Vicksburg officials today barricaded the long-troubled Washington Street bridge over railroad tracks at Clark Street after engineers said vehicles were exacerbating chances of a collapse.

“The bridge is locked in a state of stress,” said John McKee of ABMB Thursday. “It’s not vertical, but it’s a torque issue working against that bridge.”

Restricted to light traffic for more than two years, the bridge had a short life expectancy anyway. It is to be replaced with a tunnel design on which construction may start within weeks.

Still, it is a major disruption for traffic on Washington, one of the city’s few north-south thoroughfares. Northbound traffic is being detoured onto North Frontage Road, while southbound vehicles are being sent to Lee Street, Mayor Laurence Leyens said.

Erosion on banks that support the bridge has accelerated since a partial collapse in the mid-1980s. That led to an earlier blockade of the bridge, lasting more than a year while shoring up took place. The short bridge, about 100 yards, has a long history of problems due to the unstable bluffs rising from the Mississippi River. In recent days, easterly movement has been measured at 1 1/2 inches.

Plans to replace the bridge were succeeded by a design that calls for a tunnel through the deep ravine with a road atop. Vicksburg set aside $5 million of a$16.9 million bond issue in 2006 for the work and the Federal Railroad Administration is to reimburse $4 million of the cost.

Kansas City Southern will oversee construction of the tunnel, which has been slated to start in mid-February if construction contracts are finalized.

The tunnel was to be built in sections to allow traffic to flow as normal without detours. Street blockages of 30 to 45 days were forecast last year as city officials worked to transfer the project to federal and railroad oversight. The closure changes that and indicates detours may be required until the project is complete.

Weight limits set by the city on the bridge at 10 tons, or 20,000 pounds, have been enforced sporadically since 2006. Thursday night, police cars were stationed as Lee Street and North Frontage to steer heavier vehicles, especially 18-wheelers, away from the area.

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Contact Danny Barrett Jr. at dbarrett@vicksburgpost.com.