Riley County, KS
When the existing steel stringer bridge on Mineral Springs Road over Deep Creek was deemed structurally deficient, Riley County contracted with BG Consultants to design the replacement. The site posed several issues that BG had to consider in their design.
First, the existing steel bridge provided the only travel-way in and out of the area for some residents, and therefore the roadway could not be closed for construction. The topography of the area, which included extremely steep grades approaching the bridge, provided further challenges. For safety reasons, the roadway was raised at the intersection of Deep Creek Road and Mineral Springs Road. Although the final grade of the road from the west was eight percent, a smoother alignment and gentler transition curves improved the previous roadway vertical alignment. The roadway alignment was also moved to the north of the existing alignment, so the existing bridge could remain open without interruption during the majority of the construction. Once the new road was ready to be transitioned to the existing roadway, one lane of traffic could be open at all times during the short period of time required to construct the transitions.
Finally, BG Consultants had to take special care not to disturb the endangered species in Deep Creek. The existing steel stringer bridge was replaced with a 75’ prestressed concrete beam bridge with 2-35’ flat slab approach spans. By using the prestressed concrete K3+3 beams for the middle span of the bridge, Deep Creek was spanned without placing a pier in the creek and allowing for little disturbance of the endangered species. BG Consultants worked closely with Riley County and environmental permitting agencies to ensure the most protection for the endangered species while providing a larger capacity bridge. Once the new roadway was complete and opened for traffic, the existing roadway and structure were removed and the area re-graded and seeded.