NiSource Inc. (NYSE: NI) unit NiSource Gas Transmission & Storage (NGT&S) and MarkWest Liberty Midstream & Resources, LLC, a partnership between MarkWest Energy Partners, L.P. (NYSE: MWE) and The Energy & Minerals Group, which prior to March 15, 2010, was named Midstream & Resources Funds, today announced continued joint development of new natural gas gathering, processing, and transmission projects to support increased Marcellus production volumes in the northern West Virginia area of the Appalachian Basin.

NGT&S and MarkWest Liberty are in discussions with a number of natural gas producers and intrastate pipelines regarding plans to provide new rich-gas gathering and processing services in association with NGT&S assets near its Smithfield, W.Va., compressor station. The gathering and transmission assets are part of NGT&S’ extensive pipeline network and will serve producers in Marshall, Wetzel, and Doddridge counties in West Virginia. Natural gas will also be gathered through non-affiliated gathering systems in Marion, Harrison, Tyler, and Pleasants counties.

The affiliated and non-affiliated pipeline systems will deliver gas into Smithfield where MarkWest Liberty plans to install a 120 million cubic feet per day (MMcf/d) cryogenic processing facility as early as mid-2011 and could increase the capacity to approximately 240 MMcf/d by mid-2012. MarkWest Liberty would complement these processing facilities with fractionation services provided at its Houston, Pennsylvania NGL fractionation, storage, and marketing complex to take advantage of the premium regional markets and to maximize the value of the producers’ gas.

The gathering capacity would be made available in the near future with access to NGT&S’ regulated transmission and storage services. A portion of the transmission capacity could be available for service as early as November 2010, with the remaining capacity available by April 2011. Additional expansions of gathering and processing capabilities in the region will be made available as producers expand their drilling activities in the area. Initial primary delivery points from MarkWest’s proposed processing facility at Smithfield would be to the NGT&S Columbia Gas Interruptible Paper Pool (IPP) or to the Segmentation Pool (Seg. Pool) at Leach, Kentucky (MA19).

“With the significant increase in drilling activity and recent uplift in deliverability in the Marcellus Shale, there is an immediate need for capacity to allow producers to move their gas out of the basin and further develop the area,” said Christopher A. Helms, executive vice president and group CEO for NGT&S. “Providing new solutions for delivering supplies to high-value markets is an important growth area for NGT&S, and this joint project with MarkWest Liberty is a great opportunity for all concerned. With this and other projects, we are working hard to advance the NGT&S strategic plan to meet customer needs and generate long-term, sustainable earnings growth.”

“We are pleased to announce this proposed expansion of our Marcellus midstream infrastructure to meet producers’ rich-gas processing and fractionation needs in one of the fastest growing resource plays in the U.S.,” commented Frank Semple, Chairman, President and Chief Executive Officer of MarkWest. “MarkWest Liberty is the largest provider of midstream services in southwest Pennsylvania and northern West Virginia and the Smithfield processing facilities would be the third major gas processing hub that MarkWest Liberty has developed to support Marcellus production. This proposed expansion in West Virginia, where we have worked closely with NGT&S for more than 20 years, further demonstrates our long-term commitment to provide the critical midstream infrastructure necessary to economically develop the Marcellus.”

For information regarding securing capacity, contact Brian Blount, NGT&S supply and origination business manager, at 304-357-2626, or bblount@nisource.com .

For more information about NiSource Gas Transmission & Storage, please visit www.ngts.com .

As units of NiSource, Inc., the NGT&S companies include Columbia Gas Transmission, Columbia Gulf Transmission, Hardy Storage, Millennium Pipeline and Crossroads Pipeline. Combined, the companies operate about 15,000 miles of interstate natural gas pipeline and 37 storage fields, delivering over 1 trillion cubic feet of natural gas per year.

About NiSource

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 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 southwest, Gulf Coast, and northeast regions of the United States, including the Marcellus Shale, and is the largest natural gas processor in the Appalachian region.

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; actual operating experience of NiSource assets; the regulatory process; regulatory and legislative changes; changes in general economic, capital and commodity market conditions; counter-party credit risk; and other risks as disclosed in NiSource’s Form 10-K for the year ended December 31, 2009 as filed with the SEC. NiSource expressly disclaims any duty to update any of the forward-looking statements discussed in this release.

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 operations, financial performance, and other factors as discussed in filings with the Securities and Exchange Commission. Among the factors that could cause results to differ materially are those risks discussed in the periodic reports filed with the SEC, including MarkWest’s Annual Report on Form 10-K for the year ended December 31, 2009. 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.

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