Go East Corp Landfill

The Remedial Investigation/Feasibility Study and Cleanup Action Plan were finalized following a public comment period from March 7 to April 7, 2024. Ecology prepared a Responsive Summary Report for the public comments received. The Responsiveness Summary Report describes the activities that were completed following the public comment period and describes the next steps for the Site. The Cleanup Action Plan will be implemented by a Compliance Monitoring Plan under the permitting authority of the Snohomish County Health Department. Ecology’s Solid Waste Management Program continues to provide technical support to the health department. Ecology plans to perform a periodic review of the cleanup in 2029. Periodic reviews are subject to public comment.

The nominal 40-acre Site property sits atop the Vashon advance outwash sand formation, which outcrops where steep slopes are present on the east side of the property. The Vashon advance outwash sand formation is underlain by low-permeability silt deposits referred to as the pre-Vashon lacustrine silt unit. The pre-Vashon lacustrine silt unit is estimated to be at least 110 feet thick beneath the property.

In 1969, a conditional use permit was issued for sand excavation. Workers excavated sand from a ravine on the northern part of the property and used it as construction fill for nearby construction projects. 

Rekoway, Inc. purchased the property in February 1972 and operated the landfill until 1980. Rekoway obtained a 10-year conditional-use permit from Snohomish County in March 1972 to excavate sand and gravel and to operate a landfill by filling the excavated area with solid waste. The permit authorized the disposal of “wood, mineral, and concrete solid materials, but not garbage or putrescibles.” In 1974-75, Rekoway was approved to accept “tires and bulk packaging material such as cardboard, pallets, large parcel wrappings, shredded paper, and warehousing waste material.” 

In 1974, Rekoway accepted approximately 200 cubic yards of baghouse dust containing magnesium, phosphate, and aluminum into the landfill. A fire resulted from the oxidation of the buried metal dusts. Workers excavated the material, spread it on the ground, extinguished the fire, and covered the material with soil. Partially burned trees and stumps caused another landfill fire in November 1976 that persisted through 1979. Snohomish County Health Department (formerly known as Snohomish Health District) suspended the landfill permit in November 1977.

Go East Corporation conditionally purchased the property in 1979. They requested reinstatement of the landfill permit to allow additional filling to level the landfill area for future development. Snohomish County Health Department issued a permit to operate a wood waste landfill in November 1979. The permit expired in September 1982. Go East Corporation stopped accepting waste in the summer of 1983 when Snohomish County issued a stop work order. Another landfill fire began in October 1983 and burned out by January 1986. The landfill was covered with soil in conformance with the minimum functional standards for solid waste handling in WAC 173-301, which was repealed and superseded by WAC 173-304 in October 1985, but was not closed in accordance with the governing landfill regulations in 1986.

P&GE, LLC (P&GE) acquired the property from Go East Corporation in May 2009.

P&GE consolidated and closed the landfill and re-graded the Site from March 2021 to July 2022 under the permit authorities of Snohomish County Planning and Development Services, Snohomish County Health Department, the Washington Department of Fish and Wildlife, and Ecology’s Water Quality Program.

P&GE completed landfill closure in July 2022 in accordance with current regulatory requirements for limited purpose landfills in Chapter 173-350 of the Washington Administrative Code (WAC).

The Construction Quality Assurance Report summarizes the permits and requirements, the project team, landfill closure activities, and the construction documents. This report provides supporting documents and records in appendices, including:

• The amended Landfill Closure Plans & Specifications are provided in Appendix B.
• The Construction Summary Report is provided in Appendix E.
• The Landfill Gas Probe Installation technical memorandum is provided in Appendix K.
• The Northeast Slope Reconnaissance and Observations technical memorandum is provided in Appendix L.
• The Monitoring Well Soil Boring and Construction Logs are provided in Appendix N.
• The Record Drawings are provided in Appendix O.

Landfill construction photos are shown on our Flickr account. The July 6, 2022 drone flight shows the construction of the final landfill cover.

The tracts of land that contain the landfill are subject to an Environmental Covenant for Limited Purpose Landfill.

Snohomish County Health Department issued Solid Waste Facility Permit No. PT0004938 (SW-027) to the Alpine Estates Owners Association for the Go East Landfill, effective from July 1, 2024 to June 30, 2025. The permit requires the permittee to perform post-closure requirements for limited purpose landfills.

