Background The 74-foot single-span steel stringer bridge on Day County Highway 1 over Blue Dog Lake had faced flooding for several years, as the road is only two feet higher in elevation than the outlet of the lake. IMEG initially conducted a hydraulic analysis, and a single-span concrete girder bridge was selected as the replacement structure, but, by the time the design was initiated, the site sustained back-to-back 100-year storm events that caused the lake to rise considerably–making the existing structure selection unusable. IMEG reanalyzed the hydraulics and a four-cell cast-in-place concrete box culvert was selected as the structure. Construction was completed over the winter season, from November to April, which created challenges with protecting the concrete during the curing process in extreme cold temperatures.
Impact The road serves as the primary paved connection between City of Waubay and the Enemy Swim Day School District as well as several residences and small businesses along Blue Dog Lake and Enemy Swim Lake. Because the bridge was prone to flooding prior to the construction of the box culvert, residents were faced with long detours around the lake to reach their destinations. The new box culvert significantly improves travel times and accessibility for the community, and is designed so that the road grade can be raised an additional four feet to help alleviate flooding issues going forward. Technical Aspects • Revision of hydraulic and hydraulic analysis to provide design for new equalizer box culvert to conduct water from one side of the road to the other and protect it from flooding • Utilization of thermal concrete blankets to keep concrete above 50 degrees for three days and above 40 degree for two additional days
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December 2023
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