In the years since moving from upstate New York to Burnsville’s Walden neighborhood, Gil Dedrick and his wife, Pat, talked frequently about the challenges of starting over in a new place.
Dealing with sediment contamination didn’t often come up in those conversations. That is, until recently.
The cleanup of a nearby stormwater retention pond, which he believes has been contaminated by decades of runoff laced with toxic chemicals, has been on his mind for months.
The issue has pitted residents of this verdant neighborhood tucked near the Birnamwood Golf Course against the city, which contends that more sophisticated testing has to be done before any cleanup is possible.
Dedrick said neighbors waited for the city to address the pollution, even as concerns increased about possible pollution of the pond’s sediment by the chemicals leaching out of coal tar-based driveway and parking lot sealants. In the meantime, other cities across the metro considered banning the sealants, which research increasingly linked to cancer and other health problems.
“They had eight parking lots up at the townhouses. Well, every other year they coated it with asphalt, coal-tar derivatives, and that washed down and went right into the pond because we only have two tubes that are feeding the pond,” the retired poultry firm owner said.
Burnsville officials said the pond, is one of about 270 that dot the city, and is inspected every five years.
Frustrated by the lack of meaningful response by city officials, Dedrick said, he went out and tested the sediment himself last fall. He said he found traces of polyaromatic hydrocarbons, or PAHes — a toxic byproduct of once-common coal-tar-based sealants — whose use the Legislature recently banned.
Residents wanted to know whether the contaminants could attach themselves “to particles of sand that’s in the sediment and they can float in the air and you get some real health problems,” Dedrick said, patting a sheath of letters and newspaper articles sitting on his kitchen table.
Armed with the test results, Dedrick says he wrote to neighbors, and state and local pollution officials requesting action.
“To add insult to injury to Walden, we suggest you stop along the west side of Welcome on 130th, look down and see the stormwater dumped on the floor of the most pristine part of our common grounds,” he wrote in a letter to Walden residents. “There is no pond here, just standing water with a big invitation for mosquitoes to breed. All from the storm sewer off 130th St. Heaven knows what we will find when we take a soil sample here.”
Amid mounting public concern, the city announced recently it would conduct its own testing.
It will check for the need for any cleanup of the pond, which was built in 1969 to “capture stormwater and allow pollutants to settle out before it’s passed down downstream,” said Terry Schultz, the city’s parks and recreation director.
Currently no data is available to indicate how much sediment pollution was left from years of collecting PAH-tinged runoff. But, city officials said they would be testing concentration levels at the site to see if the pond will need to be dredged, as environmental regulations suggest it should be every 15 years.
The city’s “plans for removal or other remediation options will need to be formulated after the test results are known,” city engineer Ryan Peterson said in a written response to Dedrick. Burnsville “has been unable to test these sediments earlier due to the wet spring and early summer conditions we experienced.”
Some Walden residents recently said they knew of the sediment contamination, but were never notified by the city about the severity of the problem.
The 2-acre pond is located east of Parkwood Drive and surrounded by woods that Dedrick says are home to wildlife, including deer, foxes and wild turkeys.
Officials said that if their tests, which will be conducted according Minnesota Pollution Control Agency (MPCA) guidelines, reveal any sediment contamination, then cleanup efforts will follow.
The contaminated sediment would be hauled away to a nearby landfill.
The MPCA requires communities to keep storm ponds in good working order and to dispose of contaminated pond sediment.
In recent years, costs associated with cleaning up contaminated sludge in stormwater ponds across the metro have shot past $1 billion, although the pollution agency does award grants for cleanup efforts.
Determined to reduce pollutants found in stormwater, state lawmakers passed a law banning the use of coal-tar based sealants — which some studies have shown can pose a risk of cancer in humans, as well as being harmful to fish and other wildlife — used on driveways, parking lots and recreational trails. The law went into effect on Jan. 1.
An MPCA study found that about 67 percent of PAHes found in the sediments of 15 metro-area stormwater ponds were from such sealants, a claim the sealant industry has repeatedly denied.
“We know that won’t be a problem moving forward, but this is a pond that has been in place for more than 30 years,” said Schultz, the parks and recreation director. “So it would have received runoff from driveways that were potentially sealed by coal-tar sealants.”