The Bee Branch Creek Railroad Culvert and Pedestrian Tunnel Project in the City of Dubuque, Iowa, has been awarded an American Council of Engineering Companies (ACEC) 2024 National Engineering Excellence Recognition Award. The City of Dubuque has a history of localized storms that send stormwater rushing off steep bluffs to lowland areas where it then slows, eventually making its way to the Mississippi River. Construction of a levee system in the early 1970s provided protection from Mississippi River flooding but complicated the localized city drainage system. Over a 12-year period starting in 1999, the city suffered through six, localized flash flood events, resulting in a series of Presidential disaster declarations.
With tens of millions of dollars in both public and private property damage, in 2011 the City began implementing the multi-phase Bee Branch Watershed Flood Mitigation Project. The third phase, completed in 2022, involved improvements to pass stormwater and connect pedestrians from the Upper Bee Branch Creek through an active Canadian Pacific and Kansas City (CPKC) rail yard to the Lower Bee Branch Creek.
The proposed construction corridor through the CPKC yard was bounded by a rail yard maintenance building, a furniture store, industrial storage buildings, and the Lower Bee Branch Creek. Additionally, the active rail yard needed to remain fully operational during project construction, so little track settlement was permitted. This made geometric layout and construction staging challenging. In addition, the hydraulic demands of the proposed gravity culvert system and pipe cover requirements of the CPKC limited options for the installation of a conveyance system and pedestrian pathway.
The project team coordinated closely with the CPKC and conducted extensive geotechnical investigations, structural evaluations, and hydraulic analyses before employing microtunneling as the proposed construction solution. This solution involved:
- Design of six, 101-inch-diameter steel stormwater culverts, each 200 feet long, to convey up to a 500-year storm event safely beneath the CPKC rail yard.
- Use of interlocking mechanical joints to connect individual pipe sections of the new culverts, reducing overall tunnel construction time to just 4 months.
- Design of the conversion of existing twin 11- by 10-foot concrete drainage culverts to a pedestrian tunnel, providing a grade-separated rail crossing and connecting the 30-mile Heritage Trial system to the Mississippi River Trail.
- Use of ground penetrating radar and 3D laser scanning to assess and design repairs to the twin box culverts.
- Continuous ground monitoring to ensure minimal settlement of the railroad tracks above the tunnels.
This project successfully improved stormwater conveyance and accessibility of a pedestrian multi-use path by using creative engineering tactics to exceed stakeholder needs for the Bee Branch Creek Railroad Culvert and Pedestrian Tunnel Project.
The Bee Branch Creek Railroad Culvert and Pedestrian Tunnel Project also won a 2024 ACEC Wisconsin Best of State Award and an ACEC Iowa Grand Prize Award.
Read more about previous Bee Branch projects:
