Tunnel Business Magazine Spotlights 2.5-Mile Tunneling Project Using NWP Spiralweld Steel Pipe, Permalok

The large-scale L.A. water infrastructure project replaces an aging trunk line with a 78-inch engineered steel system by Northwest Pipe

The Los Angeles Department of Water and Power is currently constructing the River Supply Conduit Improvement Project Upper Reach-Unit 7, a 2.5-mile drinking water trunk line designed to replace an existing line built in the 1940s. To support this project, Northwest Pipe Company supplied 13,400 feet of 78-inch spiralweld steel water transmission pipe and 505 feet of 102-inch Permalok steel casing pipe, installed by Frontier-Kemper Constructors, Inc.

The project’s first section is a 500-foot long microtunnel crossing underneath the L.A. River, bored using an outsized Akkerman MTBM. Here, Frontier-Kemper installed the 102-inch Permalok pipe to serve as casing pipe for the 78-inch water transmission pipeline. The main tunnel alignment consists of an 11,755-foot drive starting at Johnny Carson Park and ending at the intersection of Burbank Boulevard and Biloxi Avenue. This tunnel is being mined with a 13.5-foot Herrenknecht tunnel boring machine. The remaining 1,000-foot section of this project utilizes traditional open-cut installation to complete the 78-inch steel water pipeline.

The new system will reliably transport water from the North Hollywood Pump Station the Headworks Reservoir in Griffith Park. The tunneling portion of this project is scheduled for completion this fall, and the pipeline is expected to be in service in the spring of 2022.

Read more about the project here in Tunnel Business Magazine.