City-County Drain Flood Mitigation

The project was an emergency study to evaluate alternatives to repair the City County Drain Outfall. During the 2018 peak flood flows, the Yellowstone River washed into the existing City County Drain, resulting in a significant increase in backwater that caused flooding of streets and basements in a subdivision located on the north side of the interstate. The project evaluated short- and long-term solutions to prevent backwater from the Yellowstone River during peak runoff events. The project included installation of nearly 4,400 linear feet of storm drain to a new outfall location to reduce backwater effects from the Yellowstone River. In addition, a new 38-foot-wide, two-way flood protection/stormwater gate was installed in the existing City County Drain ditch to balance floodwater backwater while still passing high runoff flows from the City County Drain.