Major limestone quarry proposed for Parleys Canyon

Salt Lake County mayor ‘gravely concerned’ project would alter a landscape enjoyed by thousands

(Leah Hogsten | The Salt Lake Tribune) The area in Parleys Canyon, Nov. 22, 2021, where a proposed open-pit limestone quarry would be located, according to Utah mining regulators.

Parleys Canyon may soon be home to an open-pit limestone quarry, according to a proposal filed with Utah mining regulators this month.

A recently formed LLC called Tree Farm proposes using explosives and drills to mine beneath the northeastern flank of Grandeur Peak, a popular hiking destination from Mill Creek Canyon, with the intent of extracting 2 million tons of crushed rock a year.

Prior to receiving queries from a reporter this week, Salt Lake City and Salt Lake County officials had been unaware of the project, which County Mayor Jenny Wilson said she is “gravely concerned” about.

“Mining will change the landscape, habitat, and health in Parleys Canyon. But it is also less than one mile from Grandeur Peak, and thousands of hikers, bikers, and skiers safely recreating in Mill Creek Canyon,” she said in an emailed statement. “This is not in harmony with Salt Lake County’s vision to protect the unique qualities of our canyons and public health for generations to come. Instead, the development could potentially scar the natural contours of the landscape and could irreversibly disturb the experiences of countless residents in these two canyons.”

On Nov. 12, Tree Farm’s principal Jesse Lassley filed a notice of intent, or NOI, to “commence small mining operations.” This application seeks approval from the Utah Division of Oil, Gas and Mining (DOGM) to mine the foothills and process extracted limestone on-site immediately east of Salt Lake City. The well-developed 344-page filing sets in motion a process that could result in a significant extractive operation inside one of the Wasatch Mountains’ busiest canyons, traveled daily by thousands on Interstate 80, connecting Utah’s main metropolitan area with Park City.

A smaller existing quarry is cut into the hillside on the opposite side of the freeway.

Operations could begin as soon as 30 days after the filing under the expedited process Tree Farm requested. While Tree Farm filed its notice under Utah’s rules for small mining operations, its proposal envisions a footprint much larger than the 10-acre limit for small mines, which are regulated differently than larger mines.

The mine would require a conditional use permit from the county and would have to be reviewed for compliance with the county’s Foothills and Canyon Overlay Zone ordinance.

There is some residential development near the quarry site, but the filing acknowledges the land is important wildlife habitat without referencing a nearby subdivision. Several recreation destinations are close by such as Mount Aire, Mountain Dell Golf Course and Little Dell Reservoir. The proposed location does put the mine adjacent to a major transportation corridor, reducing impacts associated with getting the crushed limestone to construction sites along the Wasatch Front and Wasatch Back. The site is immediately west of the privately owned Mount Aire Canyon and is served by an existing exit on the interstate.

The site of the proposed quarry in Parleys Canyon. (Christopher Cherrington | The Salt Lake Tribune)

Limestone aggregates are used in making concrete and have a variety of applications in construction.

The so-called “Silver Mine” would not target its namesake mineral, but the NOI indicates that quarry could yield unspecified precious metals in addition to aggregates. Operators are looking to tap the Jurassic Twin Creek formation, which is 2,600 feet thick at this location and holds up to 1.1 billion tons of limestone.

The company pledged to put up a $3.1 million bond to ensure the site would be properly reclaimed.

Tree Farm owns the 634-acre parcel, which is surrounded mostly by federal land and abuts the south side of interstate about two miles below Mountain Dell Golf Course. Parleys is among the Wasatch watersheds that supply Salt Lake City with drinking water, but the mine is located downstream of the reservoirs that capture this water.

Still, sediment from the operation could be washed into Parleys Creek, which flows through an open channel through much of the city, including Sugar House Park. The director of Salt Lake City’s Department of Public Utilities, Laura Briefer, said she plans to examine the proposal and identify issues of concern.

“We feel we need more information. One [concern] is water quality from the proposed activities. While it’s not upstream from our drinking water sources, it is upstream from the city,” Briefer said. “We read through the report. It doesn’t really take into consideration downstream water-quality issues except to say the are going to put BMTs [best management practices] in place to mitigate the migration of any pollutants or sediments. It doesn’t talk about long-term degradation.”

(Leah Hogsten | The Salt Lake Tribune) The area in Parleys Canyon, Nov. 22, 2021 where a proposed open-pit limestone quarry would be located, according to Utah mining regulators in November.

Groundwater could also be impacted by the mining operations, which could have a hydrological connection with Mill Creek Canyon to the south, she said.

Briefer wondered where the mine would get the large volumes of water it would need for dust control.

“We have a lot of water rights with the Parleys. Are they planning to file for a water right or change application that could potentially impair these water rights,” Briefer said. “There’s been no public notice that has gone out on this.”

Reached by phone Monday, Lassley said he would call back, but The Salt Lake Tribune had yet to hear back by press time.

The operation would need to obtain permits from the Utah Department of Environmental Quality, specifically governing its potential impacts on air and water quality, according to his NOI filing.

Lassley’s plan is to produce 500,000 tons of limestone a year for the first 3 to 5 years of operation, then ramp up to 2 million tons or more, the document said. To move that much limestone would require 137 truck trips a day at 40 tons per load. To put this production level into perspective, Utah quarries yielded 13 million tons of crushed stone in 2019, according to the Utah Geological Survey.

The mine’s maximum production would be set a permit issued by the Utah Division of Air Quality, the NOI reported. The company, however, has yet to submit any permit applications with the division or its parent agency, the Department of Environmental Quality, according to a spokesperson.