GRAND BLANC TOWNSHIP (WJRT) (1/10/20) - Northbound I-75 just past the I-475 interchange in Grand Blanc Township remains closed until further notice after a sinkhole opened beneath the surface.
A culvert washed out underneath the northbound lanes of I-75 in Grand Blanc Township, prompting MDOT to close the freeway from I-475 to Grand Blanc Road.
The Michigan Department of Transportation says high water levels caused a culvert to collapse and erode the shoulder.
"Its gone. Unfortunately it appears that the high pressure water completely washed the pipe away," said MDOT spokeswoman Jocelyn Hall.
The road surface is bridging the 5-foot gap where the culvert was located, but there is no soil underneath to support it.
"Unfortunately, water levels were just too high and strong in this retaining area and it looks like the pressure from those water currents not only washed away materials surrounding the pipe but the pipe itself," Hall said.
MDOT says it knew this section of I-75 was vulnerable, because there's a retention pond next to it. The department was monitoring the culvert as water levels rose.
"Originally, the size of the culvert that was there was fine for those conditions," Hall said. "The conditions have changed and so we're concerned that that size is no longer adequate. It should be, but what we've seen is that it isn't."
Late Thursday, the ground eroded away underneath the road, so engineers decided to shut down the northbound lanes.
"It appears that high pressure water completely washed the pipe away," said Hall. "Certainly, anytime you've got water around a structure, you've got that much more potential for incidents that occur that need to be handled in an immediate kind of nature, and this is one of those situations."
A contractor is coming to the scene Friday to begin repairs as soon as possible. MDOT hopes to reopen all lanes sometime this weekend. The new pipe that will go in will be larger and should be prepared to handle the rising water levels.
The pavement remains intact, so repairs are only necessary to the soil underneath.
For a detour, the best options may be to take Hill Road or Grand Blanc Road via Dort Highway to northbound U.S. 23, which merges with I-75.