CAD Cell Proposed for Portland Harbor Dredge Project
October 13, 2014
The Portland Harbor Non-Federal Dredge Workgroup (NFD) will present its interim findings to the Waterfront Alliance at an October 14, 2014, meeting.
The NFD has prioritized construction of a “confined aquatic disposal” (CAD) cell as the responsible solution for disposing of contaminated sediments associated with the future dredging of Portland Harbor, and has identified 3 potential locations for it. CAD cells have been used successfully in southern New England, but never before in Maine. A CAD cell essentially is a hole dredged into the harbor bottom where contaminated dredge sediments can be safely deposited and contained. Environmentalists working with the NFD have supported the use of a CAD cell as a way to address existing pollution.
The loss of water depth along piers is also a growing problem for traditional fishing and commercial marine uses in the harbor, according to the NFD. Since January, the group has met 7 times to evaluate options for dredging private and municipal piers, wharves, and anchorages. While important navigation routes are maintained and dredged by the US Army Corps of Engineers, dredging outside of the so-called “federal channel” is the responsibility of the abutting shore-side land or pier owner. Complicating these “non-federal” dredge projects are the contaminated sediments one typically finds in urban harbors—especially in areas that have not been dredged in recent memory like many of Portland’s 19th century piers. The accumulated sediments contain reminders of the harbor’s long industrial history, as well as pollution from streets and parking lots washing into the Fore River.
Curtis Bohlen, Director of the Casco Bay Estuary Partnership, noted, “Businesses on the waterfront rely on reliable access to the water for themselves or for their customers; periodic dredging is an important part of providing that access. Properly disposing of toxic sediments would reduce the exposure of the Bay’s living organisms to hazardous materials, thus providing environmental benefits as well.”