Ames Hydro: Making History Since 1891

A 2013 inductee into Hydro Review‘s Hydro Hall of Fame, the Ames hydro plant on the South Fork of the San Miguel River in southwest Colorado made hydropower history in 1891 when it utilized alternating current for the very first time.

By Alfred Hughes and Richard Rudolph

The 3.6-MW Ames hydroelectric project near Telluride, Colo., has a long history beginning in the late 1880s. Of particular significance is the fact that it was the first hydroelectric facility to generate, transmit and use alternating current (AC) for industrial purposes in the U.S. The project, which was owned by various companies in the past, has been owned and operated by Public Service Company of Colorado, dba Xcel Energy, for the past 22 years.

There have been improvements to the hydro plant over the years, but the generation infrastructure has remained almost unchanged. The history of the plant shows that Ames is where the “battle of currents between alternating current and direct current” was decided.

Ames Hydro Station

Project description

The project’s two primary water storage reservoirs are Hope Lake and Trout Lake. Hope Lake is a high-altitude storage reservoir located above the timber line and has a capacity of about 2,300 acre-feet. Trout Lake has a total storage capacity of about 3,200 acre-feet, including about 2,500 acre-feet of active storage at normal operating water surface 9710 NGVD-29. Both reservoirs have man-made dams built for the Ames plant. Trout Lake Dam was originally constructed in about 1894 and Hope Lake in the early 1900s. Water releases from Hope Lake are controlled by three butterfly valves that send water into an approximately 3-mile-long natural channel to Trout Lake. The primary source of water for these reservoirs is snowmelt from the nearby San Juan Mountains. The water from Hope Lake is released to Trout Lake in November as augmentation water for winter generation.

The water from Trout Lake is conveyed into a penstock that extends to the Ames powerhouse, over a distance of about 13,600 feet, resulting in a static head of 1,000 feet between Trout Lake and the powerhouse.

The secondary water supply for the Ames powerhouse is Howard’s Fork on the San Miguel River. The Howard’s Fork diversion dam has limited storage capacity (about 300 acre-feet), and is operated as run-of-river given its low storage capacity. The static head between the dam and powerhouse is about 700 feet. The flow from the dam to the powerhouse is conveyed via a steel penstock over a distance of 6,500 feet. The diversion provides enough water to provide a capacity of 50 kW to 800 kW depending on the season.

The reservoir inflows from Trout Lake and Howard’s Fork, which have different hydraulic heads, are each connected to a separate Pelton turbine. Both turbines are connected on a common shaft to the single 3.6-MW generator, which is a unique feature in itself. The turbine powered by water from Trout Lake is 5,000 horsepower, while the turbine using water from Howard’s Fork River is 1,200 hp. The horsepower difference of each turbine is due to hydraulic head and inflow water. These turbines and the generator are original to the powerhouse.

The AC output from the 3.6-MW generator is sent to the grid via a transmission line owned by Tri State Generation and Transmission Company. However, it should be noted, in addition to providing electricity to the Tri State transmission and distribution system, it also provides voltage support to the local power grid.

The original powerhouse was constructed in 1891 with a single 3.6-MW generator unit attached to two Pelton turbines.
The original powerhouse, shown here in an 1895 photo, was constructed in 1891 with a single 3.6-MW generator unit attached to two Pelton turbines.

The beginning

If you look at photographs of the mountains around Ames and Telluride, Colo., in the late 1880s, the first thing you notice is the absence of trees. With the rush for gold and silver in the Colorado Rockies in full swing, the trees were the first thing to go. The wood was used to build structures, shore up the mines and fuel the steam engines.

