Willisburg Lake Dam is a high hazard structure which retains Willisburg Lake, the main water supply for the City of Springfield, KY and is used recreationally by the local communities.  Known deficiencies at the dam include insufficient spillway capacity, seepage near the downstream toe, and an inoperable low-level outlet.  The rehabilitation design had the objective of bringing the dam into compliance by designing a new spillway system and addressing the seepage that would not require property acquisition, limit future Operations and Maintenance requirements for the owner, and limit impacts to the surrounding infrastructure.  The dam is closely surrounded by a marina, a parking lot, private driveways, and a pump station.  The design constraints minimized the options for a new spillway system.

The solution to the project included a flood wall along the crest to increase storage capacity, a berm along the downstream toe, and a new auxiliary spillway through the center of the embankment.  The proposed spillway consists of box culverts discharging to a stair-stepped chute and concrete stilling basin.   This design offered the least amount of design risk and had the least amount of impacts to the surrounding areas when compared to other alternatives.  Additionally, this alternative provides the shortest alignment for a concrete chute which results in a lowered construction cost.

This presentation will discuss the design approach which included evaluating 6 alternatives.  The role of computational fluid dynamics (CFD) on the spillway and stilling basin design will be presented including a discussion on the capabilities of CFD modeling (when to use it and its limitations).  Lessons learned from the design process will also be provided.