The 242-mile Colorado River aqueduct delivers water from the river’s Lake Havasu to Lake Mathews in Riverside County, supplying water to millions of Southern Californians.
A portion of it runs beneath Mount San Jacinto. Tunneling the pipeline through the mountain during the Great Depression was a historic event, in terms of drama as well as engineering.
Drilling the Mount San Jacinto tunnel began in 1933. Workers bored a 13-mile tunnel through the 10,831-foot-high mountain. This required nearly six years. Work on the project was punctuated by surprise floods and a labor strike.
Metropolitan Water District of Southern California, based in Los Angeles, today wholesales water to 27 cities and utilities, according to the Los Angeles Department of Water and Power.
MWD was created to construct the aqueduct. It hired Milwaukee’s Wenzel and Henoch Construction Co. to build the Mount San Jacinto tunnel. Workers excavated several shafts to create the tunnel, according to “The Water Odyssey,” an MWD chronicle of the district’s history.
“Two vertical shafts were excavated to the grade level of the tunnel at Cabazon on the east and at Potrero on the west,” in addition to portals at each end of the tunnel, said “Odyssey.” The Potrero shaft was 800 feet deep, according to “Colorado River Aqueduct Recording Project 1998,” another MWD history.
Excavation proved unexpectedly difficult. “The mountain’s interior was laced with subsurface faults, streams and springs,” noted “Odyssey.” In July 1934, workers from the west portal hit an underground stream.
“Over 7,500 gallons per minute of water, accompanied by 1,000 cubic yards of detritus, rushed into the tunnel and rose to a depth of 647 feet in the Potrero shaft,” said “Recording Project.” The water was pumped out, but a second flood overwhelmed two of the three pumps.
“Then in November an even bigger deluge inundated the tunnel,” said “Odyssey.” “More than 15,000 gallons of water a minute spilled down on the miners, forcing another evacuation.” Both histories mention workers scrambling to safety up an 800-foot ladder.
Construction progressed so slowly during the first 18 months of the tunnel project — in that time, Wenzel and Henoch dug less than two miles — that MWD fired the contractor in 1935 and took on the project itself. Engineers installed larger pumps to control flooding. Then in 1937 work stalled for six weeks during a labor dispute and strike. Finally, in November 1938, the eastern and western portions of the tunnel were joined.
The pipeline and aqueduct began delivering water in 1941, said Bob Muir, press office manager for MWD.
“Water is certainly a driver for much of the economy we have today,” Muir said.
And the tunnel, like the aqueduct as a whole, provided precious jobs during the Depression. Overall, aqueduct construction employed more than 35,000 people.
The aqueduct had psychological as well as economic significance, said the introduction to “Recording Project.”
“It was during this time that the appearance and promotion of technological ‘progress’ provided the American public with a renewed sense of hope, promise and pride during the most devastating economic crisis in 20th-century American history.”