The U.S. Army Corps of Engineers recommends removing a dam on the Green River near Mammoth Cave National Park after a study cited the potential benefits for aquatic life and recreational activity.
The study from the Corps of Engineers followed a 2004 assessment that looked into the feasibility of disposing of all federal interest in Green River Lock and Dams 3 through 6 and Barren River Lock and Dam 1.
Echoing the findings of the 2004 assessment, the latest study recommends deauthorizing all five properties and relinquishing them.
The study recommends removing Green River Dam No. 6, which is north of Brownsville near Nolin River and Mammoth Cave, and filling the lock with the demolished remnants of the dam.
“Looking at the present condition of Lock and Dam 6, the river is really wearing away at it, and there’s a lot of water leaking through it right now,” said Vickie Carson, public information officer for Mammoth Cave National Park. “Eventually (the dam is) going to breach. If it can be taken out, that’s a much healthier way to go about it than just to let it breach.”
At Green River Lock and Dam No. 3 near the Butler County community of Rochester, the Corps of Engineers recommends installing a concrete plug in the lock to maintain the pool of water there.
Barricades would be erected at all five closed dams in an effort to deter trespassers.
One of the dams involved in the study – Barren River Lock and Dam No. 1 – is in Warren County near Richardsville.
Also known as the Greencastle Dam, the structure has not been used for commercial navigation since the failure downstream of Green River Dam No. 4 in 1965.
County expresses interest
Warren County has expressed interest in the past in taking over the property.
The study determined that the condition of the miter gates that keep the lock closed appear to be satisfactory, and no conditions were observed that would lead to a loss of pooled water in the foreseeable future.
The Corps of Engineers is accepting comments on the draft feasibility report and environmental assessment through March 17.
“When that period concludes, we will be making adjustments to the report based on an internal review,” said Nate Moulder, project director for the Corps of Engineers’ Louisville District.
The agency’s headquarters will be briefed on the adjustments later this year, and the report would go before the Corps of Engineers’ Civil Works Review Board and then be submitted to state and agency review.
Disposal of the properties requires the U.S. Congress to approve deauthorization of them and appropriate funds to complete the project.
None of the five lock and dam systems examined has supported commercial navigation in many years.
The decline in such navigation and on-site deterioration led to the failure of Green River Dam No. 4 near Woodbury in Butler County in 1965.
Operations ceased at some of the other dams as early as 1951, and the river has not supported commercial navigation upstream of Green River Lock and Dam No. 3 near Rochester since its closure in 1981.
A navigational study the Corps of Engineers conducted in the early 1990s determined that reopening the river to commercial navigation wasn’t feasible, and the facilities have continued to deteriorate as the federal government has maintained ownership.
The latest study predicts that the project at Green River Lock and Dam No. 6 would take more than two years to complete and would require building a temporary access road to allow for removal of the dam.
Moulder sees the removal as a preferable step to other alternatives, which the study lists as modifying the lock while leaving the dam undisturbed, simply installing a barricade and disposing of the property or taking no action and keeping the property.
“(Removal would) return approximately 17 miles of river to natural flow conditions and would have benefits to cave development,” Moulder said. “There would be a lot of ecological benefits, plus the area has seen an increase in canoers and kayakers, and removing that dam definitely removes a safety hazard in that area.”
If Green River Dam No. 6 were to be removed, the National Park Service would continue operating the Houchin and Green River ferries, which are used for commuters and visitors to and from Mammoth Cave.
Economically, local businesses catering to people who canoe on the affected stretch of the Green River may receive a boost with the removal of the dam.
“Presently, the canoe liveries on the Green River serve canoeists wanting primarily half-day trips,” the Corps of Engineers’ study said. “Removal of the dam is expected to increase demand for multi-day canoe trips, leading to increased rentals and revenues for local businesses.”
Water elevations would likely drop a few feet at each ferry within the national park, and Carson said the National Park Service has a project slated for 2018 that would lower the access roads on either side of Green River Ferry.
“We made plans on this awhile ago mainly due to low water conditions where we could not ferry cars across, and we wanted to address that,” Carson said.
The study also concludes that dam removal would have a beneficial long-term impact for the aquatic species that live in the Green River, restoring river habitat.
Endangered freshwater mussel species could thrive in the altered environment, with dam removal flushing sediments that have accumulated over the years in the river leading to a re-exposure of gravel bars that mussels and other species could colonize again.
“There is a much more diverse mussel population in the free-flowing portion of the river,” said Bobby Carson, chief of Mammoth Cave’s Science and Resources Management Division. “Mussels are really an indicator species for the health of the river. They help tell the story of everything else in the river. ... We feel like allowing more free-flowing water downstream will help us improve diversity.”
A restoration of free-flowing water would likely lead to a drop in water levels inside Mammoth Cave, which Bobby Carson said would benefit the cave’s shrimp habitat.