Williams and TransCanada Corp. threw another Rockies east-to-west natural gas pipeline proposal into the mix on Thursday with the news that they are evaluating the joint development of Sunstone Pipeline to move gas supplies to the West Coast.

The Sunstone Pipeline would be a 618-mile, 42-inch diameter pipeline with capacity of up to 1.2 Bcf/d. The project, which is proposed for service in 2011, would involve constructing a new pipeline substantially parallel to the existing Williams Northwest Pipeline system between the Opal Hub in Wyoming and Stanfield, OR. The Northwest system interconnects at Stanfield with TransCanada’s Gas Transmission Northwest (GTN) pipeline system.

“The proposed Sunstone Pipeline project is designed to ensure that our customers have access to abundant and diverse natural gas supplies in the region,” said Phil Wright, president of Williams’ gas pipeline business. “We have been reliably delivering natural gas to the Pacific Northwest for more than 50 years and have established long-standing relationships with the communities along our pipeline corridor.”

The project would offer an option to deliver gas to markets served by the Northwest and GTN pipeline systems. Sunstone’s open season is set to begin Monday (March 17), and end April 30. GTN plans to hold an additional open season to offer existing capacity available on its system between Stanfield and GTN’s terminus near Malin, OR, near California’s northern border.

Sunstone, said the companies, would involve constructing “fewer miles of pipeline along existing utility corridors, including segments of Northwest’s existing pipeline system.” Executives also pointed to the fact that “both companies have knowledge of the environment and established relationships” with area stakeholders.

“Sunstone offers customers in the West excellent access to markets and supply,” said TransCanada CEO Hal Kvisle. “Sunstone and GTN provide efficient, continued access to Western Canada Sedimentary Basin gas supply in addition to new access to growing Rocky Mountain production. The combination of new and existing infrastructure provides benefits to markets across California, Nevada and the Pacific Northwest.”

El Paso Corp. last month launched a binding open season for its proposed Ruby Pipeline LLC, a 1.2 Bcf/d pipe, which also would transport gas from the Rockies to the West Coast (see NGI, Feb. 25). The proposed 680-mile 42-inch diameter interstate pipe would begin at the Opal Hub in Wyoming and terminate in Malin. In December PG&E Corp. signed a letter of intent to acquire a 25.5% interest in the pipe, and it inked a precedent agreement for 375,000 Dth of long-term transportation capacity for 15 years (see NGI, Jan. 7). The Bear Stearns Companies Inc.’s Bear Energy LP also said it would become an initial shipper on the proposed pipeline (see NGI, Dec. 10, 2007).

In January Spectra Energy launched an open season to test market interest in its proposed Bronco Pipeline, which also would move gas from the Rockies to the Pacific Northwest and California (see NGI, Jan. 14). Results of that open season, which ended Feb. 8, have not been publicly announced.

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