In 2005, the 60-year-old Plum Creek and Marais des Cygnes bridges north of Osawatomie were deemed to be structurally deficient and functionally obsolete. Although the inspection revealed major deck deficiencies, the bridges and their foundations were structurally sound. BG provided the engineering investigation and analysis services and determined that the most feasible strategy was to remove and replace the bridge deck while keeping the existing superstructure and substructure in service. This would add another 20- to 30-years of life to the bridge at 20 percent of the cost to replace the entire bridge. BG Consultants developed plans for the removal and replacement of the old concrete decks and ornamental steel bridge rails, while salvaging the original steel plate girders, steel beams, and Art Deco piers and abutments.

The Marais des Cygnes River Bridge is a 120’-160’-120’ continuous riveted steel plate girder bridge. The structural analysis for this bridge was complex because it frequently changed shape along the three plate girders that carried the bridge across the river. The Plum Creek Bridge is a 40’-48’-48’-48’-40’ continuous steel I-beam, 45 degree skew bridge. Both bridges required a wider structure to meet current safety and design standards. To accomplish this, the pedestrian walkway was removed, which created 14’-8” driving lanes with shoulders.

This project required the placement of 540 square yards of concrete pavement and 582 cubic yards of structural concrete. Structural concrete was placed with two pumper trucks at the rate of 45 cubic yards per hour and in deck form panels designed specifically for this project. A set retarder was used to give the contractor adequate time to perfect the shape and finish texture of the concrete deck. The rate of application was 18 to 24 ounces of set retarder per cubic yard, depending on the ambient air temperature and relative humidity.