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

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


After public comment in late 2019, the Pasco Landfill Cleanup Action Plan is final. Parties responsible for this site were unable to meet a November 4, 2019 deadline declaring their commitment to participate in a consent decree process for the cleanup work. In response, we issued an Enforcement Order on November 8, 2019.

Planning work is ongoing, and cleanup construction will begin in late 2020. Plan details include:

  • ~35,000 drums of hazardous waste and associated debris from Zone A will be excavated, characterized, and transported for off-site disposal 
  • Zone B is becoming a separate site
  • The remaining municipal solid waste and industrial waste zones will continue to be maintained and monitored under their existing engineered covers

Learn more

Please click on the photo for a larger view


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 200 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 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. In July 2019, Ecology granted a request for this zone to become its own cleanup site; see the Zone B section below for more information.
    • 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 (PLPs)

Thirty-plus different parties, legally called potentially liable persons (PLPs), 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 PLPs have grouped themselves by the type of wastes each party (or their predecessor companies) disposed at the site, and shared cleanup objectives. The four groups include:
  • Industrial Waste Area Group III (IWAG) 
  • Landfill Group 
  • Bayer CropScience (Zone B) 
  • Unaffiliated
We provide regulatory oversight of the cleanup work under the Model Toxics Control Act (MTCA). Agreed orders and enforcement orders are in place between Ecology and the PLPs that require the PLPs to investigate and clean up the landfill.

Please click on the photo for a larger view


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. A 2001 City of Pasco ordinance remains in place to restrict groundwater use in areas where landfill contaminants still are detected.

Removing drums of herbicide waste from Zone B in 2002.
Please click on the photo for a larger view


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. Multi-layer cover systems designed to contain industrial and municipal wastes were installed. 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 we develop the final cleanup plan. They're also providing information about the effectiveness of different cleanup methods.

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.

In 2018, the IWAG and the Landfill Group each submitted a Focused Feasibility Study (FFS) evaluating final cleanup options for all the landfill zones. The studies compared cleanup options for the entire Pasco Landfill, taking into account the effectiveness of past and ongoing cleanup actions. The studies also helped us draft our Cleanup Action Plan, in which we shared final plans to clean up each landfill area.

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 PLPs. The order directed them 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 the Balefill Area waste 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

Changes in Zone A
During summer and fall 2016, Ecology observed changes in Zone A soil vapors and underground temperatures, and we asked the PLPs to gather more information. From January through March 2017, the PLPs investigated whether an underground fire potentially is or was present beneath Zone A. The PLPs issued their Zone A Combustion Evaluation Report (Appendices) in late April 2017. Ecology responded in a letter in early September 2017.
In April 2017, Ecology learned that non-aqueous-phase liquid (NAPL) was present in a Zone A groundwater monitoring well (MW-52S). Resampling in June 2017 confirmed an approximate 3-inch-thick layer of NAPL, containing various petroleum hydrocarbons, solvents, and PCBs (polychlorinated biphenyls), was floating on the water table. The NAPL is liquid chemicals that are leaking from the degrading Zone A drums.
Monitoring and groundwater sampling shows that the NAPL is present in a localized area beneath Zone A, and has not moved beyond the landfill property boundaries. Absorbent “socks” have been installed at well MW-52S since August 2018 to capture and remove NAPL that floats on the water table. The socks are regularly replaced when a certain amount of NAPL is captured. The amount of NAPL removed from well MW-52S has decreased over time.

The continued presence of NAPL beneath Zone A and concerns about elevated temperatures caused by underground smoldering are two important reasons Ecology is requiring the drums to be removed from Zone A. This will stop the sources of these uncontrolled releases and potential fire hazards.
Treating soil contamination
Treatment technologies have removed approximately 1 million pounds of contaminants from soil beneath Zone A since 1997. This ongoing work uses a soil vapor extraction system to vacuum contaminants from the soil above the water table. The contaminated vapors are treated on-site using a high temperature incinerator called a thermal oxidation treatment unit. 
Operation of the thermal oxidation treatment unit requires a permit from Ecology’s Air Quality Program. The permit (Approval Order) and supporting  documentation associated with this treatment unit can be found in the document repository
Ecology responded to two sets of comments on the air quality permit from two of the PLP groups. We held another comment period from March 20 through April 20, 2017, to address changes we made to the permit in response to these comments. The same two PLP groups commented on the revised permit. We responded to comments and approved the permit. 
The operating permit requires annual performance testing of the thermal treatment unit. Performance testing in 2017 and 2018 confirmed the ability of the treatment unit to meet the conditions of Ecology’s air quality permit. Annual performance testing was recently conducted in August 2019. Results from this latest performance test are pending.
Cover system
The engineered Zone A cover system was installed in 2001. The cover includes several layers of soil, plastic geomembrane, and clay that are many feet thick. The cover system was installed to prevent people, animals, and precipitation from contacting contaminated soil and waste. The system was designed to quickly shed rainfall and snowmelt to adjoining stormwater holding ponds or allow plants that grow on its surface to use the water.

