Commercial dredging operations on the Allegheny River stirred up wide swatches of sediment during a recent survey conducted by a University of Pittsburgh researcher.

Conrad Volz, director of Pitt’s Center for Healthy Environments and Communities, is identifying possible metals and toxins that were churned up by the dredging.

Volz will present his results at the end of the month at the Ohio River Basin Consortia for Research and Education conference at Carnegie Mellon University, Oct. 29 to 31.

When completed, the study could potentially be another hit at the commercial dredging industry, which for more than a century has harvested sand and gravel from the bottoms of Allegheny River for road projects and building materials.

Volz’s preliminary findings are part of a much larger study, the Allegheny River Stewardship Project, which examines contaminants in fish and the water and their impact on the public.

Volz’s earlier research revealed high levels of mercury and selenium in channel catfish at Kittanning and high levels of estrogen in fish in the Allegheny River’s Pittsburgh pool.

He and research staff staged several community fishing events this summer along the Allegheny to collect samples for the study. Those results are to be available later this month.

Preliminary findings from Volz’s dredging study on the Allegheny River yielded some unexpected results.

“What’s new is the extent to which the sediment plume — the same way we have plumes of pollution in the air — goes across the river, and from the top of the river to the bottom of the river,” said Volz of West Deer. “It is larger than we expected.”

The sediment includes organic and inorganic materials that settle to the river bottom.

In July, Volz conducted a series of water monitoring tests. His team collected samples of river water near dredging operations at three levels and at seven places downstream from Freeport, near the mouth of Buffalo Creek.

He sampled before dredging and then two hours after operations had begun.

They measured the amount of suspended solids — small particles suspended in the water — and found elevated levels during dredging operations. That is expected for any operation that involves digging in the river bottom.

“But we didn’t expect to see suspended solids at all locations and at every depth,” Volz said.

Volz’s team is analyzing what dredging turns up, studying samples for the concentration of elements and metals including arsenic, cadmium, copper, chromium, selenium, mercury, manganese, iron, lead, and cobalt.

Generally, bio-solids from sewage treatment plants settle to the bottom of the river; so do chemicals, which can bind to or be absorbed by river bottom sediment.

Volz and his team want to find out if a significant increase of heavy metals and toxic elements are in the water as a result of the dredging operations and whether wells along the river are impacted.

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