Pasco Landfill NPL Site
Kahlotus Rd & Hwy 12, Pasco, WA 99301

**Para asistencia en español: (360) 407-6097,**

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The Pasco Landfill is about 1.5 miles northeast of the City of Pasco, north of the intersection of Kahlotus Road with U.S. Highway 12. The landfill property covers nearly 250 acres and is surrounded by agriculture and commercial businesses. The Basin Disposal transfer station on Dietrich Road is at the southern end of the landfill. The landfill no longer accepts waste and is closed to the public. Gates, fencing, and signs restrict access to this active cleanup site.

The landfill opened in 1958. Waste was burned in trenches until 1971, when the site became a sanitary landfill. From 1972 to 1975, the landfill accepted industrial waste. Some was delivered in 55-gallon drums and disposed in two zones. The rest was delivered as bulk liquids that were placed into large evaporation lagoons. The landfill closed entirely in 2001.

The City of Pasco passed an ordinance in 2001 that defined a groundwater protection area around part of East Pasco that is over a plume of groundwater contaminated by the landfill. A restrictive covenant is in place that prohibits activities and land uses at the landfill that could expose people to contamination.

Waste Zones

  • The New Waste Landfill received municipal waste until closure in 2001. This area is not included in the current cleanup.
  • The Municipal Solid Waste Landfill Area received household and commercial garbage until closure in 1993.
  • The Balefill/Inert Waste Area received household waste and construction debris until closure in 1989. Garbage was compacted into bales, stacked, and buried.
  • Industrial Waste was disposed in five zones:
    • Zone A contains an estimated 35,000 55-gallon drums. The drums hold solvent and paint sludges, cleaners, and other hazardous waste.
    • Zone B contained nearly 5,000 drums of herbicide-manufacturing waste that were excavated and disposed offsite in 2002.
    • Zones C and D contain residues from disposing approximately 3-million gallons of plywood resin waste, wood treatment and preservative waste, lime sludge, cutting oils, paint and paint solvent waste, and other bulk liquid waste. These zones were combined in 2002.
    • Zone E contains approximately 11,000 tons of sludge from paper manufacturing.

Potentially Liable Persons

Thirty-two different parties share responsibility for cleanup of contamination from past landfill operations. The site was added to the U.S. Environmental Protection Agency’s National Priorities List (NPL) in 1990. The Washington State Department of Ecology (Ecology) provides regulatory oversight of the cleanup work in accordance with the requirements of the Model Toxics Control Act (MTCA). Agreed Orders and Enforcement Orders are in place between Ecology and the responsible parties to clean up the landfill.

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Many chemical contaminants have leached from landfill waste into soil and groundwater, including:

Investigations have found contamination in soil directly beneath many of the waste zones. The site is covered by silty and sandy soils that help limit downward movement of contaminants. At depth, the soil conditions tend to become more coarse and gravelly.

Groundwater typically occurs at depths of 50 to 65 feet below ground and flows in a southwesterly to southerly direction toward the Columbia River. Groundwater contamination is present at low concentrations in many monitoring wells located on the landfill property. A contaminated groundwater plume historically extended from the landfill site to the Columbia River. Ongoing cleanup efforts have greatly reduced the size and concentration of the plume, and no one uses the contaminated groundwater due to a City of Pasco ordinance.

Removing drums of herbicide waste from Zone B in 2002.
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Following the 1999 Feasibility Study, significant cleanup efforts began in the early 2000s to cover and contain the Industrial Waste Zones and the Municipal Solid Waste Landfill. Drummed herbicide waste from Zone B was removed and disposed offsite. Systems to treat contaminated soil vapors, landfill gas, and groundwater were installed and monitored. These interim actions reduced the potential threat to people and the environment while the final cleanup plan is developed.

Ongoing cleanup efforts have greatly reduced the size and concentration of the contaminated groundwater plume. In many areas, contaminant concentrations in groundwater have fallen below levels that pose a risk to human health. Groundwater quality improvements are seen both within the landfill area and in portions of the plume that are within the groundwater protection area in East Pasco. Risks to the Columbia River from the contaminated groundwater plume are believed to be negligible.

Additional investigations, monitoring, and evaluation of the interim cleanup actions from 2008 to the present have helped improve the performance of the existing cleanup systems and increased contamination removal. They have also helped Ecology and the parties responsible for cleanup move closer to a final landfill cleanup plan. A focused feasibility study is underway that will help Ecology develop a final cleanup plan for the site. A draft of the focused feasibility study will be available for public review and comment before it is finalized.

Balefill/Inert Waste Area

In November 2013, a fire was reported in the Balefill/Inert Waste Area where municipal waste and tires were compacted into bales and buried.

Early attempts to smother the fire by covering the ground above it with more soil and a plastic barrier did not extinguish it. Following that, liquid carbon dioxide was injected underground over several months to help displace oxygen from the burning areas. This helped cool the fire but didn’t put it out.

