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Taking You Back in History: The Big Ditch and The Big Gap

Written by Ted Carlsen for STCHS Newsletter, July 1988


The engineering marvel, Big Gap Flume, before its collapse in 1868.

“During the gold era of Groveland and Big Oak Flat, water, much needed by the mining community of those areas, was brought down from higher elevations via the Golden Rock Ditch, familiarly known as the Big Ditch. The water source was the South Fork of the Tuolumne River, 40 miles away.


“Impeding the smooth continuous flow of the ditch was the Big Gap, a canyon known as Conrad's Gulch. Necessity decreed that the water must be brought across the canyon at sufficient elevation to continue the gravitational flow toward Groveland and Big Oak Flat once it emptied into the continuation of the ditch on the other side.


“To effect this, a wooden flume was constructed which was considered an engineering marvel of the time. The flume was 2200 feet in length, spanning the Big Gap by suspension from a total of 22 towers built of timbers, the tallest one being 288 feet in height. The suspension over the gap was done by wire cable and varying sources set the height of the flume between 265 and 280 feet above the canyon bottom.


“To quickly put this into perspective by today's standards, consider that you are standing on the bottom of Conrad's Gulch. On approximately a north/south line from your position , eleven pairs of timber towers, each tower with a base of 50 feet square, comes into the canyon from the opposing slopes. Right next to where you are standing is the tallest tower…288 feet. The pairs, about 200 feet apart, depending on terrain, hold the flume suspended almost 300 feet up. That is 100 yards. That is one football field straight up above you, less a fifteen yard penalty. The span, from wall to wall, is over seven football fields long. As a rough guess, if the flume were still standing, it would be suspended almost 200 feet over Hwy. 120. This is purported to be the highest flume ever built in California.


But suddenly on July 9, 1868, the miners' water supply stopped. After many years of neglect and decay, the wooden flume had crashed into the canyon. It was said to have been spectacular.


Then, almost exactly one year later, the Big Ditch, severed by the crash of the flume began to flow again - - July 1869. How had that come about??”


Be sure to read up-coming Part 2 to find the answer.


Taking You Back in History is provided by the Southern Tuolumne County Historical Society (STCHS) and the Groveland Gateway Museum. The Museum is open Friday - Sunday 10a - 2p


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