Williams Partners L.P. (NYSE:WPZ) today announced that it has received interest from shippers to expand its existing Transco pipeline Leidy Line in northern Pennsylvania by up to 800,000 dekatherms of natural gas per day by late 2015. Williams (NYSE: WMB) owns approximately 68 percent of Williams Partners, including the general-partner interest. The Leidy Southeast expansion project is being designed to serve the growing needs of local gas distribution companies and electric power generators along the Atlantic Seaboard and throughout the southeastern United States. The company is currently finalizing shipper agreements and expects to initiate pre-filing with the Federal Energy Regulatory Commission (FERC) in early 2013. The final scope and cost of the project will be determined by the results of shipper negotiations. “Our Transco Leidy Line is strategically positioned through the heart of one of the most important natural gas production areas in the country,” said Randy Barnard, president of Williams Partners’ natural gas pipeline business. “This project also leverages Transco’s access to some of the fastest growing markets in the country. Linking the supply to the demand could significantly expand the Leidy Line’s currently subscribed firm capacity of 1,700,000 dekatherms by up to 50 percent.” The proposed Leidy Southeast expansion will provide firm transportation from various supply points along Transco’s Leidy Line to delivery points terminating at its Zone 4 Market Pool in Alabama, along its mainline system. The Leidy Southeast expansion represents a portion of Williams’ previously announced Atlantic Access project, which proposed firm transportation options from various Marcellus shale supply regions in Pennsylvania and West Virginia. A non-binding open season for the Atlantic Access project resulted in strong interest in expanding Transco’s Leidy Line, while other portions of the project continue to be discussed with potential shippers for a later in-service date. About Williams Partners L.P. (NYSE: WPZ) Williams Partners L.P. is a leading diversified master limited partnership focused on natural gas transportation; gathering, treating, and processing; storage; natural gas liquid (NGL) fractionation; and oil transportation. The partnership owns interests in three major interstate natural gas pipelines that, combined, deliver 14 percent of the natural gas consumed in the United States. The partnership’s gathering and processing assets include large-scale operations in the U.S. Rocky Mountains and both onshore and offshore along the Gulf of Mexico. Williams (NYSE: WMB) owns approximately 68 percent of Williams Partners, including the general-partner interest. More information is available at www.williamslp.com. Portions of this document may constitute “forward-looking statements” as defined by federal law. Although the partnership believes any such statements are based on reasonable assumptions, there is no assurance that actual outcomes will not be materially different. Any such statements are made in reliance on the “safe harbor” protections provided under the Private Securities Reform Act of 1995. Additional information about issues that could lead to material changes in performance is contained in the partnership’s annual reports filed with the Securities and Exchange Commission.