The top of the cover has settled over time, creating localized, closed depressions up to 6 feet deep in places. This ground settlement is being closely monitored to ensure the cover system is still protective and functional.

Repairs were made in 2010 to address areas that had settled at the southwest and northwest corners of the Zone A. More repairs were made 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. 
In 2018, the geomembrane was further evaluated to assess its condition and integrity. No visually evident holes, tears, punctures, or signs of deterioration were observed. During the planned drum removal work, the current cover will be removed in stages. A new cover system will be installed after the Zone A cleanup work is completed.
In 2002, nearly 5,000 drums of herbicide-manufacturing waste were excavated and 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. Without the engineered cover, rain and snow melt could flush contaminants deeper into the soil or to the underlying groundwater. Fencing further prevents access to Zone B.
Becoming a separate site

The PLPs primarily responsible for Zone B cleanup work (Bayer CropScience Inc.) petitioned Ecology in late 2018 to remove Zone B from the Pasco Landfill site and establish a new, separate cleanup site. We considered the following factors before approving the request in July 2019:

  • Zone B’s location in relation to other waste disposal areas at the site
  • storical and recent groundwater monitoring results and site-wide groundwater flow patterns
  • The previous drum removal
  • Known and anticipated engineered cover system performance

We will prepare separate cleanup documents and a separate legal agreement for Zone B. Zone B PLPs will be solely responsible for maintaining the cover and institutional controls, and monitoring groundwater. They will no longer participate in cleanup activities for the rest of the Pasco Landfill site.

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. Without the engineered cover, 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. 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. Without the engineered cover, 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.


From September 3 to October 3, 2019, Ecology held a public comment period for the Cleanup Action Plan, legal documents that include a scope of work and schedule, and State Environmental Policy Act documents (SEPA checklist | determination of non-significance). We held a public meeting at Virgie Robinson Elementary School on September 17, and our presentation is available for online viewing. You may also view our presentation at the September 23 Pasco City Council meeting. We responded to eight sets of comments. You may read them in our Response to Comments. The draft documents became final without further changes, and cleanup is moving forward under an Enforcement Order we issued November 8, 2019 because the PLPs could not meet the November 4 deadline to move forward under a consent decree.

From September 12 to October 26, 2018, Ecology held a public comment period for the Focused Feasibility Studies that evaluate final cleanup options for all areas of the Pasco Landfill (see the English/Spanish public notice). We held a public meeting at Virgie Robinson Elementary School on September 26, and our presentation is available for online viewing. The comment period end date was extended from October 12 to October 26 in response to a request from the Franklin County Commissioners. We responded to six sets of comments. You may read them in our Response to Comments.

In October 2017, Ecology mailed a Zone A Update to residences and businesses near the Pasco Landfill to inform the community about a potential underground fire and new groundwater contamination leaking from the drums in this zone.

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

**If you are part of a group interested in a presentation about the Pasco Landfill, please contact Erika Beresovoy at or 509-329-3546 for scheduling.**


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

When the Zone B draft Cleanup Action Plan, legal agreement, and SEPA documents are ready, we will make those available for public comment and notify the community using the same mailing list we have for the Pasco Landfill.

Page last updated 2/15/20.


Map showing site location as Franklin County, WA SITE INFORMATION


View Electronic Documents

Cleanup Site Details Report

Facility Site ID: # 575

EPA's Pasco Landfill website

Cleanup Site ID: 1910

Pasco, Franklin County

Status: Cleanup Started   Get definitions of Status terminology

Charles Gruenenfelder
Site Manager
(509) 329-3439

Erika Beresovoy
Public Involvement Coordinator

Document Repositories:

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

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