Dredging is an essential part of the operation of ports and harbors worldwide. The prevention or minimization of sedimentation can have significant impacts on dredging costs while the disposal or beneficial use of dredged material has environmental consequences. Dredging requires detailed planning, both short-term for construction and long-term for sedimentation control and management of dredged material placement.
Dredging of harbors and channels must be conducted in a timely and cost-effective manner while meeting environmental protection, restoration, and enhancement goals. The beneficial use of dredged material and regional sediment management must be part of dredging planning and execution. Capital dredging can include all types of material from cohesive sediments such as silts and clays to noncohesive sands and even rock. Cohesive sediments have to be checked regularly for contamination to ensure they are properly placed. Noncohesive sediments, primarily fine and medium sands, are generally not associated with contaminants. Maintenance dredging, the majority of dredging in the U.S., generally deals with cohesive sediments.
Advanced dredged material management planning must be conducted on a port or regional (watershed) scale by a partnership that includes the Federal government, the port authorities, state and local governments, and industry. Exponent personnel are skilled in the preparation of Dredged Material Management Plans as well as in the details of project management and construction planning for dredging projects of all sizes. Our staff has planned major restoration projects that beneficially used dredged material to restore wetlands. They have identified different types of dredging equipment and different techniques to remove dredged materials efficiently and with minimal environmental impact. We have also used techniques to evaluate fluid muds and their densities to assess whether channels could be navigated without dredging.
Exponent personnel are skilled in the development and application of two- and three-dimensional models of sediment transport such as the finite element model STUDH (which is part of the USACE TAB II suite of models) and finite difference models such as EFDC and ECOMSED. These models can be used to model changes to sedimentation in berths, ports, and harbors based on changes to bathymetry and hydraulics caused by new projects or significant landscape changes. Exponent is also well-known for its skill in Ecological Risk Assessment including field sampling programs, Benthic Ecotoxicology, Aquatic Ecology, and the Restoration and Construction of Wetlands. These are critical skills for properly planning long-term dredged material management.