In 2013, the Minnesota Legislature banned the sale and use of coal tar-based sealants, effective January 1, 2014. Coal tar-based sealants can no longer be sold or applied legally in Minnesota. These products were commonly applied to asphalt driveways, parking lots, and some recreational trails to protect the underlying asphalt. However, they contain high concentrations of chemicals called polycyclic aromatic hydrocarbons (PAHs), which can be carcinogenic.
PAHs in coal tar-based sealants are released into the environment through volatilization into the air and as dust when the sealant breaks up over time. This dust can be tracked into homes or transported to nearby soils and waters via stormwater runoff. An MPCA sediment study found that coal-tar sealants contributed 67% of total PAHs in 15 metro-area stormwater ponds. High concentrations of PAHs have accumulated in some stormwater pond sediments around the state. Research conducted by the MPCA, the Metropolitan Council, the U.S. Geological Survey, and the University of New Hampshire Stormwater Center shows that coal tar-based sealants are an important source of PAHs to urban waterways.
This is a concern for local governments responsible for managing stormwater ponds and disposing of sediments that have been excavated from them. Alternatives to coal tar-based sealants, such as asphalt-based sealants, have far lower concentrations of PAHs.
Sediment removal guidance
These guidance documents do not provide a comprehensive list of everything that should be considered when managing a sediment removal project, but they can help highlight important steps to be taken by those responsible for performing a sediment removal project.
- The soil reference values (SRVs) to protect human health are found on the cleanup guidance webpage.
A short video highlighting key topics for sediment removal projects supplements the guidance document and provides a few visual examples associated with the removal of sediment from stormwater collection and conveyance systems.