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Subsea power cable installation in Newfoundland

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Oilfield Technology,

Maritech International, a leading 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 US$14.5 million contract with Newfoundland Power Inc., which required Maritech to install 12km of subsea power cables spanning from Bell Island to Broad Cove, was delivered on time and within budget. Over four days, the two 6km cable segments were laid and secured on the rocky seabed in water depths of up to 135 metres, in just 22 hours.

Turnkey solution facilitates cable replacement without disrupting service

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.

“The new cable system, which has an expected service life in excess of 40 years, is set to completely eradicate the repeated power outages,” said Byron Skaftouros, Projects & Development Director for Maritech. “With annual repairs to the previous power link to Bell Island hovering near US$1 million, thousands spent in repairs will be saved. We are extremely pleased to have made it possible for the ageing cables to be replaced efficiently, without disrupting supply of electricity to Bell Island. By drawing upon our deep experience in every facet of subsea cable installation, from establishing an optimum subsea route for new cables through to installation and burial, we made certain that every step of the programme was executed properly and completed on schedule.”

Complex operation goes to plan

Replacing the submarine cable systems called for a multi-phase installation programme. 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 t, 25kV 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, 1000m of protective articulated pipe cover was fitted on the cable, then the cable was clamped to the seabed and cement bags installed to stabilise it on the rocky seabed. Finally, divers used hand-jetting and air-lifting techniques to bury 150m of cable to 1.5m top of cable.

The operation in Newfoundland illustrates the type of comprehensive turnkey solutions offered by Maritech. Over time, Maritech has carried out numerous subsea installations for oil and gas operators, as well as for the telecommunications and power generating industries in over 92 countries. Recent operations associated with oil and gas facilities in Libya, Greece and Gabon were executed safely and efficiently, saving customers time and money.

Adapted from press release by Joe Green

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