Company finds routes for pipeline challenging
THE COMPANY wanting to build a natural gas pipeline to one of two planned liquefied natural gas (LNG) plants in Prince Rupert is juggling the complexity of marine life, geography, and past industrial activity in choosing the best route for the last underwater leg of the line.
Spectra Energy has charted three possible final sections for a pipeline which would start in northeastern B.C. and emerge around the Cranberry Junction north of Terrace.
One route, an all-land one, would cut through the coastal mountains but poses geotechnical and environmental challenges which make it the least favoured option.
That leaves two underwater final sections, one which would pass near the former mining town of Kitsault before dropping underwater at Alice Arm Inlet and the second which would enter the water at Nasoga Gulf Inlet farther south, explained company engineers at an information session in Terrace recently.
Jeff Schmok, who is a senior geophysicist at Golder Associates, a consulting company hired by Spectra, spent two months on a boat compiling route information using various technologies such as side-scan sonar, showed the challenges of the Kitsault route compared to the one through Nasoga using interactive maps of the ocean floor.
The approximately 102 km underwater route through Nasoga Gulf would cross Iceberg Bay which has a rich mollusc harvest, as well an area of cultural significance to the Nisga’a where they had an early agricultural development. To avoid the cultural site, Spectra engineers are looking for a route through areas to the east.
The other underwater route, a longer one at 179 km that passes by Kitsault, is complicated by submerged tailings from a molybdenum mine that operated there briefly in the early ‘80s.
The dredging necessary to secure the pipe in these intertidal zones could disturb the submerged toxic waste, Schmok said.
Both undersea routes offer long stretches of silt on the ocean floor which makes it well suited to support the piping that will be uncoiled from a boat and allowed to settle on the bottom.
Spectra is now boring holes along the route to see what lies under the silt. Sharp rocks can damage the pipe, despite what Schmok called an extremely durable steel wall and flexible concrete coating that is also rough enough for crab populations to cling on to.
Originally planned as one wide pipe, the conduit might now include two smaller ones depending on the availability of a marine vessel capable of handling one large pipe.
Spectra wants to submit the application for an environmental assessment by early 2014. It is now looking for public comment and those doing so have until June 2 to make submissions to the provincial environmental assessment office.
Spectra’s work is going hand in hand with work by the BG Group which wants to build a large plant on Ridley Island near Prince Rupert to liquefy the gas that would be piped in for export to Asian customers. The BG Group of England has filed environmental assessment plans forecasting a construction start of a first phase by 2016 leading to completion by 2021.
A second phase is contingent upon finding additional markets.
Petronas, a Malaysian-state owned company, also has its eyes on the Prince Rupert area through subsidiary Progress Energy of Calgary by planning a LNG plant on Lelu Island near Port Edward.
It has chosen Trans Canada Pipelines as its natural gas pipeline builder but a route has yet to be announced.
In the meantime, the provincial government says it wants to do wide-ranging economic and social impact analysis of what could be as many as five LNG plants planned for Kitimat and Prince Rupert.
The analysis would include the impact to the northwest of large numbers of construction workers.