EPA Approves New Ocean Dumping Site For Dredge Material Off Isles Of Shoals | New Hampshire Public Radio

EPA Approves New Ocean Dumping Site For Dredge Material Off Isles Of Shoals

Sep 26, 2020

The dredge fill site is a circle about a mile and a half wide centered on this red dot, off the N.H. and Maine coast.
Credit Google Earth

The Environmental Protection Agency has approved a new ocean dumping site for dredged material just off the Seacoast, after a years-long permitting process.

The site is in federal waters past the Isles of Shoals, about 14 miles directly east of Wallis Sands State Beach. It covers a circle just over a mile and a half in diameter, in water about 300 feet deep.

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Over the next 20 years, the site is set to receive 1.5 million cubic yards of marine silt, clay and other dredge fill that's been deemed clean enough to dump at sea.

It’ll come from federal, state and private dredging projects in harbors and channels across southern Maine, coastal New Hampshire and Northern Massachusetts. The largest amount of material, about half of it, is expected to come from the upcoming dredging and channel widening in Portsmouth Harbor. 

The site will receive its first material from New Hampshire’s Rye Harbor, where an Army Corps of Engineers contractor will begin dredging in November for the first time in 30 years. Officials say the harbor bottom has been tested and cleared for ocean disposal.

A bathymetric map of the disposal site.
Credit EPA

Material dumped at the site is only allowed to contain contaminants in “trace” amounts that the EPA has determined won’t harm marine animals or the ecosystem.

The primary effect of dumping is from sediment that can remain temporarily suspended in the water column. The EPA has determined that the Isles of Shoals site will have the least environmental impact compared to alternative sites or on-shore landfilling.

The site is also closer to the projects that'll use it, compared to a temporary site off Cape Arundel, near Kennebunkport, Maine, that the Army Corps has used periodically since 1985. It was set to close next year.

The EPA estimates having a closer disposal site will save between $500,000 and $1 million for federal, state and private projects planned in the next 20 years.