Decomposition and Erosion Testing on the Composite Dredged Material Sediment Sample from New Bedford Harbor, Massachusetts
Abstract
Contaminated fine-grained sediments from upper New Bedford Harbor were tested to determine erosion, deposition, and settling characteristics. The study was performed to support an Engineering Feasibility Study (EFS) of dredging and disposal of contaminated harbor sediments. An important issue addressed by the EFS was the possible hydraulic dispersion of contaminated sediment material out of the upper harbor during dredging and disposal operations. Sediment transport characteristics were required to perform mathematical modeling and make predictions. Erosion was determined for newly deposited sediments. Deposition and erosion results indicated that the sediment material was composed of three fractions. The most easily eroded sediment fraction was also the slowest to deposit, and was by far the most mobile sediment fraction. This fraction comprised 29 percent of the sediment fines, or 40 percent of the bulk sediment composite, and was composed of sediments less than 14 micron. The critical bed shear stress which initiated erosion was 0.06 N/sq m, and the critical shear stress below which deposition occurred was 0.043 N/sq m for the finest fraction. Suspended sediment settling velocities were found to increase as the four-thirds power of suspension concentration at concentrations above 75 mg/l, and were found to be constant below 75 mg/l at about 0.006 mm/sec. A special closed-conduit sediment water tunnel was developed to safely test contaminated sediments.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1989
- Accession Number
- ADA208990
Entities
People
- Allen M. Teeter
- Walter Pankow