Dredging & Marine Construction

Rock Piles Provide Fish Habitat In Lower Monongahela River

The Pittsburgh Engineer District is piling rocks in the Monongahela River to create fish reefs.

Once the project is finished, the Pittsburgh District will have installed 73 reefs, each extending 50 feet perpendicular to the shoreline. Timothy Sturm, the civil engineer overseeing the project for the district, estimated it will take approximately 9,000 cubic yards, or about 12,000 tons of rocks, to complete the reefs. The project will create 28.5 acres of fish reefs as a series of dikes that extend into the river from the shoreline.

“The reefs provide fish a place to settle outside of the river flow and rest as they continue on their journey,” Sturm said. “As sediment builds up, plants grow and help provide more food for fish to eat.”

The district began work to install the reefs in late October. They are intended to offset disruptions to the river and aquatic life anticipated when the district removes Elizabeth Locks and Dam in the summer of 2024, thus changing water levels and hydraulic flow in the river pool.

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“By demolishing the Elizabeth Dam, the flow of the river will change, so we did analysis to determine the effects it would have on the fish,” Sturm said.

The stone reefs will reach 3 feet below the water surface in some areas, meaning boaters could scrape or damage their motors if they are not careful. The district advised the public to take extra caution while operating boats along the shorelines. Boaters can find a map of the new reef locations at www.lrp.usace.army.mil/Media/News-Releases/Article/3568451.

“Building these fish reefs will help us mitigate ecosystem impacts from removing Elizabeth Locks and Dam, as well as merging pools 2 and 3 together,” said Steve Frost, project manager for the Lower Monongahela River Project. “We’re excited to see this project move forward.”

The Lower Mon project includes constructing the larger lock chamber at Charleroi Locks and Dam, which has been going on for two decades, and the removal of Lock and Dam 3 at Elizabeth, Pa., next year.

Removing the dam will help equalize the pool between the Charleroi and Braddock locks and dams, forming a 30-mile stretch of navigable waterway. It will benefit the navigation industry by cutting the transportation time required to pass through the region.

“Any time the Pittsburgh District takes on a construction project, we assess the environmental impacts, as well as the benefits, and seek to develop solutions that offset the impacts,” said Bobbi Jo McClain, chief of the Environmental and Cultural Resources section for the Pittsburgh District. “These reefs will create diverse habitat that breaks up underwater flows to provide refuge and feeding habitat for fish.”

In the Monongahela River, popular fish among anglers include black bass, sunfish, walleye, sauger, white bass, striped bass, musky and channel catfish.

Michel Sauret, public affairs specialist with the Pittsburgh Engineer District, contributed to this report.