By Madeline Urbish
As we’ve reported in the past, ports contributed $4.6 trillion to U.S. GDP in 2014. In order to keep those ports and harbors functioning, the U.S. Army Corps of Engineers as well as local and state governments must dredge the channels and inlets that ships travel through to reach their destination. Billions, if not trillions, of cubic yards of sediment are removed from U.S. waters every year – but where does all the sand, salt, and silt go? Currently, much of the sediment is stored in containers or dumped into open waters. In fact, as much as 50 percent of dredged Great Lake sediment is dumped in the open lake.
Currently, the Corps dredges 1 million cubic yards of sediment from the Maumee River and enough material to fill 220,000 dump trucks twice a year from the Cuyahoga River. More than 60 commercial ports rely on open navigation channels along the Cuyahoga River. The Corps can either store the sediment in Confined Disposal Facilities containers, which is expensive and takes up valuable space, or it can dump it in an open lake, such as Lake Erie. The contaminants in dredged material such as fertilizer, however, can threaten fragile lake ecosystems, as was seen last summer when toxic algae blooms made tap water undrinkable for residents in the Toledo, OH area. Governor Kasich issued an executive order earlier this year prohibiting open lake dumping to prevent such a crisis. To offset the challenge posed by the prohibition on open lake dumping, the state is funding $10 million in pilot projects encouraging interest in repurposing uncontaminated sediment.
A team of scientists at Ohio State University’s School of Environment & Natural Resources is exploring the idea of beneficial reuse. Funded by the Ohio Sea Grant, Dr. Elizabeth Dayton and her team are working with soil blenders along the Lake Erie Shore to create custom soil blends to be used in construction and landscaping. Dr. Dayton is working on characterizing different soil blends based on their chemical and physical makeup, which will allow her and her team to create tailored soil blends for potential customers using the dredged material as the primary ingredient.
Dr. Dayton’s first customers are the City of Toledo and the Toledo Land Bank, which have commissioned her team at Ohio State to develop a custom sediment blend for remediation of building sites where abandoned buildings are being demolished. Additionally, the Land Bank has asked for an appropriate blend for turning abandoned lots into green spaces or side yards for neighboring homes. For the projects, Dr. Dayton and her team created a blend made up of 80 percent dredged material and 20 percent leaf compost from the city’s yard waste collection. The City of Toledo hopes to use the custom blends at more than 300 sites throughout the city. Following implementation, Dr. Dayton and her team plan to analyze the economic impacts of using the dredged sediment in soil blends.
Beneficial use, or the repurposing of dredged material, is not a new idea. Many states have commissioned studies of beneficial use, including the Garden State. Rutgers University’s Center for Advanced Infrastructure and Transportation produced a Manual for Beneficial Reuse of Processed Dredge Material in 2013 in partnership with the NJ Department of Transportation’s Office of Maritime Resources. The 124-page guide details research, development, and implementation guidelines for dredged material management techniques. The manual also includes case studies and examples of successful projects.
In New Jersey, on Mordecai Island, the Corps will use dredged material from the Intracoastal Waterway near Beach Haven to create marshy land. Mordecai Island covers about 41 acres just off of Little Egg Harbor, and provides some protection to the main land. Since Superstorm Sandy, the Corps has been regularly dredging the waterway, and recently found that the material is compatible with sediment already on the island. Mordecai Island has experienced significant erosion, so much so that part of the land has been separated into two areas. The Corps plans, through what it calls beneficial use, to nourish the island with sediment from the Intracoastal Waterway. The project, which is in its final stage of design, has an estimated cost of $500,000.
In Maryland, the Port Administration is also looking for innovative ways to reuse sediment that is dredged in order to keep the Port of Baltimore open – about 4.7 million cubic yards of material is removed from Baltimore Harbor and its channels every year. Some examples that have been proposed include: (1) capping brownfields or landfill; (2) transforming dredged material into lightweight aggregates; (3) reclaiming lands impaired by sand, gravel, and coal mining; (4) manufacturing bricks and blocks; (5) enhancing degraded farm land; (6) producing manufactured topsoil; and, (7) creating fill for construction projects.
The state has acknowledged several barriers to reusing dredged material, including sediment quality, regulatory issues, and cost. Sometimes, due to environmental regulations and sediment quality barriers, the cost can be prohibitive. Additionally, drying, transporting, and blending the dredged material can be quite costly. Nevertheless, the state has moved forward with three demonstration projects, two of which are investigating the use of dredged material for construction purposes. The third project will place dredged material at a defunct sand quarry and be used for growing non-food plants. The state is hopeful that these demonstrations will serve as the basis for its dredged material management strategy in the future.
There are similar efforts taking place across the country as states recognize the need to be creative in reusing dredged sediment. Dredging as a necessity will not disappear as it ensures vital economic activity can continue to take place in our ports and harbors, therefore, states must focus on finding the correct balance between cost, efficiency, and need to create more institutionalized repurposing programs. For now, demonstration project results hold the ability to prove the potential of beneficial use and enable more states to adopt and improve upon their processes.
For more information, contact Madeline Urbish at email@example.com