McCollum Park

The landfill comprises most of the northern half of the 78-acre park. The limits of the landfill extend beneath 128th Street SE to the north, across Dumas Road to the east, and is bordered by North Creek to the west and wooded parkland to the south. The remedial investigation considered the landfill and a larger “study area,” which encompassed McCollum Park, portions of the landfill that extend into public right-of-way, areas in which groundwater and surface water monitoring stations were installed, residences along Heatherwood Drive (located south of the landfill), and a trailer park located north of the landfill across 128th Street SE.

Snohomish County acquired the property in 1922. Gravel mining operations began in 1929. The gravel pit was used by the County for refuse disposal from about 1947 to 1967, and was known as the Emander Landfill during and following landfill operations. Landfilling operations were completed by 1967, and a soil cover was installed. The property was subsequently turned over to the Snohomish County Parks and Recreation Department for development as McCollum County Park, and a transit park and ride was developed over the north part of the landfill.

A periodic review is conducted about every five years after a cleanup action when institutional controls are used as part of the remedy. The purpose of the periodic review is to make sure the controls remain effective, and the cleanup still protects human health and the environment.

The 2023 Periodic Review concluded that the remedy may not be protective of human health and the environment. The Periodic Review findings included the following:

• Groundwater compliance monitoring at the site indicates that arsenic, iron, manganese, and vinyl chloride remain above cleanup levels. The current groundwater monitoring network is not sufficient to determine if contamination extends off of the property, and the site does not appear to have been fully characterized. Potential impacts to adjacent residences and other properties are unknown (including potential vapor intrusion).
• The restrictive covenant for the property is in place, but only restricts groundwater extraction. It is not effective in protecting human health and the environment from exposure to hazardous substances since there are no restrictions on the release or exposure of other contaminated media, no land use restrictions, and no requirement to maintain the landfill cap or gas management system. Snohomish County currently maintains the site to ensure the cleanup actions remain effective, but the long-term integrity of the cleanup action is not ensured by the covenant.
• The covenant restriction on groundwater extraction applies only to the subject property. There are no restrictions on any adjacent properties that may be impacted by the landfill.