Engineers’ designs to fight erosion below the east end of the U.S. 80 Mississippi River Bridge are due this week and should answer questions about the scope of the work needed.

A small retaining wall built under the bridge nearly 50 years ago is failing and has moved a foot and a half in the past year, Bridge Superintendent Herman Smith said.

Smith and engineers from the ABMB firm say it’s a dangerous situation that needs to be addressed soon.

“If that dirt comes down at one time, it could take these gas lines out and it could take Bent A clear off the concrete,” Smith said.

The first design plans are due at the Vicksburg Bridge Commission meeting at 9:30 a.m. Wednesday at the Warren County Courthouse.

Engineers have said they don’t know how expensive the project will be, but it will be costly. It also will be similar, but much smaller in scale, to a $26 million project in Natchez.

The bridge is monitored constantly for shifts of all sorts and in all directions. The erosion issue was noted after a heavy rain in April. Since, dirt washing down the hill has exposed the east abutment, the concrete base where the roadbed meets the land, and buried the concrete footings at Bent A, the first support under the roadway.

Crews at the county-owned bridge have worked to direct water away from the eroding areas, but Smith says it’s just a matter of time before the problem becomes too big for them to keep under control.

“It could be the next great, big rain storm or it could be several years,” Smith said.

Lynn Wolfe and other engineers with ABMB are working on design plans to replace the retaining wall and stabilize the bluff at Navy Circle. According to geotechnical consultants, the bluff at the Vicksburg National Military Park property has moved about 20 feet in the past 60 years.

In Natchez, a project to stabilize a half-mile stretch of the bluffs along the river took six years. The project by the U.S. Army Corps of Engineers was federally funded and is one of few in the country to use soil nails – long, nail-like beams set deep into the face of the bluff – to hold it in place.

“What we’re looking at here is a three-phased approach,” Wolfe said.

First, engineers are proposing a small project to fix some of the minor problems caused by the erosion. That would be followed by a larger contract for three to four retaining walls at different locations on the slope.

The final phase would be an effort between the Vicksburg Bridge Commission and the national park to stabilize the slope at Navy Circle. That part of the project would involve the Corps and use soil nails across 600 feet of bluff.

So far, the commission, which is responsible for maintaining the bridge, has paid $50,000 for the initial report and approved spending up to $75,000 more for the second phase of the design work.

Warren County has owned the privately built bridge since 1947 and operates it like a business, collecting tolls from railroads using the bridge and utility rentals.

Until the Interstate 20 bridge was opened in 1974, the U.S. 80 bridge was the only local crossing of the river. It is also the only railroad crossing between Memphis and Baton Rouge.

It has been proposed by recreation-interested groups and recommended by the commission that the roadbed, closed to vehicular traffic in 1998, be converted into a pedestrian and bicycle park. The commission has also contracted with ABMB for those plans.

In a nonbinding referendum, a park-conversion plan proposed in 1999 was rejected 2-1 by voters who favored reopening the bridge to vehicular traffic, but five years later that directive was rejected by Warren County supervisors.

Officials say the problem with reopening the span for traffic is the narrow width of the roadbed. The area designed for two-way traffic is 18 feet wide while modern safety highway standards prescribe 24-foot minimums.

The span has also had problems with shifting piers that have been slowly moving toward the Louisiana bank and pulling the bridge with them. Some repairs have been made and paid for out of the $6.5 million in reserves generated over the years from the railroad company and utility leases.

Erosion repair work would also be partially funded from the reserve accounts. Engineers are seeking federal funding for portions of the plan that will be on national park property.