MarkWest Energy Partners LP said May 2 that Randy S. Nickerson will retire in 2016 as executive vice president and chief commercial officer.

Nickerson joined MarkWest in 1996, and for the past nine years was chief commercial officer. Scott Garner, vice president of corporate development, will assist Nickerson with development of strategic NGL downstream projects in the Northeast and, until he retires. After Nickerson retires, he will provide consulting services to MarkWest, the company added.

“The MarkWest team is extraordinary and I have been honored to play a role in the significant growth of the company over the past 20 years,” Nickerson said. “MarkWest is incredibly well positioned and has an enormously exciting future. I look forward to supporting MarkWest’s continuing success during 2015 and beyond.”

Greg S. Floerke will be promoted as executive vice president and chief commercial officer, effective June 1. He is currently senior vice president of perations for the Northeast, and has more than 25 years’ experience in energy, engineering and construction.

Due to these changes, the responsibilities of Nancy K. Buese, executive vice president and CFO, will now include M&A and joint venture management. The responsibilities of John C. Mollenkopf, executive vice president and COO, will now include the NGL and gas marketing functions.

Also, MarkWest said David A. Fitch, vice president of engineering for the Northeast,will be promoted to senior vice president of operations, for the region. He will replace Floerke and John Paul Elder, currently the region’s director of engineering. Elder will be promoted to vice president of engineering for the region.

Denver-based MarkWest Energy Partners LP is a midstream MLP working in major U.S. shale plays.