In April 2014, Ecology issued an Enforcement Order to the parties performing site cleanup work. The Enforcement Order directed these parties to develop and carry out a plan to fully extinguish the underground fire near the Balefill Area.
During late summer and fall 2015, deep trenches were dug around the fire boundaries and filled with a clay-cement slurry, creating a barrier that prevented the fire from spreading and limited oxygen flow to it. Buried waste in the fire zone was then excavated and extinguished. Some combustible materials, such as tires and wood debris, were hauled offsite for disposal. After quenching, leftover waste was returned to the pit and reburied. A final cover of clay, soil, and cement was then placed over the top, effectively sealing off the original fire zone.

In December 2015, temperature and gas monitoring probes were installed around and within the former Balefill Area fire zone. Monitoring data were collected for several months. These data, together with observations made during the construction work, show the fire in this area is now out.

Lessons learned from this event will be used to help prevent the possibility of future underground fires. Ecology closed out the Enforcement Order in May 2017 after all required actions were completed and approved.

Zone A

The engineered Zone A cover system was installed in 2001. This cover has sunk down in places due to the ongoing cleanup actions. This settling is being closely monitored to ensure the cover system is not adversely affected. Repairs were made to parts of the cover in 2015 after a deep barrier wall of soil and clay was installed around the northern and eastern portions of the landfill during fall 2015.
Treatment technologies have removed approximately 1 million pounds of contaminants from soil beneath Zone A since 1997. This work is ongoing and uses a soil vapor extraction system to vacuum contaminants from the ground. The contaminated vapors are treated on-site using a high temperature incinerator called a regenerative thermal oxidizer that was installed in late 2015. This treatment unit is undergoing final testing to confirm its ability to adequately destroy the contaminants captured from Zone A.
Recent testing and evaluation of the regenerative thermal oxidizer found it was not meeting all emission limits in Ecology’s air quality permit. In April 2016, Ecology issued a Notice of Violation to the parties responsible for operating this treatment unit. Ecology is working closely with the parties to bring treatment unit emissions in compliance with air quality standards.

Zone B

In 2002, nearly 5,000 drums of herbicide-manufacturing waste were taken to a hazardous waste disposal facility. Some contaminants remain in the soil, so a protective, engineered cover was installed in 2013. The cover includes several layers of soil, plastic, and clay that are many feet thick. 
This cover keeps people, animals, and precipitation from contacting the contaminated soil beneath it. Rain and snow melt would cause contaminants to flush deeper into the soil or to the underlying groundwater. Fencing further prevents access to Zone B.

Zone C/D

Waste materials in Zone C/D are protected by covers installed in 2001. Portions of the Zone C/D cover also extend over a trench where garbage was burned prior to 1971.
The Zone C/D cover system prevents people, animals, and precipitation from contacting contaminated soil and waste. Rain and snow melt would cause contaminants to flush deeper into the soil or to the underlying groundwater. Fencing further prevents access to this zone.

Zone E

Waste materials in Zone E are protected by a cover installed in 2001. 

The Zone E cover system prevents people, animals, and precipitation from contacting contaminated soil and waste. Rain and snow melt would cause contaminants to flush deeper into the soil or to the underlying groundwater. Fencing further prevents access to this zone.


In April 2016, Ecology was invited to share landfill information with the Eastern Washington Chapter of the Academy of Certified Hazardous Materials Managers in Richland. Our presentation included an update on cleanup progress, an overview of the Balefill fire response actions, and a discussion of planned steps to complete the cleanup work. 

In May 2016, Ecology mailed an informational flyer (includes English/Spanish) updating the local community that the Balefill Area underground fire is out and about progress on the draft focused feasibility study.

Ecology held a public comment period December 5, 2016, through January 6, 2017, for the proposed installation of a regenerative thermal oxidizer (RTO). The RTO controls emissions removed by the soil vapor extraction system in the landfill’s industrial waste portion. Operating the RTO requires a permit from Ecology’s Air Quality Program. The draft permit and supporting information were available for public review and can be found in the document repository

Ecology responded to comments on the RTO permit from the two groups that represent the 32 parties responsible for cleanup. We held another comment period from March 20 through April 20, 2017, because of the changes we made to the permit in response to comments. The two groups responsible for cleanup commented on the revised permit, and we responded to comments and approved the permit.

In May 2017, Ecology presented information about putting out the fire in the Balefill Area at the Local Emergency Planning Conference in Chelan, Washington. 


The interim action cleanup activities will continue until a final cleanup plan is selected. Ongoing monitoring will continue throughout the landfill and in areas where the groundwater plume extends off the property.

After the ongoing focused feasibility study process is completed, Ecology will identify our preferred remedy in a draft cleanup action plan. The public will have the opportunity to review and comment on the draft focused feasibility study and the draft cleanup action plan when they are ready. 



Map showing site location as Franklin County, WA SITE INFORMATION


View Electronic Documents

Site Summary Report

Facility Site ID: # 575

Cleanup Site ID: 1910

Pasco, Franklin County

Status: Cleanup Started   Get definitions of Status terminology

Charles Gruenenfelder
Site Manager
(509) 329-3439

Erika Bronson
Public Involvement Coordinator

Document Repositories:

Eastern Regional Office
N 4601 Monroe St
Spokane, 99205-1265

Mid Columbia Library
1320 West Hopkins Street
Pasco, 99301-5097