Housing development caused 200 | Gansu Red Sun Co.,Ltd

Ann Arbor's Larcom City Hall, 301 E. Huron St., on Sept. 6, 2022.Ryan Stanton | The Ann Arbor News

ANN ARBOR, MI — Ann Arbor has reported a 200-gallon sewage spill on the city's south side believed to be caused by overuse of sealing material at a housing development site.

The city was notified of sewage spilling out of a manhole near Cloverly Court off Stone School Road at about 2 p.m. Sunday, Oct. 30. City staff immediately investigated and found a blockage in the sewage pipe, which turned out to be from overuse of sealing material from the nearby private project, officials said.

"The sealant was a self-leveling and self-compacting liquid grout mixture that was being used to fill the spacing between a casing pipe and a new sanitary sewer from a private development," said Jennifer Lawson, the city's water quality manager. "An excess of grout was pushed into the city's sanitary sewer and hardened."

The overflow caused an estimated 200 gallons of sewage to overflow onto the ground, which then drained into a nearby catch basin, but due to the quick action of public works staff, the sewage was captured and vacuumed up before it reached a nearby detention pond, according to the city.

The affected road and lawn areas were cleaned and treated with a powdered lime to neutralize and accelerate the decomposition of any remaining sewage. In accordance with regulatory protocols, the city reported the incident to the Michigan Department of Environment, Great Lakes and Energy.