By Sara Powers

STERLING HEIGHTS, Mich. (AP) — Crews are clearing debris and sediment from a section of an 11-foot-wide (3.3-meter-wide) sewer pipe not far from three suburban Detroit homes that were damaged when a football field-sized sinkhole formed on Christmas Eve in 2016.

The pipe in Sterling Heights is about a mile from where the sinkhole occurred in Fraser and was connected to a sewer line that cracked and collapsed.

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Once cleared, an impervious polymer pipe will be installed to prevent future collapses. The work is part of a $28 million infrastructure project in Macomb County.

Debris and sediment in the pipe are more than two feet (more than 60 centimeters) deep in some areas and has accumulated over the past 10 to 15 years, the Macomb County Public Works office said Monday.

The Macomb Interceptor pipe is about 50 feet (15.24 meters) underground.

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Experts determined that a “tsunami of sewage” was released too rapidly into the sewer system during a repair in 2014. The waste should have been released over hours but was let go in seven minutes.

The three damaged homes were condemned and two were demolished. Twenty families were displaced.

It cost $75 million for a bypass and a new sewer pipe after the sinkhole.

The Macomb Interceptor serves more than 500,000 residents and businesses in 11 Macomb communities.

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