Whitefish Mountain Resort’s Chair One, used in the summer season for scenic lift rides and carrying mountain bikes, will be closed indefinitely to repair a slump above tower six that likely was caused by heavy moisture this spring.

All hiking and mountain biking trails under Chair One — including the Danny On Trail and upper sections of the Go Fish and Gopher biking trails — also are closed until further notice, resort spokeswoman Riley Polumbus said.

The Summit House at the top of Chair One also is closed.

On Saturday the resort’s lift maintenance crew noticed a slump in the ground 25 feet above tower six, Polumbus said. Chair One is a detachable quad lift and is equipped with safety mechanisms, auto-stop modes and alarms that warn operators.

The lift ran until closing at 6 p.m. without any significant warnings. Saturday was the first day of Whitefish Mountain Resort’s summer season.

Lift maintenance and lift operators monitored the area and the lift throughout the day. In the afternoon, the area around the slump was marked with flags.

On Sunday morning the area was re-inspected and it was observed that the slump had grown overnight. During a visual inspection of the lift it was determined that tower six was about four inches out of plumb. Chairs and gondola cars were removed to release tension on the lift cable to enable crews to tie back and secure the tower.

The lift manufacturer, a hydrologist and a soil engineer have been contacted, Polumbus said.

“We will know more about the solution after their analysis,” she said.

A helicopter is being brought in to remove the tower.

The following activities still are available on the mountain: Alpine Slide, Zip Line Tours, Walk in the Treetops and lower-mountain cross-country biking trails.

Chair 6 and Chair 9 are running and the Base Lodge Café and bar also are open.

“We will be putting all necessary resources toward assessing the situation, finding a solution and getting our scenic lift up and running as soon as the lift is back to engineering standards,” Dan Graves, president of Whitefish Mountain Resort, said in a prepared statement. “Our main concern is for the safety of our customers and employees.”