When Steve and Connie Ault erected a milelong network of zip lines on their Provo Canyon property in 2012, they failed to get permission from the operators of a major water pipeline crossing the land, triggering a lawsuit from the Metropolitan Water District of Salt Lake and Sandy.

Providing water to some 400,000 Salt Lake County residents, the district has long held an easement along the entire 42-mile length of the Salt Lake Aqueduct from Deer Creek Reservoir to the mouth of Parleys Canyon.

The district’s ensuing six-year legal battle with the Aults over the commercial zip line operation suffered a serious setback this week, when the Utah Supreme Court reduced the scope of the easement, concluding it does not give the district regulatory authority over land it does not own.

The ruling reverses a lower court’s conclusion that the easement is 200 feet wide and enabled the district to block most development in the aqueduct corridor.

Contacted by phone Friday, Connie Ault said the decision came as a relief because it would protect her family’s $500,000 investment in the property.

“It’s absolutely ridiculous,” she said of the legal action by water district officials. “They were taking away our property rights.”

The five zip lines are the central amenity at Provo Canyon Adventures, which the Aults operate a few miles below Deer Creek Dam. The family bills the park as a “treetop canopy zip line tour.”

“You’ll experience breathtaking mountain scenery, wildlife, beautiful riverfront landscapes and mountain fresh air,” states Prove Canyon Adventures’ website. “Soar across the treetops and fly with the birds as you take in beautiful mountain vistas, stunning views of Mount Timpanogos and the Provo River.”

Since 2013, the water district has been trying to force the Aults to remove a zip line platform inside the aqueduct corridor. Before the Supreme Court ruling, the district’s rules barred landowners from constructing buildings or “other encumbrances” and planting trees or vines on their own property inside a 200-foot-wide corridor. District rules also specified what kind of fencing could be built and listed a number of substances that cannot be stored on this land.

After the Aults built the zip lines without the necessary permit, the district took them to court.

“Unencumbered access to the entire width of the [Salt Lake Aqueduct] Corridor for emergency repairs is critical to the interests of the public,” the district’s suit contended. “Different segments of the [aqueduct] consist of different classes of pipe, intended for different maximum loads. Prevention of loads beyond design capacities, resulting from the addition of fill, structures, the parking of vehicles, etc., is critical to the interests of the public. Such uses of the [aqueduct] Corridor, without [the district’s] consent, is a violation of [the district’s] real property interests.”

That argument carried the day with 4th District Judge Jennifer Brown, who ruled in the district’s favor in 2016. But the high court unanimously concluded this expansive view of the water district’s rights to the land went too far.

“Based on our interpretation of the relevant statutes, we hold that Metro’s authority over [the Ault] property does not extend beyond the authority it derives from its easement rights,” Chief Justice Matthew Durrant wrote in the 24-page opinion. The easement “merely authorizes Metro to negotiate agreements regarding Metro’s property interests.”

In other words, the district can attempt to block developments only that interfere with the purpose of its easement, which is to operate, maintain and eventually replace the waterline. The opinion went even further, concluding that easement’s width is less than the 200 feet asserted by the water district.

The high court remanded the case to the district court to reconsider the easement’s true width and determine whether the Aults’ zip line and other improvements are “unreasonably interfering” with that easement.

The aqueduct was constructed between 1939 and 1951, when the Aults’ land was owned by Utah Power and Light. Its 84-inch-diameter pipe carries up to 113 million gallons a day to various destinations in Salt Lake County, including two concrete reservoirs at the mouth Parleys Canyon and a water treatment complex at the mouth of Little Cottonwood Canyon.

The line travels down Provo Canyon and along the Wasatch Front, crossing various properties along the way. The water district has taken other landowners, including Ivory Homes, to court over unauthorized improvements encroaching on the aqueduct corridor.

Wednesday’s ruling could have a substantial impact on what these owners can do with this land.