Mountain Marvel : Cutoff of Water to Tunnel Reveals Nature’s Transformation

Miners and Mother Nature have joined forces to create a wonderland of stalactites and secret fountains deep inside one of Southern California’s tallest mountains.

Within the recesses of Mt. San Jacinto, a little-known tunnel that is a key section of the Colorado River Aqueduct was ordered built by the Metropolitan Water District in 1933. The 13-mile-long tunnel, which the MWD monitors every five years, has taken on a life of its own.

Nature has transformed exploratory parts of the tunnel into a stream bed with beaches here, a crystal-clear wading pool bounded by rough-cut bedrock there. Crayfish, Asiatic clams and small dark-colored fish swept in from the river have created safe homes in abandoned shafts.

About a week ago, the MWD shut off the five pumping stations that send Colorado River water coursing through the tunnel so that workers could descend steep metal stairs to repair fixtures and test whether the MWD is taking more than its fair share of water.

The MWD also sent down a crew to photograph and videotape the sights nature has created.

Calcium carbonate stalactites fingered their way down from metal seams that hold the concrete tunnel sections together. Some were snowy white and looked like sea foam bubbling from the ceiling. Minerals had discolored others into various shades of topaz.

Although the pumps were shut down, a never-ending stream of water raced along the tunnel floor, pushing against MWD employees’ shins when they got off a trolley to photograph a particularly interesting formation.

Underground streams and springs honeycomb the mountain and no concrete tunnel is going to restrain them. Springs bubble up from the tunnel floor and water spews from breaks in the walls. In the 1940s, the MWD tried to patch the holes, but finally gave up. Today, the valves where workers shot concrete into crevices and the concrete smears used to plaster larger breaks have taken on the appearance of gargoyles spitting water from their lips as the trolley crawls by.

A trolley powered by a John Deere tractor carried the filming crew through the dank corridor.

At several points along the way, the journey took on aspects of an amusement park ride. About three miles in, the trolley stopped at a landmark known as the Carwash, a series of three arching sprays like the cycles at a carwash. Farther on, it came across the Jet, a stream of water that shot across the tunnel with enough force to provide a deep back massage.

Modern-day engineers still sigh in appreciation of what it took to build the tunnel that stretches from near Hemet to near Interstate 10. “You know, it really humbles you,” said MWD General Manager John Wodraska, calling it a monument to Californians’ perseverance.

In 1933, when a contractor started burrowing into Mt. San Jacinto, no one knew how much water it held. The next year, miners trying to build what is known as the Potrero shaft encountered flooding three times, narrowly escaping death. The highly fractured rock in this section shattered under the blasting and covered the pumps that kept water from the tunnel. The third incident was the worst. An underground stream ripped open by blasting dumped more than 15,000 gallons of water a minute into the tunnel.

“We had some panic, pandemonium, people trying to save their lives,” said George Buchanan, MWD operations and maintenance manager. The miners raced up an 800-foot ladder to the surface as water filled the shaft below them.

Work on the tunnel crept along and, after 18 months of labor and less than two miles of completed excavation, the MWD fired the contractor, taking over the project itself.

A labor strike marked by some violence brought work to a near standstill for six weeks in 1937. When the Cabazon and San Jacinto crews from either side finally met in November 1939, the alignment was only a fraction of a foot off, a considerable achievement for 1930s-era technology, Buchanan noted.

“Imagine standing out here 70 years ago and saying, ‘We’re going to build a tunnel through here,’ ” Wodraska said, gazing at the mountain peak towering 10,831 feet into the Riverside County sky.