Spillway Optimization at Batavia Dam

The Batavia Dam is located on the Fox River in Batavia, Illinois. It is a low overflow structure with a modified ogee spillway. Shallow portions of concrete have broken from the crest, and a 15 ft-wide breach has developed at the east end of the dam resulting in deteriorated spillway performance and questionable structural integrity of the dam. These issues were addressed by a previous 1 to 30 scale model study of the Batavia Dam. Of the three alternative dam configurations tested, the study recommended replacing the existing dam with either a bathtub spillway or a 2-sided spillway design. Further analysis was also recommended to optimize the safety and performance of the spillway design.

In response to the previous study, a 3 ft wide, 1 to 9 scale sectional model was constructed to determine an optimum spillway design for the Batavia Dam. This model study considered drownproofing and hydraulic performance of the spillway, since drowning accidents have occurred frequently at low overflow dams on the Fox River. The objectives were to construct sectional spillway models appropriate for the aforementioned 2-sided spillway design including an erosive movable bed. Existing discharges at the Batavia Dam were reproduced with a model of the existing spillway shape, and the characteristics of the submerged hydraulic jump and bed scour for the existing condition were investigated. This provided a benchmark condition. Finally, several spillway alternatives were considered to eliminate the submerged hydraulic jump while preserving the existing stage-discharge relationship at the Batavia Dam.

The four spillway alternatives were:

  1. the Montgomery Dam design,
  2. the Montgomery Dam design with riprap,
  3. the Montgomery Dam design with additional steps, and
  4. an ogee shaped spillway with steps.

Alternative 1 and Alternative 4 were recommended as possible replacements for the Batavia Dam. Both designs performed well hydraulically and more safely than the existing condition. Bed scour is the main disadvantage of Alternative 1, while the feasibility of construction is the potential drawback of Alternative 4. The final selection will be highly dependent on the cost effectiveness of constructing the structure.