MarkWest Pioneer Announces Decision Regarding Option to Acquire Equity Interest in Midcontinent Express Pipeline

DENVER--(Business Wire)--
MarkWest Pioneer, L.L.C., a joint venture between MarkWest Energy Partners, L.P.
(NYSE: MWE) and an affiliate of ArcLight Capital Partners, LLC, today announced
that it notified affiliates of Kinder Morgan Energy Partners, L.P. and Energy
Transfer Partners, L.P. that MarkWest Pioneer will not exercise its option to
acquire a 10 percent equity interest in Midcontinent Express Pipeline LLC.

MarkWest believes the Midcontinent Express Pipeline is a critical component of
the pipeline infrastructure that transports natural gas from newly developed
areas in Texas and Oklahoma, including an interconnect with MarkWest Pioneer`s
Arkoma Connector Pipeline in Southeast Oklahoma, into high-demand markets in the
Eastern U.S. However, MarkWest is foregoing the option to acquire the equity
interest in order to prioritize available capital for strategic growth projects
in its core operating areas.

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.

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 we believe that the expectations reflected
in the forward-looking statements are reasonable, we can give no assurance that
such expectations will prove to be correct.The forward-looking statements
involve risks and uncertainties that affect our operations, financial
performance, and other factors as discussed in our 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 we file with the
SEC, including our Annual Report on Form 10-K for the year ended December 31,
2008, and our Quarterly Report on Form 10-Q for the quarter ended June 30,
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."We do not undertake any duty to update any
forward-looking statement except as required by law.

MarkWest Energy Partners, L.P.
Frank Semple, 866-858-0482
Chairman, President & CEO
or
Nancy Buese, 866-858-0482
Senior VP and CFO
or
Dan Campbell, 866-858-0482
Treasurer & IR Officer
investorrelations@markwest.com

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