An inside look at carving a mountain

The highly complex steps in the mountain carving process at Crazy Horse can be summed up in relatively simple terms. We are making a very large duplicate of Korczak’s sculpture to tell the story of North American Indian cultures. That artwork depicts the Lakota warrior, Crazy Horse, seated on his horse and pointing over the horse’s head as he says, “My lands are where my dead lie buried.” In order to convey that powerful story on a monumental scale on the mountain we follow three basic steps: 1) measure Korczak’s model; 2) measure the mountain; 3) remove all the rock that doesn’t fit! In reality each of these steps gets quite complex and requires the use of powerful tools and techniques, but the guiding principles remain quite simple.

The members of the Crazy Horse mountain crew are experts in precision blasting, equipment operation and engineering. They maintain a strong emphasis on safety in all steps of the operation and are proud to have an outstanding safety record. Here’s a little closer look at each of the meticulously detailed steps this team carries out to carve the mountain:

1. Measure Korczak’s model

   Measuring systems have evolved steadily during the 60-year history of the mountain carving. Korczak relied on artistic estimates and his incredibly practiced eye and natural feel for dimensions and scale. After his death, his family and the mountain crew developed a mechanical pointing system to measure the 1/34th scale model of Crazy Horse’s face. After completion of the face, we designed and built another mechanical pointing system to measure the 1/300th scale model of the entire carving. More recently laser scanning methods have been used to measure the 1/34th scale model and just in the past year brand new technology has been used to measure the 1/300th scale model with a laser scanning arm. Monique Ziolkowski is currently working to build a 1/60th scale model that will combine the artistic elements of Korczak’s story with dimensions and geologic details from the mountain. Some combination of mechanical pointing systems and laser scanning technology will likely be used to measure this model when it is complete.

2. Measure the mountain

   Korczak used a combination of his artistic eye, tape measures and a beautiful old theodolite (survey instrument) to determine the basic location of his model within the mountain and begin the process of removing excess rock. A 60-foot long measuring boom was fixed to the top of Crazy Horse’s head in 1987 to direct the work on the face. A plumb bob suspended from that measuring boom was used to transfer numbers from the pointing system on the 1/34th model of Crazy Horse’s face.

   When work moved beyond the face in 1998, a survey control system was developed and a modern survey instrument was used to measure the entire mountain. This instrument, known as a total station, measures very precise angles and distances from known control points to calculate 3 dimensional coordinates for any point on the mountain. It uses an infrared beam reflected from a hand held prism to measure distances up to several thousand feet with accuracy to the nearest 1/1000th of a foot. Measurements from Korczak’s models are transferred to the mountain using this same instrument and survey control system.

   Laser scanning equipment has been used to measure the entire mountain on several occasions over the past 10 years. These instruments work on the same principle as the total station to measure angles and distances from known control points to points of interest on the rock. They use a laser beam reflected from the rock to measure the distances without need of a prism at each point. This allows for measuring huge numbers of points very quickly and accurately to build ‘digital models’ of the mountain in our engineering computers.

   The next step in measuring on the mountain will be to apply the best possible methods to measure the geologic structure of the mountain in addition to the basic geometry of the mountain. This information becomes critical in refining the shape of the models and in planning for long term stability of the memorial.

3. Remove all the rock that doesn’t fit

   Rock is removed from the mountain primarily with explosives. Again this complex process can be summed up in basic steps: Drill precisely placed holes in the granite; load explosives in the holes; time the detonation sequence of those explosives; push the blasted rock (known as ‘muck’ in the mining industry) off the mountain with heavy equipment and finally remove the last layer of rock in the finishing stage. All blasts at Crazy Horse are designed, drilled and executed to protect the rock that is left after the blast. This is the opposite of most blasting operations, where the main concern is the final size and location of the material being blasted away. The mountain crew prepares most blasts using a system that explosives engineers call “pre-splitting.” It is similar to perforating a piece of paper to allow it to tear evenly. The rock to be removed is drilled on all sides with a series of parallel drill holes. Explosives are detonated throughout the entire length of each of the drill holes, cleanly removing the desired rock while leaving the remaining rock undamaged. Here’s a more detailed look at each of the steps in the rock removal process:

   • Drilling

     Equipment has evolved from Korczak’s use of a single-jack (sledge hammer and hand steel) to drill the holes for the first blast on the mountain. Korczak quickly advanced to pneumatic jack hammer drills powered by ‘Buda’, the ancient air compressor which quit frequently during the work day and forced him to make many trips down and back up the 741 steps to the top of the mountain. He then progressed to wagon drills, a larger drifter drill mounted on a D8 Cat and finally air track drills. These machines required less manual labor but still relied on gas or diesel powered air compressors to drive the hammer. The mountain crew did much of the drilling for Crazy Horse’s face using hand held rotary hammer drills powered by more modern, efficient electric air compressors. We still drill 1 3/8 inch or 1 5/8 inch holes up to 21 feet deep using these hand drills on rare occasions when the track drills cannot be maneuvered to the drilling site. Hydraulic drills are now the standard and our fleet includes three of these very efficient machines mounted on tracks or rubber tires. Most of our holes are drilled about 20 feet deep using 2 inch diameter carbide steel bits. Our largest machines approach drilling rates up to 10 feet per minute! The next generation of these drills will be faster and more efficient and will have enclosed cabs to better protect the mountain crew from the noise and dust generated in the drilling process.

   • Explosives loading

     When most people think of explosives, they imagine dynamite. The primary types of explosives used here at Crazy Horse, however, are not dynamites but detonating cord and small diameter water gel or emulsion based pre-split products. Dynamite is very effective at fragmenting rock, but expends all of its energy in an area equal to the length of the cartridge – a very small portion of the drill hole. Our blasts using detonating cord and pre-split products can be designed to expend the same amount of energy over the entire length of the drill holes. This provides much better control of the explosive energy and does much less damage to the rock that is not removed by the blast. In a typical blast at Crazy Horse up to several hundred drill holes are loaded with the appropriate size of detonating cord or pre-split explosives. After the product is in place the holes are filled with small crushed stone. The stone fills the open space in the hole and better focuses the explosive energy to precisely split the rock.

   • Blast timing

     The typical blast is actually a carefully timed series of smaller blasts spaced only a few milliseconds apart. The vibration and damage caused by the blast can be controlled by limiting the amount of explosive detonated in each section of the blast. The distance to what will be the finished surface of the mountain carving (“final grade”) dictates the distance between drill holes and the type and amount of explosive used in each hole. The closer to final grade, the smaller the drill hole spacing and the smaller the explosives charge weight in each hole. Timing between the blast sections is controlled by the blasting caps (detonators). This is another area where advancing technology is making a big difference in our mountain carving operation. Electric blasting caps which are susceptible to premature detonation caused by static or nearby lightning strikes or radio transmissions are no longer used. Our most common method uses non-electric delay detonators fired by sending a spark through long plastic tube or with a highly secure 2-way radio controlled remote initiation system. We have also used the latest technology – a system of electronically controlled, programmable detonators which allow nearly infinite choices in blast timing. We expect systems like this to play a key role in controlling blasts as we work closer to finished grade in the future.

   • Mucking

     Removing the blasted rock or muck from the mountain is accomplished with heavy equipment. Here again there has been a steady improvement in the type, size and efficiency of the equipment used over the past 60 years. A typical blast today produces 2000 to 3000 tons of rock fragments. These rocks range in size from small gravel up to the occasional 10 ton boulder and most remain on the blasting bench rather than falling off the mountain from the force of the blast. The mountain crew spends 2 or 3 days with a combination of excavators and bulldozers to move this rock off the mountain and clear the way for the drills to prepare the next blast. To lend some perspective to the quantity of rock being handled – the average dump truck on the highway is hauling about 15 tons of material. It would take 200 truck loads to haul away the rock from just one large blast on the mountain!

   • Finishing

     When the crew returns to finishing work it will be accomplished as it was on Crazy Horse’s face by drilling to isolate small blocks of rock (100 to 1,000 pound chunks). These blocks may be blasted off using very light explosives. In very detailed areas of the carving, drill holes are located so close together that they almost contact each other and mechanical wedges are used as an alternative to explosives. A jet torch is used to finish the surface of the mountain carving. The jet removes drill marks and smoothes the final surface. The torch runs on diesel fuel and compressed air. The 3,300 degree (F) jet flame causes tiny fragments of rock to flake off as the result of heat expansion, leaving a polished surface. The variety of minerals in the pegmatite granite makes torching a challenge because each mineral reacts differently to the heat. The final step in finishing is to seal the natural seams in the granite so that water cannot infiltrate and cause damage during freeze/thaw cycles.

Crazy Horse Memorial has received many generous gifts of equipment, explosives and technical services over the years. In the past few years, for example, donations and significant discounts have been received from the following companies:

The primary source of funding for the work of carving Crazy Horse comes from visitor admission fees. Generous contributions from corporations provide critical additional resources to make continued work on the mountain carving possible.