Mechanical Mole Opens Water Tunnel to Southern California

The mechanical mole ate its way through dirt, rocks and granite up to 1,500 feet beneath the mountain range boring out the 12 foot diameter Arrowhead West Tunnel, part of Metropolitan Water District's $1.2 billion Inland Feeder project.

When completed in 2010, the Inland Feeder will nearly double the district's water delivery capability by supplying as much as 650 million gallons of additional water each day.

During rainy winters, water flowing from Northern California will generate power at the Department of Water Resources' Devil Canyon power plant before entering the Arrowhead West Tunnel for delivery to a Metropolitan Water District reservoir for storage and use in dry seasons.

"For those of us who have followed this project since it first appeared on the drawing board 20 years ago, this is truly a thrilling moment," said Metropolitan board Chairman Timothy Brick. "This is a landmark achievement for the Inland Feeder, a vital link in securing a more reliable, higher-quality water supply for Southern Californians."

Worker examines the hole drilled by the tunnel boring machine. (Photo courtesy EPC Consultants)

Mining on the 4.3 mile Arrowhead East Tunnel was completed last May, and the eight mile Badlands Tunnel was finished in July 2001.

The feeder is expected to improve the quality of Southern California's water supply by allowing more uniform blending of water from Northern California with Colorado River supplies, which have a higher mineral content.

"Southern California is facing increasingly limited periods of time when water is accessible in Northern California and can be delivered to our region," Brick said. "So when water is available, we must be prepared to move large volumes of water during a relatively short time and then store it for use during dry periods and emergencies."

The Inland Feeder will deliver water to be stored in surface reservoirs, such as Metropolitan's Diamond Valley Lake near Hemet in southwest Riverside County, Southern California's largest reservoir.

Metropolitan General Manager Jeff Kightlinger said the project will help Southern California cope with future weather pattern uncertainties, which may bring more rain and less snowpack to Northern California, and longer periods of drought to Southern California.

"History shows that changes in climate and weather are inevitable, bringing significant uncertainties in our climate and our water demands," Kightlinger said. "Projects like the Inland Feeder will help accommodate the inevitable changes in climate and weather that our region will experience.

"By understanding our climate past and carefully considering our climate future, we have made a thoughtful, prudent investment in our future," he said.

Gene Koopman called the feeder "one of the most demanding construction projects" in the agency's 80 year history.

"Construction of the Arrowhead west and east tunnels was challenging, not only due to the physical constraints of mining in such extremely difficult geologic conditions and so close to several earthquake faults, but also because of other hazards unique to Southern California that were encountered--fires and flash floods," said Koopman, who chairs Metropolitan's Engineering and Capital Programs Committee and is the Inland Empire Utilities Agency representative on the Metropolitan board,

Koopman recalled one of the worst moments on this project happened in October 2003 when a 100,000 acre wildfire engulfed the Arrowhead West Tunnel portal in Waterman Canyon, destroying construction equipment.

Two months later on Christmas Day, a sudden winter storm drenched the charred mountain area, releasing a torrent of mud, water and rock down the canyon and flooding the same portal site and tunnel-boring machine, and washing away more equipment.

"As a testament to this project and the workers behind it, within months of these setbacks, repairs were completed and tunneling resumed," Koopman said. "That is the essence of this project - taking challenges head-on with the perseverance to get the job done."

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