KL Engineering provided the design for the CTH P bridge over the Timber Coulee Creek in Vernon County. The existing single span steel girder structure with substandard beam guard was replaced with a single span buried slab structure without beam guard.
The site is located within a mapped floodplain and is approximately 0.5 miles downstream from the Melby Dam. Per discussions with BOS, the replacement structure was designed to pass the 720 cfs peak flow for the entire watershed, neglecting the regulated flow through the dam.
A single span flat slab bridge, a 2-cell box culvert, and buried slab alternatives were investigated. The buried slab option, which has an open bottom to maintain the existing streambed, was preferred based on minimizing impacts to the high-quality trout stream and to adjacent protected Section 4(f) & 6(f) fishery property. The buried slab was extended past the clear zone to eliminate stream realignment and intersection relocation.