The Cliff/Dow Dump is a 2-acre site in Marquette, Michigan, where the Royal Oak Charcoal Company disposed of hazardous waste from 1954 to the mid-1960s. The U.S. Environmental Protection Agency (EPA) added it to the National Priorities List (NPL), the federal roster of the most serious contaminated sites, on September 8, 1983. It has since been fully cleaned up and deleted from the NPL.
The main contaminants are volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs). These substances built up in hazardous tar deposits that contaminated both soil and groundwater. EPA identified 33 specific contaminants of concern, including benzene, toluene, xylene, naphthalene, phenanthrene, pyrene, phenol, tetrachloroethene, dibenzofuran, and fluorene. All were found in soil, groundwater, and solid waste within the site's single cleanup area, known as the BIOTREAT operable unit.
Cleanup focused on excavating and treating contaminated fill material from the landfill. Workers used both in-place and above-ground bioremediation, physical separation of waste, offsite incineration, and revegetation. For groundwater, the remedy relied on monitored natural attenuation, meaning contaminants are allowed to break down naturally while EPA tracks their movement. Construction of the remedy was finished on September 25, 1995, and remedial action wrapped up by September 1996.
EPA deleted the site from the NPL on November 17, 2000, after follow-up sampling confirmed that remaining groundwater contamination poses no unacceptable risk to people or the environment. Human exposure is currently under control across the entire site. Contaminated groundwater migration is also stabilized, with no unacceptable discharge to nearby surface water. All cleanup goals for current and expected future land uses have been met, and deed restrictions on site and groundwater use have been removed. The site reached "sitewide ready for anticipated use" status on June 26, 2006.
Community members or others with questions about the site can contact the EPA's Remedial Project Manager. Ten key documents and 333 administrative records for the site are available through EPA's online database.
