Editor's Note: Gary is finishing his second term as Administrator of the Mining Practice Specialty. He directed the Practice Specialty from its inception as a branch of the Construction Practice Specialty to its current status. Gary started his career at the age of 19 working at the Homestake Gold Mine in his home state of South Dakota. We are publishing the progress of one segment of the mining industry over the years along withs some of Gary experiences in metal mining. Please feel free to contact Gary email@example.com for more details or comments.
Introduction-The Homestake Gold Mine, one of the oldest and largest gold mines in the Western Hemisphere, closed operations on December 31, 2001 after 125 years of continuous operations. The mine is located in the Black Hills of South Dakota near Lead (pronounced Leed), South Dakota and became operational in 1876. "Homestake" means "enough gold to go home and retire." The Black Hills Gold Rush of 1876 followed the discovery of gold in French Creek near Custer, South Dakota in 1874. The mine consists of levels every 100 feet down to the 1100-foot level then 150 feet to the depth of 8000 feet. The temperature on the upper levels (above 1100 feet) remains a constant 54 degrees whereas the rock temperature on the 8000-foot level is 133 degrees. There are 250 to 275 miles of tunnel catacombs in this mountain of rock that was formed almost four billion years ago. Approximately 44.7 million ounces of gold have been produced in South Dakota since 1875. The Black Hills is one of the world's richest gold metallogenic provinces, having produced about 354 kg per sq km.
Moses and Fred Manuel discovered the Homestake claim on April 19, 1876. The Manuel brothers extracted $5000 worth of gold in 1876. George Hearst (father of William Randolph Hearst) purchased the Homestake claim and another claim from the Manuel brothers for $70,000.00 in 1877. In the beginning, 5200 tons of ore were crushed per month. About $4 to $5 of gold was recovered per ton of ore with the gold recovery rate being approximately 60-70 %.
History and Mining Methods-Mining methods changed dramatically over the past 125 years. In the beginning the open cut was mined. Later, hammer and steel were used to drill 4-foot holes to be blasted. A nine-pound hammer used by one miner became known as a single jack. Two nine-pound hammers used by two miners became known as a double jack. In the 1880's Homestake was the largest gold producing mine in the world. In 1890 compressed air drills were introduced at the mine. The underground workings created a need for timber to be used for ground support and created another industry in South Dakota.
By 1880, Homestake also had created its own railroad, the Black Hills & Fort Pierre, to ship wood to the mine for use as timbers. The Fremont, Elkhorn and Missouri Valley Railroad from Nebraska soon followed, allowing the partners to import heavy equipment and safely export bullion. In 1888 Homestake purchased its first electrical generator. By 1912 the first electrical power plant was built nearby in Spearfish Canyon.
In the late 1890's Charles Morrow had developed a cyanide treatment plant that increased the gold recovery rate to an unheard of 88%. The plant processed 3500 tons per 24-hour period. Later a slime plant was added and increased the gold recovery rate to 94%.
On March 8, 1900 a fire broke out on the 600-foot level in the underground mine. The fire burned for 66 days and could not be brought under control. Mining officials decided to flood the mine to extinguish the fire. For 40 days, over 80 million square feet of water water was flooded into the mine,. Eventually the fire was put out and mining resumed.
In 1909 Homestake locked out the miners in a "Right To Work" labor battle. In 1914 Homestake agreed to a 6-day workweek. At that time the miners were working 10-12 hours per day, seven days per week. In 1917 Homestake produced $6.6 million in gold revenues.
Around the same time surface slippage became a problem and a number of sinkholes opened up above the mine. The need for ground support timbers increased in the mine. In later years the mined-out areas were backfilled with sand that was left after the gold and silver was removed. This provided additional support for the mined-out caves underground. Keep in mind that on an average approximately 0.20 ounce of gold is recovered from one ton of ore.
In 1919 Lawrence Wright announced that there was approximately 17 years of gold mining ore remaining and the ore level was pinching out at the 2000-foot level. Later Bruce C. Yates and Donald McLaughlin decided to mine a development drift that became known as the Old Main Ledge. Another major change occurred with the development of an assay department. In 1925 the gold recovery rate was $3.67 per ton and increased to $9.01 per ton in 1933. Homestake continued operating through the 1929 stock market crash and the drought in the Midwest. In 1932-1933 Homestake began building a new treatment plant and in 1934 a state-of-the-art hoist was installed in the Ross Shaft. The shaft was over a mile deep and the hoist was the first and largest in the world.
