SUNKEN BRIDGE POSES A LIFTING CHALLENGE
The Gums Crossing Bridge on County Road 21 in Yalobusha County, Mississippi provided passage to residents crossing Grenada Lake for decades. But heavy rains and historic flooding damaged the bridge in early 2019, and it was closed after failing inspection. In January 2020, a section of the bridge collapsed into the Skuna River Basin.
The resulting bridge closure caused a lengthy detour for area residents and travelers on the major county route. It was a situation that had to be remedied.
After a year of detours, the Yalobusha County Board of Supervisors awarded a $16.24 million contract for the half-mile bridge replacement to Malouf Construction, LLC, of Greenwood, Miss. The work included the removal and construction of approximately 1,368 linear feet of bridge structure and 961 feet of roadway.
The old bridge sections had to be removed first for several reasons. For example, the collapsed bridge sections posed an underwater hazard. Plus, a new bridge couldn’t be constructed until the sections were removed.
Diving crews from Mainstream Divers assisted with the rigging and recovery of the submerged sections of the collapsed bridge. They discovered that a total of three spans were partially exposed while an additional two were buried under significant substrate in the lake. The dive crews also drilled holes into the collapsed bridge spans to secure rigging in preparation for removal.
LIFTING THE SECTIONS
Barnhart was hired to provide a lift system that could recover the sunken bridge sections. The crew developed a first-time solution by assembling a Modular Lift Tower (MLT) on modular barges. They used 70-ton strand jacks to lift the bridge sections out of the river. The MLT and 5-foot girders supported the jacks and allowed positioning of the jacks over the sunken sections.
The lifts were time-critical. Once the section was uncovered and prepared, the crew had to be ready to hook up and begin lifting before the river current covered the sections back up with silt. Furthermore, very little was known about the condition of the sections from being underwater for over a year.
Barnhart successfully lifted the first section from the water and set the piece on the deck of a barge provided by Malouf. The section was relocated to a riverbank where it could be broken up and hauled away.
The Barnhart crew will recover at least one more section that is impeding the new bridge construction in the coming months. Yalobusha County officials said the project is expected to be completed by fall 2023.