A dam in the Lehigh River fish passage study

Lehigh River Fish Passage Improvement Study

Lehigh River, PA

Wildlands Conservancy, Inc.

KCI worked with the Wildlands Conservancy, the Pennsylvania Fish and Boat Commission, American Rivers, and the National Oceanic and Atmospheric Administration to evaluate fish passage alternatives that could open more than 16 miles of the lower Lehigh River to American shad after 180 years.

The feasibility study focused on achieving a minimum of 80 percent passage of fish swimming upstream to spawning grounds. Fish ladders were installed at both locations in the early 1990s, but even with adjustments to improve passage efficiency, both facilities are operating well below expectations, passing only an estimated 30 percent of fish that reach the dams. KCI researched other means including removing each dam in total, removing portions both horizontally and vertically, building a fish rock ramp, or creating inverted rock ramps.

The team considered the advantages and disadvantages of each alternative, identified potential impacts and calculated costs for implementation and maintenance. Each option posed significant challenges, including altering scenic views, affecting the adjacent historic canal systems, potentially disrupting existing land uses, and creating unstable conditions because of the materials and methodologies used in constructing the existing dams. Innovative solutions were identified and investigated to address complex issues like interrupting the water source for the historic Lehigh and Delaware canals and protecting upstream infrastructure. The results of the study provided valuable information including potential impacts, benefits, and costs associated with augmentation or removal of each of these dams, so that an ultimate technical decision about the future of these structures can be made by the dam owners.