Port New Jersey Channel Deepening

Cost: $200 million

The Port Jersey Channel is too shallow for the newest class of supersized container ships, which must enter the Port partially loaded, resulting in increased operating costs.

To keep the port competitive and maintain its pre-eminence as a hub for the East Coast, a $200-million, four-stage project is deepening the channel to 50 ft. Completion is slated for later this year.

Funding is provided by New Jersey Dept. Transportation, the Port Authority of New York and New Jersey, and the U.S. Army Corps of Engineers.

Port Jersey is part of a larger eight-year project to deepen all the major shipping channels in New York Harbor. Over the years the shipping industry has built larger ships that require deeper drafts to efficiently transport goods. These next generation vessels require depths in excess of 45 ft.

Before the start of the project, channel depths within the harbor ranged from 30 to 45 ft.

The Port Jersey Channel is located between Global Marine Terminal in Jersey City, N.J. and the former Military Ocean Terminal in Bayonne, N.J.

The first two phases of the project, completed in 2005, deepened the channel from 35 to 41 ft. The current phase, costing $84 million and started in 2008, will deepen it to 50 ft.

Dredging operations are removing 3.6 million cu yds of sand, silt and glacial till sediments from an area 10,000 ft long by 400 to 500 ft wide. This area forms a slot between the GMT and the MOT and extends several thousand feet into the harbor to intersect the main shipping channel.

The project will also improve access to GMT by removing a natural shoal, called the Jersey Flats, which is partially blocking terminal access.

All debris dredged from the channel is put to beneficially reuse. Materials fall into clean and contaminated categories.

Much of the clean material is used to cap a former ocean disposal site, located 10 mi off Sandy Hook. Clean sand was also used to construct a new shoal in an unused channel to the south of MOT compensating for the loss of Jersey Flats, which provided winter habitat for spawning flounder.

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Contaminated silt covered the bottom of this unused channel and complicated construction of the new shoal. Simply dumping clean sand on top of the silt would push a wave of contaminated mud into the harbor.

To prevent harbor contamination, the team built a dike to close off the unused channel. Clean material was then gently sprinkled over the contaminated silt.

Dirty material (silt) dredged from the Port Jersey channel, totaling about 1 million cu yds, is mixed with Portland cement and used to cap landfills and brownfields in New Jersey and New York.

Great Lakes Dredging & Dock Co. of Oak Brook, Ill., is employing the backhoe dredge New York and two clamshell dredges to remove material. The New York, powered by a 3,000-horsepower engine, scoops stiff soils and rock with a 13-cu-yd bucket or softer soils (clay and sand) with a 24-cu-yd bucket.

The clamshell dredges use environmental buckets to remove silt deposits destined for remediation work. The bucket’s overlapping side plates and rubber flaps prevent contaminated materials escaping back into the harbor. Conventional, 21- to 26-cu-yd buckets remove clay and sand.

Great Lakes is dredging the entire channel except for a 100-ft-wide swath running for 1,440 ft between the GMT and MOT. Beneath this section lies the Passaic Valley Sewage Commission outfall, a 12-ft-diameter tunnel built in 1905 from unreinforced concrete. The tunnel carries 300 million gallons a day of treated effluent.

The tunnel, located 64 ft beneath the channel, is constructed in 100-ft sections made of a top half and bottom half held together by the weight of the mud atop the tunnel. When the tunnel was built, the channel was 12 ft deep and the tunnel was covered by 45 to 50 ft of mud.

After dredging, only 10 ft of mud will be left to hold the tunnel in place. The team was concerned that too much water pressure in the tunnel without sufficient compensating downward pressure could cause the two halves to separate and collapse the tunnel, says Scott Douglas, NJDOT project manager.

Engineering analysis determined that under normal water-flow conditions, the pressure exerted by a 10-ft overburden would hold the tunnel together. But during storm conditions or when events in the harbor increase the pressure at the other end, the tunnel could collapse.

The team devised a plan to increase the weight of the overburden. Precision dredging will carefully scrape away the mud atop the tunnel, and then stone topped with 5-in.-thick steel plates measuring 5 by 30 ft will be laid over the tunnel.

This work will be bid as the fourth and final phase of the project later this year and is expected to take three months. The final project phase is expected to begin in the fall.

Team List

Project sponsors: New Jersey Dept. of Transportation, the Port Authority of New York and New Jersey, and the U.S. Army Corps of Engineers
Dredging Contractor: Great Lakes Dredging & Dock Co., Oak Brook, Ill
Oversight Engineers: Mueser Rutledge Consulting Engineers, New York
Water Quality Monitoring: Hydroqual, Mahwah, N.J.
Habitat Enhancement Design: Gahagan and Bryant Associates, Philadelphia
Subsurface Imaging: Hagar-Richter, Salem, N.H., and Earthworks, Sandy Hook, Conn.