Maritech International, a marine engineering support services company that provides subsea installations and marine works to the international oil and gas, telecommunications and power transmission industries, today announced that it has successfully completed a major subsea power cable installation in Newfoundland.
The $14.5 million contract with Newfoundland Power Inc., which required Maritech to install subsea power cables spanning from Bell Island to Broad Cove, was delivered on time and within budget. Over four days, the two 3.7 miles cable segments were laid and secured on the rocky seabed in water depths of up to 443 feet, in just 22 hours.
To achieve this, Maritech provided a complete turnkey solution, featuring cable transportation, route survey and engineering, installation, post-lay protection and burial, as well as termination and jointing works.
Replacing the submarine cable systems called for a multi-phase installation program. To establish the best – and least costly – subsea cable route with the fewest obstacles across the rocky Newfoundland coastline, Maritech performed a turnkey marine route survey and route engineering. Once the route was established, data was forwarded to the cable manufacturer to produce the two 250-ton, 25 kV power cable segments and spares. Upon completion, they were transported from Greece to Newfoundland on Maritech’s cable transportation vessel MV Trader.
In just two weeks, Maritech converted a “deck barge of opportunity” into a vessel with dynamic positioning and cable-laying capability by equipping it with a custom-designed modular cable-laying spread and portable azimuth DP-1 thrusters. With the MV Trader transporting the cables, the team travelled on the installation barge to the site. After the barge passed a series of sea trials, the cables were loaded onto it, ready for installation.
Although Phase 1, involving shore-end landing operations at Broad Cove, was complicated by the rocky shallow waters that restricted vessel movements near the shoreline, this was quickly resolved. Maritech devised a pull-in operation using smaller support vessels to float the cable off the barge to shore at Broad Cove. Once landed, a tracked excavator pulled the cable along the shore-end route, using rollers and anchored diverters to ensure that the cable was accurately pulled along the design route.
After landing and securing it, the cable was connected to a “dead man” anchor offshore to prepare for laying the north-south cable. Phase 2 began immediately thereafter, and was swiftly completed with the installation barge. While cable was laid on the surface, an ROV deployed from the barge monitored the cable’s touchdown point on the seabed to make certain it was laid uniformly along the optimum route.
After cutting, sealing and abandoning the cable on floats near the Bell Island shore-end approach, smaller boats continued pulling in the cable in shallow water, while carefully managing the cable bight on floats. Eventually, the shore waiting line was connected to the waiting cable, putting the landfall support team in direct contact to begin the final pulling phase.
Upon cable landing at the termination point onshore Bell Island, divers used GPS to rigorously check that the route was accurate and successfully aligned with RPL coordinates from the survey. They then removed the cable floats and commenced protection works. First, 3,280 feet of protective articulated pipe cover was fitted on the cable, then the cable was clamped to the seabed and cement bags installed to stabilize it on the rocky seabed. Finally, divers used hand-jetting and air-lifting techniques to bury 492 feet of cable.