Olalla Landfill

Kitsap County Public Works, Solid Waste Division is preparing a final Remedial Action Status Report that addresses Kitsap Public Health District and Ecology’s comments on the draft document. The final document will be posted on the electronic documents along with Ecology’s Opinion letter once complete.

The landfill is in southern Kitsap County, east of Highway 16 and southwest of SE Burley-Olalla Road and Bandix Roads. The closed landfill consists of two adjoining areas: Phase I to the south and Phase II to the north

Olalla landfill began accepting waste in the late 1950s or early 1960s. Municipal solid waste was disposed in the Phase I area. Construction and demolition waste, and a small volume of septic waste, was disposed in the Phase II area.

The landfill closed in accordance with an approved Closure Plan in 1989. The Phase I Area has a two-foot thick compacted bentonite-amended, low-permeability soil cover to reduce infiltration. A passive landfill gas system of perforated pipes beneath the low-permeability cover connects to three passive landfill gas flares. The Phase II Area has a soil cover.

Kitsap County Public Works Solid Waste Division maintains and performs environmental monitoring at the Olalla Landfill.

Cleanup activities began at the landfill because the concentrations of naturally-occurring metals (i.e., arsenic, iron, and manganese) and vinyl chloride exceeded the groundwater quality criteria in the upper aquifer downgradient (west) of the landfill. 

Kitsap County 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. 

This upper aquifer is the source of drinking water for three residences west of Olalla Landfill (one adjacent to the landfill parcel on SW Burley Olalla Rd, one southwest of the site, and one west of the site on the other side of Olympic Drive SE). 

Offsite water wells were sampled in 2010 and 2011 during for the Remedial Investigation Report and in 2020 and 2021 for the Remedial Action Status Report. The sampling results are summarized below and shown in the attached table. 

• The concentrations of arsenic and vinyl chloride were below the primary maximum contaminant levels for drinking water. Vinyl chloride was not detected.
• The concentrations of iron and manganese slightly or nearly exceeded the secondary maximum contaminant levels for drinking water in water wells OW-3 (screened in the lower aquifer) and OW-4 (screened in the deep aquifer). The secondary maximum contaminant levels are based on aesthetic criteria for drinking water.

Ecology’s Solid Waste Management Program oversees corrective action at the closed landfill in accordance with the state Model Toxics Control Act (MTCA) regulation (Chapter 70A.305 of the Revised Code of Washington and Chapter 173-340 of the WAC.).

Ecology develops regulations and guidelines and provides assistance to Kitsap Public Health District. Kitsap Public Health District regulates post-closure care at the closed municipal solid waste landfill under Chapter 173-304 WAC.

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.

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