Dredge No. 4

4 (Hän: Lëzrą Kä̀nëchà "s/he is looking for money") is a wooden-hulled bucketline sluice dredge that mined placer gold on the Yukon River from 1913 until 1959.

It is now located along Bonanza Creek Road 13 kilometres (8.1 mi) south of the Klondike Highway[1] near Dawson City, Yukon, where it is preserved as one of the National Historic Sites of Canada.

About 1.5 kilometres (0.93 mi) south of the dredge's current site, further into the Klondike Valley, is the Discovery Claim[3] where gold was found in August 1896 by prospector George Carmack, his Tagish wife Kate, her brother Skookum Jim, and their nephew Dawson Charlie.

[6] The Canadian Klondyke Mining Company built the Twelve Mile ditch in 1909, which would supply the water to operate hydraulic monitors on dredges.

[6] It also built dams and ditches to generate hydroelectricity, and by 1911 the 7,500-kilowatt (10,100 hp) North Fork Hydro Power Plant was operational about 50 kilometres (31 mi) from the dredges it energized.

[7][6][8] Designed by the Marion Steam Shovel Company, the bucketline sluice dredge[9] was built on site at Claim 112 Below Discovery from mid 1912 until the onset of winter.

[12] A contract for the parts dated 13 March 1912 specified their shipment to the site in the summer of 1912, at a cost of $134,800 for each dredge, and the hull was built by the Canadian Klondike Mining Company.

[7] With its installed hydraulic monitors, the eight-storey dredge would cut into gravel banks, washing down the released material for processing.

[14] A pipe was suspended within the trommel, carrying water upwards to spray the incoming material, cleaning it and breaking up larger lumps.

[15] Finer material (gold, sand, and pebbles) was sieved through 0.75-inch (1.9 cm) holes in the screen, which rotated at 7.8 revolutions per minute, into a distributor box.

[15] The larger pieces of gravel were ejected from a 32-inch (81 cm) wide stacker at its rear, a 131-foot (40 m) belt moving at 356 feet per minute (1.81 m/s).

[7] In its 46 years of operations, the machine mined nine tons of gold, dredging 22 buckets of gravel every minute,[2] about 18,000 cubic yards (14,000 m3) per day.

[18] The lowest-ranking group was known as the "bull gang", three to five members who were responsible for the machine's cables, the incoming power lines, and the "deadmen".

In 2012, Parks Canada reduced its budget, eliminating 600 jobs and stating that historic sites with low visitation would be accessible only on self-guided tours instead of being led by a guide.

Canadian No. 4 in 1916
The electric motor was maintained by the "oiler"
A sign at the National Historic Site depicting the parts of the dredge.