Source: https://www.hometownsource.com, January 10, 2019
By: John Gessner

Pavement seal the alleged culprit

Burnsville and six other Minnesota cities are suing several chemical companies over products that contaminate stormwater pond basins and raise the costs of dredging and maintenance.
Burnsville’s suit, filed Dec. 28 in U.S. District Court, seeks reimbursement for the past and future costs of removing sediment containing measurable levels of PAHs (polycyclic aromatic hydrocarbons), some of which are known carcinogens.
The companies refine and market coal tar, which contain high levels of PAHs, for use in pavement sealants, according to the suit. In Minnesota, the sealants were commonly used on driveways and other surfaces by both paving companies and homeowners until the Legislature banned their sale effective Jan. 1, 2014.
Coal tar sealants wear out, their particles washed or blown into the environment, including stormwater ponds, where they settle at the bottom.
Before cities clean or dredge ponds, they’re required by the Minnesota Pollution Control Agency to take soil tests, Burnsville Public Works Director Ryan Peterson said.
Soils with PAHs must be hauled at city expense to a regulated landfill rather than kept and reused by an excavator, Peterson said.
With 270 stormwater ponds, Burnsville budgets about $300,000 a year for cleanup and dredging projects. The work is done primarily to safeguard the water quality of downstream lakes and water bodies, Peterson said.
“The more PAH-laden sediment there is, the less far we can get each year” on pond cleanup, he said. “Our experience is approximately a quarter or a third had the PAHs at a measurable level.”
Over the years the city has paid hundreds of thousands extra to have soils hauled to landfills, Peterson said — and “a ton” of stormwater ponds still await cleanup.
The city — which uses an asphalt-based sealant on its streets instead of coal tar — isn’t liable for sediments containing PAHs, Peterson said.
“And homeowners aren’t, either,” he added. “We’re going after the company that supplied it to the people that turned it into sealants. You’re never going to see us coming after a resident because they put it in their driveway.”
The suit alleges that the chemical companies knew, or should have, of studies conducted by the U.S. Geological Survey and others showing links between the use of refined coal tar in sealants and a rise in PAH contamination levels in urban lakes and ponds.
Pittsburgh-based Koppers Inc., the first of seven named defendants, said in a statement: “Koppers does not believe there is merit to these claims and intends to vigorously defend these matters.”
Burnsville’s Walden neighborhood is familiar with the PAH problem. Walden Association homeowners paid for testing of their local pond basin, which identified PAHs in the soil. A city consultant did its own testing confirming the finding, and the city dredged the pond in early 2016, Peterson said.
Walden homeowner Gil Dedrick, who led the effort to get the pond dredged, applauded the city’s lawsuit.
“We need a uniform action, and we need it in the state,” Dedrick said. “I’m sorry that it had to go to court, but if that’s the way it has to be, it has to be. I think they’re going to find a lot of material in some of those ponds. We even found mercury.”
Walden Pond was a special case, Peterson noted, because it’s dry for much of the year, unlike most Burnsville ponds. That increases the risk people and animals will be exposed to contaminated soil.
PAHs sink to the bottom of water bodies instead of dissolving, Peterson said, stressing that their presence doesn’t threaten the city’s drinking water.
The other cities filing suits are Bloomington, Golden Valley, Maple Grove, Eden Prairie, White Bear Lake and Minnetonka.