Mine Timbers
Some mine workings on the Butte Hill passed through stable rock, and some passed through unstable ground that needed to be supported by mine timbers. Shafts also needed to be timbered to support the guides for the cages and skips used for hoisting men and ore.
The greatest need for mine timbers was in the stopes, the large underground voids created as miners removed the ore from a vein. Miners stood on timber structures in a stope as they worked upward along the vein, and then the structure of mine timbers served to stabilize the walls of the stope until it could be backfilled with waste rock from elsewhere in the mine. All of these uses for mine timbers created a huge demand for trees to cut, which Anaconda Copper Mining (ACM) and other companies met initially by logging all the suitable timber in the Butte area and then by acquiring timber and timberlands elsewhere in Montana. In 1907 ACM acquired forested sections of land from the Northern Pacific Railway that NP had originally received from the U.S. government to capitalize construction of its transcontinental railroad.
Every mineyard in Butte once had its own framing shop for making mine timbers. The Butte mines used what were called square-set timbers, which were logs sawn to make them square instead of round, and then sawn at the ends so that the tops of posts and the ends of horizontal members would fit together snugly and stay together under pressure, without needing to be nailed. Beginning in the 1880s, the Gagnon mine began to let the timbers remain round, milling only the ends where the timbers fit together. This practice spread to the other mines so that in the early 1900s, virtually all Anaconda mines used round timbers. After the turn of the twentieth century, W. A. Clark and ACM both established centralized timber-framing mills, Clark’s at the West Steward mine and ACM’s at Rocker, three miles west of Butte. ACM’s Rocker mill, built in 1902, was designed specifically to cut round timbers rather than squared timbers. Although the centralized mills made timbers of standardized size for mines on the Butte Hill, each mine still needed the capacity to make non-standard timbers for its own workings.
In the early years, untreated mine timbers were placed underground to shore up unstable ground, but hot, humid conditions led to their rapid deterioration. At the turn of the twentieth century, the conservation movement began advocating for the preservation of timber in many applications to reduce demand for cutting the nation’s forest resources. The U.S. Forest Service became one of the leading advocates of conservation, both through improved forestry practices and by encouraging the producers of railroad ties and mine timbers to treat the wood with preservatives (creosote, made from coal tar and shipped to the nearby community of Rocker by rail) to relieve the pressure on the nation’s forests to cut more trees. The Forest Service and ACM cooperated in expanding the Rocker mill to function as a timber-treating plant. The Forest Service helped design the plant so it could disseminate technical information about the process to other potential adopters of wood preservation, and ACM participated in the project so it could save money on mine timbers.
The only timber-framing shop left in Butte is at the Anselmo mine. It stands just west of the headframe, housing a cut-off saw like that shown in the photo below of the framing shop at the West Steward mine. Operating west of the core mining area on the Butte Hill, the Anselmo Mining Company had been independent until ACM acquired it and took control of its operations in the late 1920s. Meanwhile the Anselmo had its own timber treating plant just northeast of the mineyard, which stood until the early stages of the Superfund remediation on the Butte Hill.
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