INLAND FEEDER SYSTEM
Metroplitan Water District
This $1.2 billion Inland Feeder Program comprises a 44-mile alignment of large-diameter tunnels and pipelines running from the foothills of the San Bernardino Mountains to the Colorado River aqueduct in Riverside County. The feeder provides the southern Californians with as much as 650 million gallons of additional water each day. The program comprised of the Riverside Badlands contract (8 miles), the Arrowhead East contract (6 miles) and the Arrowhead West contract (4 miles). The tunnels pass through granite, gneiss, and marble rock formations. Ground conditions in the tunnels range from massive, hard, strong and abrasive rock to very blocky and seamy rock and crushed ground. Near the portals, much of the rock is weathered and sheared. Controlling groundwater inflows was critical to avoid impacts to the San Bernardino National Forest and San Manuel Indian Reservation.
Arrowhead East Tunnel Project
While the Arrowhead East Tunnel (AET) was the first of the four large tunnel contracts to begin construction, it was actually the second tunnel section downstream of the start of the Inland Feeder at Devils Canyon. Arrowhead East’s upstream end consists of 1,500 linear feet of 12-foot diameter welded, steel pipe, installed in a cut and cover trench. This pipeline then connects with a 30,000+ linear feet tunnel through the San Bernardino Mountains.
EPC was a sub consultant in the construction management effort of this project.
Arrowhead East & West Tunnel Project
The Arrowhead West Tunnel (AWT) involved the construction of 19,884 feet of 12-foot finished diameter tunnel and 6,630 linear feet of similarly sized, buried pipeline. The depths of the portals were 60 feet to 100 feet below surface. The soil and rock cover above the tunnel is generally greater than 400 feet and ranged up to as much as 1000 feet, with groundwater head of up to 30 bar. Surface features above the tunnel line include Old Waterman Canyon Road and State Highway 18. The tunnel also crosses the Arrowhead Springs Fault and is near the North Branch of the San Andreas Fault.
EPC provided construction management support to the consultant team.