Historic Structures

History Shoshone Hydroelectric Plant Complex, Glenwood Canyon Colorado

In June, 1903, the Colorado Power and Irrigation Company was organized "to furnish electrical power to the various towns in the western part of the state..." A new hydroelectric plant was to be constructed at Shoshone Falls in the canyon of the Grand River (later called Glenwood Canyon). Glenwood Springs, located eight miles west of Shoshone Falls, had built its own small hydro plant in the summer of 1886, but the canyon project was on an entirely different scale and would provide power for a much larger market.

Colorado Power and Irrigation never got its Shoshone Falls project off the drawing board, but the idea and location passed on to the Central Colorado Power Company which incorporated in November, 1906. Central Colorado Power began construction before the end of 1906 and completed most of the work in 2 1/2 years.

Development of the Shoshone complex involved four major construction projects: the main hydro plant itself, a water diversion tunnel, a diversion dam, and a power transmission line. In addition, a small 1000 horsepower generating plant was built on the north side of the river just below Shoshone Falls to provide limited electrical power during construction of the main plant. This first plant was removed after the Shoshone complex was completed.

The Shoshone Hydro Plant complex was designed to take advantage of the drop in elevation through the central part of Glenwood Canyon. Water was to be diverted from the river just above Shoshone Falls and delivered to the plant through a long tunnel drilled in the north canyon wall. Original company plans called for construction of a 12.9-mile tunnel and pipeline extending from just east of the falls to a storage reservoir 4.8 miles west of Glenwood Springs. Economic problems forced Colorado Power to reduce the scale of their project considerably and settle on a "temporary" location for the plant within the canyon.

Construction on the diversion tunnel began in January, 1907, and required two full years to complete. To facilitate this labor, eight adits were driven into the canyon wall to allow work to proceed from both ends and at eight intermediate points along the way. (A ninth adit was driven in 1915.) When completed, the tunnel was approximately 12,450 feet long and averaged 13 feet in height by 16'8" in width. The floor and sides were lined with concrete to reduce friction and turbulence, and in places where the rock was weak or fractured a concrete arch was built as well. The tunnel was constructed with a very low hydraulic grade and had an original capacity of 1250 cubic feet per second. In 1929 the capacity was increased to 1408 cubic feet per second by forcing air into the tunnel through Adit #2. Air pressure reduced wave motion in the tunnel, further reducing friction and turbulence.

Construction of the 245-foot wide Shoshone Intake Diversion Dam began during 1907 and was completed in the spring of 1910. The original dam was a complex "bear trap" structure designed to release excess water near the river bed level through a series of large V-shaped wooden gates. These gates, or "bear traps", formed the central part o£ the dam and were supposed to lift up through the combined effect of water pressure and an overhead hoist system. When the traps were elevated, the dam was closed; when lowered, water was allowed to pass through.

Apparently this bear trap system was never effective, and required modification almost immediately. The first modifications occurred as early as 1911 and have continued to the very recent past. The bear traps were finally removed beginning in 1930 and replaced with far more efficient radial arm taintor gates. The present dam has four taintor gates and two heavy wooden flash board gates made up of removable sections. The flash boards are removed by use of an overhead hoist and appear to be original features of the dam.

In spite of these river control modifications, the dam continues to serve its original purpose of deflecting water from the Colorado River into the diversion tunnel. Most hydroelectric plants in this country rely on a stored capacity of water such as a reservoir or natural lake as a source of power rather than on the normal flow of a river. At Shoshone, the river backs up behind the dam, creating a holding pond which eliminates daily fluctuations in water capacity used for hydroelectric power generation. This does not eliminate seasonal variations in power.

Construction of the power plant itself appears from early photographs to have been completed in early 1909. The original plant was a simple 138x32 foot steel framed structure which housed two 9,000 horsepower Francis turbines and two 5,000 kilowatt alternating current generators. Water was directed from the end of the diversion tunnel to the turbines through two 9-foot diameter steel pressure pipes, or penstocks. The original penstocks are still in place and measure 287 feet in length. The static head or drop in elevation from the tunnel to the generators is 165 feet.

Operations at the new plant began in late spring 1909, though some uncertainty exists over the exact date. In 1910, the first full year of production, the Shoshone plant generated 38,096,600 kilowatt hours of electricity, far below its projected power rating of 90,000,000 kilowatt hours. Several modifications have increased the plant's output to about 104,000,000 kilowatt hours per year.

