Bullock Pen Lake Dam Rehabilitation
Constructed in 1953, the high hazard potential Bullock Pen Lake Dam could only pass approximately 24% of the PMP without overtopping. Within a few years of its construction, erosion of the dam’s excavated rock spillway was observed. A spillway breach and loss of the reservoir was a significant concern. As a result of these deficiencies, the Commonwealth of Kentucky ranked this project the first priority for rehabilitation among all state-owned dams.
Schnabel was selected to assess the condition of the dam and spillway, conducting a subsurface investigation and developing alternatives for addressing the identified deficiencies. Following the alternatives analysis, Schnabel designed the selected alternative and obtained the necessary permits required for construction. Extensive coordination with multiple state agencies, the USACE, the local water supply district, and local landowners was required throughout the project. Modifications included the construction of a 12½-cycle, 260-foot-wide reinforced concrete labyrinth spillway over the dam embankment, including a reinforced concrete stepped chute and stilling basin. This passive labyrinth spillway system was sized to pass the PMP without overtopping the dam, while also minimizing changes to upstream and downstream flooding. Other modifications included grouting the rock foundation, closure of the existing spillway, abandonment of the existing reservoir drain, installation of a new permanent siphon, and various other site improvements.