SALT LAKE CITY — The Salt Lake County Board of Adjustment on Monday preliminarily derailed Snowbird's plans to build a mountain coaster at its resort in Little Cottonwood Canyon.

The board found that the County Planning Commission misapplied the county's Foothills and Canyons Overlay Zone ordinance in granting a slope waiver for construction and operation of the coaster, which would be built entirely on private land.

The Board of Adjustment, which is appointed by Salt Lake County Mayor Peter Corroon, has limited authority in overturning planning and zoning decisions. It can overturn decisions it deems arbitrary, capricious or illegal. Its decisions can be appealed in 3rd District Court. The board will take formal action on May 11 after a written decision is drafted, said ad hoc chairman Gary Sackett.

Tom Stephens, one of two people who appealed the planning commission decision, said the Board of Adjustment's preliminary decision that the decision to grant a slope waiver was arbitrary and capricious was a positive development.

"It's not over until it's over," Stephens said of the decision. "I'm very cautious. This is very tentative."

The second appellant, Carl Fisher, executive director of Save Our Canyons, said the Board of Adjustment had spent two or three times as much studying the issues as had the planning commission.

"I think the Board of Adjustment gave this issue the amount of dialogue that was warranted," he said.

But Snowbird officials said the four-season resort had a 40-year record of offering a wide array of recreational options with no adverse impacts to the watershed.

"Snowbird agrees with the Planning Commission's original decision," said public relations director Jared Ishkanian. "We are a ski and summer resort with a long history of approved activities," such as its Alpine Slide and ZipRider.

The board found the proposed coaster did not meet the definition of a snow-related activity for a ski resort. Some board members said they were troubled that the Planning Commission did not state in the record their reasons for granting a slope waiver to allow the construction and use of the coaster on a steep slope.

"It's very concerning," said board member Bob Frey. "If I was the mayor, I'd take them out to the woodshed, quite frankly."

Frey also took issue with a letter to the planning commission by county planner Curtis Woodward to support the staff's position to grant a slope waiver for the use. "The wording he used to make his case is not in the ordinance," he said.

As proposed, the coaster would travel on a raised track resting on a trestle varying from 2 to 13 feet high. A cable would pull riders to the top of coaster and gravity would pull riders down a curving 3,300 foot track that drops nearly 400 feet in elevation as it winds its way back to the starting point. According to documents filed with the county, the track would cross state Route 210, a scenic byway, on a bridge.