• You are here: EPA Home
• Region 8
• Superfund
• Colorado Cleanup Sites
• Lowry Landfill

Superfund Program

Lowry Landfill

Site Type: Final NPL City: Aurora County: Arapahoe Street Address: 4200 S. Gun Club Rd. ZIP Code: 80018 EPA ID: COD980499248 Site ID: 0800186 Site Aliases: Denver Arapahoe Disposal, Denver Arapahoe Chemical Waste Processing Facility, Conoco City & County of Denver Landfill, City & County of Denver Landfill Congressional District: 4

View an image of the Lowry Landfill Remedy Components (PDF, 1 pg, 56K, about PDF files)

Site Status & Updates

1,4-Dioxane in Shallow Groundwater Lowry Landfill Superfund Site Fact Sheet available
In March 2008, EPA, in conjunction with the Colorado Department of Health and the Environment (CDPHE) and the Tri-County Health Department (TCHD), released a fact sheet providing information about the plume of 1,4-dioxane found in the shallow groundwater north of the Lowry Landfill Superfund site. The plume is under investigation because 1,4-dioxane has been classified as a probable human carcinogen. EPA found no significant health risk associated with 1,4-dioxane with either surface water or groundwater. The fact sheet can be found in the Site Documents section of this Web page.

EPA Announces the Availability of the Explanation of Significant Differences Document for Lowry Landfill (see Site Documents section below)

EPA, in consultation with the CDPHE, has released an Explanation of Significant Differences (ESD) for the Lowry Landfill Superfund Site in Arapahoe County. The ESD describes changes made to the remedy for extracted landfill gas at the site.

The treatment process for extracted landfill gas has been changed from treatment by burning in an enclosed flare to using the gas in a landfill gas-to-energy facility that has been constructed at the site. The landfill gas will be used as fuel for four internal combustion engines that generate electricity that is made available to a local utility company.

The beneficial use of landfill gas at the Lowry Landfill is consistent with the mission of EPA's Landfill Methane Outreach Program, which is to reduce methane emissions by promoting the development of cost-effective and environmentally beneficial landfill gas-to-energy projects. The landfill gas-to-energy project at the site provides several benefits, including destroying hazardous substances in extracted landfill gas, offsetting the use of non-renewable energy resources for the generation of electricity, and reducing emissions of sulfur dioxide, nitrogen oxides, carbon dioxide and particulate matter from the use of non-renewable resources.

This change does not fundamentally alter the site-wide remedy presented in the Record of Decision for the site, signed by EPA in 1994. The site-wide remedy remains protective of human health and the environment.

CDPHE concurs with the ESD and the changes to the selected remedy described in the document.

The complete site files and administrative records are available at the EPA Denver location; selected site documents are available at the library.

If you would like a copy of the ESD sent to you, or for more information, please contact Community Involvement Coordinator John Dalton.

Top of Page

---

The City and County of Denver (Denver), Chemical Waste Management Inc., and Waste Management of Colorado, Inc. (WMC) recently proposed a modification to the landfill gas remedy. The remedy selected by EPA for the Lowry Landfill Superfund Site requires landfill gas to be collected at extraction wells and delivered, via a network of pipelines, to a large burner that destroys methane and organic compounds in the gas. Landfill gas from the adjacent Denver Arapahoe Disposal Site is also delivered to the Superfund Site for treatment.

Landfill gas from municipal solid waste landfills consists of approximately 50% methane, 45% carbon dioxide and a balance of other gases (primarily nitrogen); it is created by biological decomposition of organic matter in landfills under low oxygen conditions. The landfill gas collected from the Lowry Landfill Superfund Site may also contain volatile organic compounds, semi-volatile organic compounds, and other chemicals from the industrial waste that was disposed there from the mid-1960s until 1980.

