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

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


Changes in Zone A

Ecology and the parties responsible for cleanup are monitoring and deciding how best to respond to changing conditions in Zone A, the area of the landfill where an estimated 35,000 55-gallon drums of hazardous waste are buried. These changes include:
  • Field observations and monitoring information that may suggest pockets of buried waste are or recently have been burning
  • Non-aqueous-phase liquid (NAPL) on groundwater
For more information, please see the Zone A section below. You may also download the Zone A Update we mailed to nearby residences and businesses.

Focused feasibility studies final November 2018

The Industrial Waste Area Group III (IWAG) and the Landfill Group, which represent the majority of the potentially liable persons (PLPs) responsible for Pasco Landfill cleanup, each submitted a draft Focused Feasibility Study (FFS) to the Washington State Department of Ecology (Ecology) evaluating final cleanup options for all the landfill zones. The studies built upon the investigation completed in 1999 that determined the extent and locations of contamination at the landfill. They compare cleanup options for the entire Pasco Landfill, taking into account the effectiveness of past and ongoing cleanup actions.
The studies were available for public comment before becoming final. You may read our Response to Comments. We are now considering the cleanup options evaluated in the studies and public input as we write the draft cleanup action plan. The draft cleanup action plan also will be available for public comment.

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 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 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 (PLPs)

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 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. 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. They, along with the FFS reports, have also helped Ecology and the PLPs move closer to the final landfill cleanup plan that we are now drafting. 

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. Communications with the PLPs are in progress.
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 Zone A drums.
The PLPs are developing a monitoring, sampling, and analysis plan for our review. The goal of this plan is to quickly determine the NAPL’s composition, its likely source and extent, and possible ways to prevent the NAPL from flowing down to the underlying aquifer. 
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. 
Testing and evaluation of the original thermal oxidation unit found it was not meeting all emission limits in Ecology’s air quality permit. In April 2016, we issued a Notice of Violation to the PLPs. They then installed and operated a temporary, smaller-capacity thermal oxidation unit until a full-size replacement could be secured. 
Ecology held a public comment period December 5, 2016, through January 6, 2017, for the proposed installation of a replacement, full-size thermal oxidation unit. Operating the replacement unit 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 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 PLPs drafted a plan to test the performance of the new, replacement thermal oxidation unit and its ability to treat vapors from Zone A. Ecology approved that plan, and the performance test has been completed. For safety reasons, the soil vapor extraction operations were limited during performance testing to comply with agreed-upon limits affecting air flow and vapor temperature. The PLPs are preparing a report documenting the performance test results and will submit that to Ecology for review.
Cover system
The engineered Zone A cover system was installed in 2001. The cover includes several layers of soil, plastic, 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. 
The PLPs recently completed a preliminary study of the main areas of the Zone A cover that have settled. Discussions with the PLPs are ongoing to determine appropriate cover repairs and maintenance that may be needed to restore the cover system's design function.
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 would cause contaminants to flush deeper into the soil or to the underlying groundwater. Fencing further prevents access to Zone B. 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 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 received and 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. 

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.

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.

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


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

Ecology is identifying our preferred, long-term remedy in a draft cleanup action plan. We are also negotiating the associated legal agreement with the PLPs. The public will have the opportunity to review and comment on the draft cleanup action plan and legal agreement when they are ready. 


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 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