Coal tar-based sealcoat FAQs

Coal tar-based pavement sealants have been found to be a significant source of contamination of storm water-pond sediments by polycyclic aromatic hydrocarbons (PAHs). This page provides answers to questions frequently asked by municipalities and others responsible for managing contaminated sediments in stormwater collection systems that they own and operate.

PAHs (polycyclic aromatic hydrocarbons) are chemicals that occur naturally in coal, crude oil and gasoline, and are also present in products made from fossil fuels, such as coal-tar pitch, creosote and asphalt. PAHs also come from the burning of carbon and are present in the smoke of forest and grass fires, volcanoes, vehicle exhaust, cigarette smoke, and even in char-broiled foods.

PAHs are potentially toxic chemicals, of which some are listed in Minnesota as possible or probable carcinogens. PAHs are being discovered in concentrations of concern in the sediment of stormwater ponds across the state, primarily in urbanized areas.

The largest sources in Minnesota (based on current research and data) are coal tar-based sealants (67%), and vehicle emissions (29.5%). Pine wood burned in fireplaces makes up the balance of the remaining 3.5%.

No. Acrylic sealers do not contain PAHs, but these products are a minority of the sealer products in commerce and are not used as frequently as asphalt- and coal tar-based sealers.

Yes. Sealcoat comes in two basic varieties: coal tar-based and asphalt-based. Research shows that coal tar-based sealcoat products have much higher concentrations (containing up to 1,000 times more) PAHs than the asphalt products.

Yes. Chip-sealing uses an asphalt-based emulsion product that contains trace amounts of PAHs, but not in sufficient concentrations to accumulate to problem levels.

Yes. PAHs are accumulating in man-hole sumps, catch basins, rain gardens, ditches, underground treatment systems, street sweepings, and other parts of stormwater collection and conveyance systems where sediment accumulates. PAHs are also accumulating in the sediments of natural lakes, streams, rivers, and wetlands that receive untreated stormwater runoff.

Disposal options depend on the concentration of PAHs in the sediment. Current standards and guidance provide two viable options for reuse or disposal. One option allows sediment to be placed as fill at an already contaminated industrial site. The MPCA does not have cost estimates for this option. The second option requires contaminated sediment be disposed of as a solid waste at a Municipal Solid Waste (MSW) landfill that has an industrial solid waste management plan. This means contaminated sediment must go to a landfill that has a liner and a leachate collection system. Disposal costs for this option are determined by whether the sediment is being received as a daily cover material or a waste for disposal with other mixed municipal wastes. Neither option is sustainable at the expected volumes that will be generated in the coming decade.

Disposal costs include testing and laboratory analysis of the sediment to characterize the waste. Other costs include excavation, transportation, and tipping fees if those apply. Management costs vary based on the size and location of the excavation, volume of sediment being removed, and laboratory analysis. In some cases costs can be as much as $250,000 per pond when sediment removal projects include sediment contaminated above the industrial and commercial soil reference values. Anecdotal information provided by metro-area cities indicates typical costs range from $75,000 to $125,000 per pond when sediments need to be disposed of at an MSW facility. Projects costs to remove and manage uncontaminated sediment (not regulated as a solid waste) are substantially less when transportation and disposal costs are limited and/or not incurred.

A dredging cost equation was developed for the City of Minnetonka in 2009 as a way to estimate long term stormwater pond maintenance costs. The cost equation includes 30% for engineering and administration costs and 20% for contingencies. The equation was developed using 2009 dollars and volume is measured in acre-feet. It does not include landfill disposal costs if that applies.

Dredge Cost = 78,515*Volume^0.6727

In the seven-county Twin Cities metropolitan area there are an estimated 15,000 stormwater ponds. Conservative estimates suggest management costs may be measured in the billions of dollars for just these ponds. Most municipalities report they can’t afford the costs, so maintenance projects are currently being delayed. Possible negative impacts of delaying pond maintenance may include increased flooding, damage to public and private infrastructure, and pass-through of contamination to lakes, rivers, and wetlands as a result of stormwater retention systems not functioning properly.

