National Priorities List (NPL) History
Site Type: Final NPL
Street Address: 4200 S. Gun Club Rd.
ZIP Code: 80018
EPA ID: COD980499248
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
Updated October 2012
We have completed the third five-year review of the remedial actions implemented at the site. In the Record of Decision (ROD), and subsequent decision documents, the EPA selected a remedial action that will leave hazardous substances, pollutants or contaminants on-site above levels that allow for unlimited use and unrestricted exposure; therefore, five-year reviews of the site remedy are required by the Superfund law. The review was conducted from September 2011 through September 2012. The final report is available in the Site Documents section below.
North Area Response Action: The organic compound 1,4-dioxane has been detected, at concentrations slightly higher than the Colorado groundwater standard, in groundwater monitoring wells up to 2.4 miles north of the Lowry Landfill site. The EPA has evaluated the health risk associated with public exposure to 1,4-dioxane at these concentrations north of the site and found no significant health risk associated with surface water or groundwater. The extent of the groundwater plume has been determined through a groundwater investigation conducted by the City and County of Denver and Waste Management of Colorado under oversight by the EPA, Colorado Department of Public Health and Environment and Tri-County Health Department.
Denver and Waste Management have implemented a groundwater extraction and treatment response action immediately north of the Lowry Landfill site to minimize the potential for additional contaminant mass to migrate northward beyond Section 31 (located within a one-square-mile area immediately south of Yale Avenue). Several groundwater extraction wells in the area of the plume are currently extracting contaminated groundwater, which is being conveyed to the on-site wastewater treatment plant via a pipeline. The wastewater treatment plant treats the collected groundwater, along with other site groundwater, then discharges the treated water to the sanitary sewer system for additional treatment at the metro and Aurora municipal wastewater treatment plants. Denver and Waste Management are continuing to monitor groundwater in the area of the plume to ensure response action objectives continue to be met and to monitor concentration trends. Additional extraction wells will be added as necessary.
New Background Well Installed: Recent groundwater results indicated that monitoring well MW05-WD, designated as representative of background groundwater quality for inorganic compounds, may have been impacted by the site. Since background wells are used to establish trends in the area, the EPA required Denver and Waste Management to install a replacement well to use to compile background statistics. Denver and Waste Management selected monitoring well MW127-WD as an appropriate replacement for monitoring well MW05-WD.
The approximately 507-acre Lowry Landfill Superfund Site is located northeast of the intersection of Quincy Avenue and Gun Club Road in unincorporated Arapahoe County, 15 miles southeast of the City and County of Denver and 2 miles east of Aurora, Colorado. The Denver Arapahoe Disposal Site (DADS), 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 degreasers, paint, pesticides, hospital and veterinary waste, metal-plating waste, petroleum products, sewage sludge, tires and household waste.
The 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 (an area where only tires may be disposed), on the east side of the site for potential future reuse as fuel. The area and three waste pits that lay under the tires became known as the Former Tire Pile Area or FTPA.
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. The EPA placed the site on the National Priorities List on September 21, 1984.
Groundwater, surface water, soils and sediments on-site are contaminated. Current health risks from the site are limited because access to the site is restricted and off-site groundwater used as drinking water is not contaminated by wastes from the site. The heavily contaminated on-site shallow groundwater is not used as a drinking water source. Because of the large volume of liquid waste destined to remain on-site as part of the containment remedy, it will be necessary to maintain on-going, diligent operation of the containment systems. Groundwater and landfill gas monitoring will be necessary to ensure the remedy remains effective.
|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|
The contaminants of concern at the site include volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), metals, pesticides, polychlorinated biphenyls, and methane and other gases. The liquid industrial wastes at the site include sewage sludge, metal plating wastes, petroleum-derived products, pesticides and industrial solvents. Small amounts of radioactive materials have also been detected in the waste pits, sediments, groundwater and soils. (See the Radionuclides and the Lowry Landfill Superfund Site fact sheet in Site Documents, below.) This is likely due to a combination of naturally-occurring radionuclides, along with hospital wastes and other household or commercially-related low-level radioactive materials historically disposed in the landfill (e.g., lantern mantles and smoke detectors). More than 50 chemicals of concern have been identified through the risk assessment process. These include, but are not limited to, volatile organic compounds (e.g., vinyl chloride, 1,2-dichloroethane, 1,1-dichloroethylene), semi-volatile organic compounds (e.g., 1,4-dioxane), polynuclear aromatic hydrocarbons (e.g., benzo(a)anthracene) and metals (e.g., arsenic and lead).
From 1984 until 1993, the EPA conducted and the responsible parties performed remedial investigations/feasibility studies to determine the nature and extent of contamination, assess potential risks to human and ecological receptors, and develop and evaluate remedial alternatives.
