A second pipeline expansion project has been sparked by a natural gas market shuffle on the Canada’s east coast that would replace depleted offshore supplies with western production.

TC PipeLines LP announced on Thursday a $100 million expansion for the Portland Natural Gas Transmission System (PNGTS).

Titled Westbrook XPress, the addition would receive deliveries at the Quebec inlet to PNGTS from a C$250-million ($188 million) expansion announced in December for TC affiliate TransCanada Corp.’s gas Mainline.

The Canadian cross-country route ends in central Quebec. PNGTS intersects with the Canadian east coast’s gas conduit, Maritimes & Northeast Pipeline (M&NE).

Offshore Nova Scotia production stopped last year, ending M&NE’s original role as an export pipeline. The gas flow has been reversed to supply Canada’s Atlantic region with imports from the United States.

The TC and TransCanada capacity increases would both be done with new pipeline compressors. Both are billed as added service for central Canada and the northeastern U.S. as well as New Brunswick and Nova Scotia.

A 70% increase in PNGTS capacity to about 350 MMcf/d would result from adding the new Westbrook XPress facilities to a current expansion project called Portland XPress, TC said. Staged delivery increases are planned with November start dates in 2019 and 2021.

On the western side of its American gas network, TC disclosed its fourth quarter financial results would include a $537 million write-off of the full value of its Bison Pipeline connecting Wyoming production to the Midwest.

TC said new uses are being explored for Bison after two shippers terminated and paid out delivery contracts. All other Bison contracts expire in 2021 and persistent unfavorable market conditions make the value of the asset currently impossible to estimate, TC added.