Editor’s note: This article has been updated to clarify and correct some details.

Unit 5 is pretty much history at the coal-fired Martin Drake Power Plant, and the next issue is how soon Unit 6 can be decommissioned, too, Colorado Springs Utilities managers reported Wednesday.

The three-unit downtown plant is to close completely by 2035, but the Utilities Board has questioned whether Units 6, 7 or both could be closed earlier.

The board wanted Unit 5 decommissioned by Dec. 31, 2017, but much of that work already is done, said Aram Benyamin, general manager of Utilities’ Energy Supply Division.

The unit hasn’t operated since March, and its main natural gas supply has been severed and capped. “No weak links” have been found since, Benyamin said.

The crew still has some tasks, such as isolating the coal ports from those for Units 6 and 7. And it plans to explore the market for selling the entire unit or, if the parts are more valuable than the whole, dismantling it to sell piece by piece, he said. The unit also could be used for training.

If a total sale is in order, the staff will invest about $40,000 a year to rotate the shafts and keep the unit in good shape, Benyamin said.

As for Unit 6, much hinges on how the state wants to implement the federal Clean Power Plan, what other air quality regulations may arise and what regional partnerships might be available, such as with the Mountain West Transmission Group, said Electric Planning Manager Susan Lovejoy.

Board Vice Chairman Tom Strand said he’ll be 90 by the time Drake is set to close, and he’d like to see it happen sooner.

Many factors are at play, Lovejoy said, but more will be known in the next two to six years.

She said the energy transmission flows south to north, and removing Drake’s 240 megawatts from the middle of the system disrupts the flow.

Building replacement power near the city center “is better for us,” Lovejoy said, because it reduces the transmission distance and costs.

One option she listed is to build a wall around the Drake substation.

The Downtown Partnership, development leaders and clean-air advocates have lobbied to get Drake out of downtown, saying the unsightly plant and its white plume are in plain view from Interstate 25 and detract from an otherwise progressing downtown.

With the U.S. Olympic Museum to be erected adjacent to Drake, such concerns have multiplied.

“Even getting the tall eyesore out of there is what I’m talking about,” said board member Don Knight.

“Whether to replace it,” Lovejoy said, “is really up to the community.”

Colorado Springs Utilities is a city-owned public enterprise.

She said the staff will report back in December with potential alternatives to Drake, the tradeoffs, rough cost estimates and timing considerations in case more transmission must be built.