A helicopter will ferry a work crew to the top of the Haiku Stairs this morning to remove a makeshift swing from the ridgeline, where hikers have been swinging over the edge of a cliff that soars thousands of feet.

“It is a very dangerous situation,” Ernest Lau, Board of Water Supply manager and chief engineer, said Monday. “It was done without our knowledge, and it is, I’ll make it very clear, illegal to have done that.”

The swing rests at an elevation of about 2,750 feet. The board hired a contractor to remove the swing because it is on Board of Water Supply land, part of the Haiku Valley watershed in Windward Oahu. The seat of the swing hangs on metal chains attached to poles that are remnants of the former Coast Guard OMEGA station.

“The two poles appear to be set on concrete pedestals, and they go up pretty high, I’m not sure how high,” Lau said. “So just putting the swing up must have been quite a task and also quite a risk for those individuals.”

Haiku Stairs, also known as the Stairway to Heaven, has been closed to the public since 1987. Hikers who climb the stairs or watershed land can be cited for trespassing and fined up to $1,000. But many continue to trek up the ladderlike metal stairs.

The swing recently caught public attention as hikers posted online videos of their companions soaring out over the mist-shrouded mountain cliff, including one where a young woman appeared to slip.

“Basically, it looks like she slipped off the seat of the swing and was dangling by her arms, and her companions were having trouble actually bringing her back safely to the stairs,” Lau said. “That was very frightening.”

The Board of Water Supply heard about the swing a few weeks ago and began making plans to remove it.

The operation will cost $23,000, including helicopter time. The money will come from funds that Oahu residents pay to maintain the water supply, and thus detracts from the board’s mission, Lau said.

“We are about providing safe, dependable and affordable water to our community now and into the future,” Lau said. “We are not about managing stairs like this. We’re not about taking care of hiking features and trying to prevent people from injuring themselves. We do that out of necessity to keep our community safe.”

Only the swing, chains and poles will be removed today. The helicopter will transport both workers and debris, and avoid flying over residential areas and the H-3 freeway as much as possible.

The Board of Water Supply has been trying for years to transfer the stairs and the watershed to another government agency, whether city, state or federal.

“Unfortunately, we’ve been unsuccessful, so we’re moving forward with preparation of an environmental impact statement to allow us to look at the option of complete removal of the stairs,” Lau said.

“There are supporters of the stairs and people that want the stairs removed,” he added. “Board of Water Supply is somewhat caught in the middle.”

The board also plans to do a survey to determine whether other landowners own parts of the stairs, which run along the border of its parcel.