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Annual General Conference Assemblée générale annuelle

Edmonton, Alberta

June 6-9, 2012 / 6 au 9 juin 2012

Re-Creating the Yukon Ditch Near Dawson City, YukonKen Johnson AECOM

Abstract: The "Yukon Ditch" is an extraordinary example of the water supply technology that advanced the post gold rush era of mining in the Klondike region of the Yukon. Water was an essential element for the extraction of gold from the gold bearing soils of the valleys in the Klondike area. This need for water did not change from the use of gold pans and rocker boxes to the industrial era of gold dredges. In fact, the need for water increased dramatically with the industrial age of placer mining in the Yukon, along with the need for power to energize the industrial age machinery.

Valley slopes contained as much gold as the river bottoms, and the mining of these elevated benches was accomplished by washing the material using "hydraulic" mining, with nozzles delivering water in excess of 1030 kPa (150 psi). The pressure and volume of water to accomplish hydraulic mining was delivered to the Klondike River valley through a series of flumes, ditches and pipes, which transported water 110 kilometres from the mountain range to the north of Dawson City. This project became affectionately known as the Yukon Ditch.

The design, supply and construction technology applied to creation of the ditch used experience gained from the California gold rush 35 years before, with innovations associated with the extreme climate and geography. Very little remains of the Yukon Ditch today, but with the help century old photos, century old reports and design manuals, and topographic mapping, it has been possible to re-create the ditch and gain a new sense of the scale of this extraordinary project.

1. The Rush and the Consolidation of the Claims

George Carmack and two aboriginal companions, Skookum Jim and Dawson Charlie, made history on August 17, 1896, when they discovered gold on Bonanza Creek, a tributary of the Klondike River in the Yukon Territory. News of their discovery did not reach civilization until the following summer, but when it did it started the gold rush which spread across the continent.

Men and women sold their shops and belongings to buy passages at Vancouver, Victoria, or Seattle on one of the coastal ships going north. From there they carried their supplies for 60 kilometres on their backs, climbing either the rugged White Pass or the Chilkoot Pass to the head of Bennett Lake. Once at Bennett Lake they constructed makeshift boats and rafts for an 800 kilometre trip to Dawson City. Before the 1898 winter freezeup more than 7,000 watercraft, carrying 30,000 gold seekers, were registered with the North West Mounted Police on the Klondike River system.

The so called gold rush was short lived, and as much as it left a cultural legacy for the Yukon, it had limited influence on the long term gold mining of the Yukon. The reason for this is that the mining technology was crude and only effective for capturing the richest deposits of placer gold. More efficient technologies were needed to capture the deeper low grade deposits. In addition, the individual claim system (152 metres wide) itself was inefficient because the size of an individual claim would not support anything more than mining by hand. The third limiting factor

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was the availability of water, which was essential for the separation by washing of the heavy gold from the gravel and sand.

After the rush ended enterprising individuals began the process of removing the limitations. Machines, called gold dredges were brought in to undertake the large scale mining and the individual claims were consolidated to provide the working space for the dredges. The final missing piece to the puzzle was the water needed to wash the gold or hydraulic mine from the higher elevations in the valleys, and electrical power for the bigger dredging machines.

Figure 1: Hydraulic Mining in the California Goldfields

In 1906 the Yukon Gold Company was formed and, with the financial resources of the Guggenheims of New York, plans were made to harness water for dredging and power generation. The Klondike River was first considered for water supply, but the 100 plus metres of hydraulic head required for hydraulic mining would require the construction of a conveyance system more than 140 kilometres upstream from the goldfields at an estimated cost of $7 million (1906 dollars). This was due to the fact that the Klondike River had such a low gradient. The Chandindu River (12 Mile River) watershed from the Tombstone Mountains was considerably closer and had sufficient grade and flow for the hydraulic mining in the goldfields. "It was estimated that a water conduit to the mines near Dawson, with a capacity of 125 cubic feet per second, under a head varying from 850 to 350 feet, would be 70 miles long and would cost $3,000,000."

An integral part of this plan was also a hydro electric development to provide the power for the electrically run dredges to mine the Bonanza Creek claims. Dredges were large floating facilities that dug up the gold bearing gravels and separated the gold from the gravel by washing it through a large rotating screen and ultimately capturing the gravel in a series of riffles and mats. This was essentially the same process used for gold extraction by the individual miners, but at a much larger scale. The dredging process would leave a "worm like" mound of tailings, which may be referred to as "dredge pooh."

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Figure 2: Plan of Yukon Ditch Alignment from Tombstone River to Grand Forks

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After a great deal of lobbying in Ottawa and court battles in Dawson, the Yukon Gold Company consolidated sufficient claims and acquired the water rights for 5,000 “miners inches” (55,000 US gallons of water per minute or 210 cubic metres per minute) from the Tombstone and Little Twelve Mile Rivers north of the goldfields.

2. The Start of Construction

Ditch construction started in 1906 with an initial priority of constructing the water supply for a power plant at the confluence of the Little 12 Mile and Chandindu Rivers. A steam operated saw mill was built, and local spruce was milled for the construction of the flume to feed the power plant. A 9 kilometre flume system (900 mm by 1200 mm) was constructed from an intake up river on the Little 12 Mile to the penstock feeding the Little 12 Mile hydroelectric plant, which consisted of two Pelton wheels connected to two 650 kilowatt generators operating under 198 metres (650 feet) of head.

The initial construction also included roads and maintenance camps to accommodate a self sufficient operation. Easy access to the outside world from the construction zone was limited to the winter months because permafrost ground becomes a spongy mass in the summer and a quagmire almost impassable when torn by traffic. For practical purposes the construction operations were as self-sufficient as possible.

All the materials and supplies needed for construction had to arrive by sternwheeler from Whitehorse before the shipping season on the Yukon River closed - this generally happened in mid to late October. The freight was unloaded and stockpiled at the Chandindu River landing 35 kilometres north of Dawson City. With the onset of cold weather freighting roads were built by clearing the land, removing the snow and building up an ice driving surface for the heavy sleds used to haul the equipment. The supplies were hauled 50 kilometres upstream to the construction camps.

As soon as the surveying was complete, the 20 metre (66 foot) right-of-way was cleared. Thick brush, deep moss, and tangled spruce trees had to then be removed. Swamp and permafrost increased the difficulty of initially clearing the land.

3. Excavating the Ditch

Six steam shovels were purchased and mobilized from the United States to dig the ditch. The steam shovels were mounted on standard railway tracks that were moved manually as the shovel advanced. Over the course of a 24 hour day, the shovels could advance 90 metres of ditch (2.7 metres wide at the base) excavating 34 cubic metres on average. The largest of the shovels weighed 33,000 kilograms (36 tons) and was powered by a 34 kilowatt (45 horsepower) steam engine. The shovel crew consisted of the fireman, craneman, and the engineer, and a “roustabout” hauled wood and water for the shovel. In places that were too narrow for the steam shovels to work, horse drawn slipscrapers were used.

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Figure 3: Profile of Yukon Ditch Alignment from Tombstone River to Grand Forks

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Figure 4: Various Ditch Cross-sections used in Construction of the Yukon Ditch

Ditching was commonly used to move water in other areas of mining; however, the construction of the Yukon Ditch required new and diverse techniques. The ditch was the cheapest and most durable way to transport the water, but was dependent on the topography. The standard ditch was 2.7 metres wide at the base and 1 metre deep. The average slope of the ditch was 0.11 percent (six feet per mile) with a range of 0.08 percent (4 feet per mile) to 0.13 percent (7 feet per mile).

The ditch construction itself required innovations for construction in thaw sensitive permafrost soils prevalent around Dawson City. Excavation required two construction seasons to achieve a stable cross-section. The ditch was initially excavated during the first summer, and then left to establish a thaw equilibrium. The upper and lower embankments usually collapsed into the excavation, and the next season, the ditch was re-excavated into thaw stable ground. The material excavated in the second season was used to create the lower embankment of the ditch. Moss was then used to insulate the upper bank and minimize further thawing.

Depending upon the base material (sand, silt or bedrock) various construction techniques were used to create a stable, low permeability cross-section. The characteristic of the bedrock in the Dawson region is its fractured nature, which required lining with moss and mud (puddling) to create a low permeability cross-section. A road or path was built on the lower bank to provide an access route.

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Figure 5: Complete Excavated Ditch Section

4. Flume and Piped Sections of the Ditch

Flumes and pipelines were used extensively on the Yukon Ditch where ditch excavations were impossible because of steep terrain. The flume was built from local spruce and was 1.8 metres wide (six feet), 1.2 metres deep (four feet) and had an average slope of 0.27 percent (fourteen feet per mile). The flume was generally placed on timber and log trestles to provide a stable structure for the flume. Depending upon the base material, the trestles were either anchored with pins to the slope or placed on piles driven into the ground.

The northern section of the ditch up to about kilometre 50 was predominantly constructed using flumes and pipelines. Pipelines were used to cross valleys, and the pipelines were either wood stave pipe or iron pipe. Wood stave pipe was preferred because it was about one-third of the cost of iron pipe, this included the shipping of pipe, which could be collapsed into the individual 50 mm by 300 mm (2 inch by 6 inch) wood staves. However, the wood stave pipe was generally limited to pressures of less than 61 metres of head (200 feet or 85 psi). The wood stave pipe was fabricated from California redwood.

Figure 6: Completed Flume Section of Yukon Ditch

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The wood stave pipe was constructed on site from individual 50 mm by 300 mm (2 inch by 6 inch) tongue and groove pieces that were planed before shipment. There were thirty staves to the perimeter, encircled with half inch iron bands. The bands varied in the spacing on the wood stave pipe from 25 mm to 250 mm apart depending on the anticipated pressure in the pipe.