Denver and WMC have made a proposal to EPA and the Colorado Department of Public Health and Environment (CDPHE) to construct a new landfill gas-to-energy plant in which landfill gas will instead be burned in four combustion engines that will generate electricity for a local utility. The gas will serve as a source of "green" energy akin to wind, solar and other renewable energy sources. Similar systems are in place at landfills around the country, though most are municipal solid waste landfills. If approved, this will be the only operational plan utilizing this innovative technology in Colorado to date. Pending EPA and CDPHE approvals, construction on the new plant is expected to begin in the spring of 2007 and be completed by late summer.

Denver and WMC have applied for a construction permit from CDPHE to allow installation of four new landfill gas-fired internal combustion engines at the Lowry Landfill Superfund Site. The Colorado Air Pollution Division has declared that the proposed construction warrants public comment. More information on how you can comment can be found at: http://www.cdphe.state.co.us/ap/airpublicnotices.html.

On August 12, 2005, EPA signed a Record of Decision (ROD) Amendment that modified the cleanup plan for the two remaining waste pits in the "Former Tire Pile Area (FTPA)". The ROD Amendment is a result of EPA's consideration of and response to new information received since EPA signed the original ROD in 1994, and consideration of public and State comments on EPA's proposed modifications to the remedy for the FTPA waste pits.

In the ROD Amendment, EPA selected "Capping with Product Recovery" as the cleanup plan for the two remaining FTPA waste pits. This was the alternative proposed by EPA in the "Proposed Plan for the Former Tire Pile Area" issued by EPA in May, 2005.

EPA's selected remedy for the remaining FTPA waste pits is changed from excavation to:

• Extraction of non-aqueous phase liquid from within and immediately outside the waste pits;
• Onsite temporary storage of extracted liquids;
• Transportation and offsite treatment and disposal of extracted liquids;
• Maintenance of the existing cap on each waste pit; and
• Groundwater monitoring downgradient of the FTPA waste pits.

Construction of the remedy for the FTPA is slated to begin during the summer of 2006.

In late 2005, 1,4-dioxane was reported in groundwater collected from monitoring wells north of the site. The concentrations were greater than the Colorado Department of Public Health and Environment's (CDPHE) recently-established ground and surface water standard of 6.1 parts per million. An investigation is underway to determine the source and extent of the contamination. There is no indication that anyone is currently being exposed to 1,4-dioxane in the groundwater or surface water near the Lowry Landfill. Plans for addressing the problem will be developed and implemented as quickly as possible.

Top of Page

---

Site Description

The approximately 480-acre Lowry Landfill Superfund Site is located near the intersection of Quincy Avenue and Gun Club Road in Arapahoe County, 15 miles southeast of the City and County of Denver and 2 miles east of Aurora, CO. The Denver Arapahoe Disposal Site, an operating municipal solid waste landfill northeast of the intersection of Gun Club Road and East Hampden Avenue, forms the northern boundary of the site. In 1964, the land was deeded to the City and County of Denver, which still owns the site.

From the mid-1960s until 1980, the City and County of Denver operated a "co-disposal" landfill at the site, which means that both industrial waste (solid and liquid) and municipal solid waste were accepted for disposal there. The liquids were placed into 78 unlined trenches over approximately 200 acres, and then solids such as soil, old tires and household refuse were added to the trenches to absorb the liquids. The types of waste disposed at Lowry Landfill using this practice included industrial de-greasers, paint, pesticides, hospital and veterinary waste, metal-plating waste, petroleum products, sewage sludge, tires and household waste.

EPA estimates that approximately 138 million gallons of industrial wastes were disposed of at Lowry Landfill. Nearly all of these wastes were disposed in the southern half of the site within the 200-acre main landfill. A much smaller volume of waste was placed north of the main landfill in ponds and waste pits. Some liquids were sprayed directly onto the soil in large "leachate spraying" areas located in the northern part of the site.

