Public Notice: EPA Begins Seventh Review of Marshall Landfill
Summary
EPA is conducting a five-year review of the Marshall Landfill Superfund site in Boulder County, Colorado. The Superfund law requires regular checkups of sites that have been cleaned up or where cleanup has been ongoing for at least five years . Five-year reviews provide an opportunity to evaluate the implementation and performance of a remedy to determine whether it remains protective of human health and the environment.
The 160-acre Marshall Landfill site consists of two adjacent 80-acre landfills. These are not active landfills. The northern landfill is Marshall Landfill, and the southern landfill is Boulder Landfill. Marshall Landfill began operating in 1965 as a solid waste composting and disposal operation. Between 1969 and 1974, Marshall Landfill accepted municipal waste, unstabilized sewage sludge, and many unknown, potentially hazardous, wastes. In 1974, Boulder County discontinued use of Marshall Landfill when Boulder Landfill opened to the immediate south. Boulder Landfill closed in January 1992. Sources of contamination include areas of saturated refuse, waste disposal trenches, small areas where organic solvents were disposed and two unlined leachate lagoons. Landfill operations contaminated surface water and on-site shallow groundwater.
The site’s remedy included a groundwater collection and treatment system, landfill improvements and environmental monitoring programs. The remedy began operating in 1993. EPA placed the collection and treatment system on a stand-by mode in November 2004 after influent to the treatment system consistently met the discharge requirements for the main contaminants of concern. Operation and maintenance activities and groundwater monitoring are ongoing.
Community members are encouraged to share information that may be helpful in the five-year review process. Community members who have questions or who would like to participate in a community interview, are asked to contact Dania Zinner, by November 14, 2025.
Learn more about the site: Marshall Landfill Superfund Site website