Bronx River Double Dam Fish Passage Assessment

Princeton Hydro was on the team to study the Bronx River Double Dam for New York City Parks (the dam owner). The project goal was to present an economically, environmentally, and socially sustainable long-term fish-passage solution for the Bronx River Double Dam.

The culmination of the project was a fish passage Alternatives Analysis for the dam site, where the cost and benefits of various long-term solutions for the project site were assessed, including dam removal and an engineered fishway. To inform the Alternatives Analysis, Princeton Hydro first studied the feasibility of the removal of the Bronx River Double Dam.

To inform the dam removal feasibility study and a conceptual dam removal design, Princeton Hydro supplemented data from a previous technical fishway design with data collected from additional field investigations. Princeton Hydro led the field collection effort, including sediment sampling, sediment probing, and a bathymetric survey to shed light on the impounded sediment concerns. Field investigations also included an investigation on the infrastructure, an updated topographic survey, and a seismic refraction survey to understand the potential for underlying bedrock to inform a conceptual design for dam removal.

Based on the data reviewed, Princeton Hydro concluded that dam removal is feasible and that its removal would 1) Restore the Bronx River to its historical flowpath, 2) Likely restore transparent fish passage at the site, and 3) Not impact infrastructure.

In comparing the dam removal alternative to the engineering fishway, the dam removal would provide a greater ecological benefit, while also reducing long term liabilities related to dam failure and costs associated with dam maintenance and inspection. Despite uncertainty associated with the dam removal alternative at this stage in the concept design, it is expected the upfront construction cost of the dam removal would be higher than the engineering fishway alternative.

The feasibility study and alternatives analysis set the stage for the US Army Corps of Engineers to further study fish passage at the Bronx River Double Dam.