BHI provided engineering services to mitigate over 4’ of scour and erosion at the outlet of the double barrel 120” corrugated metal pipe (CMP) crossing along Willow Creek at Maximus Drive in Lone Tree, Colorado. Willow Creek is a sandy drainage way characterized by highly erodible soils. With development on each side, it was critical that scour be addressed along with bank degradation downstream of the existing CMP crossing.

BHI reviewed existing data and assessed the site conditions. To develop repair alternatives, a HEC-RAS hydraulic model analysis of the existing outlet and downstream channel was completed and a zero-rise floodplain certification was prepared. After conceptual design, the alternatives were ranked based on cost, safety, sustainability, and feasibility. BHI’s unique broken-back culvert extension was selected as the best option for the site, topography, safety, and for cost effectiveness. The culvert extension included a downstream stilling basin consistent with UDFCD criteria and provided a nationwide permit from the USACE for construction.