As part of the surrender and removal of the Saccarappa Hydroelectric Project on the Presumpscot River, Verdantas, formerly Alden Research Laboratory, provided fish passage analysis, conceptual design, and final design services to Sappi North America. The work included hydraulic design of a double Denil fish ladder within the existing tailrace and final design of nature-like fishways through the former dam site.
A key component of the nature-like fishway design was three-dimensional computational fluid dynamics (CFD) modeling. Verdantas incorporated CFD throughout the 30%, 60%, 90%, and final design stages to evaluate hydraulic conditions and understand how each design iteration would perform before construction. The modeling allowed the project team to optimize water depths and velocities throughout the proposed fishway for the target fish species.
CFD results were used to refine channel roughness and features including step pools, resting pools, rock benches and berms, and a dissipation pool. Fish passage effectiveness was reviewed by Verdantas biologists using model results to assess potential velocity impediments based on fatigue, survivorship, and work. This integration of advanced hydraulic modeling and biological expertise helped inform design decisions and supported coordination with Sappi and reviewing agencies.
Following final design and agency review, Verdantas provided engineering consultation and site visits during construction. First-year monitoring demonstrated fish passage effectiveness of greater than 95% for the nature-like fishway.
Project Highlights:
- 3D CFD modeling at the 30%, 60%, 90%, and final design stages
- CFD optimization of water depth and velocity throughout the nature-like fishway
- Model-informed refinement of roughness, step pools, resting pools, rock benches and berms, and the dissipation pool
- Integration of hydraulic modeling with biological evaluation of fish passage conditions
- Hydraulic and operational design of a double Denil fish ladder
- Agency coordination and construction-phase engineering support
- Greater than 95% first-year effectiveness for the nature-like fishway
