TEXT-S&P release on Markwest Energy Partners LP

(The following statement was released by the rating agency)

April 7 - Standard & Poor's Ratings Services today affirmed its 'B+' corporate credit rating on midstream energy company MarkWest Energy Partners L.P. MWE.N (MWE).

The outlook is stable. MWE is a master limited partnership (MLP) engaged in the gathering, processing, and transmission of natural gas; transport, fractionation, and storage of natural gas liquids; and gathering and transport of crude oil in the Southwest, Northeast, and Gulf Coast.

The rating on MWE reflects a weak business risk profile due to the company's commodity price sensitivity, small asset base, historically acquisitive growth strategy, and large capital-spending plan.

Somewhat mitigating these risks are increasing geographic diversity and the stability garnered from the company's hedging program. The rating on MWE also reflects the company's high proportion of percentage-of-proceeds contracts, which exposes it to commodity price risk.

MWE's asset base is small and it has been rapidly acquisitive since its formation.

The company also has a sizable organic capital-expenditure plan, particularly in the Woodford shale, for 2008. In addition, we expect the merger with general partner owner MarkWest Hydrocarbon Inc. to add keep-whole exposure, and increase leverage over the next two years.

The outlook on MWE is stable. Capital-spending needs are expected to remain high and the merger is expected to increase commodity price sensitivity. "Continued ratings stability will rely on prudent financing for expansions and the ongoing management of commodity price exposure through a comprehensive hedging policy," said Standard & Poor's credit analyst Plana Lee.

"Conversely, a negative outlook revision or downward rating action could result from heavily debt-financed expansions, disappointing margins, or the greater commodity price sensitivity of the MarkWest Hydrocarbon business," she continued.