Lucien Lucius (L.L.) Nunn in 1880 left Boston, where he studied law, to move to Colorado. After brief ventures in Leadville and Durango, Nunn made his way to Telluride. By 1888, he found himself at the top of the local business world. With business interests in the Illium and Keystone mines, he became a major stockholder in the Gold King Mine, which at the time was one of the most reliable producers. The Gold King Mine, as well as other mines in the area, was struggling because of the high cost of producing steam power to run the engines in the mines. The steam power used wood as fuel, but the timber in the area was rapidly disappearing. Further, the cost of shipping coal or other fuels was prohibitive because there were no railroads in the rugged, high mountain area. Therefore, Nunn faced the challenge of powering the Gold King Mine with other methods to keep it profitable.

Nunn looked at the hydropower potential of the two mountain streams that formed the South Fork of the San Miguel River 2,000 feet below and 3 miles from the Gold King Mine. He considered DC electricity, compressed air and cable drive to provide the needed power. None of these alternatives were practical, and all were extremely uneconomical. DC power would require large-diameter conduits with high voltage losses and was costly. Compressed air and cable drive required operating equipment that required power, such as steam, which was the reason to seek other power sources.

Nunn then contacted his brother Paul, an engineer in the east, who told L.L. Nunn of a new technology developed by George Westinghouse called AC. This system was able to generate and transmit electricity at high voltage over great distances with smaller-diameter conductors. From a historical point, it should be noted that shortly after completion of the Ames plant, multi-mile transmission systems carrying AC power in Germany and Oregon were successfully used. Transformers were used to convert the electricity to lower voltages for end use with equipment.

In 1890, L.L. and Paul Nunn contacted George Westinghouse and convinced him to provide the technology and equipment to build a hydro-powered AC generating plant at Ames to provide power to the Gold King Mine. Westinghouse agreed, seeing the opportunity to finally win the “battle of the currents.”

The “battle of the currents” between DC and AC power was going on between Westinghouse and Thomas Edison of General Electric Company in the east. Edison and General Electric, owners of multiple patents and firm supporters of DC electricity, proclaimed AC as the “death current” because of their claim that in the event of a transformer being short circuited or part of a high tension system being accidently grounded, the customer turning on a light might be instantly electrocuted.

Edison’s folks at General Electric were conducting public demonstrations of the danger by electrocuting animals with AC power in public demonstrations in Pennsylvania, while Nikola Tesla was putting on demonstrations in Colorado Springs, Colo., allowing AC to flow safely through his body. And, of course, Edison’s first AC patent was the electric chair, touted as the humane way to execute the condemned. Therefore, Westinghouse’s new system was not receiving widespread acceptance. This illustrates what was at stake in developing the Ames project.

Ames Hydro Station
Although portions have been overhauled and modified, the original powerhouse is still generating power for Public Service Company of Colorado.

Building the project

Construction of the Ames project started in 1890, in spite of strong objections from investors in the East, and in June 1891 the plant generated its first electricity. Westinghouse provided a generator to operate at 3,000 volts, single phase, 133 Hertz at 100 hp. It was powered by a 6-foot-diameter Pelton water wheel with less than 320 feet of head. The head was developed by diverting water via a wooden flume from Trout Lake to a storage tank and then by a single penstock to the powerhouse. The generation powered a 100 hp motor located at the Gold King Mine 2.6 miles away from the powerhouse via a single-phase transmission line consisting of two 0.229-inch-diameter bare copper wires mounted on short Western Union cross arms and insulators. The copper cost was about 00 – only 1% of the estimated cost for DC conductors. It was estimated by Westinghouse that less than 5% power loss would occur over the transmission line.

The generator and motor at the mine and hydro plant were identical, with the exception that each was excited separately. This was part of the invention by Tesla, a Yugoslavian inventor, electrical engineer, mechanical engineer and physicist who had previously worked with Edison before demonstrating AC current and selling his patents and motors to Westinghouse. However, the overall system design was completely by Westinghouse. The Ames plant ran for 30 days without interruption, transmitting the needed power to the Gold King Mine. The operators later admitted that they let it run for fear they would not be able to successfully start it a second time because it was new, unfamiliar technology.

