Willoughby: How to feel your way into the dark and avoid a costly detour
Legends & Legacies
Many of Aspen’s mines easily kept within their claim boundaries. Larger mines contended with the serious problem of not spreading onto a neighbor’s claim. On ranches a trespasser might be seen from a mile away. But those who worked underground could inadvertently, or intentionally, mine someone else’s ore.
Engineers and surveyors helped miners keep their place in the underground world. In 1881, Aspen comprised barely more than a tent town. However, the community supported seven surveyors: H. B. Bates, H.M. Saunders, George Lloyd, W.A. Illsley, C H. Demorest, H. Pfeiffer and John Brooks. At that time, tunnels and shafts reached only feet into the mountains, and most surveying involved laying out claim corners and lines.
Within a few years Aspen’s mine owners became embroiled in a famous lawsuit, one where existing mining law did not fit the type of mineral deposits mined. A debate arose over whether you could follow a vein underground into an adjoining claim, as long as the vein surfaced on your own claim. The battle lasted a few years. The dimensions of ore were mapped underground, but no one dug it out due to fear of eventual ownership challenges. To find out the position of the mineral veins, a three-dimensional challenge, required exact surveys.
Later, well-established mines encountered a new need for surveys that would allow them to connect separate underground workings. Several of Aspen’s longest tunnels tapped into mineral from a lower elevation, rather than follow the mineral zone from one location. Two tunnels may be driven to meet at a specific juncture. But if the direction of either tunnel was off by just a few feet, it would miss the target in a costly error.
Mining engineers usually had a degree in civil engineering, and managed surveys. The Colorado School of Mines required that its seniors work in the field, where they learned to locate claim corners and lines, and to survey underground. Surveyors would run a line, and then survey their way back to the starting point to verify their work. They would triangulate with known locations. You can’t triangulate underground, so an underground survey line is coordinated with a surface line. If you surveyed underground correctly, a surface location would be identified directly above the underground location. More importantly, the reverse was true — based on an above ground survey, you could determine a location underground.
The surface surveyors in Aspen encountered a particular difficulty: slopes, often very steep slopes. Underground surveyors ran into a similar problem when they surveyed a tunnel at one level, and then continued their work in a lower level tunnel not directly below the first one.
The Midnight Mine tunnel illustrates many difficulties for surveyors. The mine was planned to tap into the mineral zone, hundreds of feet below previous workings. The tunnel started a mile away from the mineral zone, to allow exploration for ore deposits that might be revealed along the fault zone. The fault did not run in a straight line, naturally, and the tunnel changed directions to follow fault splinters. Then it would head in the intended direction until it found another fault splinter. Fred D. Willoughby, my grandfather, engineered the tunnel and carried out the underground surveying.
As the tunnel approached the intended target, it had not intersected the mineral zone. Despite calculations, something seemed amiss. Perhaps the survey was wrong.
It turned out that the underground survey was correct. But the old surface survey, the one on which they had based their underground calculations, held a 200 foot survey error. Had they not double-checked the surface survey, they would have continued a stab in the dark.
Tim Willoughby’s family story parallels Aspen’s. He began sharing folklore while teaching Aspen Country Day School and Colorado Mountain College. Now a tourist in his native town, he views it with historical perspective. Reach him at email@example.com.
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