From a vantage point 70 feet above the waterline, the mate and drag tender aboard the articulated tug-barge (ATB) Douglas B. Mackie/Ellis Island collaborated to keep the unit working safely and efficiently. The job entailed sucking up tons of sand from dozens of feet below the surface at a designated location several miles off Sandy Hook, N.J., then delivering it to a nearby beach.
The two crewmembers, positioned in the wheelhouse within six feet of each other, concentrated on relevant screens and controls. They spoke sparingly as they jointly directed the two trailing drag heads with a single mission: Fill the massive hopper with sand slurry and then deliver the maximum load to the beach.
“These two guys are the moneymakers on this project,” said ATB Capt. Chris Harvey, a 40-year veteran of Great Lakes Dredge & Dock (GLDD) projects all over the world. “Everyone else, myself included, is just support. If these two crew don’t maximize loading sand into the hopper, we’re not making money.”
Douglas B. Mackie/Ellis Island is a game changer for GLDD. Between December 2021 and March 2, 2022, the massive trailing suction hopper dredge (TSHD) delivered almost a million cubic yards of sand onto Monmouth County, N.J., located just south of Staten Island, N.Y. Federal, state and local money paid for the beach replenishment project.
With a hopper capacity of 14,800 cubic yards, each load Mackie/Ellis delivered to the fill area deposited the equivalent of almost 1,500 over-the-road dump trucks onto a designated beach. “It’s incredible to compare the capacity of Mackie/Ellis to dump trucks,” said David Dye, site manager for GLDD.
Mackie/Ellis is the largest TSHD operating in the United States. It’s also the first U.S.-flagged ATB dredge. It has stayed busy since leaving Eastern Shipbuilding in 2017. In approximately 100 trips beginning in late December between a “borrow area” off Sandy Hook and the “fill area” on Monmouth County beaches, the ATB transported the equivalent of almost 15,800 dump trailers worth of sand.
“The fill project started at the very southern end of Deal, N.J., and then worked in both directions eventually to the southern border of Loch Arbour, N.J., and the Deal-Long Branch town line,” New Jersey Department of Environmental Protection spokesperson Caryn Shinske said.
Mackie/Ellis can work 24/7, year-round in a broad range of adverse weather and sea conditions, Harvey said. Wind speed and wave height are among the factors that influence whether dredging can proceed safely. These conditions can also stress the Articouple FRC 80 friction engagement system (hard rubber pins in steel grooves) joining the tug and barge into a single unit.
Unlike the pin system in other ATB applications, such as those moving petroleum products, the system on a dredge must constantly adjust as dredge spoils increasingly “draft down” the barge. One unique feature is the very deep notch on the barge Ellis Island.
Since leaving the shipyard late in 2017, the ATB dredge has done more than beach replenishment. It has executed port channel deepening and jobs maintaining shipping lane depths in Mississippi, Texas, Alabama and the Carolinas. Its beach jobs, meanwhile, have occurred in the Gulf and along the East Coast.
In selecting projects for beach replenishment and associated borrow areas, the U.S. Army Corps of Engineers (USACE) along with state and local authorities consider several factors. One is the suitability of sand from a potential borrow area. Geophysical and geotechnical sub-bottom surveys are conducted to identify the nearest sources of acceptable sand offshore.
Surveys can be conducted by GLDD’s crew boat, the USACE or a licensed survey company. Potential borrow areas must be checked for pipelines, telecom cables, electrical cables and other utilities. Another consideration in borrow sites like the one off Sandy Hook is unexploded munitions and explosives. Special screens on the dredge mitigate hazards these objects could otherwise pose. Other sites in the Southeastern U.S. and Gulf need to be checked for unwanted seashells.
Contracted wildlife biologists work aboard dredges to monitor unintended “take numbers” of protected and endangered species. Turtle-excluder devices and physical screens with prescribed mesh sizes facilitate monitoring for compliance with National Marine Fisheries mitigation strategies for turtles, sturgeon and whales.
Having worked previously in ship-configured TSHDs, Harvey described the benefits of the ATB Mackie/Ellis as inherent in the design: None of the space in Ellis Island’s 480-by-92-by 28-foot hull is devoted to crew quarters. That allowed for larger hopper capacity and space for the piping and engines associated with dredge pumps. Douglas B. Mackie, meanwhile, is specially outfitted for crew comfort during four-week hitches.
“The ATB is a game-changer because the drag heads have the weight and the tug has the power to push through some harder borrow areas,” Harvey said. The speed the tug can move a loaded barge between the borrow area offshore and the pump-out area is another benefit.
As the dredge heads and arms send a slurry of sand and water into the hopper, skimmers mounted there allow excess water overboard. Once the barge is loaded to the draft marks with sand, the ATB travels to the pump-out area.
The pump-out process involves bringing Mackie/Ellis to an offshore mooring “cube” installed before the replenishment project begins. The helmsman guides the ATB near the Norwegian buoy attached by a floating probe-tipped hose to the cube. Meanwhile, another crewman uses a grappling hook to capture this hose. Then the hose is winched into position and the probe connected to the “bell” structure on the bow of the dredge and secured. Jet pumps draw in water to re-liquify the spoils in the hopper to create a slurry of a density that can be pumped to the beach. The centrifugal pumps, which earlier had sucked the sand into the hopper, now pump fluidized sand to the beach.
On shore, two dozen union workers using an excavator and three bulldozers work three shifts around the clock. They move the sand to desired locations and thickness on the beach itself.
Raising and lowering Ellis Island’s trailing drag arms, as well as opening/closing the bottom dump doors and using the barge winches, requires hydraulic pumps powered by the Indar Ingeteam shaft generators. These operate on one of two output shafts turned by each of two MaK diesel main engines. The other output shaft connects to the two Schottel controllable propellers in nozzles. All engines on the ATB meet EPA Tier 3 standards. Power for the two centrifugal pumps and two jet pumps on Ellis comes from two EMDs located toward the bow of the dredge barge. Ballast tanks are in the bulbous bow.
Chief engineer John Tidrick, who has worked on other GLDD dredges since 2007 and on Mackie/Ellis since it came out of Eastern Shipbuilding, described the benefits of working on a new vessel. “Overall, there’s less maintenance, including of the living areas,” he said. But on the other hand, he oversees two complete engine rooms, several hundred feet apart, on the tug and barge. His staff typically consists of six people, each with specific duties and expertise for the vessel.
Included in Tidrick’s purview are a set of two watermakers. Because of the amount of sand in suspension around a dredge, fresh water must be created by distillation rather than reverse osmosis.
The automation on Mackie/Ellis is so extensive that GLDD employs a roving senior electrical technician. “Without a doubt,” technician Chris Slimmer said, “Mackie/Ellis is the most automated dredge GLDD operates.” As the ATB finished up in Monmouth County, Slimmer boarded with a USACE inspection team to assist with an annual check of dredge production instrumentation.
Once Mackie/Ellis had completed the replenishment project, the drag arms and other gear were stowed for travel, and the ATB headed off to the next project. Less than a week after departing the New Jersey site, Ellis/Mackie was up and running on another channel deepening and maintenance project off Charleston, S.C, almost 600 miles away. •