PHOENIX – Daytime blasting to remove potentially hazardous rocks resumed yesterday in an effort to protect workers and motorists along State Route 77 south of Globe. SR 77 will be closed in both directions between mileposts 154-161 from 10 a.m. to 3 p.m. every Monday through Thursday.

In addition, lane closures are expected each work day from 7-10 a.m. and from 3-5 p.m. Drivers should expect delays of about 15 minutes during those times. The restrictions are expected to remain in place until March.

ADOT crews had been working at night to remove rocks that could have fallen along SR 77 near Dripping Springs. The work was switched to the safer daylight hours after a loosened 18-foot limestone boulder fell 150 feet and landed on the roadway on November 30.

The incident underscored the risk for construction crews and the potential hazard to motorists. In addition to the instability of the rock face that is being removed, blasting creates flying rock that could be dangerous to workers, especially in the dark between sunset and sunrise.

During the closures, drivers can travel SR 177 and US 60 between Globe and Winkelman. That route will add about 20 miles to the trip.

As with any work zone, drivers are asked to drive slowly and cautiously in the work area and watch for construction workers and equipment.

Out-of-State travelers should be aware that Arizona Revised Statute 28-710 §B. provides for double fines for speeding through a marked highway work zone.

PHOENIX — To protect workers who are blasting potentially hazardous rocks along State Route 77 south of Globe, the Arizona Department of Transportation will close the road for five hours a day, Mondays through Thursdays, for the next four months.

Beginning Monday, December 12, SR 77 will be closed in both directions between mileposts 154-161 from 10 a.m. to 3 p.m. Closures will be in effect Mondays through Thursdays with no closures planned between Monday, December 26, and Tuesday, January 3.

In addition, lane closures are expected each work day from 7-10 a.m. and from 3-5 p.m. During those times, a pilot vehicle will guide motorists through the work zone. Drivers should expect delays of about 15 minutes.

The restrictions are expected to remain in place until March.

ADOT crews have been working at night to remove potentially dangerous rock that could have fallen along SR 77 near Dripping Springs. Work is switching to the safer daylight hours after an 18-foot limestone boulder fell 150 feet during previous nighttime blasting and landed on the roadway on November 30.

The incident underscored the risk for construction crews and the potential hazard to motorists. In addition to the instability of the rock face that is being removed, blasting creates flying rock that could be dangerous to workers, especially in the dark between sunset and sunrise.

During the closures, drivers can travel SR 177 and US 60 between Globe and Winkelman. That route will add about 20 miles to the trip.

As with any work zone, drivers are asked to drive slowly and cautiously in the work area and watch for construction workers and equipment.

An Arizona Department of Transportation project is blasting rock from a limestone cliff to prevent it from falling onto State Route 77 between Winkelman and Globe.

Illustrating the need, one of the rocks dislodged early Wednesday was far larger than expected, an 18-foot-tall block that dropped onto the highway from 150 feet above and forced crews to keep the route closed four hours longer than scheduled.

Crews on the overnight project worked until nearly 6 a.m. to break up the rock and push it off the highway. As a result, a detour using State Route 177 and US 60 remained the only way around the work area as area residents began their morning commutes.

The project requires working nights under a full closure of SR 77 between mileposts 154 and 161, in the Dripping Springs area, using explosives to remove potentially hazardous rocks from a cliff that hangs over the highway.

ADOT strives to provide timely information on restrictions, closures and detours, but occasionally the unexpected happens and announced schedules aren’t met.

Sometimes rocks break at naturally occurring joints beneath the surface that cannot be seen or anticipated, said J.J. Liu, manager of ADOT’s Geotechnical Services division. When the charge is ignited, it opens the crack at that joint and the rock detaches itself, he said.

Having an unexpectedly large rock come down increases the time needed to remove it, particularly with some of the extremely dense types of rock common in Arizona.

“The mountain is composed of the Mescal Limestone Formation with large blocks of limestone up to 155 feet above the highway, periodically falling with great energy and destructive potential,” said Brent Conner, a senior geotechnical engineer with ADOT.

The nature of the geology in the Dripping Springs area could mean more unanticipated delays before the project is complete, he added.

“The large block that fell required drilling and blasting at the roadway level to remove it from the travel lanes,” Conner said. “Last night’s work was one of the most difficult for the contractor on this project, but a couple more difficult sections remain.”