Since its listing in 1984, Lowry has undergone remedial activities. A 200-acre soil cover now covers the main landfill, and an 8,800-foot long underground groundwater barrier wall of soil and clay encloses the west, east and south sides of the main landfill. Water from the north side of the site is collected for treatment. Additionally, a landfill gas collection system was installed in 1997 that collected and simply burned the gases through a process called flaring. The EPA selected a comprehensive site-wide remedy, described in detail in the site Record of Decision (ROD) signed by both the EPA and the Colorado Department of Public Health and Environment (CDPHE) on March 10, 1994. The remedy consists of remedial actions to address groundwater, surface water, landfill gas, landfill solids, soils and sediments.
The site-wide remedy uses containment, collection, treatment and monitoring to address the contamination at the site. The remedy required the construction of a combination of engineered components to prevent off-site migration of contamination above performance standards. If performance standards are not met during implementation or operation, the remedy requires appropriate contingency measures to be implemented. In the ROD, the EPA established points of compliance for the landfill gas remedy and the groundwater remedy at locations inside the site boundaries. The selected site-wide remedy also requires the implementation of on-site and off-site institutional controls. The containment remedy involved installing underground barrier walls (slurry walls) and groundwater collection systems on the site; constructing of a new water treatment plant to treat the highly contaminated groundwater; excavating three accessible waste pits which were under the old tire piles; and collecting and converting landfill gas to reusable energy.
The site-wide remedy is based on the concept of containment, which means protective measures are put in place to prevent off–site movement of contamination above safe levels. The site is divided into six operable units (OUs) for cleanup actions. The OUs are grouped according to the media they address.
|Operable Unit||Media Addressed|
|1 and 6||shallow groundwater, subsurface liquids and deep groundwater|
|2 and 3||landfill solids and gas|
|4 and 5||soils, surface water and sediments|
All of the components of the plan are currently in place and operating to achieve the remedial action objectives described in the 1994 ROD. The below table summarizes the remedy and status of each component.
|Slurry Wall||An underground clay barrier wall that encloses the landfill on three sides to minimize clean groundwater flow onto the site and reduce contaminated groundwater flow off the site.||Ongoing|
|Landfill Cover||Minimizes amount of rainwater seep into the landfill, which could become contaminated upon contact with buried landfill wastes.||No further action|
|North Toe Extraction||A trench extracts contaminated groundwater from the landfill reroutes it to an onsite water treatment plant (WTP) for treatment.||Ongoing|
|North Boundary Barrier Wall||A subsurface clay barrier located at the intersection of the unnamed creek alluvial channel and the northern site boundary that provides a barrier to groundwater flow. Migrating contaminated groundwater is collected and rerouted to the onsite WTP for treatment.||Ongoing|
|Water Treatment Plant (WTP)||Contaminated water collected from the site is treated at the WTP to a level safe for discharge into a sanitary sewer line.||Ongoing|
|Surface Water Remediation Action||Contaminated groundwater is kept separate from clean surface water within the unnamed creek streambed by a channel of permeable material installed beneath the streambed and covered by a clay barrier. This provides a pathway for groundwater to flow to the north without contacting surface water. Clean surface water flows above the permeable channel without coming into contact with contaminated groundwater flowing underneath the clay barrier.||No further action|
|Landfill Gas Extraction||Landfill gases are extracted and used as fuel for internal combustion engines to generate electricity.||Ongoing|
|Former Tire Pile Area||Three waste pits with similar contamination but separate from the large main landfill in the southern part of the site. Remediation is completed on two of the three pits and continuing on the third.||Ongoing|
|Long-Term Monitoring||Long-term monitoring programs for all media are in place to evaluate the effectiveness/overall protectiveness of the cleanup actions.||Ongoing|
View an illustration of the Lowry Landfill Remedy Components (PDF, 1 pg, 56K, about PDF)
Community involvement plays an important role in the Superfund process. The EPA uses a number of different tools and resources to promote effective, on-going, meaningful community involvement. The goals of the Superfund community involvement program are to:
- Keep communities affected by sites informed throughout the cleanup process.
- Provide opportunities for communities to comment and offer their input about site cleanup plans.
- Facilitate the resolution of community issues tied to a site.
The EPA has an ongoing outreach program at the Lowry Landfill site. Since 1984, we have conducted a proactive community involvement program consisting of public meetings, opportunities for public comment, fact sheets, a technical advisory grant to allow a citizens group to review the remedial action, technical meetings, open houses, site tours and community interviews to obtain feedback from the community. Additionally, community interviews were conducted during the five-year review in 2012.
