NiSource unit Columbia Gas Transmission and MarkWest Energy Partners Announce Additional Plans to Expand Natural Gas Midstream Services in West Virginia

NiSource Inc. (NYSE: NI) unit Columbia Gas Transmission Corp. and MarkWest Energy Partners, LP (NYSE: MWE) today announced their intention to jointly expand natural gas gathering and processing services to support increased production volumes in the Appalachian Basin of central West Virginia.

Columbia Gas and MarkWest are in discussions with several natural gas producers regarding plans to provide new gathering and processing services near Columbia Gas’ Cobb aggregation system in Kanawha, Jackson and Roane counties of West Virginia.

The expansion includes MarkWest’s previously announced expansion of its Cobb gas plant, which will increase the total processing capacity to approximately 70 MMcf/d by mid 2009.

The natural gas liquids recovered at the Cobb gas processing plant will continue to be fractionated at MarkWest’s Siloam fractionation, marketing and storage complex, which is in the final stages of a significant expansion. The Cobb and Siloam expansions are currently under construction and require no additional capital beyond that included in MarkWest’s previously announced growth capital forecast.

The expansion would also include Columbia adding horsepower to its existing Cobb compressor station and installing new field gathering and compression facilities to bring new gas volumes to the Cobb gas processing plant. As increases in production warrant, additional capacity could be added with incremental horsepower and additional expansion of the Cobb gas processing plant.

These plans for expansion of gathering and processing services are in addition to the Columbia Gas Transmission and MarkWest announcement in August of 2008 to expand similar services near Majorsville, W.Va., serving the northern panhandle area of West Virginia and western Pennsylvania.

Producers and natural gas shippers should direct questions to Brian Blount, NiSource Gas Transmission & Storage Business Manager of Appalachian Supply and Origination, at 304-357-2626 or bblount@nisource.com.

About Columbia Gas Transmission and NiSource

Columbia Gas Transmission Corp. (TCO) is an interstate gas transmission and storage company, operating 37 storage fields and a more than 10,000-mile network of natural gas pipelines in 10 Mid-Atlantic, Northeastern and Southern states. TCO transports approximately 1 trillion cubic feet of gas per year to 72 local gas distribution companies.

NiSource Inc. (NYSE: NI), based in Merrillville, Ind., is a Fortune 500 company engaged in natural gas transmission, storage and distribution, as well as electric generation, transmission and distribution. NiSource operating companies deliver energy to more than 3.8 million customers located within the high-demand energy corridor stretching from the Gulf Coast through the Midwest to New England. Information about NiSource and its subsidiaries is available via the Internet at www.nisource.com. NI-F

About MarkWest Energy Partners

MarkWest Energy Partners, L.P. is a growth-oriented master limited partnership engaged in the gathering, transportation, and processing of natural gas; the transportation, fractionation, marketing, and storage of natural gas liquids; and the gathering and transportation of crude oil. MarkWest has extensive natural gas gathering, processing, and transmission operations in the southwestern and Gulf Coast regions of the United States and is the largest natural gas processor in the Appalachian region. The primary business strategy of MarkWest is to provide outstanding customer service at competitive rates and to expand its assets and cash flow available for distribution through a balanced combination of organic growth projects and selective acquisitions.

NiSource Forward-Looking Statements

This news release includes forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Those statements include statements regarding the intent, belief or current expectations of NiSource and its management. Although NiSource believes that its expectations are based on reasonable assumptions, it can give no assurance that its goals will be achieved. Readers are cautioned that the forward-looking statements in this presentation are not guarantees of future performance and involve a number of risks and uncertainties, and that actual results could differ materially from those indicated by such forward-looking statements. Important factors that could cause actual results to differ materially from those indicated by such forward-looking statements include, but are not limited to, the following: weather; fluctuations in supply and demand for energy commodities; growth opportunities for NiSource's businesses; increased competition in deregulated energy markets; the success of regulatory and commercial initiatives; dealings with third parties over whom NiSource has no control; the success of NiSource's restructuring of its outsourcing agreement; actual operating experience of NiSource assets; the regulatory process; regulatory and legislative changes; changes in general economic, capital and commodity market conditions; and counter-party credit risk.

MarkWest Energy Partners Forward-Looking Statements

This press release includes "forward-looking statements.” All statements other than statements of historical facts included or incorporated herein may constitute forward-looking statements. Actual results could vary significantly from those expressed or implied in such statements and are subject to a number of risks and uncertainties. Although MarkWest believes that the expectations reflected in the forward-looking statements are reasonable, MarkWest can give no assurance that such expectations will prove to be correct. The forward-looking statements involve risks and uncertainties that affect MarkWest’s operations, financial performance, and other factors as discussed in MarkWest’s filings with the Securities and Exchange Commission. Among the factors that could cause results to differ materially are those risks discussed in MarkWest’s Annual Report on Form 10-K, as amended, for the year ended December 31, 2007, as filed with the SEC. You are urged to carefully review and consider the cautionary statements and other disclosures made in those filings, specifically those under the heading "Risk Factors.” MarkWest does not undertake any duty to update any forward-looking statement except as required by law.