The deteriorating Lewis River Bridge in Yellowstone National Park will be replaced/NPS

The paperwork has been approved, but when crews actually begin to replace the decrepit Lewis River Bridge in Yellowstone National Park depends on when the money is available.

Nearly six decades into its life, the bridge has reached old age and has deteriorated to the point where it either needs "extensive rehabilitation" or to be completely replaced. Constructed in 1960, a recent Federal Highway Administration Inspection Report cited problems with the bridge’s concrete surface, foundation, and railings, and judged it to be in poor overall condition. Along with the decking and railing problems, the foundation that sinks beneath the river is being impacted by "scouring," in which the river currents essentially dig out the sediments and rubble around the abutments.

Continued scouring could jeopardize the stability of the abutments, according to the park staff.

Right before the partial government shutdown took effect in late December, National Park Service's acting director for the Intermountain Region, Kate Hammond, signed a Finding of No Significant Impact for an environmental assessment to replace the bridge, which is located just south of the Lewis Lake Campground on the South Entrance Road.

The replacement will be built on a new alignment directly east of the existing bridge. Parking and pedestrian areas located north and south of the existing bridge will be redesigned and reconstructed.

The park considered two alternatives in its EA. Alternative B, the approved action, will shift the South Entrance Road several hundred feet to line up with the new bridge. Traffic will continue on the existing bridge while the new bridge is under construction. Alternative B was selected to ensure excellent bridge structure integrity into the future, improve pedestrian safety, and reduce localized vehicle congestion.

This graphic shows the location of the proposed Lewis River Bridge in relation to the existing bridge/NPS

Under the plan, the existing bridge would continue to carry traffic while a new bridge is built alongside it. After the new bridge is ready, the old span would be demolished.

According to a park release, roadwork could begin as early as spring 2020 and last for two consecutive years followed by the spring of a third year. When the proposed project is implemented, construction delays would normally be limited to 30 minutes. There may be up to six temporary road closures as long as six hours each to set bridge girders. The Lewis River Falls Overlook Trail and parking areas would be closed during construction.