Dredge number 601

Dredge No. 601 is the world's largest river scoop dredge for gold mining , operated on the Maracan gold placer from 1969 to 1992.

Dredge number 601
Sailing area	Maracan River
Owner	Lenzoloto
Manufacturer	Irkutsk Heavy Engineering Plant
Launched	1969
Withdrawn from the fleet	1992
Main characteristics
Displacement	11,000 tons
Length	236 meters
Width	50 meters
Height	54 meters
Draft	3.8 meters
Performance	550 m³ / hour

In 1950, a deep-lying gold placer was explored on the Marakan River in the Bodaibo district of the Irkutsk Region ; the average depth of which is about 50 meters . In 1963, the State Commission for Reserves of the USSR approved the number of explored reserves in the deposit - 58 tons of gold . However, in the world there were no precedents for gold mining from the bottom of a river of such depth; dredges of the corresponding mining depth were not produced either. Only the American company , Cyrus-Erie , had the experience of building 45-meter drags with a bucket capacity of 510 liters . Negotiations on the acquisition of such dredge were unsuccessful - the deal was blocked by the government of the United States of America; such a unit was considered a strategic commodity banned for export to the USSR.

As a result, a unique unit that surpasses its American counterpart in its characteristics was designed and built by the Irkutsk Heavy Engineering Plant named after Kuybyshev . The lead designer of the project was Grigory Ilyich Sergeev, who had previously developed the project of a 250-liter dredge. Dredge mechanisms and components were manufactured and supplied by more than 50 enterprises from all over the Soviet Union ; only orders for the most critical components (dump truck, bucket chain) were placed at UK enterprises (subsequently, during repairs, they were also replaced by Soviet ones). For the installation of dredge, a tower crane with a lifting capacity of 50 tons was built. In 1968, the dredge was adopted by the state commission, and on September 30, 1969, it was put into operation.

The dredge with a displacement of 11 thousand tons was a full-fledged floating enrichment enterprise equipped with a complex of modern technological devices that ensure the entire process of extracting gold from gold-bearing sands . The unit is 236 meters long, 50 wide and 54 meters high; weighing 10 300 tons; equipped with 169 three-ton buckets of 600 liters each, made up to 22 scoops per minute and had a capacity of 550 cubic meters of ore per hour. The total capacity of 300 electric motors , which set in motion the technological mechanisms of the dredge, was 7300 kilowatts . All enrichment processes were mechanized and controlled from a central console.

A number of technical solutions were implemented on this dredge for the first time. The monorail , laid through the entire surface part, provided the lifting of any unit. For the first time in the history of drag construction, a self-trapping device was installed in the technological chain, capable of automatically sifting out native gold from waste rock. The diving station provided the opportunity to inspect and repair the pontoons under water.

The washing season usually lasted from March to November, and in the warm years it could also have taken December. Dredge could not reach full design capacity. The reason for this was both difficult geological conditions and the actual non-confirmation of previously approved reserves. The karst of the raft (that is, the bizarre relief of the main rock on which the placer lies, with the formation of “pockets”) caused the non-waste of gold. In 1976, reserves at the Marakanskoye field were revised and reduced to 26 tons. Nevertheless, the volume of precious metal mined during the season ranged from 500 to 1,500 kilograms. Over the entire period of operation, the unique unit mined about 20 tons of gold.

November 26, 1992 at an air temperature of minus 46 degrees, the main farm of the unit was raised. In order to prevent the icing of metal structures immediately starting, they were washed with hot water. A temperature drop of 120 degrees led to the sudden destruction of the main dredge farm. Fallen structures destroyed the pontoons into which water began to flow. At the same time, the electric power cable was interrupted, which caused the shutdown of the life support systems of the unit, including pumps pumping water from the pontoons. In less than two hours, the dredge sank to the bottom to a depth of about 40 meters. Fortunately, people managed to evacuate.

Subsequently, the dredge was able to get out of the water, putting it afloat. However, large investments were required to restore the unit, and the deep gold reserves in the deposit were almost exhausted, so the dredge was mothballed in a dilapidated state. In 2001, dredge No. 133 was launched at the same site with a bucket capacity of 400 liters, transferred from another washing site.

As of the mid-2010s, the upper part of the dredge, half-buried by rock dumps, is visible on the right bank of the Marakan River opposite the Maly Satalakh stream.