Olalla Landfill

Olalla Landfill is a closed landfill that is regulated under WAC 173-304 (Minimum Functional Standards for Solid Waste Handling). Kitsap County Public Works (Public Works) Solid Waste
Division is the owner and operator of the closed landfill.

Waste disposal began in the late 1950s or early 1960s. The types of waste included construction and demolition materials, mixed municipal solid waste, and a small volume of septic sludge. The waste was reportedly burned and covered with soil on a monthly basis until the early 1970s, which was common practice in the 1950s and 1960s. Kitsap Public Health District (Health District) first issued a landfill permit to a private operator in 1969. Public Works began operating the landfill in 1971. Mixed municipal solid waste was disposed in the Phase I area on the south end of the landfill, while construction and demolition waste was disposed in the Phase II area on the north side of the landfill. The Health District authorized the disposal of 300,000 gallons of septic tank waste in 1978. The landfill stopped receiving waste in the spring of 1985 when the transfer station at the north end of the property began operations. Public Works implemented a closure plan to close the landfill in
1989.

The landfill does not have an engineered composite liner beneath the solid waste, which is a requirement for new landfill units constructed after November 1985. The 6.5-acre Phase I closure area is on the south side landfill, while the 4.5-acre Phase II closure area is on the north side of the landfill. The Phase I area is covered with an engineered low-permeability, clay-amended vegetated protective soil cap, while the Phase II area is covered with vegetated soil. The Phase I area has perforated landfill gas collection pipes beneath the low permeability cover that allow methane to discharge through three passive landfill gas flares.

The Phase I and II areas are surrounded by a gravel perimeter access road that encompasses approximately 12 acres. The closed landfill is served by a groundwater monitoring network, a surface water conveyance system and stormwater detention pond, a passive landfill gas collection system, public access controls, and a surrounding vegetation buffer.

Post-closure care includes periodic monitoring and evaluation of groundwater and landfill gas to confirm the integrity of the landfill containment systems. Post-closure care is required until the landfill generates little or no leachate and landfill gas, landfill settlement has stabilized, and groundwater protection standards have been satisfied.  

Ecology listed Olalla Landfill on the Contaminated Sites List because the concentrations of naturally-occurring metals (i.e., manganese, iron, and arsenic) and vinyl chloride exceeded groundwater protection standards in the upper aquifer downgradient (west) of the landfill.

Public Works is performing an independent cleanup action in accordance with WAC 173-340 (Model Toxics Control Act Cleanup Regulations), with input from Ecology and Public Health.

Public Works prepared a Remedial Investigation/Feasibility Study (Volume I and Volume II) in May 2014 and a Cleanup Action Plan in December 2014. The Cleanup Action Plan requires the monitored natural attenuation of contamination in the upper aquifer and land use controls. The monitored natural attenuation cleanup was implemented in a Compliance Monitoring Plan in March 2015, which includes a sampling and analysis plan for groundwater, surface water, and landfill gas. Additionally, Public Works periodically requests to sample offsite water wells west of the landfill. Annual monitoring reports are available to download in View Documents link. 

Public Works prepared a Remedial Action Status Report in March 2023 to evaluate the performance of the cleanup action, and Ecology provided an opinion letter in April 2023.

Public Works is currently evaluating additional cleanup activities while continuing to implement the Compliance Monitoring Plan and periodically sampling offsite water wells.

Kitsap Public Health District is the jurisdictional health department that permits the landfill. Public Works submits landfill reports to the Health District, according to the permit. For more information, please contact Steve Brown at (360) 633-9321 or email steve.brown@kitsappublichealth.org.

Ecology’s Solid Waste Management Program maintains regulatory standards and provides technical assistance to the jurisdictional health departments. Ecology oversees cleanup actions at permitted landfills in accordance with the state’s cleanup law, the Model Toxics Control Act, when hazardous substances have been released from the landfill. The jurisdictional health department supports this work.

Permitted landfills are potentially subject to the state’s cleanup law, the Model Toxics Control Act (MTCA) if there has been a release of hazardous substances from the landfill.

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

To report an environmental problem or concern, any time, day or night, use the online reporting form.

Counties: Island, King, Kitsap, San Juan, Skagit, Snohomish, and Whatcom
Email: nwroerts@ecy.wa.gov
Phone: 206-594-0000

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