CLINTON TOWNSHIP, Mich. (AP) — A hole drilled through a concrete sewer line nearly 40 years ago may have led to soil erosion beneath another section of the pipe and the football field-sized sinkhole that has forced 22 families from their suburban Detroit homes.
Macomb County Public Works Commissioner and former Congresswoman Candice Miller called it a "theory" on Wednesday, but said officials are looking into it as they try to uncover the cause of the Christmas Eve sinkhole in Fraser.
It was discovered after a family awoke to find their home sinking. Their house and two others have been condemned.
"It seems to be so coincidental. We may have found what actually caused this break," Miller said at a news conference at the county's Public Works office in Clinton Township.
The 11-foot-wide sewer line is about 50 feet below 15 Mile Road, which stretches east and west through a number of communities north of Detroit. There've been two other line collapses — 1978 and 2004.
After the 1978 collapse, a contractor bored 11 two-inch diameter holes into the top and bottom of the pipe to determine how much soil settled in the sewer and the condition of the soil beneath the pipe, according to county engineering consultant Jason Edberg.
Officials believe the holes later were filled in with grout.
Most of the borings were made along a length of pipe that no longer is being used, but borings also were done on the eastern and western ends of that section — which are connected to the current sewer line.
One of the two holes was beneath the pipe that collapsed in 2004 in Sterling Heights; it took months and about $55 million to repair the pipe and sinkhole.
The other is near the current sinkhole, where groundwater may have seeped up and caused soil to erode and the pipe to collapse.
"Even though they are very small, over time the integrity of the borings become compromised," Miller said, cautioning that officials "may never know for sure" because the current sewer is compromised.
Miller said it could cost of tens of millions of dollars to repair the current problem. She and Macomb County Executive Mark Hackel are looking for ways to pay for it, which may include rate hikes and bonds.
Officials also are looking into helping the owners of the houses that have been condemned to see if "there is a way to work out a negotiated deal with these individuals to get them out of those homes," Hackel said.
The 19 other families could be back in their homes by Monday.