Houston, Texas June 18, 2008 – Cardinal Gas Storage Partners LLC (Cardinal) announced today that it has acquired two natural gas storage development projects from CenterPoint Energy Gas Transmission Company (CEGT) an indirect, wholly-owned interstate natural gas pipeline subsidiary of CenterPoint Energy, Inc. (NYSE: CNP). The projects, located near the Perryville HubSM, in north Louisiana, include a salt dome storage development project and a depleted reservoir storage development project.

The salt dome storage development project, Perryville Gas Storage SM, is expected to consist of up to 22.5 billion cubic feet (Bcf) of high-deliverability working gas storage capacity with multiple interconnects, including CEGT’s Perryville HubSM header system near Delhi, Louisiana. Cardinal expects commencement of operations in 2012 and has recently announced that a non-binding open season will begin on June 23, 2008.

The depleted reservoir storage development project, Cadeville Gas Storage, is expected to consist of up to 16.5 Bcf of working gas capacity with three major interconnects and potential for up to four turn capability. Cardinal expects commencement of operations in 2011.

Cardinal President and CEO, Jeff Ballew said “The Perryville area is an important natural gas liquidity point, but it lacks one key component - storage. With the recent shale gas discoveries west of this location, including the recently announced Haynesville Shale, and the new pipelines bringing this gas to the Northeast, Midwest, Mid Atlantic and Florida markets, Perryville will become even more important. We look forward to developing these complementary projects. The addition of both reservoir and salt storage with multiple interconnects at the Perryville HubSM will bring enhanced reliability and value to our customers.”

“We’re pleased to be entering into this important and strategic transaction with a proven storage developer and we look forward to the expeditious development of these key assets,” said Cy Zebot, CEGT Senior Vice President and Chief Commercial Officer. “As we move forward with our plans to further develop our Perryville HubSM, having storage available is a key component to the overall strategy of becoming the premier natural gas market center in the United States.”

About Cardinal Gas Storage Partners LLC
Cardinal is a joint venture between Energy Capital Partners (“ECP”) and Martin Resource Management Corporation (“MRMC”) that is focused on the development, construction, operation and management of natural gas storage facilities throughout North America. Through its wholly-owned subsidiary Arcadia Gas Storage, LLC, Cardinal is currently developing a 13.8 Bcf salt cavern natural gas storage facility located near Arcadia, Louisiana. For more information, visit www.cardinalgs.com.

About Energy Capital Partners
ECP is a private equity firm dedicated to investing in the power generation, midstream gas, renewable and electric transmission sectors of North America’s energy infrastructure. The firm’s management has substantial experience leading successful energy companies and energy infrastructure investments. ECP has offices in Short Hills, N.J., and San Diego, Calif. For more information, visit www.ecpartners.com.

About Martin Resource Management Corporation
MRMC is a private company based in Kilgore, TX that was founded in 1951 and has a long history of operations in the midstream energy business. MRMC markets several energy products including sulphur, sulfuric acid, fuel oil, liquid petroleum gas, asphalt, chemicals, lube oils, and other bulk liquids. MRMC is also the 100% owner of Martin Midstream GP LLC (“MMGP”), the general partner for Martin Midstream Partners LP (“MMLP”), a master limited partnership formed by MRMC in 2002. For more information, visit www.martin-gas.com.

About CenterPoint Energy
CenterPoint Energy, Inc., headquartered in Houston, Texas, is a domestic energy delivery company that includes electric transmission & distribution, natural gas distribution, competitive natural gas sales and services, interstate pipelines and field services operations. The company serves more than five million metered customers primarily in Arkansas, Louisiana, Minnesota, Mississippi, Oklahoma, and Texas.
Assets total over $17 billion. With about 8,600 employees, CenterPoint Energy and its predecessor companies have been in business for more than 130 years. For more information, visit the Web site at www.CenterPointEnergy.com.

Cardinal Gas Storage Partners LLC
Jeff Ballew