A Bellingham-area private landfill where incinerator ash was disposed in the 1980s has met the criteria to safely discontinue environmental monitoring.

The Olivine Corporation Landfill is located just north of Bellingham at 928 Thomas Road in Whatcom County. Whatcom County Health & Community Services (WCHCS) regulates Olivine Landfill in accordance with Chapter 173-304 of the Washington Administrative Code (WAC) (Minimum Functional Standards for Solid Waste Handling). Ecology's Solid Waste Management Program provides technical support to WCHCS.

Olivine Corporation received and incinerated municipal solid waste at its Resource Recovery Facility and disposed of bottom ash and fly ash residual in two solid waste management units on the property. Olivine reportedly disposed of 6,135 tons of ash waste in Ash Cell No. 1 between January 1985 and December 1986 and 6,921 tons of ash waste in Ash Cell No. 2 between May 1988 and December 1989.

The ash cells are unlined landfills constructed within a low-permeability geologic formation called the Bellingham glaciomarine drift.

• Ash Cell No. 1 was closed with a cover that met the requirements in the mid-1980s.
• Ash Cell No. 2 was closed with low-permeability cover. The cover includes a 2-foot layer of low-permeability soil and a 1-foot layer of topsoil that was seeded with grass. Beneath the paved parking lot, the landfill cover consists of a geosynthetic liner, a 3-inch layer of finely-ground Olivine rock dust material, and an asphalt pavement layer. Olivine constructed a sump within Ash Cell No. 2, where leachate was extracted from a leachate standpipe, stored onsite, then transported to a wastewater treatment plant for disposal.

Olivine constructed a groundwater interceptor trench south and east of the landfill to divert groundwater from flowing through the ash. Groundwater samples were collected from monitoring wells upgradient and downgradient of the landfill.

DDJ Investments purchased the property from Olivine Corporation in 2018 and redeveloped the property. Mount Baker Roofing now operates from the property. DDJ Investments assumed permitting responsibilities for the property and continued to perform post-closure care from 2019 to 2026.

Post-closure monitoring and care is required by WAC 173-304 until the landfill becomes functionally stable based on little to no leachate generation, landfill gas production, landfill settlement, sufficient cover integrity, and groundwater quality. Ecology provides ending post-closure care guidance in Ecology Publication No. 11-07-006.

Key reports and findings

• Ecology's June 29, 2021 recommendation letter is based on review of the Thomas Road Ash Cell No. 2 Post-Closure Monitoring Variance Technical Memorandum (June 2021). Ecology concluded that the ash landfill was functionally stable for landfill gas production and landfill settlement. Ecology recommended that leachate pumping be discontinued for a 2-year evaluation period, while continuing to evaluate impacts to groundwater collected from the leachate sump and monitoring wells.
• Ecology's March 21, 2024 recommendation letter is based on review of the Olivine/Thomas Road Ash Cell No. 2 - Groundwater Metals Outlier and Natural Background analysis (December 2023). Ecology suspected that an additional source of groundwater contamination exists upgradient from the ash landfill. Ecology concluded that no further leachate pumping was warranted and recommended that records be reviewed to identify potential contamination sources upgradient of the landfill.
• Ecology's September 15, 2025 recommendation letter documents upgradient sources of contamination. Woodwaste was disposed on the upgradient property south of the ash landfill property in the 1980s, prior to construction of the groundwater interceptor trench in 1993.
  • WCHCS permitted disposal of woodwaste, but no groundwater monitoring was required since less than 2,000 cubic yards of woodwaste were disposed. The biodegradation of woodwaste consumes oxygen, creating anaerobic reducing conditions in groundwater that mobilizes naturally-occurring manganese and iron. Although impacted groundwater is diverted away from the landfill by the groundwater interceptor trench, elevated concentrations of manganese and iron are observed in wells northwest and downgradient of the ash landfill.
  • The incinerator ash is not subject to biodegradation reactions and the ash does not mobilize metals in groundwater. The impact of the ash is noted by elevated concentrations of sulfate and chloride in a well northeast of the landfill that slightly exceeds secondary maximum contaminant levels for drinking water based on aesthetic criteria, i.e., taste, color, and odor.

Ecology concluded that the Olivine Corporation Landfill satisfies the criteria for ending post-closure care and that no further groundwater monitoring is required for the landfill. Ecology recommended that the property owner voluntarily record an environmental covenant on the property.

• WCHCS (June 24, 2026) concurs that the landfill meets the criteria for ending post-closure care and that an environmental covenant should be recorded on the property. WCHCS requested that DDJ submit a permit modification application to end post-closure care.
• The draft Environmental Covenant documents the landfill, restricts land use to preserve the landfill cover and groundwater diversion trench, restricts groundwater use on the property, and provides access and notification requirements.

Next steps

• WCHCS is providing a public notice that DDJ Investments has satisfied the criteria for ending post-closure care and that a landfill permit is no longer required.
• DDJ Investments plans to decommission the leachate standpipe, a landfill gas vent, and the monitoring wells on the property.
• DDJ Investments intends to record the environmental covenant on the property.

Contacts

Bill Angel, Whatcom County Health & Community Services, 360-778-6000, [email protected]

Alan Noell, Ecology Solid Waste Management Program, 425-213-4803, [email protected]

Tim O'Connor, Ecology Solid Waste Management Program, 425-389-2695, [email protected]