Dredging and Disposal

Boston Harbor CAD Cell Project

Boston Harbor, MA

Owner: US Army Corps of Engineers

Ocean Surveys played an integral roll in the Boston Harbor Navigation Improvement Project - a US Army Corps of Engineers funded program involving monitoring and improving the use of Confined Aquatic Disposal (CAD) cells as an alternative for contaminated sediment management.

Since 1997, management of sediments determined unsuitable for ocean placement from the Boston Harbor Navigation Improvement Project (BHNIP), have been placed into several CAD cells dredged below the Federal navigation channels of the inner harbor. Following placement of the maintenance sediments, sand dredged from the Cape Cod Canal was used to create caps over the cells. This unique, large-scale project has provided an excellent opportunity to improve the understanding and application of this management approach.

Geophysical surveys and vibratory coring within the cell areas were conducted following final placement of the capping material. Hydrographic and subbottom profiling survey transects were run both longitudinally and laterally with vibratory core samples taken at the transect intersections. The subbottom profiles contained reflectors indicative of a sand cap, which was confirmed by the sediment cores.

The Boston Harbor CAD cells represent the most extensive use of this alternative in the United States.

This text was abstracted from "The Boston Harbor Navigation Improvements Project CAD cell: Recommendations for Future Projects Based on Field Experience and Monitoring." (T.J. Fredette, P.E. Jackson, C.J. Demos, D.A. Hadden, S.H. Wolf, T.A. Nowak, and E. DeAngelo, 2000)

Figure 1: Aerial photograph with CAD cell locations/overlays - Boston Harbor Navigation Improvement Project.

Figure 2: Digital photographic images of vibratory core samples superimposed on high resolution “Chirp” subbottom profile of CAD cell following completion of “capping” operations.