Following the 2011 flood event, Burleigh County identified the Tavis Road causeway as the location for the alignment of future permanent flood protection. Burleigh County, ND retained Apex to provide the engineering services to accomplish flood mitigation and prevention due to intimate involvement in previous flood events.

The Tavis Road causeway was modified to be used as a flood control structure and the location to pump internal runoff from South Bismarck and Burleigh County during a Missouri River ice jam or open water flood event. Apex used the City of Bismarck’s existing XP-SWMM model to determine the 60-cfs (38.8 mgd) pumping rate requirement for the contributing watershed. Many scenarios were created in the model to analyze various design events, and inundation mapping was created for the upstream Riverwood Golf Course and adjacent homes.

From the modeling process, it was determined the best solution to protect both private property and public infrastructure was to modify the existing box culvert through the causeway to include a 16-foot wide flood control gate. The roadway was raised to the required freeboard, and three, 24-inch forcemain pipes with an outlet headwall and erosion control mats were installed to protect the embankment. A 60-cfs pump station was constructed as a utilitarian cast-in-place concrete structure. Submersible style, axial flow pumps were selected for their low level of required maintenance and the inherent ability to easily remove and reinstall the pumps as needed. The pump station is designed to remove internal stormwater from South Bismarck and Burleigh County by pumping the stormwater from the protected side to the river side of Tavis Road.

Apex provided Burleigh County with hydraulic analysis, funding options, final design and bidding documents for the grade raise, control structure, flood control gate, and outlet piping. The project was completed in 2014.