Figure 7: Construction of Wood (California Redwood) Stave Pipe Section of Yukon Ditch

Iron pipe imported from Pittsburg and Germany was utilized for areas that had a large vertical difference, as it could withstand greater water pressure; however, it was considerably more expensive to purchase and to mobilize.

Pressure boxes and spillways were built as the pipeline intake structures. The pressure box was a 3.0 metre cube constructed with board and batten, and it was connected to a flume entering the back or side of the box. A spillway with a gate system was also part of the intake structure, allowing the water level to be controlled before the water entered the pressure box.

Figure 8: Klondike River Pipeline and Bridge Crossing of Klondike River (2008 photo)

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The largest single undertaking in the construction of the Yukon Ditch was the Klondike River pipeline. This was an iron pipe that crossed the Klondike Valley at Bear Creek with an inlet elevation of 700 metres dropping to the valley bottom at 350 metres. The construction of the Klondike River pipeline employed over 300 men for two summer seasons. The pipeline itself was 5 kilometres long and consisted of lap welded iron pipe, which was constructed using air compressors and pneumatic riveters to withstand the 350 metres of head (1150 feet or 500 psi). A four span iron bridge carried the pipeline across the Klondike River.

The Yukon Ditch was completed and water was delivered to the area around Grand Forks on June 4, 1909. The conduit consisted of 62 km of ditch, 31 km of flume and 20 km miles of pipe.

5. Operation and Closure of the Ditch

Maintenance camps for the Yukon Ditch were built approximately every 8 to 20 kilometres. The ditch line was categorized into Divisions, usually each Division had a camp situated within its boundaries. These housed the crews who maintained and repaired the system. Maintenance camps in the flumed areas were larger because the flumes needed additional maintenance work associated with compensating for the foundation movement by leveling the flumes and repairing leaks in the flumes. Individuals known as “ditchwalkers” completed daily inspections for leaks.

Figure 9: Abandoned Hydraulic Monitor for Hydraulic Mining on Bonanza Creek (2008 photo)

The Yukon Ditch functioned with a full maintenance crew from May to October. The regular operations shut down for the winter months, but the freighting of supplies and materials began once the winter supply roads were constructed. The general winter decommissioning of the system involved draining pipes and flumes and shutting down the power plant.

Groundwater within the active layer of the soil was a significant seasonal problem. When the active layer began to freeze back in the fall, the groundwater would flow to the surface and accumulate by glaciation in the flumes. This would put pressure on the flume walls to a point that they would break. In order to protect the flume, it was filled with snow, then the groundwater would freeze on top of the snow diverting the flow over the flumes. Start-up crews headed out in the early spring to thaw the system, and complete other maintenance activities such as leveling the flumes, tightening the iron bands on the wood stave pipe, and repairing the foundation systems for the flume and pipe.

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The hydraulic mining operations of Bonanza Creek continued to show a profit until the end of the season in 1933. In 1933, a study was completed on the estimated cost of maintaining the Little Twelve Mile Power Plant as an alternative to the expanding the more accessible North Fork Power Plant (North Fork of Klondike River). The estimated cost of repairing the Yukon Ditch was $440,000, while the estimated cost for expanding the North Fork Power Plant was $530,000. However, because of the high cost of freighting materials and supplies, the difficulty of access, and the shorter operating season on the Little Twelve Mile, it was decided to expand the North Fork system.

As mining technology advanced, so did the manufacturing of larger and more efficient pumps. A comparison of operating seasons for the ditch, versus pumping recycling water at the mining sites suggested that the hydraulic mining season would be increased by at least thirty days by pumping. As well, the use of pumps would provide more dependable and mobile operating for hydraulic mining activity. Too expensive to maintain, and delivering approximately one-fifth of the water it used to supply, it was decided in 1933 to close the Yukon Ditch permanently.

Much of the Yukon Ditch remained intact over the decades following the closure, however, with time, the spruce board flumes have rotted, and the ditch excavation and right-of-way have grown over. The redwood sections of wood stave pipe would have remained intact, but these sections were salvaged in the 1960's leaving kilometres of iron bands. Much of the iron pipe has been salvaged as well, where it was easily accessible, with the exception of a small section of the Klondike River pipeline.

Figure 10: Iron Bands Remaining After Removal of Wood Stave Pipe (2011 photo)

References

Bowie, A.J. A Practical Treatise on Hydraulic Mining in California. Van Nostrand. 1885.

Hogan, B. The History of the Yukon Ditch. Unpublished Report, Dawson City Museum. 1993.

Johnson, Kenneth. Personal Photographs of Klondike Mining Operations. 2008 and 2011.

Rickard, T.A. The Yukon Ditch. The Mining and Scientific Press. January 16, 1909.