Yes. Effective January 1, 2014 the sale and use of coal tar-based sealers is banned in Minnesota.  Actions to restrict or ban the use of coal tar-based sealers started in Minnesota in 2009. In May of 2009 the Minnesota Legislature restricted state agencies from purchasing coal tar sealants (2009 Session Laws, Chapter 172, and HF1231, sections 4, 26, and 28). The 2009 legislation restricted Minnesota state agencies from purchasing undiluted coal-tar sealant effective July 1, 2010. Some Minnesota cities passed their own ordinances to ban the use of coal tar-based sealers, but those local bans were confined to the jurisdictions of those municipalities. During the spring of 2013 the Minnesota Legislature took action to ban the sale and use of coal tar-based sealers in Minnesota.

Research has been conducted by the MPCA as well as the Metropolitan Council, the U.S. Geological Survey (USGS), and the University of New Hampshire Stormwater Center. Studies have concluded that coal tar-based sealants are an important source of PAHs to urban waterways. MPCA research conducted on 15 metro-area stormwater ponds was consistent with the findings of a national USGS peer-reviewed study. The MPCA used environmental forensic techniques in the spring of 2013 to determine sources of PAHs to metro area stormwater pond sediments as shown in the following chart. The City of Austin, Texas is also conducting research on this topic and that information is available through a link on the MPCA web page.

Sources of PAHs in Metro Stormwater Pond Sediments

Contractors and consultants for the sealcoating industry have used unpublished data in addition to an industry-sponsored study in Austin, Texas to try to discredit the research that shows coal tar-based sealants are an important source of PAHs to urban environments. The MPCA determined there are data-quality problems with some of the unpublished data used by the sealcoating industry and with their environmental forensic analysis. The MPCA also determined that the industry made inaccurate comparisons between sediment data and stormwater runoff data in their analyses. The MPCA concluded that the industry’s conclusions are flawed and inaccurate, and the agency supports the findings of the research mentioned in the FAQ related to “What research has been done on this topic?”

A model ordinance was developed by the MPCA and the League of Minnesota Cities in 2009 and is available on both the MPCA and LMC web sites.

Most major retailers, local hardware stores, and commercial applicators started making the transition away from coal tar-based sealers to asphalt-based sealers many years ago. Coal tar-based sealants were (for the most part) already off the shelves of Minnesota retailers by 2009. In the spring of 2013, coal tar-based sealants were still being sold by few retailers and commercial applicators as well as a few Minnesota suppliers and manufacturers that service small hardware stores and commercial applicators that operate outside of metro-area municipalities that have enacted bans. As of January 1, 2014, the sale and use of coal tar-based sealers is banned in Minnesota.

Yes. However, the risks from food-derived sources of PAHs and medicinal uses of coal tar can not be compared fairly since these exposures are a matter of consumer choice. The choice to use a product containing coal tar as a treatment for a medical condition is weighed against the potential benefits of the exposure. Generally, medical treatments should be limited to those suffering a disease. Consumption of food containing PAHs (such as charcoal-grilled meat) is also a matter of choice. While food exposures may be the greatest exposure to PAHs for most people, typically carcinogenic PAH concentrations in contaminated sediment and soil are two or more orders of magnitude greater than carcinogenic PAH concentrations in food. Environmental exposures to PAHs can be significant for some people. Homeowners and business alike are encouraged to ask retailers and commercial applicators for products that are not coal tar-based.

The most up-to-date information about the restriction of coal tar-based sealants in Minnesota is available on the MPCA Coal tar based sealants web page.


FAQs about the Coal Tar Sealant Ban

Laboratory analysis with an accredited lab experienced in testing for PAHs is the most accurate way of determining this. However; odor may also help indicate the presence of coal tar and a field screening method developed by the City of Austin, Texas may be used as an indicator. Coal tar-based sealcoats typically have a strong mothball-like odor. Asphalt and acrylic sealcoats do not. The City of Austin, Texas has developed an inexpensive method to check for coal tar content using a simplescreening test. The Austin screening test requires collection of pea-sized samples of the top layer of sealcoat, with care taken to scrape, or shave off, a thickness similar to about 2 sheets of paper.   The Austin screening test relies on a color change as an indicator.

