PORTLAND — The Army Corps of Engineers announced its plans last week to perform a maintenance dredge of Portland Harbor.
The work on the estimated $10 million project is expected to take place over a five- to six-month period, from November to April, as soon as federal funding is available, most likely in the next two years.
The maintenance dredging is needed to restore a 35-foot channel in Portland Harbor, the largest commercial port in Maine and one of the largest in New England. Years of silting from storm water runoff has reduced the channel depth – used by oil tankers, cargo vessels, cruise ships and fishing vessels – to only 33 feet.
The Army Crops said in a press release that a private contractor will work day and night to remove about 600,000 cubic yards of silt and clay to restore the channel’s depth. Also, five rock pinnacles that rise above the 35-foot depth will be removed.
Dredged material from working harbors is generally considered to be toxic, because of pollution that washes into the bay from city streets strewn with motor oil, gasoline and other pollutants.
The Army Crops said the harbor bottom has undergone physical, chemical and biological testing and is clean enough to be dumped at sea without reasonable environmental degradation. That disposal site is located about seven nautical miles off the Cape Elizabeth coast.
Meanwhile, local waterfront officials are hoping to use the upcoming maintenance dredge to move ahead with the creation of confined aquatic disposal cell that could hold 300,000 cubic yards of contaminated dredged materials.
South Portland Transportation and Waterfront Director Tom Meyers said that building the disposal   the Arm Corps performs its maintenance dredge would reduce the overall cost of the project, since the large “mobilization fee” dredging companies charge.
Ed O’Donnell, New England Army Corps chief of navigation, said mobilization and demobilization fees can range from $500,000 to $1 million, depending on the size of the project.
Meyers estimated the CAD cell, which may be located between the Eastern Promenade and the Maine State Pier near Portland Yacht Services, would cost about $8 million, but officials hope to secure federal funding for the project.
The CAD cell would give pier owners who do not qualify for federal maintenance dredging, including municipalities and private pier owners, a cost-effective means to maintain their pier depths. Harbor bottom near piers is generally more polluted because of sewer overflows and storm-water runoff.
Meyers said pier owners currently must have their dredged material tested for contamination, at a cost of about $80,000. If the material is too polluted to dump offshore, it must be sent to an inland landfill, the cost of which is usually too expensive for pier owners to shoulder.
“They need a (dump) site that is not cost-prohibitive,” Meyers said.
Portland Harbor was last dredged in 1998. That project involved the relocation of more than 300,000 lobsters.
At that time, nearly 410,000 cubic yards of harbor bottom was removed and disposed of at Portland’s offshore disposal site. 

Randy Billings can be reached at 781-361 ext. 100 or rbillings@theforecaster.net.