Politics & Government

Build Up of Harmful Chemicals in City Ponds Behind Proposed Ban

Elected officials have approved the first reading of an ordinance forbidding the use of coal tar sealant.

That black, coal tar-based sealant you use on your driveway is harmless, right?

Wrong, according to city and state officials.

Coal tar sealant contains chemicals classified as suspected carcinogens—and those compounds, called polycyclic aromatic hydrocarbons (PAHs), have accumulated for years in the city’s stormwater ponds and basins.

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For that reason, Inver Grove Heights City Council approved last week the first reading of a citywide ban against the sealant. If the final reading of the ordinance is approved, Inver Grove will join a handful of municipalities in the state—including White Bear Lake—who have already enacted restrictions on the sealant.

What Are PAHs?

Polycyclic aromatic hydrocarbons are the byproducts of incomplete combustion and can be found in car exhaust, tobacco smoke and even the “char” on grilled meat, according to Minnesota Department of Health official Carl Herbrandson.

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PAHs include hundreds of different types of chemicals—some of which may be carcinogenic or toxic, according to the Environmental Protection Agency. Prolonged, direct exposure to PAHs is risky, but even short-term exposure to high concentrations can cause skin irritation, Herbrandson said. Mice that ingested high amounts of PAHs were more likely to have offspring with birth defects, laboratory studies have shown.

PAHs are also found in coal tar sealant, which was used prevalently on driveways in the 1950s and 60s, City Engineer Tom Kaldunski said, but is slowly being phased out in favor of less harmful asphalt-based sealant.

Coal tar sealant can flake off pavement and, carried by runoff or rainwater, build up in stormwater systems, Kaldunski said.

Where Were PAHs Found in Inver Grove Heights?

Testing has found high concentrations of PAHs in the sediment beneath two city ponds and a low concentration of PAHs beneath a third pond, Kaldunski said. Those ponds were typically located in older, developed neighborhoods in the city, Kaldunski said. The city has only tested 12 of its 578 stormwater basins for the presence of PAHs.

The levels found in the two ponds are high enough that Inver Grove Heights officials may have to follow expensive disposal procedures if they dredge the ponds as part of regular maintenance efforts. Sediment taken from ponds with high concentrations of PAHs must be disposed of at a landfill, and the city could be charged anywhere from $40 to $60 per cubic yard of contaminated soil, Kaldunski said.

A large dredging project can involved thousands of cubic yards of soil, making landfill fees exorbitantly high, Kaldunski said.

What is the State Doing?

In 2009, the state legislature enacted a bill prohibiting state agencies from purchasing coal tar sealants. The legislation also called for the development of grant funds to help cities alleviate problems—on the condition that municipalities requesting help ban coal tar sealants.

So far, the legislature has shied away from a statewide ban on coal tar sealants, but that may change in 2012 legislative session, predicted Minnesota Pollution Control Agency State Program Administrator Don Berger.

New research by the MPCA concluded that as much as 60 percent of the PAH contamination found in stormwater ponds may come from coal tar sealant, Berger said. The finding may add momentum to the effort to enact a ban, he added.

By passing a ban on the sealant, Kaldunski hopes the city may qualify for grant money from the agency to help dispose of PAH-contaminated soil.

What’s Next?

The Inver Grove Heights City Council must pass a second and third reading of the ordinance before it takes effect. If the ordinance is added to the books, it will become a misdemeanor offense to use coal tar sealants in Inver Grove, City Administrator Joe Lynch said.

But the city, he added, wants to focus on public education—not enforcement. If the ordinance passes, city officials plan to post information about the health hazards of coal tar sealant on the city’s website, send out information in city newsletters and host meetings for the public and business community.

“We’ll try it on three fronts, and hopefully we’ll be able to reach as many people as possible,” Lynch said.

Do Your Homework

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