Upgrading canyon roads to provide a relatively high-speed, safe shortcut between Tooele and southern Salt Lake County would cost an estimated $328.7 million, a new study says.

Tooele County Commission Chairman Wade Bitner said Friday with that high price tag, “It’s just not realistic at this time.” He adds, “$329 million — my goodness there’s an awful lot of things we could do with that to provide more benefit than going over the mountain.”

And Bitner said his commission agrees.

A just-completed $200,000 feasibility study funded by the Legislature for the Wasatch Front Regional Council looks at several options for shortcuts using different canyons across the Oquirrh Mountains.

The preferred option identified would allow a 50 mph drive from Herriman to Tooele, going up Butterfield Canyon in Salt Lake County and down Middle Canyon in Tooele County.

The new two-lane road — with 10-foot shoulders to allow snow storage, plus serve bicyclists and pedestrians in the summer — would require a nearly mile-long tunnel to maintain a maximum 6 percent grade.

That tunnel alone would cost an estimated $132 million.

Al Hartmann | The Salt Lake Tribune Barrier and signs blocks the entrance to Butterfield Canyon Road at about 13100 South and 9000 West. The right side of the road is Kennecott property and left side is BLM land both are posted no trespassing. A toll road or tunnel up Butterfield Canyon and down Middle Canyon on the other side of Oquirrh Mountains has been proposed as an improved shortcut between Tooele and southwest Salt Lake County.

Other options considered — one up Pass Canyon in Tooele County and down Barney Canyon in Salt Lake County, and another Ophir-Oak Canyon route — would require even longer, more expensive tunnels.

A road now exists in Butterfield and Middle canyons, but it is narrow, winding and steep with some unpaved sections in Middle Canyon. It allows speeds no faster than 35 mph. It is also closed during the winter.

And Bittner says every other year or so, some large truck trying to save mileage gets stuck in the canyon not realizing how narrow and winding it is.

The new study, performed by AECOM, figured that in 2050, the preferred, upgraded route would take 41 minutes from Herriman to Tooele, compared to an estimated 52 minutes if Interstate 80 were used instead.

“If it saves only 10 minutes or so, it’s probably not realistic,” Bitner said.

But an improved shortcut has been a dream of many officials in southern Salt Lake and Tooele counties for years — and they had even talked of perhaps of making it a toll road to allow financing.

One of its benefits would be providing an alternative when accidents close I-80 between the two counties where the Oquirrhs meet the Great Salt Lake, which also happens a few times a year and causes long delays.

Bitner said transportation officials are also exploring the possibility of extending State Road 201 there to closely parallel I-80 to provide a second option if accidents close I-80. “That would be about a third of the cost, and wouldn‘t require a tunnel,” he said.