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The Yukon Ditch was an engineering marvel

The "Yukon Ditch" was one of the most ambitious engineering projects in Yukon history and should be ranked near the top of the list with the building of the White Pass and Yukon Route Railway, and the construction that took place during Second World War.

The “Yukon Ditch” was one of the most ambitious engineering projects in Yukon history and should be ranked near the top of the list with the building of the White Pass and Yukon Route Railway, and the construction that took place during Second World War.

In its time, the “Ditch” was compared with the construction of the Panama Canal because of its scale and challenges.

All that is visible now to the casual viewer is a vertical scar running down the hill on the north side of the valley nine kilometres from Dawson City on the Klondike Highway. What you can’t see from the highway are the remains of the intricate network of ditches, flumes and pipelines that span 112 kilometres of Klondike landscape. What hasn’t been removed as salvage is slowly being overgrown by Mother Nature.

At the turn of the 20th century, the rich, easily worked placer deposits had been depleted, and miners were resorting to machinery to replace the costly use of hand labour. Consequently, the population of the region was declining.

Placer mining was slowly becoming the realm of the engineers and investors. Two big corporate mining interests became involved in the Klondike: the Rothschilds and the Guggenheims. Joe Boyle eventually wrestled the control of the Canadian Klondyke Mining Company from the Rothschilds. The Guggenheims maintained control of their interests under the name of the Yukon Gold Company.

These were highly capitalized, large scale mining companies, capable of making money on ground where it was no longer viable for the smaller miners. The big companies bought out the little guys and consolidated their holdings on Creeks like Bonanza and Eldorado where they could bring in more sophisticated and expensive machinery.

The Guggenheim project was very ambitious and to finance the initial work required millions of dollars. When the construction was complete, they had a fleet of dredges and the entire infrastructure to support their operations in the goldfields. The Yukon Ditch was central to all of this.

The construction of the Yukon Ditch was complicated by the isolation and the complexity of the local conditions. Their supply line was over 5,600 kilometres long and the equipment had to be ordered one to two years in advance of the actual work. Heaven protect the supplier who neglected to ship all of the necessary parts and equipment!

Once the supplies and equipment arrived at the dock in Dawson, it still had to be shipped out to the construction site. One eyewitness described what the roads were like:

“Everywhere the surface is wet and sloppy. Our horses splashed through it. We stumbled over the spongy mass. It is a dismal swamp, which becomes almost impassable when torn by traffic. Wherever a trail was worn by use, it became a quagmire and it was best to turn our horses to the untrodden moss alongside; in this their feet would sink to a depth of six or eight inches ... in places ... the thaw had reached deep enough to make progress impossible.”

It is easy to understand why all the heavy supplies were hauled to the construction site during the winter for the work undertaken the following summer.

The “Ditch” started high in the Tombstone Mountains where water from both the Tombstone and Twelvemile Rivers was diverted into a pipe and flume system. Where the two rivers met, some of the water from the “Ditch” was directed into a penstock where it powered three 686 kilowatt generators. The electricity was stepped up to 33,000 volts and sent through 85 kilometres of high tension lines to supply the fleet of dredges and other mining operations, with power.

The remainder of the water was carried through a system of carefully built ditches (61 kilometres), flumes (31 kilometres), and pipes made either of redwood staves, or heavy steel (20 kilometres). When it reached Gold Hill, above Grand Forks at the confluence of Eldorado and Bonanza Creeks, it was used for hydraulic mining.

A sawmill was constructed to cut 7 million board feet of lumber for the construction of the flumes. Six giant steam-powered shovels were imported to excavate the ditch through which the water was to run.

The most ambitious of the pipe sections was where the water was transported across the Klondike River valley. The lowest point in this inverted “U”, where the water was under pressure of 500 PSI (3450kPa), was 352 metres below the discharge end. With a drop of 61 metres between the intake (north side of Klondike Valley) side and the discharge (south) end, water flowed through the pipe powered by gravity.

There was a flaw in the riveting of the seam of this pipe, and when water was first introduced into it in the spring of 1909, the 2.2-centimetre-thick steel wall ruptured. The water pressure was so great that it mowed down trees up to 15 centimetres in diameter within a radius of 60 metres. When this problem was repaired, 680 cubic metres of water per minute could be delivered to hydraulic operations in the Bonanza Creek valley. The “Ditch” continued to operate until the fall of 1933.

The ditch construction was executed during three summers of construction (1906-1909). At its peak, it employed 1,800 men, with a monthly payroll of $300,000 ($7.5 million today). When it was complete, water and electricity were being distributed to Yukon Gold’s operations all over the goldfields.

The best surviving accessible fragment of the original construction can be found at Parks Canada’s industrial Complex at Bear Creek, where a three-span 90-metre bridge carried the 1.2-metre steel pipe across what was once the Klondike River (before dredging moved the river to the far side of the valley).

Recent work by Parks Canada has stabilized the structure of the bridge, which still supports a section of the steel pipe that once carried water across the Klondike Valley to supply the mining on Bonanza Creek.

Michael Gates is a local historian and sometimes adventurer based in Whitehorse. His book, History Hunting in the Yukon, is now available in good stores everywhere in the territory.