WATER RESOURCES RESEARCH GRANT PROPOSAL
Project ID: 2004MD58B
Title: Beneficial reuse of Baltimore Harbor dredgings and coal fly ash in engineering applications and effects on the Chesapeake Bay
Project Type: Research
Focus Categories: Surface Water, Sediments, Treatment
Keywords: Dredging, Chesapeake Bay, coal fly ash, stabilization, beneficial reuse
Start Date: 03/01/2004
End Date: 03/01/2005
Federal Funds: $7,322
Non-Federal Matching Funds: $14,854
Congressional District: 5th District of Maryland
Ahmet H. Aydilek
University of Maryland
Currently, majority of the sediments dredged from the Chesapeake Bay is disposed on islands, such as Poplar Island. Dewatering of these disposed sediments has been a major issue for the Maryland Port Authority, and in some cases leaching of effluent with undesirable pH levels. It is believed that beneficial reuse of these sediments will reduce the disposal by landfilling and will provide tremendous potential for conserving the environment. As part of the proposed study, reuse of the Chesapeake Bay sediments in two applications, slurry walls and landfill liners, will be evaluated.
Slurry wall have been widely used as passive vertical barriers or treatment system. These systems control the horizontal flow of groundwater and mitigate the movement of contaminants. A trench is excavated and a backfill material is placed. The backfill material is expected to have high water content, sufficient flowability and low permeability. Some of the dredged sediments from the Chesapeake Bay have particular characteristics making them ideal materials for these applications. These materials have significant amount of fine-grained particles (i.e., silt and clay) which makes them promising materials for construction of vertical barriers.
Second proposed application area is use of the sediments as part of landfill liner construction. Two steps are required before the evaluation of feasibility of these sediments as liner materials: dewatering of sediments, and stabilization of sediments. Dewatering of the sediments is generally performed by using geotextile tubes and has widely accepted by the U.S. Army Corps of Engineers and Maryland Port Authority. The stabilization of the dredged sediments can be obtained by addition of Class F fly ashes that have high organic carbon content. Widespread use of these fly ashes has not yet been realized. As a consequence, approximately 70% of the fly ashes are usually landfilled or stored in lagoons in Maryland These applications have particular promise because, fly ashes are fine-grained and thus impede the movement of contaminated liquids; that is, they generally have low hydraulic conductivity. Leaching of undesired constituents (i.e. metals) from the fly ashes into surface water has also been a concern; therefore it is believed that beneficial reuse of the fly ashes as part of landfill liners will prevent this problem.
The proposed research focuses on developing a re-use for a waste material that is currently landfilled or impounded. It will also be conducted in cooperation with Maryland business (handling of the fly ash is managed by the Maryland Power Plant Research Program) generating the waste product. Concurrently, successful implementation of this research will address another important environmental issue -contamination of Chesapeake Bay with inorganic and organic chemicals. It is believed that beneficial reuse of dredged sediments and fly ash will reduce landfilling and will provide tremendous potential for conserving the environment.