Marine transportation study identifies best practices for dredged material

4/24/2023 McCall Macomber

The U.S. marine transportation system contains 25,000 miles of waterways, and dredging, or removing sediment from the bottom of a body of water, allows ships to navigate those waterways.

Reusing dredged material in other projects may have environmental and economic benefits, but only 20% to 30% of dredged material is reused, according to the U.S. Army Corps of Engineers.

Illinois Center for Transportation and Illinois Department of Transportation aim to boost this percentage in the joint project, “R27-212: Evaluating Beneficial Uses of Dredged Material from the Illinois Marine Transportation System.”

Timothy Stark (University of Illinois Urbana-Champaign CEE Excellence Faculty Scholar) leads the project with IDOT’s B.J. Murray (section chief, marine transportation program and planning) and Heather Shoup (central office geotechnical engineer).

Here researchers aim to identify possible reuses of nonhazardous dredged material from Illinois’ waterways.

“This IDOT-ICT project was an opportunity to both identify possible reuses of nonhazardous dredged material from IDOT projects instead of landfilling the material at great expense and assist the U.S. Army Corp of Engineers by identifying uses of their dredged material for not only IDOT projects, but also private sector uses as well,” Murray said.

“We needed to initially find out what the properties were of the material and whether there were contaminants that would restrict the use, and then what type of projects this material could be used for,” he added.

Potential reuses of dredged material may span from restoring habitats, protecting shores and structures, and nourishing beaches, to reducing construction costs in roads or other transportation projects, among other uses.

Key to reusing dredged material safely is determining whether the material contains contaminants, a process regulated nationwide by the U.S. Army Corps of Engineers.

Dredging — the removal of sediment from water — allows ships to travel safely and efficiently. Illinois’ marine transportation system, which connects the state to the Atlantic Ocean and Gulf of Mexico, is responsible for transporting 90.6 million tons of goods per year, according to the Illinois Department of Transportation.
Dredging — the removal of sediment from water — allows ships to travel safely and efficiently. Illinois’ marine transportation system, which connects the state to the Atlantic Ocean and Gulf of Mexico, is responsible for transporting 90.6 million tons of goods per year, according to the Illinois Department of Transportation.

To increase Illinois’ reuse of dredged material, Stark and his team examined case histories involving the reuse of dredged material as well as state and federal statutes and regulations, agency jurisdiction and application processes in Illinois.

The researchers identified typical characteristics of dredged material in Illinois from three main rivers — Mississippi, Illinois and Kaskaskia — most of which is classified as sandy material.

Stark’s team also investigated the properties of dredged material from five project sites in Illinois: Beardstown, Bull’s Island, Starved Rock Lock and Dam, Mackinaw River and McCluggage Bridge.

Through their efforts, they found there are many projects in Illinois with a high potential for beneficial reuse of dredged materials.

“Initially, there was some thought that a large percentage of the material was potentially contaminated,” Murray said. “Through the study we’ve determined that there is a significant amount of it that is not contaminated beyond the ability to use in certain applications and projects.”

Stark’s team also suggested a proposed guideline: if the dredged material is greater than 80% sand and is from a site without a history of contamination, then the material is likely uncontaminated and may require little to no contaminate testing.

The proposed guideline, which was not violated in the study, requires further testing before validation.

Murray notes that dredged material for reuse is available for the public and private sector and urges interested parties to contact the U.S. Army Corps of Engineers.