Century Communities of Washington, LLC (Century Communities) purchased the property from P&GE on May 24, 2022. Century Communities developed the 96-lot Alpine Estates community (formerly known as the Bakerview) on the property. Snohomish County Planning and Development Services approved the Alpine Estates, A Plat Community plat map on October 24, 2023. The tracts that contain the landfill were granted and conveyed to the Alpine Estates Owners Association. Century Communities currently controls the homeowner association but plans to cede control as the homes are sold. Residential lots adjoin the northwest, southwest, and southeast boundaries of the closed landfill. The closed landfill is used for stormwater detention, a publicly-accessible recreation area, an emergency access road, and an open area. 

Ecology determined that the former landfill owners, P&GE and Century Communities, are potentially liable persons (PLPs) for the release of hazardous substances at the site.

The Agreed Order and its amendment required the PLPs to perform investigation activities under the state cleanup law, the Model Toxics Control Act. MTCA establishes standards that protect human health and the environment, which apply to all environmental media beyond the final boundary of the permitted landfill at this site.

The following documents were developed pursuant to the Agreed Order:

• The Interim Action Completion Report documents confirmation soil sampling performed during the excavation of the wedge area along the periphery of the original landfill. The report also describes confirmation soil sampling of imported fill material, the pre-construction sampling results (Appendix A), soil disposal documentation (Appendix C), asbestos-containing material documentation (Appendix D), an asbestos inspection summary for the excavated landfill material (Appendix E), and the lot exploration plan execution memorandum (Appendix F). The reconnaissance of the northeast slope is reported separately and included in Appendix L of the Construction Quality Assurance Report. An interim action addendum report was prepared that confirms soils were not impacted by potentially-contaminated stormwater management practices south of the landfill.

• The Remediation Investigation Work Plan describes the landfill property and history, the environmental setting, previous investigations, the preliminary conceptual site model, data gaps, and the remedial investigation field activities.

• The Remediation Investigation/Feasibility Study describes the regulatory background, the landfill property and history, the environmental setting, and previous and current field investigations. The historical infiltration of water through the landfill is evident by leachate impacts to groundwater beneath and beyond the landfill, where elevated concentrations of metals and polycyclic aromatic hydrocarbons were detected in groundwater and surface water. The Remedial Investigation/Feasibility Study proposed cleanup standards for groundwater, surface water, and sediment at the site. The soil beyond the landfill and the sediment downstream of the landfill complied with the cleanup standards. Elevated concentrations of manganese persist in groundwater beneath the former waste areas and in surface water that originates from the toe of the landfill. The surface water also contains elevated concentrations of iron. Naturally occurring iron and manganese are mobilized under anaerobic conditions caused by the biodegradation of organic waste in the landfill. The Feasibility Study developed and evaluated cleanup action alternatives that could be performed after landfill closure in July 2022. The cleanup action alternatives included no additional actions, monitored natural attenuation of contamination in groundwater and surface water, and monitored natural attenuation with surface water treatment. The Remedial Investigation/Feasibility Study recommended the monitored natural attenuation cleanup alternative.

• Ecology’s Cleanup Action Plan establishes the cleanup standards and selects the cleanup action for the site. The Cleanup Action Plan selected the monitored natural attenuation cleanup alternative. Landfill materials were removed from beyond the landfill boundary and the engineered landfill cover prevents the infiltration of precipitation water through the underlying waste. The Cleanup Action Plan describes the specific prohibitions and requirements in the environmental covenant. The diversion of Stream 1 and the groundwater interceptor trench reduce the infiltration of water and flow of groundwater beneath the landfill to its discharge point at the toe of the northeast landfill slope. The flow of naturally aerobic groundwater is anticipated to decrease the concentrations of iron and manganese to background conditions beneath the wedge area and to decrease their concentrations in groundwater and surface water downstream of the landfill. The monitoring of groundwater beneath the wedge area and groundwater and surface water downstream of the landfill are required until the concentrations attenuate to below their cleanup levels. The Cleanup Action Plan identifies the groundwater and surface water sampling locations and identifies the compliance criteria.

• The Compliance Monitoring Plan provides the sampling plan that implements the Cleanup Action Plan. The Compliance Monitoring Plan also includes additional sampling required for compliance with WAC 173-350-500.

Ecology provided a Satisfaction of Agreed Order letter to the PLPs. The letter states that the Compliance Monitoring Plan will be implemented under the permitting authority of Snohomish County Health Department.

