MarkWest Energy Partners, L.P. (NYSE: MWE) (“MarkWest or the Partnership”) announced today an operational update regarding the development of midstream infrastructure projects in the heart of the rich-gas areas of the Marcellus and Utica Shales. MarkWest continues to expand its leading midstream presence throughout the Northeast and currently has 21 major processing and fractionation projects under construction. These projects are occurring at eight large-scale complexes in Ohio, Pennsylvania, and West Virginia and are expected to increase the Partnership’s total processing capacity to over 4 billion cubic feet (Bcf/d) and total fractionation capacity to nearly 300,000 barrels per day (Bbl/d) by the end of 2014. In the Marcellus, MarkWest has commenced operations of Majorsville V, a 200 million cubic feet per day (MMcf/d) plant at the Majorsville complex in Marshall County, West Virginia. The new plant supports growing rich-gas production from Chesapeake Energy Corporation (NYSE: CHK), and Statoil ASA (NYSE: STO) and increases the total processing capacity at the complex to 670 MMcf/d. The Partnership expects to complete an additional 200 MMcf/d plant during the first quarter of 2014 and will bring online a sixth plant in early 2016. Upon completion of these facilities, the Majorsville complex will have over 1 Bcf/d of capacity. Over the next month, MarkWest will also bring online its second large scale de-ethanizer in the Marcellus Shale at the Majorsville complex. The new facility will double the Partnership’s purity ethane fractionation capacity to 78,000 Bbl/d in the Marcellus Shale and provide producer customers’ with the ability to meet residue gas quality specifications and downstream ethane pipeline commitments. Ethane produced at the new Majorsville fractionation facility will initially be delivered into the Mariner West pipeline and, in the future, to the ATEX and Mariner East pipeline projects. In the Utica Shale, MarkWest Utica EMG, L.L.C. (“MarkWest Utica EMG”), a joint venture between MarkWest and The Energy and Minerals Group (EMG), has commenced operations of its first cryogenic processing plant at the Seneca complex in Noble County, Ohio. The 200 MMcf/d Seneca I plant will be followed by a second 200 MMcf/d plant by the end of this year, and a third 200 MMcf/d plant by the second quarter of 2014. The Seneca complex is MarkWest Utica EMG’s second major processing complex in the core area of the rich-gas Utica Shale. By the end of 2014, total processing capacity in Ohio will reach almost 1 billion cubic feet per day.