to protect human health and the environment.
• Long term monitoring: A Landfill Site Coordinator (or similar arrangement) must be designated to perform the long-term monitoring required to ensure the cleanup action is meeting cleanup standards.

Next steps:  
These legal agreements will go into effect at the end of the comment period. Ecology will consider all comments received during this public comment period and may make changes to the documents.  If the documents require significant changes, we will hold another public comment period.

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.

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.