Dam Good Fishing Without the Snags Fish Passage at a Low Head Dam

What better way to rehabilitate an old low head dam than helping the fish out at the same time? That is what occurred at Conewago Creek Dam in Pennsylvania in 2021. The aging, timeworn low head dam needed more than just a face lift. It had numerous problems including structural deficiencies, lack of a drawdown mechanism, possible formation of a reverse roller hazard, and was a barrier to fish passage. Including a rock ramp fishway addressed safety concerns at the dam and removed a long-standing obstacle to the migratory American shad. Unique design challenges and construction considerations included: 1) Evaluation and selection of rock ramp dimensions including sizing of boulders, spacing and depth of pools, and ramp slope to fit within the existing terrain limitations and support the passage of regional migratory fish 2)Application of models used to analyze flow conditions for fish passage to consider maximum flow velocity and patterns along the rock ramp 3) Careful balance of priorities to maintain river flow, impound water for municipal use, and efficiently construct the new dam and rock ramp and 4) Extensive temporary control of water measures designed to protect construction during small rain events that were put to the test during numerous thunderstorms and Hurricane Ida