Located on the east side of Highway 24 in Manhattan, Kansas, the existing ten foot deep stormwater channel had steep, weedy side–slopes that made maintenance impossible. It was regarded as an eyesore by neighboring businesses and the community. In Phases I-II of this project, BG Consultants designed 2,800 feet of channel improvements, including terraced modular block retaining walls and a concrete ditch liner system in the bottom of the channel. This improvement increased the hydraulic efficiency of the channel while also enhancing its aesthetics.
The channel is located at the bottom of a large urban drainage basin. At the end of this channel is a large sluice gate that is manually closed when the Kansas River elevation is high. When the sluice gate is closed, the Poyntz Avenue Pump Station pumps stormwater over a levy for discharge into the Kansas River. Flooding along this channel was fairly commonplace, with water inundating parking lots of adjacent businesses. Detention was not a viable option with the location of the channel. To improve flooding conditions, the hydraulics of the Tuttle Creek Boulevard Channel needed to be enhanced. HEC-RAS modeling software was used to determine the optimum channel cross-section in terms of area and material for lowering the peak flow elevations during open channel flow conditions.
BG Consultants’ services in this area continued in 2014, when our team provided construction engineering and administration services for the City’s Phase III and IV stormwater improvements. The project involved 770 linear feet concrete ditch lining (41 feet high), 18,200 square feet of KDOT-approved modular block retaining wall, existing RCB headwall modifications, existing storm sewer extensions, a new concrete access ramp to channel, landscaping, and irrigation. Like the previous project phases, Phase III and IV further enhanced the aesthetics of the area and the flow of stormwater.