To carry its generated electricity across the state, Colorado Central Power erected a 153-mile transmission line from the Shoshone plant to Denver by way of Leadville, Georgetown and Idaho Springs. A second line ran to Glenwood Springs. About 37 miles of the Denver line were completed east of Leadville in 1907, and the entire line to Denver was finished by late 1908 or early 1909. After rising more than 1500 feet from the canyon floor, the line crossed some of Colorado's most rugged terrain, including Hagerman Pass (12,055 feet), Fremont Pass (11,346 feet) and Argentine Pass (13,532 feet). When it was completed, the Shoshone line was the highest transmission line in the world. Today the alignment remains essentially the same as the original, but the transmission towers have been replaced, and the entire network has been significantly altered.

During the nearly 2 1/2 years of peak construction activities, Central Colorado Power employed between 1000 and 1500 men. Most of these employees were housed at a large camp in the canyon built just east of the dam site. The camp was called Shoshone. Shoshone was originally a railroad siding and small construction camp on the south side of the river built by the Denver and Rio Grande Railroad during the late 1880s. Central Colorado Power erected buildings on both sides of the river with the vast majority of structures on the north bank. The power company provided housing, meals, medical care, a post office, apartment units for married workers, and even a school for employees' children. A large receiving warehouse was built on the south side of the river near the railroad depot, and the Colorado Provision Company, a subsidiary of Central Colorado Power, built a large company store on the north shore among the bunk houses. A two-span through truss bridge crossed the river at the east end of the camp to provide easy access back and forth. Like many other construction boom camps, Shoshone quickly faded when the work was done. Today, nearly all traces of the camp have disappeared.

While construction activities were under way in the canyon, and for several years after the plant began operations, the only road through Glenwood Canyon was the primitive Taylor State Road constructed on the north side of the river between 1899 and 1902. It was narrow and rough and was closed to all traffic through most of the winter and during periods of high water in the spring. The condition of this road forced Central Colorado Power to bring in most of their equipment, food and supplies by railroad and transport it across to the north shore on an overhead cable. One cableway with a 558-foot span was erected beside the power plant, and a second cableway with a 351-foot span was erected above the dam.

When construction activities ended. Central Colorado Power built housing at the hydro plant and dam site for workers who operated the complex year round. From the beginning, a large bunk house and an apartment house were in use at the plant, and a small house and garage were built for the chief operator at the dam. Sometime around 1920 two small houses were built along the river just east of the plant for the Shoshone Hydroelectric Plant superintendent and his chief operator.

Changes at the hydro plant have occurred continuously through the years but have not substantially altered the general appearance, setting or historical importance of the plant. Almost immediately after operations began in 1909, a machine shop was constructed onto the east end of the plant. A lean-to shaped washroom (now a washroom and lunchroom) was added onto the east side of the machine shop in 1935, and several support buildings were built and moved around the outside of the plant in the early years. Sometime before 1920 the roofline of the main plant was modified to provide a row of ventilation louvers, and two small horse barns fell victim to the automobile age and were torn down. In the late 1930s, when the Glenwood Canyon highway was substantially widened and paved, the boarding house was torn down, the two houses at the plant and the single house at the dam were moved away from the complex, and a new office building/garage was built on the west side of the plant. In 1963 the old apartment house was torn down to make room for a new 115,000 volt substation which stands on a small terrace west of the office building.

Central Colorado Power's financial problems not only resulted in construction of a "temporary" plant at Shoshone but ultimately led to foreclosure in 1913. At the same time that construction was underway in Glenwood Canyon, the company was at work on even larger hydroelectric projects in Boulder Canyon and Gore Canyon (both in Colorado) and had a number of survey crews in the field on other projects. Over expansion and rapid expenditure of capital forced a financial reorganization. On April 2, 1913, the Colorado Power Company was created and absorbed the assets and properties of Central Colorado Power, including the Shoshone hydroelectric complex.

The Colorado Power Company retained ownership of the Shoshone Hydro Plant for eleven years and directed many of the changes described above. In September, 1924, Colorado Power merged with the newly formed Public Service Company of Colorado. Public Service retains ownership today.