During the 1970s and 1980s, millions of tires had accumulated at the site. The tires were laid on top of other waste that had been placed in three separate pits, each approximately 20-30 feet deep. From 1989 through 1992, the City and County of Denver and its contractors removed, shredded and consolidated the tires and placed the tire shreds in a monofill on the east side of the site for potential future re-use as fuel. The area and three waste pits that lay under the tires became known as the Former Tire Pile Area or "FTPA".

In 1980, Denver stopped co-disposal practices. Landfill operations continued at the site until 1990, but were restricted to disposal of municipal solid waste only. From 1980-1990, Waste Management of Colorado (WMC) operated the Lowry Landfill under a contract with Denver.

The waste disposed at Lowry Landfill contaminated the soils at the site and eventually contaminated shallow groundwater. Additionally, gases from the buried wastes contaminated the air spaces in subsurface soil. In 1984, EPA designated Lowry Landfill as a Superfund Site. This designation allowed EPA to access federal funding from the Superfund trust fund to conduct investigations into the environmental problems there. The Superfund designation also allowed EPA to compel those responsible for disposal of hazardous substances to perform investigations or otherwise contribute to the effort.

In 1990, all landfill operations stopped at the site to allow environmental investigations to proceed without interference. The landfill operator, WMC, constructed a soil cover over the 200-acre main landfill in the southern part of the site. The landfill cover is at least 4 feet thick and up to 12 feet in thickness in some places. After investigating the contamination at the site, evaluating the potential risk the site posed to human health and the environment and considering alternative strategies for cleaning up the site, EPA selected a comprehensive plan in 1994. The plan is described in detail in the ROD signed by both EPA and the Colorado Department of Public Health and Environment (CDPHE) on March 10, 1994.

The plan is based on the concept of "containment," which means protective measures are put in place to prevent movement offsite of contamination above safe levels. EPA requires proof that safe levels are achieved at locations inside the site boundaries, called the "point of compliance". Most of the components of the plan are currently in place and operating to achieve the objectives described in the 1994 ROD. The completed components are described below.

An 8,800-foot-long underground Groundwater Barrier Wall of soil and clay encloses the west, south and east sides of the main landfill in the southern part of the site. The wall is below the ground surface, approximately 40 to 75 feet deep. The wall minimizes the flow of clean groundwater onto the site from the south and west, and the flow of groundwater away from the site to the east, reducing the volume of contaminated groundwater produced by contact with the wastes buried in the landfill. This component was completed in 1998.

The landfill cover is maintained as part of the plan selected in the ROD. The cover minimizes the amount of rainwater that can seep into the landfill, thus reducing the amount of groundwater that could become contaminated by contact with the wastes in the landfill and require treatment. In 1999, two feet of additional soil cover were placed on the 29-acre north face of the landfill to provide a minimum cover thickness of four feet over the entire closed landfill area. At the northern limit of the main landfill, a trench collects contaminated groundwater flowing north from the buried wastes. The groundwater collected in the trench is pumped to the water treatment plant located at the northern boundary of the site. This system, known as the North Toe Extraction System, was completed in 1998. At the intersection of the unnamed creek alluvial channel and the northern site boundary, contaminated groundwater is captured in another system called the North Boundary Barrier Wall or "NBBW". This 1,000-foot-long and 30-foot-deep clay wall, built in 1984, provides a barrier to groundwater flow to the north. At the upstream side of the NBBW, a gravel bed allows collection and removal of migrating groundwater. Groundwater from the gravel bed is pumped to the water treatment plant.

