Searsport Dredge Project

    In the summer of 2002, a beneficial use project using dredged material and cement kiln dust was taking place in Searsport, Maine. Sediment was dredged from Mack Point in Searsport, and H.E. Sargent, Inc. was in charge of using cement kiln dust from Dragon Products in Thomaston as a drying agent for the very wet dredged material.
    Material was first dredged and placed on a barge to allow some settling and dewatering. Initially, the plan was to move the material to an onshore settling area, but the process didn't result in the runoff of any more water. The material was instead loaded into trucks and dumped where it could be mixed with cement kiln dust.
     Before mixing, the dredged sediment essentially had a moisture content of 100%. Each truckload of sediment was then mixed with three bucket loads of CKD, visibly resulting in an instant change in the sediment's consistency. The material was then allowed to set for 24 hours, and in this time, the moisture content was lowered from 100% down to 40-50%. After some experimenting, H.E. Sargent determined that this was as low as the water content would go. Adding 20% or 40% cement kiln dust, or allowing the material to set longer than 24 hours didn't lower the moisture content any further.
    Although the moisture content of the dredged material was practically cut in half, the sediment still wasn't manageable enough to be used as construction material. Plus, humid conditions and rain caused moisture problems as well. The sediment-CKD mix was spread out in another area on the project site, and rotatilled to try to dry it further.
    The treated dredged sediment was then trucked to Bucksport, or kept on-site to be used as construction material. Overall, there was less treated material than originally predicted for the project.
    Environmental problems with both the dredged material and cement kiln dust were minimal. There were no dust problems with CKD, as it seemed to have a high water content itself. Solid contaminants like wood and steel pieces were removed from the dredged material as it was mixed with the cement kiln dust. Also, any overly contaminated dredged material was disposed of at a landfill facility in Norridgewock.

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Photos taken by Will Manion.

Information courtesy of Jim Conley of H.E. Sargent, Inc., Stillwater, ME