In 1933 Homestake replaced the stamp batteries with modern grinders. 7,500 tons of ore was milled per 24 hours. Homestake installed two gyro crushers, one 8-inch and the other ½-inch. The rock was ground to a face-type powder and a cyanidation process that relied on gravity in its separation process. Gold bricks were poured and later transported to Salt Lake City, Utah. The final gold brick pour was in May 2002.
In 1934 the Federal Gold Reserve Act increased the price of gold from $20.67 to $35.00 per ounce. That price remained constant until 1975 when the federal government removed the restrictions and the price of gold jumped to $163.00 per ounce. The price of gold reached an all-time high in the early 1980's, selling for over $800.00 an ounce. The high price of gold prompted a new gold processing called "heap leeching." Companies purchased old mining grounds and mined the ore that previously was not cost effective to mine.
In 1941 Homestake abandoned work in the Open Cut. The mine continued operations after the start of World War II until 1943 when the Federal War Production Board closed over 500 mines including Homestake. Homestake was allowed an extension until June 8, 1943 to process the mined ore. The gold mine stood idle with pumps being manned until July 1, 1945. In December 1946, 745 miners resumed mining gold at Homestake. The mine peaked at approximately 3500 miners who were actively mining on 36 levels at the same time.
The jackleg machine was introduced to the miners. The miners were guaranteed their previous month's earnings to try a jackleg-drilling machine. After the first month, the miners were to receive a 12.5% cut in contract prices should they agree to use the jackleg. The jackleg-drilling machine increased the drilling production of the miners and the contract miners recovered and exceeded the 12.5% cut they received. Later jumbo drills replaced the jackleg-drilling machines.
Homestake reached the 4850-foot level in the 1940's, the 5900-foot in the 1950's, 6800-foot level in the 1960's, and the 8000-foot level in the 1970's. The Ross and Yates Shafts were used to access the working levels of the mine. The hoist drums were 25-feet in diameter. Over 5600 feet of cable was used in the multi-compartment shafts for the cages and ore skips. The hoists were some of the largest hoists in the world. The cages traveled at a rate of three times the speed of the fastest elevator. The cage would travel from the surface to the 4850-foot level in about two and a half minutes. There were two underground shafts, known as winzes.
In early years men hand shoveled ore into one-ton mine cars and pushed the cars to the dumps on narrow gauge tracks. Later, horses and mules were used to pull the ore cars. From the 1940's through the 1970's air and electric locomotives were used to pull the ore cars. During the same time air powered mucking machines replaced the hand shoveling. In the 1980's rubber-tired load, haul, and dump (LHD) equipment replaced the rail haulage equipment. In underground stopes where the rock might be unstable, the LHD's could be operated via a remote control option. Explosives used consisted of black powder, then dynamite, and later ammonium nitrate (ANFO or Prill). Detonators consisted of fuses, then electric blasting caps, and later primer cord.
Since the rock temperature on the 8000-foot level is 133 degrees, Homestake developed and installed a unique cooling system on the 6950-foot level at a cost of 3 million dollars. The system recycled 98% of the water and brought the temperature down to 85 degrees with about 75% humidity. The temperature underground remains pretty much constant and is not affected by the temperature on the surface. When its 30 degrees below zero outside, the temperature on the lower levels remains about 85 degrees. There was virtually no water encountered during mining, i.e., underground streams or lakes. There were a number of ventilation shafts that brought fresh air into the working areas and exhaust the air from the mine. Ventilation fans provided one-half million cubic feet of air per minute. On the 8000-foot level the rock pressure was about 1 million pounds per square inch. Rock bursts were a problem on the lower levels.
Diamond drill exploration facilitated the development and the mining plan in locating ore bodies that were assayed and therefore cut the developmental expenses that prior to that included mining exploratory drifts that many times did not locate ore bodies that could be mined in a cost effective manner. As of 2001 approximately 26,508 diamond drill holes were drilled. Diamond drills got their name from the diamonds that were set in the drill bits. Diamond drill holes were usually 200 to 2000 feet in length. A core was removed from the rock and that core was crushed into a powder and assayed to determine the amount of gold, if any, in the sample. A majority of the samples tested out to be part of what is known as the Allison formation, it was dry rock and contained no ore.
