On-Post Double-Lined Hazardous Waste Landfill
This fact sheet summarizes the remediation process for the On-Post Hazardous Waste Landfill. As determined by an extensive public involvement process, and in accordance with the Record of Decision (ROD) for the On-Post Operable Unit, the Army will construct a double-lined hazardous waste landfill for the placement of contaminated soils and debris. The triple-lined landfills, which will contain material from the Basin F waste pile and the Lime Basins, will be described at a later date.
As shown by the attached map (attatchment 1), the double-lined landfill will be located within the eastern 1/2 of Section 26 and western 1/2 of Section 25 and will encompass approximately 24 acres of RMA. The landfill is required to meet all Resource Conservation and Recovery Act (RCRA) requirements with regard to site selection and performance and will be part of a Corrective Action Management Unit (CAMU) as designated by the CDPHE. The landfill is being built to isolate the waste from groundwater and other environmental pathways, and represents the safest, most cost-effective and time-efficient option available for disposal of contaminants located on the Arsenal. A CAMU is a regulatory designation that allows for the treatment, storage and disposal of remediation wastes. Facilities will be located in the CAMU to help support operations including a decontamination facility, a leachate treatment plant, and clean material staging areas.
The Rocky Mountain Arsenal Superfund Site (RMA) is located near Commerce City, Colorado. The On-Post Record of Decision (ROD), which describes the sitewide remedy for the RMA, was signed by the U.S. Army, the U.S. Environmental Protection Agency (EPA) and the Colorado Department of Public Health and Environment (CDPHE) on June 11, 1996 with concurrence of the U.S. Fish and Wildlife Service (the Service) and Shell Oil Company (Shell). The U.S. Army, serving as the lead agency and Shell will implement the selected remedy which includes 31 different cleanup programs for soils, structures and the treatment of groundwater contaminants. This remediation project will be coordinated under the supervision of EPA, CDPHE and Tri-County Health Department (TCHD).
Summary of Site History and Contamination Issues
The Arsenal is located near Commerce City, Colorado, approximately 10 miles northeast of downtown Denver. In 1942, at the height of World War II, the U.S. Army purchased 17,000 acres of land on which to manufacture chemical weapons, such as mustard gas and white phosphorus.
To foster economic growth in the area, offset operational costs and maintain the facilities for national security, private industry was encouraged to lease facilities at RMA after the war. Under the lease program, Julius Hyman and Company began producing pesticides in 1946. In 1952, Shell Chemical Company acquired Julius Hyman and Company and continued to produce agricultural pesticides on-site until 1982. Common industrial and waste disposal practices used during these years resulted in contamination of structures, soil, groundwater and, to a lesser extent, surface water and surface water sediments.
Many alternatives, such as soil incineration and capping were considered for the treatment of RMA materials found to contain high levels of contaminants. With the involvement of the public, the parties selected the double-lined landfill as the alternative that is both protective of human health and the environment and can be constructed in a cost-effective and time-efficient manner.
The double-lined landfill will hold approximately 1.2 million cubic yards of material consisting of soil, buried debris and building debris which present a potential risk to human health. The hazardous waste landfill will only be used for disposal of waste originating on RMA. The CAMU Designation Document requires that the landfill be designed to provide reasonable assurances that waste will be isolated from environmental pathways for 1000 years. To accomplish this requirement, both liners of the landfill will be constructed of 3 feet of compacted clay. The double-lined landfill will consist of two 36” thick compacted clay liners overlain by two flexible membrane liners and leachate collection and leak detection systems. The cover for the landfill will include 4 feet of soil and vegetation above a 1 1/2 foot crushed concrete biota barrier and a combination geosynthetic clay/flexible membrane liner to minimize infiltration of water into the landfill, isolate the waste from contact, and prevent animal access to landfill contents.
Most of the fill for the landfill will be taken from the Arsenal and will not need to be imported on-site. However, other construction materials such as sand, gravel, road base and synthetic liners will be transported onto the Arsenal.
Any potential odors occurring during this project will be controlled using the implementation of air quality monitoring, air emission control plans and project construction modifications developed by the parties. The Arsenal will continue air quality monitoring and control programs throughout all phases of the remediation. If odors are detected above Colorado regulations and other established operational parameters, modification to the remediation activity will be taken to resolve the problem.
Construction of the first phase of the double-lined landfill began Spring of 1998. The landfill began accepting wastes Spring of 1999. Operations are currently planned to last approximately nine years. There are 18 other remediation projects which are contingent upon the construction and successful operation of the landfill. Once completed, the soil cap will be vegetated to blend-in with existing topography.
Public Notification Milestones
January 9, 1997 30% Design presented to the Restoration Advisory Board
July 11, 1997 60% Design Notice published in The Rocky Mountain News, The Denver Post
August 7, 1997 60% Design presented to the Restoration Advisory Board
August 28, 1997 Adams County Planning Commission Hearing– 1:30 p.m.
September 8, 1997 Adams County Board of County Commissioners Hearing – 10:00 a.m.
September 10, 1997 95% Design Draft Final
October 2, 1997 95% Design presentation to the Restoration Advisory Board
Get current updates on the Arsenal’s progress on the web at www.pmrma.army.mil. or call the Arsenal’s information line at 303-286-8032.
For more information, please contact:
Remediation Venture Public Relations Office Rocky Mountain Arsenal
Commerce City, Colorado 80022
U.S. Environmental Protection Agency
Remedial Project Manager
Colorado Department of Public Health & Environment
State Project Officer
All reference materials are available at the following locations:
EPA Superfund Records Center
999 18th Street
Denver, Colorado 80202
Joint Administrative Records Facility (JARDF)
Rocky Mountain Arsenal
Technical Information Center
Building 129 Room 2020
Commerce City, Colorado 80022