FARGO — North Dakota and Minnesota public works officials have indefinitely closed the North Broadway Bridge in Fargo to vehicle traffic and pedestrians due to concerns about its structure.
During routine monitoring, Fargo officials learned of a tilt in one of the bridge's piers caused by the movement of surrounding soil, according to an announcement from the city.
The shift is not an immediate threat to the bridge's structural integrity but calls for a closer analysis before transportation officials can start repairs or take any other action, the city said.
As a precaution, Fargo, Cass County and the Minnesota Department of Transportation closed down the bridge to vehicle traffic and pedestrians at 10 a.m. Thursday, Feb. 11.
Officials have redirected traffic across the North Broadway Bridge to the nearby Cass County Road 20 bridge along 40th Avenue North, about half a mile northwest.
Jeremy Gorden, transportation division engineer for the city of Fargo, said a bridge engineering consulting firm, SRF Consulting out of Minneapolis, was hired by the city in 2018 to do a study of the bridge and the soils supporting it.
As part of that study, the bridge was monitored for 19 months. At the end of that time, SRF recommended that funding be sought to rehabilitate or replace the bridge and that in the short term the tilt angle of the north pier supporting the bridge be monitored regularly.
Last week, a crew from Clay County, which operates the bridge along with the city of Fargo, surveyed the north pier and provided information to SRF.
SRF determined the pier had moved 0.44 degrees in one year and recommended that the bridge be monitored weekly or, in the alternative, that it be closed to all vehicular and pedestrian traffic.
"So we had a discussion yesterday and we thought, 'Hey, let's just close this thing,''' Gorden said Thursday, adding that the bridge will remain closed until its future is determined. He said options include rehabilitation, replacement, and removal without replacement.
"From a purely technical, engineering perspective, it probably makes the most sense to remove the bridge, but from a political perspective people that use the bridge, they may want it rebuilt," Gorden said.
"We don't have the funding in place currently to replace it, or to do anything with it," he added.
The bridge, which was built around 1990, replaced an older, much smaller bridge.
Gorden said the Minnesota Department of Transportation criticized the current bridge as being poorly designed.
Based on information from 2015, about 1,800 vehicles a day cross the bridge, compared to about 6,000 vehicles that use the Cass County Road 20 bridge and the more than 10,000 vehicles that daily use the 12th Avenue North bridge, formerly known as the toll bridge, Gorden said.
According to Gorden, a major issue with the tilting pier is that it is anchored in clay soil, which he said is notoriously prone to weakness, especially given the cycle of flooding the soils are subject to.
When the ground supporting the pier is saturated by floodwater, it increases the soil's weight and accelerates its movement toward the river, Gorden added.
There have been efforts made in the past to prevent the pier from shifting, but they failed to stop the significant shift recently discovered, Gorden said, adding the bridge's future will be determined by the city of Fargo in collaboration with Clay County officials.