Study Looks at Alternatives to Open Lehigh River for Fish Passage

Lehigh-River-Fish-Passage-Improvement-Study-infographic1At one time, American shad were among the predominant fish in most major river and tributary systems draining to the Atlantic. Legend has it that the 109-mile-long Lehigh River boasted historical catches of more than 1,000 fish in a single day. That was until the 1830s, when run-of-the-river dams were erected, creating a barrier the shad couldn’t overcome. Although there has been some success with stocking and fish ladders, scientists are still finding only a fraction of the fish expected beyond the first two impediments—the Easton and Chain dams. KCI is working with the Wildlands Conservancy, the Pennsylvania Fish and Boat Commission (PFBC), 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 full or partial removals of the Easton and Chain dams to achieve a minimum of 80 percent passage of fish swimming upstream to spawn. Fish ladders were installed at both locations in the early 1990s, but even with adjustments to improve efficiency, both facilities are operating well below expectations, passing only an estimated 30 percent of fish that reach the dams.

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“We evaluated doing partial vertical and partial horizontal removals, combinations of both, and complete removals,” said KCI project manager Nathan J. Hoffman, who is from the area and has been a champion behind the project throughout KCI’s involvement. “We investigated all the ins and outs of each configuration—what they would look like and what they would do to the impoundment—to gather enough data to be able to realistically estimate the cost and challenges associated with each.”
Partial removals consist of lowering the height or reducing the width of a dam, or some combination of the two, and would be combined with ramp or step-like structures that provide a gradual increase in water elevation to allow fish to pass over the remaining portion of the dam left in place.

Lehigh-River-Fish-Passage-Improvement-Study-Easton-Dam
The Easton Dam has a timber crib core made of logs and rock in-fill. After a mid-century breach, a concrete cap was installed to stabilize the structure. Any partial removal option would require cutting into the dam, possibly affecting the structure’s stability.
Lehigh-River-Fish-Passage-Improvement-Study-Chain-Dam
The Chain Dam is a combination of two structures. The original dam was breached during a 1965 ice flow and only ten feet of the structure remains in place under the water surface. The new dam, which was built downstream in 1974, is 700 feet long, 20 feet high and 70 feet wide. The distance between the two dams was filled in to a height of 10 feet, creating a colossal structural more than two football fields long and nearly a football field wide.

During the study, engineers and environmental scientists considered the advantages and disadvantages of alternates at each location. “It is a large-scale project from every front,” said Kristie Fach, Director of Ecological Restoration at the Wildlands Conservancy. “Understanding all of what’s underground, what they are working with, what is upstream and downstream, KCI really had to be thorough to identify everything.”

Lehigh-River-Fish-Passage-Improvement-Study-Upstream-Structures
A partial or full dam removal would require scour protection measures for bridges like these carrying railroad traffic and 3rd Street that are located in the impoundment above the Easton Dam. As the river returns to its natural state, the impoundment area would encounter faster moving waters.

Scientists also had to identify possible impacts to surrounding land and water uses, which could involve a 20-foot drop in the water surface, altering scenic views and vistas, and significantly affecting the adjacent historic canal systems.

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Pipe-based gravity flow systems and/or pump stations were investigated to provide water to the historic Lehigh and Delaware canal systems.

“The main reasons the dams are there is to provide water to the Lehigh and Delaware canals,” said PFBC Director of Fisheries Leroy M. Young Jr. “Those canals are not utilized for what they were originally constructed for, but they have historic and tourism importance today.” The study outlined how each alternative affected flow into the canals, in most cases cutting it off completely, and investigated methods to supplement their water supplies.

We were able to utilize our past experience in dam removal and fish passage throughout the East and bring it to bear on a scale that is somewhat unique to Pennsylvania. This type of project and experience for our staff represents the next generation of fish passage projects at KCI.

James E. DeriuVice President, Regional Practice Leader

James E. Deriu

Complexity aside, the project’s main goal is fish passage, and full removal appears to be the only feasible option to pass 100 percent of the shad swimming upstream. “In general, dam removal would provide full fish passage and be a critical step in restoring the ecological function of the river system,” said Fach. The next step falls to the dam owners—the city of Easton and the Pennsylvania Department of Conservation and Natural Resources—in conjunction with the Pennsylvania Fish and Boat Commission and other project partners to discuss the report findings and determine a path forward. With the completion of this feasibility study, American shad may be one step closer to reaching these historic spawning grounds, possibly reinvigorating sport-fishing-related economies and returning the Lehigh to a free flowing river as it once was.