San Jacinto Tunnel

The San Jacinto tunnel is considered the key link in Colorado River Aqueduct system. The 13 mi (21 km) long, 16 ft (4.9 m) diameter tunnel runs beneath the San Jacinto Mountains between Cabazon, California and Gilman Hot Springs in Riverside County, California.

The $23 million project started on April 8, 1933. Tunnel crews dug from four directions: the two main portals and two shafts.

On July 1, 1934, one of the tunnel crews narrowly escaped the tunnel as ground water burst in and began filling the tunnel and shafts at a rate of nearly 8,000 US gallons per minute (0.50 m3/s). Metropolitan Water District of Southern California (MWD) Chief Engineer Frank E. Weymouth had noted in his 1930 report on the tunnel routes that the Parker route “involves less risk than any of the other proposed lines.” The continued intrusion of water was more than the original contractors could handle, and in February 1935 the MWD terminated the contract and took over the job. More pumps were brought in and a portion of the tunnel was re-routed. Three crews of 34 men, working eight-hour shifts worked on the tunnel.

The MWD continued to encounter tunnel seepage. The amount varied but never dropped below 540 US gallons per minute (0.034 m3/s), and sometimes topped 30,000 US gallons per minute (1.9 m3/s). By 1935 the seepage had become a concern around the San Jacinto Valley as springs, creeks and streams began to run dry. On October 21, 1935 the Riverside County Board of Supervisors passed a resolution calling on the MWD to prevent water from entering the tunnel or from flowing away from the place it was encountered. The MWD responded by stating that water entering the tunnel during digging is nearly unavoidable, and that lining of the tunnels near the end of construction should prevent further inflow. Lawsuits were filed against MWD by nearby landowners and most of these were settled out of court, with MWD paying out over $350,000 between 1936 and 1944.

The largest and most controversial settlement was known as the Poorman contract. The Poorman family owned a 1,700 acres (6.9 km2) dairy ranch on the south side of the San Jacinto River, across from Gilman Hot Springs, along with 3,600 acres (15 km2) of grass and grazing in the upper Perris valley. The ranches were managed by Ed Poorman, known locally as the founding president of the Ramona Pageant Association. Ed Poorman's brother, Samuel Poorman, was an attorney for the Los Angeles Department of Water and Power. In 1937, after noticing a drop in groundwater, Samuel Poorman negotiated a settlement with the MWD for the loss of groundwater, but instead of taking cash, the Poormans took their share in water.

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