PITTSBURGH – Look up in the sky! It’s a bird. It’s a plane. It’s a … tree??
“Seeing a helicopter flying back and forth with a bunch of trees dangling from beneath it is something you don’t see in Pennsylvania every day,” said Matt Rother, the chief of the civil design section for the U.S. Army Corps of Engineers Pittsburgh District.
Rother is the lead engineer who designed the plan to repurpose cut-down trees into fish habitats. He took over the project last year, with plans that began in late 2021. Rother said the project is rewarding because of its challenges and different design aspects.
“This was a fully custom-made and unique project,” Rother said. “We had to use our engineering judgment throughout. There’s not a manual out there to show us how to do this.”
The helicopter transported 29 bundles of trees, completing the job in one day, Aug. 8. The chopper crossed the Ohio River multiple times, picking up bundles of trees bound together with steel cable from one side of the river and placing them down in the water on the opposite side. It took most of the day for the helicopter to complete the job, placing the bundles throughout a pool of marshy water.
Each delivery weighed between 500 and 2,800 pounds. The trees went into the slough approximately 32 miles downriver from Pittsburgh. The slough is a unique backwater habitat upstream from the Montgomery Locks and Dam. The helicopter also delivered 2,600-pound concrete blocks, which a boat crew attached to each bundle to ensure the trees remained in place underwater.
A wide range of freshwater species lives in the Ohio River, including shiners, catfish, carp, herring, bass, walleye, and more. The brush bundles will help juvenile fish by providing cover and hiding places from larger predator fish.
The Pittsburgh District added the habitat to anticipate disruption caused by several construction projects in the coming years. The district plans to replace the auxiliary chambers at the Montgomery, Dashields, and Emsworth locks and dams, with larger navigation chambers.
The district’s planning team conducted a study to determine construction’s impact on fish habitats. Studies showed the noise and turbidity in the water and sediment would disrupt fish living near the locks. The new habitat will mitigate the construction impact for all three locks in advance.
“We install mitigation methods before any potential loss occurs to the environment,” Rother said.
Completing the mitigation project first gives nature the ability to adapt to the new benefit in advance rather than try to recover after the impact is done, he said.
“Any time we construct a project, there’s an impact on the environment,” said Bobbi Jo McClain, the chief of the Environmental and Cultural Resources Section for the Pittsburgh District.
The habitat in the slough benefits fish, not only Montgomery but all the fish that will be disturbed eventually by construction at Dashields and Emsworth as well.
“We looked at a lot of different options. The slough offers a unique habitat in the Ohio River throughout this region. It provided a unique opportunity to benefit fish reusing materials that we sourced on site,” McClain said.
The trees came from a plot of land uphill from the Montgomery Locks. The Pittsburgh District cleared 3.4 acres of land earlier this year. The corps will use the space to build a concrete batch plant to produce large quantities of concrete for construction at Montgomery.
“This was a very different way of thinking. We are building something new while preserving materials we already had here. It’s good for us,” said Jenna Cunningham, the resident engineer for the Montgomery construction project.
The district’s environmental team suggested repurposing them for the fish habitat rather than wasting the trees or shredding them into mulch or woodchips. Rother said planners coordinated with the U.S. Fish and Wildlife Service to determine the best habitat design possible using the trees.
The district cut down the trees in March to avoid conflict with the northern long-eared bats’ summer roosting period. The endangered bats roost beneath loose bark or in tree cavities in the spring, summer, and fall, hibernating in caves in the winter.
“We try to find that balance between meeting our mission of developing structures that serve people while doing it in a way that protects the environment,” McClain said.
The construction of the three new locks is part of the Upper Ohio Navigation Project, a multi-billion-dollar project that will benefit inland navigation. The aging locks have reached the end of their operational lifespan and are too small for today’s commercial barges.
The project will replace the auxiliary chambers, measuring 56 feet wide by 360 feet long, with larger locks measuring 110 feet wide by 600 feet long. Approximately 15 to 20 million tons of goods, valued at more than $2 billion, pass through the upper Ohio River system annually. During maintenance, these smaller locks can cause navigational bottlenecks.