The EPA places a high priority on land reuse as part of its Superfund response program mission. The agency tries to select cleanup options that encourage and support future use of a site. The EPA uses two fundamental methods to facilitate reuse of Superfund sites:
- Exploring future uses before the cleanup remedy is implemented, an approach that gives the Agency the best chance of designing cleanup remedies to support the likely future use of a site.
- Working with landowners and communities to remove barriers not considered necessary for the protection of human health or the environment at those sites where remedies are already in place.
One option for reuse is the siting of clean and renewable energy projects on contaminated (or formerly contaminated) lands. At the Lowry Landfill Site Denver, Waste Management and local utility Xcel Energy partnered to find a productive use for the site’s landfill gas. In July 2007, construction began on a landfill gas-to-energy plant at Lowry Landfill and the adjoining Denver Arapahoe Disposal site. The plant, which opened in September 2008, uses four combustion engines to convert 630 million cubic feet of methane gas annually from both sites into 3.2 megawatts of electrical power, reducing greenhouse gases and providing electricity for approximately 3,000 households. The facility is built for expansion to provide greater benefits to the community if gas production levels allow. The gas-to-energy facility minimizes methane emissions that could contribute to climate change. Other benefits include: destroying hazardous substances in extracted landfill gas, offsetting the use of non-renewable resources for the generation of electricity, and reducing the emission of sulfur dioxide, nitrogen oxide, carbon dioxide and particulate matter from the use of non-renewable resources. The Lowry Landfill gas-to-energy facility shows how former contaminated waste sites can be returned to safe and productive uses for communities.
Land Use Controls and Other Institutional Controls
Land use controls are the most common type of institutional control (IC). ICs are administrative or legal controls that help reduce the likelihood for human exposure to contamination. ICs can also help protect the integrity of the remedy. Examples of ICs are:
- Zoning ordinances.
- Environmental covenants.
- Deed notices.
- Well-drilling restrictions.
- Building permits.
- Informational advisories.
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, the EPA and CDPHE have the authority to enforce the on-site controls.
Site land use is restricted by institutional controls, which include restrictive covenants that run with the land, zoning and an executive order of the mayor of Denver. Within the site boundaries, the restrictive covenants limit land use to landfilling, monitoring or remediation activities and other uses not inconsistent with the selected remediation.
Water rights within the aquifers beneath the site are also owned by Denver. Restrictive covenants that run with the water rights limit the drilling of any new wells on-site except for monitoring or remediation purposes necessary for implementation of the remedy. An Aurora City Ordinance prohibits development or construction of buildings within one quarter mile of the east, south or west exterior boundaries of Section 6 if the properties are annexed into Aurora. The ordinance also prohibits drilling, development or use of any wells in the Dawson aquifer within on half mile of the exterior boundaries of the site, except for wells used for monitoring, extracting groundwater for remediation or re-injecting treated groundwater. A detailed description of ICs at the site and immediate vicinity of the site can be viewed in Attachment 1 of the Third Five-Year Review Report.
The EPA or the lead agency conducts five-year reviews following the start of a Superfund cleanup when contamination is left on the site. These reviews are repeated every five years. We use these reviews to determine:
- How the remedy is working.
- If the remedy remains protective of human health and the environment.
We completed the third five-year review for the site in September 2012. A copy of the report generated from the review can be viewed in Site Documents, below.
You will need Adobe Acrobat Reader to view some of the files on this page. See the EPA's PDF page to learn more.
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Third Five-Year Review Report, September 2012 (PDF, 156 pp, 12.2MB)
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)
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)
Remedial Project Manager
U.S Environmental Protection Agency, Region 8
1595 Wynkoop Street (8EPR-SR)
Denver, CO 80202-1129
800-227-8917 ext. 312-6224 (toll free Region 8 only)
Community Involvement Coordinator
U.S Environmental Protection Agency, Region 8
1595 Wynkoop Street (8OC)
Denver, CO 80202-1129
800-227-8917 ext. 312-6633 (toll free Region 8 only)
View Documents at:
Aurora Central Library
14949 E. Alameda Parkway
Aurora, CO 80012
EPA Superfund Records Center
1595 Wynkoop Street
Denver, CO 80202-1129
800-227-8917 ext. 312-6473 (toll free Region 8 only)
State Project Officer
Colorado Department of Public Health and Environment
Hazardous Materials and Waste Management Division
4300 Cherry Creek Drive South
Denver, CO 80246-1530
800-886-7689 ext. 3453 (toll free in Colorado)
Community Relations Manager
Colorado Department of Public Health and Environment
4300 Cherry Creek Drive South
888-569-1831 ext. 3373 (toll free)
Citizens for Lowry Landfill Environmental Action Now
Bonnie Rader, Director
71 Algonquian Street
Aurora, Colorado 80018
A Superfund Success Story…about turning pollution into electricity