Jessica Mathews /

Costly repairs are in the works for a large sinkhole on a street in the City of Howell after a deteriorated sanitary sewer main collapsed.

City Council met Monday night and authorized having staff move forward with the emergency sewer repair.

The sinkhole is on West Street at the intersection of Factory Street, near the West Street Park. A portion of the road remains blocked off to thru-traffic.

The deterioration was caused by hydrogen sulfide that was being released from the sewage, due to the way two force mains enter the manhole.

City DPS Director Matt Davis gave a detailed presentation during the meeting. He said force mains traditionally have issues with hydrogen sulfide because of a change in velocity and the sewage. Davis said that change in velocity releases hydrogen sulfide, which is not good for concrete pipes, and it will actually eat away at concrete pipe.

The estimated repair cost is roughly $75,000. Staff has been working with local contractors to perform the necessary work in a timely manner.

Davis noted they’re working to coordinate repairs with four different contractors as each specialize in different areas. However he said one Howell company has agreed to waive mobilization fees if done at a certain time, which would be a huge savings. The timing of the work is also dependent upon material availability.

Davis said they’ll be back for final approval once exact prices are known.