By Timothy J. Dugan, USACE, New England DistrictApril 2, 2018
Improvement dredging of portions of the Boston Harbor Federal Navigation Project Main Ship Channel in Boston, Massachusetts will be conducted under the terms of a $122,223,000 contract issued recently by the New England District.
Work will be accomplished by Cashman/Dutra, Joint Venture of Quincy, Mass. The contract was awarded on Feb. 15, 2017. The dredging is expected to take approximately three years to complete to deepen the project to its newly authorized depths. Dredging is anticipated to start in the spring of 2018.
The dredging project is to accommodate large container ships that are calling on the U.S. east coast now that the Panama Canal improvements are completed.
Approximately 11.7 million cubic yards of silt, blue clay, till and weathered rock will be dredged to improve the following components of the Boston Harbor Federal Navigation Project: deepening and widening the Broad Sound North Channel to -51 feet Mean Lower Low Water (MLLW); deepening and widening the Main Ship Channel to the Conley Terminal, including the turning basin to -47 feet MLLW; and deepening the President Roads Anchorage and deepening the lower Reserved Channel to -47 feet MLLW.
The material dredged will be placed at the Massachusetts Bay Disposal Site (MBDS) approximately 20 miles offshore of Boston Harbor, with the exception of a small fraction of the material being placed as a cap to the Main Ship Channel Confined Aquatic Disposal (CAD) cell, just downstream of the inner confluence of the Chelsea and Mystic Rivers.
Boston Harbor is the largest seaport in New England and the principal distributing point for regional commerce.
More than 87 percent of Boston Harbor commerce is the receipt and shipment of petroleum products. Principal commercial traffic consists of the import of distillate petroleum products, residual fuel oil, sugar, limestone, and lumber; the receipt and shipment of other petroleum products; and the export of iron and steel scrap.
Initial work in Boston Harbor began shortly after the Civil War. The most recent improvement work was completed in May 1966. The current project includes the harbor proper and four access channels: the Chelsea River, the Fort Point Channel, the South Boston Reserved Channel, and the Weir River at Nantasket Beach. They are described below.
The Harbor Proper Work previously completed by the Corps in the harbor proper consists of:
A six-mile-long, 40-foot-deep main channel extending from Massachusetts Bay, through Broad Sound, to the entrance of Mystic and Chelsea Rivers. The channel is 900 -1,100 feet wide from the sea, through Broad Sound, to President Roads. The channel is 600 feet wide from President Roads to the entrance of Mystic and Chelsea rivers.
A 35-foot-deep channel that runs parallel to, and on the northerly side of, the aforementioned 40-foot-deep channel. The 35-foot-deep channel is 600 feet wide and extends from the sea, through Broad Sound, to a point opposite the fish pier.
A two-mile-long, 35-foot-deep channel that extends from an area abreast of Fort Point Channel to a point almost one mile past the Chelsea Street Bridge. The channel, which has widths varying from 100 to 1,000 feet, starts in the harbor in front of Fort Point Channel and adjacent to the 40-foot-deep channel. It extends down the harbor parallel to the 40-foot channel, past the Mystic River Bridge, except the portion in front of the former Charlestown Navy Yard which was deauthorized by Congress in 1992, and ends at the General Andrew P. McArdle Bridge at the entrance to the Chelsea River. The channel also splits at the Navy Yard and goes down the Charles River before ending at the Charlestown Bridge.
A two-mile-long channel 30 feet deep and 1,200 feet wide from the sea through Broad Sound to President Roads. This channel is situated south of the 35 and 40-foot-deep Broad Sound channels.
A three-mile-long channel 27 feet deep and 1,000 feet wide extending from Nantasket Road through the Narrows to President Roads.
A 550-foot-long stub channel, 15 feet deep and 300 feet wide, located at the northeast head of Long Island in the vicinity of Nix's Mate Shoal.
An approach channel (not originally built by the Corps) to the former U.S. Navy Dry Dock Number 3 in South Boston that was deepened to 40 feet.
A 40-foot-deep anchorage along the northern limit of President Road. The anchorage, 350 acres in area, measures 6,200 feet east to west and 2,500 feet north to south.
A 35-foot-deep area lying west of the anchorage.
Stone seawalls that protect the harbor's exposed headlands and islands.
Chelsea River Channel - The percentage of traffic passing through the Chelsea River has been increasing over the past several years. A recent study indicated that 46-percent of the traffic in Boston Harbor utilized the Chelsea River.
Corps' work on the Chelsea River includes a main ship channel 1.8 miles long extending from the General Andrew P. McArdle Bridge to the end of the Chelsea River. From the McArdle Bridge to the Chelsea Street Bridge, the channel is 35 feet deep and approximately 225-250 feet wide. From the Chelsea Street Bridge to a point near the river's end, the channel is 250-430 feet wide. At the end of the channel there is a turning and maneuvering basin 35 feet deep and approximately 800 feet wide and 1,000 feet long.
Fort Point Channel - The Fort Point Channel extends from Boston Harbor to the Northern Avenue Bridge in South Boston, a distance of about 1,000 feet. It is 23 feet deep and 175 feet wide.
South Boston Reserved Channel - The Reserved Channel extends from the 40-foot-deep channel in Boston Harbor to the L Street Bridge in South Boston, a distance of about 5,400 feet. It is 35 feet deep and 430 feet wide.
The Weir River at Nantasket Beach - The 1.7-mile-long channel in the Weir River, 12 feet deep and 150 feet wide, provides access to the Nantasket Beach terminal in Hull. The channel extends from Sunset Point on Nantasket Beach, through the Weir River, to Nantasket Pier.
Planned Improvements - The Water Resources Development Act of 1990 passed by Congress authorized a $26.2 million Navigation Improvement Project for Boston Harbor. The project proposes deepening the Mystic River and the Reserved Channel from the existing 35 foot depth Mean Low Water (MLW) to 40 feet and the Chelsea River from 35 feet to 38 feet. In addition, the Inner Confluence, which provides access to the Mystic and Chelsea rivers, and a widened maneuvering area at the entrance to the Reserved Channel would be dredged to 40 feet. The size of the President Road Anchorage will be increased by almost 70 acres at no cost by establishing new channel limits that would extend into naturally deep areas.
The deepening of the channels would primarily benefit local petroleum product importers and scrap exporters, who together account for about 93-percent of all shipping in the Port of Boston. Project benefits would be realized through reduced tidal delays for larger vessels and the capability of Boston Harbor to receive and ship larger cargos.
The Massachusetts Port Authority is arranging the nearly $10 million in local cost-sharing for the project.
For more information on the Boston Harbor Federal Navigation Project visit the website at: www.nae.usace.army.mil/Missions/Civil-Works/Navigation/Massachusetts/Boston-Harbor/. A map is available at: www.nae.usace.army.mil/Portals/74/docs/Navigation/MA/BOS/BOSMap.pdf.