Denver originally built an onsite water treatment plant in 1984. The plant has undergone several upgrades, most recently in 2004. Contaminated water collected from various areas of the site is treated at the plant to a level safe for discharge into a sanitary sewer line. The discharged water eventually reaches the Metro Wastewater Reclamation District and Aurora's wastewater treatment facilities located offsite. The City of Aurora and the Metro Wastewater Reclamation District issued the industrial pretreatment discharge permit for the water treatment plant at the site. The offsite facilities only accept water that complies with the terms of the site industrial pre-treatment discharge permit. North of the closed landfill area, contaminated groundwater is kept separate from clean surface water within the unnamed creek streambed by permeable material that has been placed in the streambed and covered with a clay layer. The permeable material provides a pathway for groundwater to flow to the north without contacting surface water. The top of the clay cover is now the streambed, allowing clean surface water to run off the surrounding site areas and migrate to the north without coming into contact with contaminated groundwater flowing underneath the cover.

A landfill gas collection system of 54 extraction wells was installed in 1997 in the main landfill to remove and burn gases generated from the buried waste. All of the extracted gas is routed to an enclosed flare at the northern end of the site where it is burned. Emissions from the flare are monitored to ensure that they meet environmental standards and are safe for the surrounding community.

As an extra measure of protection from exposure to the wastes remaining at the site, the City and County of Denver, Arapahoe County and the City of Aurora enacted controls of land and groundwater usage. These controls work to prevent people from coming into contact with the contaminated soil, water or landfill gas that remains on the site. In addition to the City and County of Denver, EPA and CDPHE have the authority to enforce the onsite controls.

Long-term monitoring programs for groundwater, surface water, air, and subsurface soil vapor are in place to evaluate the effectiveness of the containment and collection systems, and the overall protectiveness of the cleanup actions. The ROD was revised by EPA 1995 and again in 1997. EPA informed the public of the revisions by issuing an "Explanation of Significant Difference" or "ESD" for each. The first ESD was issued on August 14, 1995 to explain changes to the site performance standards based on new information that EPA received subsequent to the 1994 ROD. The second ESD was issued on October 24, 1997 to allow (a) pretreatment of contaminated groundwater collected at the site and discharge of the treated groundwater to a sanitary sewer for further treatment at an offsite wastewater treatment plant under the terms of an industrial wastewater discharge; and (b) on site treatment and disposal of contaminated materials excavated from the FTPA waste pits.

The FTPA comprises approximately 54 acres located immediately north of the main landfill area and east of the unnamed creek. Initial investigations found three waste pits there. These pits are separate from the large main landfill in the southern part of the site, although they contain similar wastes.

The 1994 ROD called for digging into the FTPA waste pits to remove surface and subsurface drums, associated free liquids and other visible contamination to the extent practicable. Contaminated materials were to be disposed of offsite. As described above, in 1997, EPA changed that plan to allow the contaminated materials to be treated using controlled aeration and disposed of onsite. This approach was implemented successfully at the middle waste pit in 1998. However, when excavation began in the northernmost pit in May 1999, highly contaminated waste liquids were encountered at depths of 6 feet and below. Some contaminated vapors were expected and precautions were taken such as digging within an enclosed structure and ventilating and treating vapors within the structure. However, the amount and toxicity of vapors produced were not expected, overwhelmed the safety measures in place and became dangerous to the workers. As a result, EPA granted permission for the digging to stop. Subsequently, EPA required additional investigations and studies in the FTPA waste pits.

Between March 2002 and January 2003, a new approach to cleaning up the FTPA waste pits was tested in a "pilot study." The study was called "pilot" because it was implemented only at the south waste pit as a test. EPA used the pilot study information to determine if that approach should be implemented at both the north and south waste pits. The new approach was to use electricity to heat the waste pit and extract contaminated liquids and vapors. Heating enhances the volume of liquids and vapors that can be extracted. The pilot study was only partially successful.

At the conclusion of the pilot study in 2003, conditions at the FTPA north and south waste pits remained significantly different from those that had been anticipated when EPA selected the cleanup plan in 1994. Whenever there is a change in scope, performance or cost of a selected cleanup plan, EPA evaluates the significance of the change. If EPA determines that the change no longer reflects the plan selected in the ROD, it is considered a "fundamental" change, and EPA will formally modify the ROD. In 2003 through 2004, EPA evaluated excavation as described in the 1994 ROD against other alternatives to determine if a fundamental change in the cleanup approach for the FTPA waste pits is warranted. . On August 12, 2005, EPA selected "Capping with Product Recovery" as the cleanup approach for the remaining two FTPA waste pits.

