In the 18 months since White Bear Lake became the first Minnesota city to forbid a common type of driveway sealant, about a dozen others have followed, as evidence mounts that chemicals from the sealants are creating a hazardous and expensive problem in storm-water ponds.
The bans on coal-tar sealants apply to homeowners who seal their own driveways and contractors who apply sealants commercially. Both are now expected to choose safer, asphalt-based sealers.
Although the sealant industry disputes the findings, research by the Minnesota Pollution Control Agency shows a connection between coal-tar sealants put on driveways and parking lots and the PAHes (poly aromatic hydrocarbons) that are showing up in city storm-water ponds, said Don Berger, state program administrator of storm-water policy in the MPCA's municipal division. The PAHes are believed to be harmful to humans, fish and other aquatic life.
"Data we have collected over the last year indicate that there is a good percentage of these pollutants tied to coal-tar sealants," Berger said.
"The MPCA will continue to support municipalities who choose to phase out the use of coal-tar-based sealants to reduce a known source of contamination to storm-water collection systems," he said.
With an estimated 20,000 storm ponds in the metro area, cities are discovering that many ponds contain PAHes. Because the MPCA requires cities to keep storm ponds clean and in good working order, and to dispose of contaminated pond sediment in specific ways, some cities face astronomical storm-water costs.
Indeed, the cities that have outlawed the sealants have done so to become eligible for MPCA cleanup grants.
Circle Pines put a ban in place and received $45,000 from the state to help pay $100,000 in pond sediment disposal costs, said City Administrator Jim Keinath.
Inver Grove Heights, the latest city to forbid use of the sealants, also is counting on a grant after its ban takes effect, City Engineer Tom Kaldunski told City Council members.
After testing just 12 of the city's 578 storm-water ponds, he has found three ponds with contaminated sediments -- two with such high levels of PAHes that they must be disposed of in a sanitary landfill at a cost ranging from $120,000 to $180,000.
"Every city is in the same situation -- it's a huge problem," said White Bear Lake public works director Mark Burch.
Before the end of the year, an MPCA work group is expected to release new research and recommendations to give cities further options for disposing of pond sediments.
Industry disputes MPCA claim
The MPCA is talking with the Pavement Coatings Technology Council -- which represents the sealant industry -- in hopes of encouraging the group to voluntarily phase out the material.
Anne LeHuray, executive director of the group, said the council will look over the MPCA's latest research, but "it remains our view -- and I think we have the science to back it up -- that the original claim made by MPCA is incorrect."
Car exhaust and wood smoke are greater sources of PAHes than coal-tar sealants, LeHuray said. "The bans will not do what they think they will do."
But outlawing the sealants has worked well for White Bear Lake, Burch said. "From our perspective there wasn't a down side."
To cooperate with the ban, many large retailers have taken coal-tar sealants off their shelves and replaced them with asphalt-based sealants, he said.
Acceptable products carry a label that says "asphalt immersion,'' he said.
Businesses also switched to asphalt products, Burch said. "The [sealant] industry was very concerned, but I talked to private commercial guys doing applications on driveways. They told me that they've got all types of products."
The cost of disposing of sediments starts when a city hires someone to take a sample and test it. Cleaner sediments can be scooped out of ponds and spread on the ground as fill, but costs climb if it must be taken to a landfill, Berger said.
Even if cities could afford it, there isn't room in landfills to accept all the contaminated pond sediments.
With that in mind, White Bear Lake is now testing the prospects for storing sediments in a berm close to Varney Lake, where they were removed.
"We will deposit the sediments, cover it over, seed it and put a trail on top," Burch said. If follow-up monitoring shows that the contaminants stay put and don't become a problem, will be a less-expensive option for handling the sediments, Burch said.
Laurie Blake • 952-746-3287