October 2015 Vol. 70 No. 10
Newsline
Cook Inlet Crossing And Best Choices
Crossing Cook Inlet is about deciding the best route and the best construction methods, while acknowledging that although the shortest distance between two points is a straight line, it’s not necessarily the best line.
Beluga whale critical habitat, salmon fisheries, 40-foot boulders, 15-foot-tall sand waves along the ocean bottom, strong currents, shallow water close to shore, ice scouring that could expose or damage a pipeline – all present problems best avoided as much as possible as Alaska. LNG teams continue refining the preferred route for the natural gas pipeline to cross Cook Inlet on its way to shore in Nikiski, site of the proposed liquefied natural gas plant.
“Cook Inlet is a very, very unique place in the world,” a project team member said. “There is a lot going on here.” That includes currents that move at four to six knots and a tidal range that can vary up to 25 feet between high and low water in the main body of the inlet.
Not that a pipeline can’t be safely built in Cook Inlet. The first was built more than 50 years ago, and many oil and gas lines have been added since. But this one would be bigger and heavier and carry more natural gas than any other pipeline sitting on the ocean floor in the extensively developed area.
The 40-foot-long sections of 42-inch-diameter, inch-thick steel pipe for the Alaska LNG project’s Cook Inlet crossing would be coated with as much as six inches of concrete to protect the pipe and weight it down on the seafloor against the currents. Each section would weigh as much as 33 tons, the equivalent of 15 pickup trucks.
Summer field work for the project continues, with crews sampling soils, measuring currents and judging the options for where best to enter the water on the west side of Cook Inlet, how to install the pipe across the inlet, and where to come up at Nikiski for the final miles to the plant site.
Alaska LNG currently plans to submit more detailed maps and environmental data to the Federal Energy Regulatory Commission in perhaps February, producing the second draft of the project’s “resource reports” – 13 volumes of engineering, construction, environmental and other data that will go into the environmental impact statement.
The project teams have looked at multiple options for crossing Cook Inlet and are now focused on what they call the West Route. It comes down the west side of the inlet and enters the water just south of the small community of Beluga, an area of gas wells, a few industry-support jobs, some retirees and beach set net fisheries, some rudimentary roads, a modest collection of homes surrounded by public lands – and a gas-fired power station serving Southcentral Alaska.
The teams earlier this year dropped active consideration of the East Route, which would have steered the pipeline at the southern end of its trek from Prudhoe Bay on an eastward course toward Point MacKenzie (across Knik Arm from Anchorage) and then into the inlet for its undersea run to the Kenai Peninsula.
The East Route has significantly more hazards, hurdles and handicaps, including undersea power cables, an onshore military gunnery range, Area 1 critical habitat for endangered beluga whales, and additional ice load close to shore, an actively dredged shipping channel, and a much longer run from shore to reach water deep enough for a pipe-laying barge to gain access. “We’re trying to stay out of other people’s way,” a team member said.
Alaska LNG is planning on two construction seasons for the Cook Inlet water crossing, working April through September, or thereabouts, to avoid any ice. The West Route runs generally due south cross Cook Inlet to Nikiski, staying east of offshore oil and gas platforms.
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