The wood waste that was disposed in the landfill between 1972 and 1983 continues to biodegrade and produce diminishing quantities of methane gas. Methane gas that accumulates beneath the engineered landfill cover is collected and ventilated from a geomembrane-lined gas ventilation trench that extends between the landfill and the adjoining residential lots. Methane is a non-toxic gas that is capable of combustion at concentrations above 5 percent. The landfill gas does not contain non-methane volatile organic compounds.

Snohomish County Health Department regulates explosive gas control under the Solid Waste Handling Standards in WAC 173-350-400. Methane concentrations are regulated at the landfill property boundary and in the surrounding structures. The Alpine Estates homes are being constructed with gas barrier and ventilation systems that provide additional protection and assurances.

Century Communities contracts Herrera Environmental Consultants to oversee and monitor landfill gas at the landfill. The Landfill Gas Monitoring Readiness Report and the Landfill Gas Monitoring Update and Mitigation Plan describe the occurrence and mitigation of landfill gas at the landfill.

The Solid Waste Facility Permit issued by Snohomish County Health Department requires the permittee, though their Landfill Gas Engineer, Herrera Environmental Consultants, to monitor landfill gas in accordance with the Landfill Gas Monitoring and Contingency Plan and to perform their recommended mitigation plan.

Century Communities coordinated with the adjoining property owners, Olympic Pipe Line Company, Ecology, Snohomish County Planning and Development Services, and Washington Department of Fish and Wildlife to restore the wetlands and stream.

Incident
A mudslide occurred on northeastern portion of the Go East Corp. Landfill property on Sept. 17 and 18, 2021. The mudslide swept an estimated 500 to 700 cubic yards of imported clean soil downslope beyond the toe of the landfill. The incident occurred while crews constructed a planned access path to the toe of the landfill slope.

The mudslide occurred after clean fill material placed on the steep slope mobilized due to groundwater seepage and stormwater intrusion. The mudslide originated beyond the landfill boundary and deposited fill material beneath and beyond the toe of the landfill. No landfill material was observed in the mudslide. The mudflow extended across a wetland and to a stream on properties north and east of the property. The mudslide flowed across land owned by the 108th Street Point Homeowners Association, the Pinehurst at Waldenwood Homeowners Association, and the easement corridor for the Olympic Pipe Line Co.

A stable access path was subsequently constructed to the toe of the landfill to allow completion of the landfill closure activities. The property owner coordinated with the 108th Street Point Homeowners Association to stabilize the slope where the mudslide originated on their property.

Voluntary Actions

Century Communities planted wetland vegetation on the mudflow downstream from the landfill in March 2023, in accordance with a wetlands mitigation plan. The mitigation plan includes annual site inspections for five years and periodic maintenance, such as removing competing grasses, irrigating, fertilizing, replacing dead plants, and replacing mulch. Additionally, Century Communities purchased wetland mitigation bank credits from the Skykomish Habitat Mitigation Bank to offset temporary wetlands loss.

Snohomish County Health Department 
Snohomish County Health Department issued a landfill permit for the closure of the Go East Corp Landfill in accordance with Chapter 173-350-400 of the Washington Administrative Code. The Health Department’s approval of the Go East Landfill Closure Plan was affirmed by the state Pollution Control Hearings Board. Snohomish County Health Department intends to renew the closed landfill permit annually.

Ecology’s Solid Waste Management Program supports the Health Department but is not the regulatory agency for the landfill permit. 

Snohomish County Planning and Development Services
Snohomish County Planning and Development Services issued an initial land disturbing activity permit for the initial rough grading (including landfill closure activities) and a second land disturbing activity permit for plat development. The land disturbing permits were subject to the State Environmental Policy Act.

Washington State Department of Ecology
Ecology’s Water Quality Program grants a Construction Stormwater General Permit. Ecology maintains Bakerview Everett stormwater permit documents on a separate website.

Ecology’s Solid Waste Management Program oversees cleanup of the site under the Model Toxics Control Act.

Ecology’s Shorelands and Environmental Assistance Program works to ensure the protection of wetland resources.

Washington Department of Fish and Wildlife
Washington Department of Fish and Wildlife issued a Hydraulic Project Approval permit for the relocation of a stream on the property.  Hydraulic Project Approvals ensure that construction projects in or near state waters are done in a manner that protects fish and their aquatic habitats.

What's In My Neighborhood shows contamination cleanup sites in Washington state. Ecology works to clean up these sites to protect the health of people and the environment. Cleanups are construction projects that remove, treat, or contain potentially harmful substances.

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