TULSA, Okla., CALGARY, Alberta, and SAN DIEGO – Sunstone Pipeline, a venture of Williams (NYSE: WMB) and TransCanada Corporation (TSX, NYSE: TRP), announced today that Sempra Pipelines & Storage, a unit of Sempra Energy (NYSE: SRE), has signed a memorandum of understanding with the existing partners to acquire a 25 percent ownership interest in Sunstone Pipeline and for a Sempra Energy affiliate to contract for a significant amount of capacity in the proposed natural gas pipeline.  The estimated US$2.34 billion pipeline project would run from the Rockies to Oregon.

        The news that Sempra Pipelines & Storage intends to acquire a stake in Sunstone came shortly after the conclusion of an open season for transmission capacity from the Rocky Mountain supply area at Opal, Wyo., to Stanfield, Ore. Seven other shippers have made commitments to the proposed pipeline. 

        “We are encouraged by the results of the open season and are pleased to welcome the proposed partnership with Sempra Pipelines & Storage,” said Phil Wright, president of Williams Gas Pipeline Company.  “This strong showing provides the momentum to continue discussions with several potential customers – including both market area and producer customers.  This is a clear demonstration of the growing level of market support for the Sunstone project.”  

        “We believe the Sunstone Pipeline is the most promising of the proposed westbound natural gas pipelines from the Rocky Mountain producing region,” said George S. Liparidis, president and chief executive officer of Sempra Pipelines & Storage.  “With expanding production in the Rockies, the Sunstone Pipeline will provide needed transportation from this basin to meet growing demand in the Pacific Northwest and California markets and offer a critical supply alternative for these gas customers.” 

        “Many of those that executed Sunstone Pipeline precedent agreements have agreed to cost-based rates for the project,” said Hal Kvisle, president and chief executive officer of TransCanada. “Their support underscores Sunstone’s advantages in providing western states with cost-effective new access to growing Rocky Mountain production.”

        Sunstone Pipeline is a proposed 585-mile, 42-inch-diameter pipeline with capacity of up to 1.2 billion cubic feet per day.  The project, which is proposed for service in 2011, would involve constructing a new pipeline substantially parallel to the existing Northwest Pipeline system which is jointly owned by Williams and Williams Pipeline Partners L.P. (WMZ).  Sunstone will originate at the Opal Hub in Wyoming and extend to Stanfield, Ore., where it will interconnect with Williams Northwest Pipeline system and TransCanada’s Gas Transmission Northwest (GTN) pipeline system.

        From Stanfield, natural gas can reach California and Nevada markets via GTN. Natural gas could also flow to Pacific Northwest markets such as Seattle and Portland via Williams Northwest Pipeline system and the proposed Blue Bridge Pipeline. Natural gas could also reach Oregon markets off of GTN via the proposed Palomar Pipeline.

        About Williams
        Williams, through its subsidiaries, finds, produces, gathers, processes and transports natural gas.  Williams’ operations are concentrated in the Pacific Northwest, Rocky Mountains, Gulf Coast, and Eastern Seaboard. More information is available at http://www.williams.com.  Go to http://www.b2i.us/irpass.asp?BzID=630&to=ea&s=0 to join our e-mail list.

        About TransCanada
        TransCanada is a leader in the responsible development and reliable operation of North American energy infrastructure. TransCanada’s network of more than 36,500 miles of pipeline taps into virtually all major gas supply basins in North America. TransCanada is one of the continent’s largest providers of gas storage and related services with approximately 355 billion cubic feet of storage capacity. A growing independent power producer, TransCanada owns, controls or is developing approximately 8,300 megawatts of power generation.
 
        About Sempra Pipelines & Storage
        Sempra Pipelines & Storage acquires, builds and operates natural gas pipelines and storage facilities in Mexico and the United States.  Sempra Energy, based in San Diego, is a Fortune 500 energy services holding company with 2007 revenues of more than $11 billion.  The Sempra Energy companies’ 13,500 employees serve more than 29 million consumers worldwide.