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State plans LiDAR study for gas line route Laser technology can find faults under brush; study to cover zone along Alaska Highway from Delta Junction to Canada Wesley Loy For Petroleum News
The Alaska Department of Natural Resources plans to study part of the proposed natural gas pipeline route with a laser-powered technology known as LiDAR.
LiDAR, an acronym for light detection and ranging, is highly effective at locating faults that could pose a hazard to a pipeline.
The DNR in April posted a request for proposals seeking a contractor to conduct LiDAR data acquisition for the gas line corridor between Delta Junction and the border with Canada. The study would cover an area of about 325 square miles. The contractor also would study a 50-square-mile area within the Salcha seismic zone.
The state planned to accept bids until May 11. The one-year contract is worth between $300,000 and $500,000.
How it works LiDAR is a technology developed over the past 20 years. It’s similar to radar but uses light energy instead of radio waves.
To acquire LiDAR data, aircraft fly over the study area with equipment that fires rapid laser pulses to scan the ground. The reflected signals can be used to create high-resolution imagery of the land surface, including “bare-earth” terrain models with trees, brush and manmade structures edited out.
“LiDAR provides us with a really good way of locating potential faults,” said Trent Hubbard, a geologist with DNR’s Division of Geological and Geophysical Surveys in Fairbanks.
The beauty of LiDAR is that it can see faults in the land surface better than other technologies such as satellite imaging or aerial photography. LiDAR can penetrate thick vegetative cover to map the ground, and it can handle very steep or rough terrain than can hamper human investigators.
Geologists can walk the land to try to locate faults, but they can easily miss faults that show up on LiDAR, Hubbard said.
Preparing for a pipeline Energy companies are proposing a natural gas pipeline from the North Slope into Canada, and part of the route would run along the Alaska Highway between Delta Junction and the border.
Two pipeline proposals are now on the drawing boards, one involving a partnership of ExxonMobil and TransCanada and another involving a partnership of BP and ConocoPhillips. Each partnership is holding an open season this year to solicit gas shippers.
The state LiDAR study is part of a broader effort to study the terrain along the potential pipeline route.
The Division of Geological and Geophysical Surveys has been conducting a multiyear project to “evaluate the geology, geohazards, and material resources in a 12-mile-wide corridor centered along the Alaska Highway between Delta Junction and the Canada border,” a project description says. “This effort is largely in preparation for the proposed natural gas pipeline, so that baseline geologic data are publicly available on which preliminary decisions can be made.”
The division’s 2009 annual report adds that the project will provide detailed geologic information on which to base alignment decisions, engineering design, permitting and planning for future development along the Alaska Highway.
Final reports and maps are expected to be published in 2011 and 2012, the annual report says.
Salcha seismic zone Under the LiDAR contract, the state wants to study not only the proposed gas pipeline corridor but also an area within the Salcha seismic zone outside of Delta Junction.
“One of the largest known historical strike-slip earthquakes in Alaska occurred in this area in 1937; however evidence for surface rupture has not been documented,” the DNR request for proposals says. “The proximity of the Salcha seismic zone to the existing Trans-Alaska Pipeline and the proposed natural gas pipeline corridor make acquisition and interpretation of LiDAR data important to better characterize active faulting in this area.”
Strike-slip faults are vertical or nearly vertical fractures where opposing blocks of earth move, or slip, against one another horizontally.
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