Friday, June 15, 2012

Gold Dredge No. 8: A giant that helped save Fairbanks

The Fairbanks Exploration Co.’s Gold Dredge No. 8 at Fox (shown in the drawing) is perhaps the most visible and well-known dredge in the Fairbanks area, but the FE Co. actually operated eight of these giants near town. No. 3 can be seen at Chatanika.

Four others are tucked away from sight: No. 2 on Fairbanks Creek, No. 5 at Dome Creek, No. 6 on Sheep Creek and No. 10 at Cripple Creek. Dredge No. 4 (operated on Pedro Creek) was dismantled in 1959 and moved to Chicken, and No. 7 (at Fish Creek) was demolished when Fort Knox gold mine was developed.

The Fairbanks dredges were not the first ones in the North. Dredges were operating in the Canadian Klondike by 1900 — eventually about two dozen worked there. On the far western  side of Alaska, ancient tundra-covered beaches containing rich gold deposits were discovered in the Nome area in 1905, and by the mid-1910s there were at least a dozen dredges in that area. All told, there were about 50 dredges scattered across the territory before World War II.

These gold dredges were immense structures, and their use predicated the availability of relatively inexpensive and reliable means of freighting heavy equipment into the country. The Klondike dredges came by ocean to Skagway, were shipped via the White Pass and Yukon Railroad to Whitehorse, and then transferred to steamboats for the final leg to Dawson City. Dredges on the Seward Peninsula were shipped the entire way via ocean-going vessels. With the opening of the Alaska Railroad in 1923 large gold dredges finally arrived in Fairbanks.

Dredges are essentially floating gold processing plants. Most in Alaska were “bucket-line” dredges that used a continuous line of heavy steel buckets (the digging ladder) to scoop goldbearing gravel from the bottom of a man-made pond.

The gravel was dumped onto screens and washed — the heavy gold being separated and the waste rock (tailings) dumped into tailing piles out the back of the dredge. These dredges could economically work ground with extremely low gold concentrations and recovered about 96 percent.

The Oakland Museum of California (gold dredging was a huge industry in California) reports that on average it took 250 giant dredge buckets filled with gravel to produce one ounce of gold!

Gold Dredge No. 8 is a five-story, 1,065-ton structure. The bow gantry is 43 feet tall and supports a belt-driven bucket line containing 68 steel buckets. Each bucket holds six cubic-feet and weighs 1,583 pounds.

The bucket line could tear gravel from 35-feet below water level. As impressive as that sounds, No. 8 was one of the smaller dredges in the FE Co.’s fleet. The largest dredges in Fairbanks sported 10 cubic-foot buckets and could reach down 60-feet.

No. 8 was constructed in 1928 and operated until 1959. During that time it traveled 4.5 miles and recovered 7.5 million ounces of gold. It was listed as a National Historic Site in 1984 and as a National Historical Mechanical Engineering Landmark in 1986.

No comments:

Post a Comment