Editorial - Remember lakes when repairing your driveway

Talk about it

If you’re thinking about seal coating your driveway, you should consider what it could do to the environment.

The Douglas County Lakes Association (DCLA) published a story about seal coating in its newsletter this spring.

Here were some of the main points the story shared:

Seal coating makes old asphalt look new and protects its surface, but there are serious environmental concerns with its use. Seal coat comes in two basic varieties: coal tar-based and asphalt-based. The coal tar variety is more resilient, but it contains much higher levels of a class of chemicals called PAHs (polycyclic aromatic hydrocarbons) that harm fish, and with prolonged exposure, pose a risk of cancer in humans.

Coal tar is a waste material generated in the conversion of coal to solid carbon residue or coke. Manufacturers choose coal tar for seal coat because of its resistance to petroleum products like gasoline and oil, which drip from cars and deteriorate asphalt surfaces. In time, sunlight and vehicle traffic wears down seal coat and seal coat flakes are washed away by rain or carried away by wind, contaminating stormwater ponds, streams and lakes with PAHs.

PAHs cause tumors in some fish, disrupts the reproduction of aquatic organisms, and causes some water-bottom species to avoid sediment altogether. Health risks to humans related to PAHs are based on the length of exposure to vapors or sediments contaminated with PAHs.

Coal tar contains as much as 30 percent PAHs by weight. A study in Austin, Texas, compared the level of PAHs in water coming off parking lots. Those with asphalt-based seal coat runoff contained 10 times more PAHs than the uncoated parking lots and the coal-tar seal coat runoff had concentrations of PAHs that were 65 times higher than the uncoated lot.

Besides the health effects and the danger to the environment, PAHs are making routine maintenance of stormwater ponds by cities and townships many, many times more expensive because sediment with high enough concentrations of PAHs must be disposed of differently. In Minnesota, when some cities removed sediment from their stormwater ponds as part of regular maintenance, they found elevated levels of PAHs. This discovery required them to find special disposal areas.

If you want to learn more about how to protect lakes, you’re encouraged to attend the next DCLA meeting. It will take place Wednesday, June 13 at 4:30 p.m at the Douglas County Public Works building.

Tags: opinion, editorials