The GenOn coal-fired power plant in Alexandria. (Gerald Martineau/The Washington Post)

The production cycle was short-lived; when the frigid air passed, so did the need for the coal-fired plant’s power. Despite the brief return to operation, GenOn (formerly known as Mirant) is still on track to close the Potomac River plant permanently Oct. 1, said GenOn spokeswoman Misty Allen.

The sudden power generation last week came about since the 485-megawatt plant operates on the wholesale market. It responds to requests by PJM Interconnection, a regional transmission organization that coordinates the movement of electricity in a great swath of the East Coast and Midwest. GenOn’s plant is classified as an intermediate facility, so other, less expensive plants are called upon first to produce electricity for the region.

Since the winter weather has been mild, and natural gas prices are low, the demand for electricity from coal-fired plants has not been high this year, Allen added.

The plant shutdown came about after local residents Elizabeth Chimento and Poul Hertel began raising questions about the pollution from the plant 10 years ago. Eventually, the city of Alexandria and the state of Virginia joined their crusade, national environmental organizations made the closure of coal-fired plants a priority, the economics of energy production changed and updated federal regulations made power generation from older facilities like the 62-year-old GenOn plant more expensive.

The 25 acres upon which the plant sits has become a minor issue in the ongoing controversy over the future of the Alexandria waterfront. Opponents of the city’s proposed plan want to include the 25 acres in the city’s planning; the city has resisted that call.

While GenOn owns the plant and holds a 99-year lease on the property, with 89 years to go, Pepco actually owns the land itself.