Is it possible to tunnel through part of Provo Canyon in order to widen a portion of canyon road? Utah Department of Transportation officials will know the answer to that question in a couple of months.
A drilling project is under way in Provo Canyon to determine whether it's feasible to put two westbound traffic lanes in two or three tunnels through the "Narrows" section of the canyon.The supplemental environmental impact statement drafted for the Upper Falls to Wildwood section of the canyon road identifies tunnels as one option for keeping a wider road out of and away from the Provo River in the "Narrows" portion of the canyon. Another option is to stack traffic lanes in that area.
"We've been told tunnels could run as high as $25 million, but we don't know (the cost) for sure," said Dan F. Nelson, director of UDOT District No. 6 in Orem. "In other areas we see tunnels running on average $10,000 a linear foot.
"It may be cheaper to do tunnels than to put a stacked structure in there."
The tunnels would run from just south of Wildwood near the Sundance turnoff to just north of the Riverbend Trailer Park in Provo Canyon, Nelson said. One proposed tunnel would be 700 feet to 800 feet long, while the other would be about half that length.
Saturday, Rocky Mountain Helicopter airlifted drilling equipment from Vivian Park to the project site. That equipment was to be set up on Monday, and between now and mid-January Boyles Brothers Drilling Co. will drill 11 holes into the mountain using a 3-inch bit, said Ed Keane, UDOT geotechnical engineer.
The drilling samples will be used to estimate the kind of rock and its strength, jointing characteristics and quality in the proposed tunnel locations. Based on that information, UDOT will be able to fine-tune alignment and grade of the tunnels and determine what kind of roof support will be necessary through the tunnels and at the tunnel portals, Keane said.
The drilling samples will range from 30 feet to 200 feet deep. "We've mapped the surface areas. Now we're mapping what's under the surface," Nelson said.
Once the drilling work is completed, UDOT plans to revegetate the project area. The tunnels are being designed by Parson, Brinkerhoff, Quade and Douglas Inc. of Murray.