The mining plan included the following: (1) drilling test holes to determine the gold ore content and location, (2) drilling holes in the ore body, (3) blasting the ore body, (4) moving the rock from the stope to the surface, (5) crushing and extracting the gold, and (6) pumping the waste sand back underground to backfill the mined out areas. Mining took place on 36 levels at one time. There were basically two types of stopes. "Stope" is just the name given to an area where the ore is mined. Timber stopes were areas where ore was mined in 6 ft. by 6 ft. by 6 ft. sections and timber was immediately installed as the ore was removed to keep the rock from collapsing. Open cut and fill stopes were much larger and did not require the support timber. Ground control was accomplished with expansion and later resin bolts, wire mesh, and sheets of steel.
Narrow gauge railroads took ore to collection bins on each level of the mine. The ore passes were 6-feet by 8-feet holes cut by a borehole reamer machine. Hydraulic rock picks broke up the large rocks. The rock was loaded into 5-ton skip cars that were hoisted to the surface where the ore was processed through a series of crushers and eventually ground to a fine powder that entered a refined gold recovery process.
In 1974 women began working underground. Early myths had said that women were bad luck and should not be allowed to work or visit underground.
In 1978 Homestake built a state of the art wastewater treatment plant that broke down the cyanide treatment and discharged environmentally safe water into Whitewood Creek and trout streams. Prior to that time the cyanide discharge killed all vegetation and fish in Whitewood Creek. Homestake processed over 3.5 million gallons of water daily at its "one-of-a-kind" biological wastewater treatment plant.
In 1983 the Open Cut was reopened for mining. Benches 80-feet high and 60-feet wide were mined by drilling and blasting 20-foot holes. The ore was transported in 40-ton haulage trucks to a crusher. The crushed ore was transported via a two-mile long environmentally sound conveyor belt to the gold processing plant. Approximately 230 million tons of ore were mined and 800,000 ounces of gold recovered. Mining continued at the Open Cut until 1998.
Buffington's Experience-At the age of 19, I had no previous underground work experience when I started working at Homestake. I remember getting on the cage with 31 other miners and the cage dropped to the 3950-foot level in less than two minutes. I exited the cage, got into a mancar that was pulled by an electric locomotive and was taken to 56 crosscut west Main Ledge which was 5600 feet from the Ross Shaft. I was told to shovel sand into 1-1/2-ton mine cars. The first night I hand-shoveled 10 cars or 15 tons. I received no safety training other than being given a safety handbook that I was told to read on my own time, sign and turn in the last page. I was assigned to work alone. Note: Present day regulations require 40-hours of training and no one is allowed to work alone unless proper communications are established to maintain contact with the worker. About half way through the shift there was a huge explosion, the ground shook, and the air immediately filled with black smoke that was so thick that I couldn't breathe or see anything. The smoke dissipated in about twenty minutes and I could breathe and see again. I thought that the mine had caved in. I later found out from a shift boss who checked on me that timber stopes were allowed to blast at mid-shift, I was told that I could take a half-hour for lunch, then return to mucking the sand.
The only light I had was a cap light. When you turned the light out it was so dark you could not see your hand in front of your eyes. About an hour before quitting time my light went dead. I walked between the narrow gauge rails to the main line and waited for the motorman with the mancar to pick me up and transport me to the shaft to catch the cage and return to the surface.
When ore production was low I would assist the miners and they taught me how to operate a jack-leg drilling machine. The jack-leg drilling machines weighed approximately 185 pounds with a telescopic leg. The drill was air powered and the noise exposure was in excess of 110 decibels. Earplugs were provided. In later years mufflers were designed for the drills that brought the noise level down to about 95 decibels.
After my first year, I began contract mining. I was blasted on the first explosive round I loaded as a contract miner. I was loading a slab round (blasting the walls) that eventually produced 1000 tons of ore. Dupont and Atlas Explosives officials investigated the pre-detonation of an electric blasting cap and one stick of dynamite. Lucky for me the hole was on the outside and was not loaded with ANFO. I was standing to the side of the hole and my face and upper torso were sprayed by the rock that was similar to standing in front of a shotgun blast. My cap light was knocked out, I couldn't see and I felt blood running into my eyes and burning. Initially I thought I was blinded. It seemed like forever before my partner came over from about 50 feet away. I could barely make out his light as my eyes, face and upper body felt like they were on fire. My safety glasses were sandblasted by the rock and had I not been wearing the glasses I would have lost both eyes. Just prior to the blast I thought about taking my safety glasses off, I didn't take them off because I would have had to remove my gloves. It was extremely hot, about 90 degrees with 95% humidity. The nitro glycerin powder would cause extreme headaches when it came in contact with the skin through your nose or face when you would wipe the sweat away.
