When rain and wind consistently dislodged rock on State Highway 14 in Santa Clarita, CA, a $7.5 million slope stabilization project was required by District 7 of the California Department of Transportation (CALTRANS).
The project began in February by general contractor Peterson Chase General of Irvine, CA.
The scope of work requires that the slopes be cut and stabilized by exaction and installation of cables with mesh netting along various areas, according to Peterson Chase General’s Project Manager, Lew DeLucia.
DeLucia explained that the 19,619 cu. yd. (15,000 cu m) excavation will be at “Location No. 1, an off ramp to Soledad Canyon Road.”
He said there will be six additional locations where cable mesh will be installed to prevent rock slides.
Eight locations will be installed with a twisted mesh drapery system that will total 52,624 sq. yd. (44,000 sq m) and 32,292 sq. yd. (27,000 sq m) of cable mesh drapery will be installed at eight other slope locations between Soledad Canyon Road up to Escondido Road, he noted, adding that the project’s total length is 7.5 mi. (12 km).
DeLucia also said that the scope of work includes pavement replacement and the installation of drainage for underground water at four locations; the installation of 3-ft. high concrete barriers that will total 755 ft. (230 m) at two locations; and striping and re-striping the highway to accommodate the temporary traffic flows throughout the duration of the project.
Among the project’s challenges is the installation of the netting and drapery work on the slopes because the slopes are hazardous, rocky and vertical, rising 40 ft. (12.2 m) and going back 20 ft. (6.1 m), he said.
The solution to this project challenge, he said, is to have the project’s subcontractor for this work, AIS Construction of Ventura, CA, drill anchors into the rock, grout them, and affix cables to the anchors and netting “like a giant rolled out chain link fence attached to cables.”
The weather is also a challenge on the project, he said. Wind and fog frequently affect the work. As a result, “we frequently monitor weather forecasts using the Internet and local weather reports,” he explained.
DeLucia said personnel and highway safety are also issues.
“Workers on a slope are tied off like mountain climbers. For highway safety, we shut the road down from 6 a.m. to 9 a.m. only on Sundays,” he noted.
During the week, he continued, anchors are drilled, pavement is replaced and barrier and drainage construction is performed.
“We must wait until all netting is installed at a location before this work can begin,” he added.
Continuing, he explained that before a slope is excavated, loose rock is scaled off a slope by hand. The loose rock is dropped into nets. Then excavation can begin.
To excavate a slope, the slope is cut back 120 ft. (36.6 m) off the roadway, DeLucia explained.
“We have to recontour benches back into the slope 30 feet to stabilize each slope,” DeLucia said, adding that each slope has been under the ocean for several millions of years.
The solution to this project challenge is to install a protective system. First, 3-ft. high temporary concrete barriers will be installed. A recommendation has been made by Peterson, Chase General to replace the temporary concrete barrier system with a 10 to 12-ft. (3-3.7 m) high steel or wood-lagging barrier system in 200-ft. (61 m) sections, which would facilitate State Highway 14’s traffic flow, he noted.
Heavy construction equipment on this project being used by AIS Construction include a Spyder Waling Excavator, Ingersoll Rand compressors and a Ford 2,000 gal. water truck.
Heavy construction equipment being used by Peterson Chase General include a Caterpillar D6 tractor with slope boards, both a Caterpillar 235 and 225 crawler excavator, a John Deere 710 rubber-tired backhoe, a P&H 14.5-ton rubber-tired truck crane, and eight Peterbilt and Mack dump trucks.
This project is scheduled to be completed in January 2008.