Spring construction picks back up on Idaho Highway 55 between Smiths Ferry and the Rainbow Bridge Monday, March 15. The Idaho Transportation Department’s project will widen shoulders, add guardrail, and straighten this curvy one-mile stretch of highway to improve safety. Watch the video below to see the project.
Earlier this month, crews removed snow and set up construction equipment in the canyon. Starting March 15, travelers should plan for full road closures Monday through Thursday from 10 a.m. to 2 p.m., due to controlled rock blasting needed to widen the road. When ID-55 is not closed, there will be one-way alternating traffic with 15-minute delays. This work schedule is expected through May, when crews will transition into summer operations.
Rock blasting is underway between Smiths Ferry and the Rainbow Bridge as road construction continues on ID-55.
The goal is to make this narrow, curvy mile-long stretch of state highway safer, by building wider shoulders, adding guardrail, and straightening the road.
140,000 cubic yards of rock need to come off the canyon, and it’s happening one controlled blast at a time. How do they do it? It takes a lot of work and careful planning.
Strategically spaced holes are drilled into the rock differing in size and depth depending on the situation, then the explosives are placed inside.
“We’re using a nitro glycerin based dynamite as a primer, and then we use ammonium nitrate as a blasting agent,” said Blast Operator Ryan Miller. “Each hole is timed, a 40th of a second. We shot that in a V, and the reason it stayed on the hill is because we shot the center first, and kind of sucked it uphill.”
Each blasting design plan is closely reviewed.
“The whole idea is to move the rock in the direction we want it to. We don’t want to launch into the river, fly rock is our enemy,” Miller added.
Through late November, weather permitting, the work zone is closed to traffic every Monday through Thursday from 10 a.m. to 2 p.m. so crews can safely blast and haul away the rock.
Drivers are urged to plan around the closures or use US-95 as a detour.
“We don’t want people or cars traveling through the work zone during blasting. It’s also an incredibly tight work zone with the river off to the east and the rock faces out to the west. So giving the contractor that four hours is really letting them be as efficient as possible,” said Project Engineer Alex Deduck.
Steel containers and temporary barrier keep the falling rock from getting in the travel lane, and protect the crews working in this steep canyon. When the road is not fully closed, one lane is open to alternating traffic.
“Now that we’ve reduced it to one lane it’s even tighter, and just a hard area to work in,” Deduck said.
This winter, construction will pause and both lanes will be open.
In the spring, blasting picks back up with full road closures Monday through Thursday from 10 a.m. to 2 p.m., and during the busy summer, one lane will be open to alternating traffic Monday through Friday morning. Both lanes will be open Friday afternoon through Sunday.
The Idaho Transportation Department (ITD) starts road work on the Idaho Highway 55 safety-enhancement project between Smiths Ferry and Round Valley on September 8.
The public is invited to attend a virtual public meeting on Wednesday, September 2, from 6 p.m. – 7 p.m. where ITD representatives will give an overview of the project and take questions. The link to attend will be posted on the project website, itdprojects.org/ID55smithsferry, 15 minutes prior to the meeting.
Work will largely be done in fall, spring and summer months, with construction stopping during the winter. This fall, travelers can expect full closures on the roadway Monday through Thursday from 10 a.m. – 2 p.m. to allow for blasting and rock removal.
Motorists can find additional details on road closures and traffic patterns on the project website, and can sign up for email and text updates.
“Our goal with this project is to enhance the safety of this mile-long section of the roadway,” Project Manager Alex Deduck said. “Construction crews will remove about 146,000 tons of rock from the hillside, which we want to do very carefully to not create rockslides or impact the river.”
Crews will work on widening shoulders and straightening the curves of the road. This project will also provide a smoother, safer ride for motorists by adding guardrail.
Motorists should anticipate reduced speeds and lanes reduced to one-way alternating traffic during construction. Seasonal closures and traffic patterns will be as follows:
Fall (September – November): One-way alternating traffic controlled by a temporary signal; daytime and nighttime work, seven days a week; full road closures Monday – Thursday from 10 a.m. – 2 p.m.
Winter (December – Mid-March): No construction expected; all lanes open
Spring (Mid-March – Mid-May): One-way alternating traffic controlled by a temporary signal; daytime and nighttime work, seven days a week; full road closures Monday – Thursday from 10 a.m. – 2 p.m.
Summer (Mid-May – August): One-way alternating traffic controlled by flaggers; daytime and nighttime work, Monday – Friday
The project is expected to be completed by late fall 2022. ITD and the Idaho State Police advise motorists to slow down and pay attention when driving in work zones, where increased speeding fines and other penalties apply. Motorists are encouraged to plan ahead and dial 5-1-1 or visit 511.idaho.gov for information on the state highway or interstate system.