Remnants of South Dakota’s historic gold rush litter the gulches of the Black Hills. Telltale timber frames mark hillsides where gold ore once jutted through the rock. Steel headframes straddle shafts that extend deep into the earth. Most have been back filled, fenced off and marked with "no trespassing" signs to prevent hikers from exploring them.
Two shafts, however, have withstood the test of time, gaining iconic status in the region. These shafts reached more than a mile deep, cutting through the largest ore body ever discovered in the Black Hills. The Ross and Yates Shafts were built in the 1930s and served as powerhouses for Homestake Mining Company for years. When asked what is most remarkable about these shafts, the experts unanimously agree — the engineering and craftsmanship that allow these shafts to be used to this day by Sanford Underground Research Facility (Sanford Lab).
“Most mining shafts have a lifespan of about 50 years. It is because of the workmanship and ongoing maintenance that we are operational today,” said Syd DeVries at a recent Deep Talks presentation about the shafts. DeVries is the senior principal engineer for building and site infrastructure working on the Fermilab-managed Long-Baseline Neutrino Facility at Sanford Lab.
This year, we celebrate 80 and 85 years of the Yates and Ross Shafts, respectively.
Powerhouses and pathways
The towering headframe structures above the Yates and Ross Shafts are perhaps the most recognizable landmarks left from mining operations in the Black Hills. These steel structures are covered with corrugated iron and rise more than 150 feet above ground. Their height, however, is diminutive compared to the depth of the shafts below.
The shafts are vertical openings from the surface that allow access to underground levels. The Yates reaches just below the 4850 Level and the Ross reaches the 5000 Level. Each shaft had multiple compartments for the lowering and hoisting of men, materials, supplies and ore; pipelines that carried water and compressed air for drilling, hoisting, scraping and locomotion; and electric-power cables and communication lines.
The real power to these systems rests in the hoistrooms, the unassuming brick buildings sitting just a few hundred feet from the base of the headframes. Here, the hoisting system, comprised of thousands of feet of steel rope, massive drums and powerful AC/DC motor-generator sets, is controlled by a hoist operator.
“The shafts cannot be separated from the hoisting systems in my mind. They are feats of engineering accomplished in ways that we can’t even imagine today,” said Allan Stratman, director of engineering at Sanford Lab.
Also built in the 1930s, four of the original Nordberg hoists are still in use today in the Yates and Ross hoistrooms. Sanford Lab is the only facility in the world operating hoists with this specific design, which was patented by a former Homestake employee.
“The American ingenuity in those days was amazing, and they built sturdy stuff. This hoist system is a testament to this,” said Greg Crotty, a Yates Hoist operator.
Raising the shafts and hoisting ore
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In November 1932, Homestake officials decided to construct a new shaft designed to meet production requirements for Homestake, when the Ellison, which had been the main production shaft, began to suffer from subsidence. The new shaft was named for Homestake Superintendent Alec J. M. Ross. It was close to the south-plunging ore body, providing access to an additional 6.5 million tons of ore in an area known as 9 Ledge. The ore averaged 0.269 ounces of gold per ton, with the average price for an ounce of gold at $20.67 by 1938.
Conventional shaft-sinking methods were employed to sink the Ross Shaft 137 feet to the tramway level. But rather than digging down for the entire length of the shaft, the construction crew used access drifts from the Ellison Shaft to “raise” the Ross Shaft.
“If you have a pre-existing shaft that allows you access from below, it is advantageous to raise a shaft because you are letting gravity move the rock rather than having to clam it (lift) and skip it,” said David Vardiman, geotechnical project engineer. “It’s labor-intensive to hoist the rock from the hole.”
According to Steven Mitchell, author of “Nuggets to Neutrinos: The Homestake Story,” access drifts were driven from the Ellison Shaft to the downward projection of the Ross on the 300, 800, 1400, 1700, 2000, 2750, 2900 and 3050 Levels. An interconnecting pilot raise was driven upward from each of these levels, with the uppermost raise reaching the tramway level in 1933. The first ore was hoisted at the Ross Shaft on November 19, 1934, just two years after construction began.
In May 1938, Homestake approved the construction of another shaft to replace the then-crumbling Ellison Shaft. Named for Bruce C. Yates, the general manager of Homestake Mine from 1918 to 1936, the shaft was built with the same “raising” technique as the Ross had been.
Access drifts were driven from the Ross to the location for the Yates on the 800, 1100, 1,700, 2300, 3050, 3650 and 4100 Levels. One marked difference between the shafts was the support structure. While the Ross was lined with steel beams, the Yates Shaft was lined with timber, due to scarcity of steel leading up to the second World War. The first ore was hoisted through the Yates Shaft on Oct. 1, 1941.
For nearly 70 years, the Ross and Yates Shafts served as the main conduits for thousands of miners and millions of tons of ore. In 1956, the Ross Shaft was deepened to the 5000 Level. That same year, the Yates Shaft reached the 4850 Level. Through 2001, the mine produced 39,800,000 troy ounces (43,700,000 oz; 1,240,000 kg) of gold and 9,000,000 troy ounces (9,870,000 oz; 280,000 kg) of silver.
Transition and future
When the mine closed in 2002, water levels rose to the 4550 Level, leaving portions of the shafts under water. Although the shafts had been expertly designed and crafted, debris, water and time took their toll on the structures. When the facility reopened as an underground research laboratory in 2008, the structures needed to be rehabilitated to meet the needs of science.
Beginning in November 2008, the Yates Shaft underwent a full examination to determine its structural soundness. Just 18 months later, it was pronounced fit for duty. A new cage, specifically designed for science purposes, was installed and a tower constructed to support the rope dogs—a safety system designed to stop the cage in an emergency. Since then, ongoing top-down maintenance ensures the shaft remains safe and sound. On May 19, 2012, the Yates Shaft began full operations, opening the door to science research and providing the infrastructure for continued expansion to a world-class underground laboratory at Sanford Lab.
“It’s a feat of engineering, to be sure,” said Martin Brosnahan, who maintains facility infrastructure at Sanford Lab. “It’s astounding how Homestake engineers in the 1930s were able to create such a reliable, durable system that we still operate today.”
For the past seven years, the Ross Shaft rehabilitation project has prepared the shaft for its role in the construction of the Long-Baseline Neutrino Facility, which will house the Deep Underground Neutrino Experiment (DUNE) hosted by the Fermi National Accelerator Laboratory. When complete, the project will be the largest experiment ever built in the United States to study the properties of mysterious particles called neutrinos. Before scientists begin installing the DUNE detectors, the Ross Shaft refurbishment needs to be completed to the 5000-foot level and a rock conveyor system installed to excavate the caverns that will house DUNE.
For more details about the Ross Rehabilitation project, see DeVries' recent Deep Talks presentation.
Information for the story was taken from Steven Mitchell’s “Nuggets to Neutrinos: The Homestake Story”; previous Sanford Lab publications; and Sharp Bits magazine (editions October 1953 and October 1954). Special thanks to the Homestake Adams Research and Cultural Center.