Burnsville sewage leaks onto Minn. Valley refuge

Bloomington, Minn. — A blocked sewage line caused an estimated 100,000 gallons of residential sewage to leak onto the Minnesota Valley National Wildlife Refuge in Burnsville last month, and workers this week were expected to complete cleanup. Between eight and nine cubic yards of solid waste (roughly the capacity of a single-axle dump truck) were expected to have been removed from the refuge when the work was done.

A refuge official says the leak occurred when the bottom rung of a ladder that likely long ago was left in a manhole broke off and lodged in the Burnsville city line – a 10-inch pipe – and collected pieces of sewage until the line was blocked. Then, the waste crept up the 8-foot-deep manhole until overflowing onto refuge property.

Jeanne Holler, deputy refuge manager at Minnesota Valley, a 14,000-acre refuge that stretches along the Minnesota River from Henderson to Bloomington, said a railroad worker doing maintenance discovered the leak Feb. 21. Eagan officials first investigated, but determined the line was that of the city of Burnsville. On Feb. 23, a Burnsville crew and a contractor bypassed the blockage and began to remove the sewage, which had seeped along “the path of least resistance” to a creek, Holler said, spilling into a wetland, and, eventually, Black Dog Lake.

The sewage leaked from the 3-foot-diameter manhole for at least two days, she said. “How long it was flowing before that, who knows?” she said.

While much of the solid waste will have been removed, it’s likely liquids seeped into refuge waters, according to Holler. What might be the results? Among the possibilities, she said, are fish kills and increased algae blooms. The possible effects on waterfowl are unknown.

Outcomes are somewhat unpredictable, Holler said, considering “all the things people put in the toilet.”

Holler added that because water from Black Dog Lake is used for cooling at an Xcel Energy plant, it circulates more, something that could better mix and dilute the waste that makes it to the lake.

Linda Mullen, utilities superintendent for Burnsville’s Public Works Department, said the leak will cost the city about $17,000, much of that paid to contractors who’ve helped with cleanup. That amount doesn’t include the time city workers responded to the incident, she added.

Mullen said there are about 130 residential homes connected to the line, first run in the 1980s.

“Any release is too much,” she said, adding that if it were an industrial line, much more could’ve leaked onto the refuge.

Holler said Burnsville crews initially removed about six cubic yards of waste from the area – by scraping solids off the ice and snow – and considered the cleanup complete. However, refuge officials inspected the site and decided more could be done. “It’s federal property, and you have to (clean up) to our satisfaction,” she said. “They thought they’d done all they could, and we thought they could do more.”

Mullen said the cleanup work was challenged by both weather (snow and melt), as well as steep grades hindering the movement of equipment. That’s why, she said, the final phase of cleanup will be done by a company – Minnesota Native Landscape, which specializes in ecological restoration services – contracted by the city. Weather-permitting, Mullen expected MNL to finish the job, which could include the removal of another two to three cubic feet of waste, this week.

Both city and federal officials say the issue will lead to improvements in both planning and response to such an incident, albeit an uncommon occurrence. Mullen said Burnsville officials will put in place a plan to more easily access manholes for both routine maintenance, as well as emergencies.

“This was an oddball one,” said Mullen, who’s been in her position for 20-some years.

Refuge officials will continue to monitor the effects of the sewage as the spring and summer progress, Holler said. And they’ll add to their refuge plan how to react should a similar leak occur in the future.

“This is kind of the eye-opener, (that) we don’t have a good plan for that,” Holler said.

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