Yes. Cities who have already enacted their own ordinance to restrict the use of coal tar-bases sealcoats, or cities who enact an ordinance in order to exercise the enforcement authority of the 2013 state law, codified as Minnesota Statutes section 116.202 may require property owners to remove and properly dispose of coal tar-based sealcoat within the cities discretion and enforcement authority.

If you are a homeowner you may dispose of unused or unusable product, at your local Household Hazardous Waste collection site. State-wide collection sites are listed at this link: 

If you are a business and a Very Small Quantity Generator of hazardous waste you can find general information in the following document: PDF icon VSQG Collection Program Requirements for Generators

On or after January 1, 2014, Minnesota contractors, retailers, suppliers or other companies who can’t return unused coal tar sealcoat should treat it as a hazardous waste unless they have it evaluated and determined not to be hazardous. Businesses should contact either a company that is authorized to manage hazardous waste, or a Very Small Quantity Generator collection site (see PDF icon VSQG Collection Program Requirements for Generators) to arrange for disposal.

Yes. The ban applies to companies outside Minnesota who may be under contract to maintain properties in Minnesota. Coal tar-based sealcoat may not be applied in Minnesota on or after January 1, 2014 unless specifically exempted by Minnesota Statutes section 116.202

Yes. The new law, which was enacted in 2013 and codified as Minnesota Statutes section 116.202, grants cities the authority to enforce the state-wide ban on the use of coal tar based seal coats. However, a city must first enact an ordinance in order to exercise this enforcement authority. The League of Minnesota Cities has drafted a model ordinance that cities can adopt for use in enforcing the new law, which can be found here. Members of the League are encouraged to contact the League of Minnesota Cities Research department with any questions they have regarding the new law.

If the coal tar-based sealcoat product is new, unopened, and usable; you should check with the seller or the outlet where you purchased the product to see if it can be returned. If not; follow the FAQ for disposing of the unused, or unusable, product as a waste. Minnesota residents who can’t return unused coal tar-based sealcoat should take it to a Household Hazardous Waste collection site (find yourhousehold hazardous waste collection site).

No. Coal tar-based sealant may not be sold, or applied in Minnesota on, or after January 1, 2014. Sales by Minnesota companies or individuals to buyers outside the state are not affected by the new law. 

Small contractors who only apply sealcoat and don’t generate other hazardous waste may fit into the category of "one-time" generator, in which case they must obtain a hazardous waste identification number from the MPCA using the agency's Notification of Regulated Waste Activity online e-Service. However, you may not be required by the MPCA to be licensed. Contractors in the Twin Cities metropolitan counties must contact their county for local licensing requirements. See contact information for the Twin Cities metropolitan counties below.

Contractors who provide more services than just sealcoating, such as asphalt pavement installation or parking lot line striping, may already be licensed hazardous waste generators. If your company is a Very Small Quantity Generator, you may take up to 220 pounds (~25 gallons) of coal tar-based sealcoat per month to a VSQG collection site (for a fee and only with prior approval). If your company is a Small Quantity or Large Quantity Generator of hazardous waste, you may not use VSQG collection sites; you must ship and manifest remaining coal tar-based sealcoat as you would other hazardous wastes.

Yes; except within city jurisdictions that had already banned or restricted the use of coal tar-based sealcoat. Those cities included: Albertville, Buffalo, Cannon Falls, Centerville, Circle Pines, Eden Prairie, Edina, Elk River, Falcon Heights, Golden Valley, Hutchinson, Inver Grove Heights, Little Canada, Maplewood, Medina, Minneapolis, Newport, New Hope, Oakdale, Prior Lake, Rosemount, Roseville, Shoreview, Shorewood, Vadnais Heights, Waconia, West St. Paul, White Bear Lake, and Woodland.