Top of Page

---

Site Risk

Media Affected	Contaminants	Source of Contamination
liquid waste, soil, solid waste, debris, surface water, groundwater, sediment, leachate	chemicals, solvents (VOCs, SVOCs), sludges, landfill gas	landfill wastes

Top of Page

---

Cleanup Progress

The federal law that created the Superfund process requires that EPA thoroughly review a contaminated site every five years to determine if the prescribed remedy is protective of human health and the environment. The first five year review of the Lowry Landfill Superfund Site was completed in September of 2001, five years after initiation of the remedial action. EPA conducted the review in cooperation with CDPHE and gathered input from other regulatory agencies and municipal officials, as well as the general public. The first review found that a majority of the remedy elements were protective of human health and the environment but that a statement about the overall protectiveness of the remedy could not be made until all remedy components were complete. The next five-year review is underway and scheduled to be completed by September, 2006.

EPA approved the Sitewide Groundwater Monitoring Plan on February 18, 2005. Information collected under the groundwater monitoring plan is expected to support the next Five Year Review. In addition, EPA approved the Feasibility Study for the FTPA Waste Pit Remedy on December 30, 2004. EPA relied on the evaluation of alternatives in the Feasibility Study in proposing a new approach to remedial action at the two remaining FTPA waste pits. EPA issued a proposed plan for the two remaining FTPA waste pits in May, 2005 and provided a public comment period from May 26, 2005 until June 27, 2005. During the public comment period, EPA held two public meetings. After considering the public and State comments, EPA selected "Capping with Product Recovery", and issued a ROD Amendment on August 12, 2005.

Top of Page

---

Community Involvement

EPA has implemented an aggressive community involvement program for the Lowry Landfill. There have been numerous fact sheets, site tours and open meetings since the site first gained the public's attention.

In addition, a group of concerned community members, called Citizens for Lowry Landfill Environmental Action Now (CLLEAN), has a Technical Assistance Grant (TAG)from EPA to hire a technical advisor and help inform community members about technical issues related to site cleanup.

Top of Page

---

Site Documents

You will need Adobe Acrobat Reader to view some of the files on this page. See EPA's PDF page to learn more.

Best way to open a very large file: right-click and save it to a folder.

Annual Update to the Five-Year Review, January 2011 (PDF, 3 pp, 39K)

1,4-Dioxane in Shallow Groundwater Lowry Landfill Superfund Site, March 2008 (PDF, 4 pp, 155K)

Third Explanation of Significant Differences, May 2007 (PDF, 10 pp, 584K)

Second Five-Year Review Report, February 2007 (PDF, 157 pp, 2.2MB)

1,4: Dioxane and the Lowry Landfill Superfund Site, July 2006 (PDF, 6 pp, 276K)

Update No. 17: Remedial Activities Continue and Second Five-Year Review Begins, July 2006 (PDF, 12 pp, 546K)

Lowry Landfill Site ROD Amendment for FTPA Waste Pits, August 2005 (PDF, 45 p, 1.5MB)

Lowry Site Remedy Progress Continues - Update 16, Fact Sheet, March 2004 (PDF, 8 pp, 571K)

Radionuclides and the Lowry Landfill Superfund Site - Fact Sheet, June 2001 (PDF, 13 pp, 655K)

Top of Page

---

Contacts

Top of Page

---

About Region 8

Area Navigation

• A-Z Index
• About Region 8
• News & Events
• Grants

  ---

• Air
• Water
• Superfund
• Waste
• Revitalization
• Green Building and EMS
• Enforcement & Compliance
• Tribal Nations