Raw sewage spills into Huron River in Nichols Arboretum after sewer pipe clogs
A clogged sewer pipe in Nichols Arboretum caused an undetermined amount of raw sewage to flow into the Huron River, Ann Arbor officials said on Friday.
The city was notified by the University of Michigan on Thursday afternoon of reports of a "sewer odor" and "some gray pooled water" in the Arb, city officials said.
Ryan J. Stanton | AnnArbor.com
"We actually were out there immediately to take care of it," said Jennifer Lawson, the city's water quality manager.
Lawson said the city found out about the problem around 3 p.m. Thursday, but it's unknown how long it had been going on.
"Visible flow was observed yesterday," she said, adding the water made its way to the surface through a manhole cover in a grassy, wooded area where people don't normally go.
The area of the Arb where there are stone steps leading out to the river is where the sewage entered the river, she said, though the water came from a manhole about 30 yards south of there.
About 5:45 p.m. Thursday, the city's field crews began jetting the line from the downstream manhole, and within a few minutes a blockage was relieved, city officials said.
After that, the water stopped flowing to the surface. Tree roots were identified as the cause of the blockage.
While on site Thursday, the city's field staff learned from joggers and other users of the Arb that the area has smelled for about the last week, Lawson said.
She said no one ever called the city to complain about the problem, though, as some just assumed it was either a dead animal or rotting vegetation.
"We don't know when it started," she said. "We don't know what the duration of the overflow was — if it was one day or 10 days."
The sewage that flowed into the river was on its way to the city's wastewater treatment plant and included toilet water, though there were no visible solids, Lawson said. She said the grayish water was leaking out of the manhole at about half the speed of a garden hose.
The city has applied a lime product to the affected ground area to kill any remaining bacteria. It appears as a white, powdery substance.
Because the sewage reached the river, the city took the precaution of closing canoe livery trips in the vicinity — from Argo to Gallup — on Thursday and through Friday.
Body contact is not recommended for at least 24 hours after a known release of raw sewage to waterways, city officials said.
The city has completed testing and plans to evaluate water quality samples over the next 24 hours for presence of harmful bacteria in the river.
The determination whether to resume canoe livery operations between Argo and Geddes will be made at 8 a.m. Saturday, based on water sampling results.
"At this point, we're monitoring to make sure the water quality is safe, but that test takes 24 hours to do," Lawson said.
In accordance with regulatory protocols, city officials said they contacted the Michigan Department of Environmental Quality to inform the state of the incident.
Lawson said the city will be coordinating with the Arboretum on any plant restoration that's needed, as there was some damage to surrounding vegetation.
An estimated 10,000 gallons of raw sewage spilled into the Huron River during a June 27 storm that quickly flooded Ann Arbor streets and knocked out power.
Ryan J. Stanton covers government and politics for AnnArbor.com. Reach him at email@example.com or 734-623-2529. You also can follow him on Twitter or subscribe to AnnArbor.com's email newsletters.