At the time Homestake had a safety program that contained disciplinary procedures of three strikes and you are out. If you were caught breaking any of the company safety rules three times you were removed from the mine. Regardless of the reason why I didn't take my safety glasses off, I was glad that I didn't.
Another example of the necessity of wearing safety glasses occurred when I was pulling chute, two rocks crashed together and a bullet-shaped rock fragment penetrated my safety glasses stopping just short of my eye. When I blinked I could feel the tip of the rock with my eyelid. I would have lost one eye and depending on the velocity of the rock fragment I could possibly have lost my life. Needless to say, I have continued to wear safety glasses religiously throughout my career.
After graduation from college I continued working at the Homestake mine mainly due to the excellent pay and benefits. I worked at the Ross Shaft, which was a mile deep, steel shaft, helping to maintain the shaft and I was responsible for rigging all loads that were lowered or hoisted to and from the mine during my shift. I drilled holes and installed rock bolts in the the walls of the shaft with fall exposures of several thousand feet up to a mile and no fall protection being provided. I would place two steel ladders across the shaft, one for me to walk on and the other to position a jack-leg drilling machine with the drill steel. Should the steel stick or break, it could cause you to lose your balance and fall into the hole. The jack-leg machine's water and air hoses could possibly save the machine but likely would not support the worker.
I look back at my time at Homestake with both fond and sad memories. There were a number of fatalities that occurred and in my opinion each one was preventable. The worst accident I can remember occurred when two supervisors and a miner were crushed by a 6000-ton rock that fell on them. When you walked around the rock, all you could see was one man's hand sticking out. It took several miners and me an entire shift to dig under the rock and recover the three crushed bodies. This particular stope should never have been mined as an open-cut stope; it should have been a timber stope, which it became after the triple fatalities. I talked with one of the miners the day before the accident and he described the loose ground. I told him that if I was he, I wouldn't work in there. He said that they were going to finish this lift and then go timber. The men were inspecting the stope when the rock caved in.
My experience at Homestake was one of the driving forces why I got into the safety profession. I lost several friends in the mining industry over the years. One of my contract partners was killed just two weeks prior to his retirement. His brother was killed in the mine several years earlier. I believed in pre-planning safety when I was a miner and over the years I have repeatedly reinforced and expanded that premise. Despite the fatalities at the Homestake mine, overall Homestake had one of the best safety records in the country when one considers the number of employees and the hours worked versus the injuries incurred. Homestake was the largest gold mine in the Western Hemisphere for many of the years it operated and was the largest mine in the world during some of the early years of operation. Keep in mind, Homestake had a safety department in 1916 and a written safety program with disciplinary procedures decades before federal mandate required it.
Many naysayers maintained that if you preplanned safety you would never finish the project and it was impossible to meet the budget and schedules desired. I strongly and vehemently disagree with that statement and that line of reasoning is totally unacceptable.
Closing-It is with great sadness that the Homestake mine closed down its operations that were a mainstay in the Lead-Deadwood communities for 125 years. Several generations worked in the mine and many of us thought as George Hearst once wrote "neither our generation nor the next generation will see the day that gold cannot be mined at a profit at this mine." My father-in-law worked at Homestake, I worked there, and my nephew was one of the last miners laid off before the closure. I have always had a tremendous amount of respect for the work ethic and integrity of the underground miners.
Next Month-I will discuss one of the promising proposals to turn the 8000-foot level of the Homestake Mine into a national laboratory.
Jensen, Debra and Wayne Paananen, "Homestake: The Legend and the Legacy", 2002.
Gary L. Buffington, CSP, CRSP, CSHM, is the owner of American Safety Consulting in Los Angeles. He is the Administrator of the Mining Practice Specialty and a recipient of the SPY Award from the Construction Practice Specialty. Buffington worked at the Homestake Mine for approximately seven years.