The next move to widen the natural gas freeway for imports into Canada from the United States began Tuesday when Spectra Energy’s Union Gas called for bids to increase traffic on its share of the route.

Union announced an open season auction of new capacity on three legs of its Ontario pipeline web, offering up to 350,000 gigajoules/d (332,000 MMBtu/d) as of November 2018 plus 600,000 GJ/d (570,000 MMBtu/d) in November 2019.

The proposed delivery increases arise from growing use of gas conduits radiating out from Union’s Dawn storage and trading hub in southern Ontario, where shale supplies from the United States compete with western Canadian production for eastern markets.

Union’s open season comes two weeks after TransCanada Corp. filed an application with the National Energy Board (NEB) for a C$221 million (US$166 million) addition to its Mainline share in the Ontario, Quebec and northeastern U.S. pipeline grid.

Titled the Vaughan Mainline Expansion after its suburban Toronto site, TransCanada’s project anticipates large-scale traffic by using jumbo pipe 42 inches in diameter and grows out of a cooperative growth agreement with Union, Enbridge Gas and Gaz Metro.

Union said its open season “offers firm access to the liquidity and diversity of the Dawn Hub in addition to access to Appalachian supply expected to be available at the Dawn Hub imported through Dawn, Niagara and Chippawa in 2018 and 2019.”

TransCanada’s NEB application predicts northbound flows from the United States of Marcellus and Utica shale gas on the recently reversed, former Canadian export route via the Niagara Falls-Chippawa region will more than double to 1.1 Bcf/d from the current level of 400 MMcf/d.