Weeks dredger built for a day at the beach, and then some
While the sun rose, the trailing suction hopper dredger Magdalen, like a caterpillar working a leaf, was feeding off the seafloor six and a half miles from Surf City on New Jersey’s Long Beach Island.
As the morning brightened, the vessel’s hopper filled. The suction arm was raised to the deck and the 356-foot vessel, laden with 7,000 cubic yards of sand, made for shore at an impressive 14.5 knots.
Magdalen joined RN Weeks and BE Lindholm in the Weeks Marine hopper dredge fleet in December 2017. The advanced vessel, designed by Royal IHC of the Netherlands and built by Eastern Shipbuilding Group of Panama City, Fla., has a hopper capacity of 8,550 cubic yards, more than the combined capacity of its two fleet mates. Designed specifically for U.S. coastal dredging conditions, Magdalen also has the edge in speed, fuel efficiency, pumping power and automation.
Jan van Helden, managing director for IHC America, explained that Magdalen was custom designed in concert with Weeks to have a high specific gravity of material in the hopper during beach nourishment projects. “And the hull form, with a large bulbous bow, is optimized for the best speeds empty and loaded,” he said.
Magdalen’s two GE 16V250 main engines deliver more than 11,300 combined horsepower. The diesels are complemented by a pair of auxiliary gensets capable of providing an additional 1,800 kW.
Those attributes will serve Weeks well as more and more beaches fall victim to ever-stronger storms and rising sea levels. A key factor is that each year, the distance increases between the dredge site, called the borrow area, and the site of beach reclamation. The business of dredging is dredging, not steaming between two points.
“With the demand for land reclamation and beach nourishment growing, we believe that better tools are needed to retain our competitive edge,” said Weeks President Richard S. Weeks. “(Magdalen) is a very important part of our continued growth as a fully integrated marine construction company.”
BAE Systems of Mobile, Ala., initially was chosen to build the ship, and the keel was laid there in 2012. Weeks contracted with Eastern in 2015 to finish construction.
“From the outset of this project, the construction of the Magdalen has been an exceptionally challenging and rewarding experience,” said J. Stephen Chatry, Weeks’ senior vice president and Dredging Division manager. “Fortunately for Weeks, the dubious start gave way to an extraordinarily successful finish, due in large part to the capabilities of Eastern Shipbuilding. In retrospect, the delivery of the Magdalen has everything to do with the partnership that was forged between Eastern, IHC and Weeks during the build.”
Magdalen mate William Joseph Smith guides the dredger into position to obtain another load of sand off the coast of Long Beach Island. The ship’s navigation equipment includes a dynamic positioning/dynamic tracking system for precise control of the drag head.
Magdalen has one suction arm located on the starboard side, a design that optimizes the dredge pump for vacuuming, with the portside booster pump optimized for discharge operations. The configuration enables the vessel to pump a longer distance to shore via its own dredging and power generation plant.
Magdalen’s captain on that day, Michael Haight, a graduate of California Maritime Academy with extensive dredging experience, explained that the pump arrangement on double-arm hopper dredges is a compromise between efficient vacuuming and efficient discharge pressure while pumping ashore.
The Surf City beach nourishment project will replace a 20-foot-high sacrificial dune that was reclaimed by the ocean during Hurricane Sandy in 2012 — one of many dunes designed to protect the properties behind them during storms, which are intended to be sacrificed.
An important consideration during Magdalen’s design phase was to build a ship that could operate as close to shore as possible in order to minimize the length of the shore discharge line and maximize the ship’s emptying speed. At Surf City, the discharge pipe connection to the shore pipe is located a mile off the beach. Magdalen’s loaded draft is 25.3 feet, a depth that can increase significantly as the ship pitches or rolls.
After the floating discharge hose is winched aboard (left), the ship’s bow coupling hydraulically locks it to the dredge’s pipe system. Magdalen can deliver up to 8,550 cubic yards of material with each hopper load.
The first phase of the discharge operation is to flush the ship’s self-emptying channel and shore delivery pipeline with water from the sea chest. The procedure clears the line and ensures it will accommodate the appropriate velocity to deliver sand ashore.
Next, pumping of the 7,000 cubic yards of material in the hopper began. Depending on the density of the sand, the process takes one to three hours. The Eco-Pump Controller, designed and fabricated by IHC, automatically controls the speed of the pump to optimize the discharge and reduce fuel consumption.
“By using the system, the operator can focus on other variables of the dredging process and operation without having to worry about pump speed,” van Helden said.
Capt. Michael Haight, at left, discusses the operation of the ship’s pumps with Mark Sickles, communications manager for Weeks Marine. An IHC booster pump is in the foreground.
Once the hopper was empty, water was pumped back into it to ballast the ship on the return trip to the borrow area 5.5 miles out to sea.
Magdalen’s power train consists of two GE 16V250 main engines producing 5,682 horsepower each, Siemens Flender reduction gears, Hyundai 3,400-kW shaft generators and Wartsila fixed-pitch propellers. The vessel is also equipped with a 979-hp bow thruster.
The shaft generators are the primary power supply for the vessel, with a GE 6L250 auxiliary generator providing 1,423 kW of additional power when necessary. A 425-kW Caterpillar C18 generator set supplies power in the event of an emergency and while the ship is in port.
Ensconced in the sparkling white dredge pump room is an IHC single-wall dredge pump and an IHC double-wall booster pump. Hyundai variable-speed AC motors that drive those pumps and the IHC jet pumps are operated from the pump motor room.
As well as providing the detailed engineering for Magdalen, IHC designed and delivered an array of specific dredge equipment, including the bow coupling, drag arm, drag head, drag arm winches and three gantry cranes.
Magdalen’s massive drag head stands ready to be deployed as the ship heads to the dredge site, also called the borrow area, more than six miles offshore.
On the spacious bridge, mate William Joseph Smith guided the dredge from a U-shaped navigation console housing equipment from Furuno, Transas, Simrad and Sperry. IHC supplied the navigation console and the drag tender’s console, and incorporated a dynamic positioning/dynamic tracking system for precise control in the dredging area and for stationkeeping while attached to the shore discharge line. IHC also installed a supervisory control and data acquisition (SCADA) package for monitoring all equipment and machinery throughout the vessel.
“The DT part of the DP/DT system will allow automated dredging of a pre-defined area at a pre-defined depth, reducing the control load on the operator and thus improving efficiency and accuracy,” van Helden said.
IHC’s recently developed Plumigator system was retrofitted into Magdalen’s overflow. “One of the main features of this system is to reduce the turbidity below and around the vessel during the loading process,” van Helden said. “This has a positive impact on the environment and should reduce wear caused by particles flowing to the aft ship.”
Once Smith brought Magdalen back to the borrow area, he directed drag tender James Willis to engage the three gantries to lower the suction tube to the hull inlet valve. After the tube was connected, Willis lowered the drag head to the seabed and the dredge resumed its back-and-forth, caterpillar-like feeding.