The switchboards were pine-shellacked wood. Only voltmeters and ammeters, which were of the solenoid and gravity-balance type, were used. Circuits were closed with jaw switches and opened by arc-light plugs.

Lightning posed a great operational problem at the Ames plant. At one time, more than 100 distinct discharges caused by lightning were counted within a single hour. This problem was so severe that it caused a nearby DC operating station with shorter transmission lines to go bankrupt. This situation may have been duplicated at Ames, if not for the iron clad “T” toothed armatures and replaceable coils on the AC generator.

With the success of the Nunn brothers, the Ames operation became the nation’s first electric utility, the Telluride Power Company, in 1891. This utility sold it’s electricity for the first time in history to the Gold King and other mines.

The experiments of Westinghouse and the completion of the Ames plant demonstrated the abilities of AC generation and transmission. The “battle of the currents” was over.

The success of AC at Ames set the stage for the AC development of the Niagara Falls hydro plant for the city of Buffalo, N.Y. Westinghouse was awarded a contract for three generating units of 5,000 hp each at Niagara Falls , which were completed in 1895. With the completion of Niagara Falls came the first widespread use of AC electricity for general industrial (such as the steel industry) and commercial purposes in the East.

Ames Hydro Station
Due to its pivotal role in the history of electricity and alternating current, the Ames hydro generating station is an important educational site for local organizations and students like the ones shown above.

Changes over the years

In 1892, a 600-hp generator of the same design was installed at Ames, along with a motor at the Bear Creek Mine, about 10 miles from the hydro plant. Later that year, one 50-hp and one 75-hp motor were installed in the Savage Basin Mines, 14 miles away. Finally, in 1895, a 100-hp motor was installed at the Pandora Mine 14 miles from the powerhouse. This expansion of the usage of power from Ames was a step forward in the usage of AC power.

In 1896, the Ames plant was updated with a 60 Hz system designed by Tesla. With the expanding use and demand for AC generation, the current 3.6-MW plant was constructed and began its operation in June 1906. Over the century of operations and innovations in available technology, improvements have been made to the plant. Steel penstocks replaced wooden flumes, fiberglass and ductile iron replaced steel, and solid state electronics replaced electromechanical protective relaying.

Lake Hope Dam was also built in 1905 to augment generation during the winter months when inflows are at their lowest. A flood and failure of the original Trout Lake Dam in 1909 resulted in replacement of the dam at the same location, with an earthen and rock structure replacing the rock and timber dam built in 1891. Additional work in the 1950s included the installation of two steel siphons to replace wooden service spillways.

Improvements to dam safety, remote monitoring and the complete automation of the operation occurred in the 1980s and continue today, with sophisticated flow differential protection of the penstock. Extensive supervisory control and data acquisition, relaying and substation upgrades have also taken place as a result of an increase in the transmission voltage from 69 kV to 115 kV in 1997. Various sections of the penstock have been replaced in the past 20 years due to failures, and additional penstock replacement is planned for the next decade. (Note: Many of the past failures were the result of external loads by unauthorized personnel who owned land through which the penstocks run, an ongoing issue with the rapid development in the Colorado Rocky Mountains).

From the original Telluride Power Co., ownership has changed frequently, including the San Juan Power Co., Western Colorado Power, Utah Light and Power, PacificCorp and the Colorado-Ute Electric Association. Public Service Company of Colorado obtained the project in 1991 as a result of the bankruptcy of Colorado-Ute. Public Service Company of Colorado merged with Southwestern Public Service in 1996 and merged with Northern States Power in 1999. (The result of those mergers is the holding company, Xcel Energy, Inc.)

The Howard’s Fork Dam and penstock, originally constructed in 1905, have been repaired, including major improvements to the dam and spillway over the past 10 years. Although the Howard’s Fork Diversion is small, it does provide additional year-round generation that would not otherwise be captured from the mountain streams.

The equipment in the powerhouse is routinely overhauled, as well as having the station step-up transformers replaced. The output of the project is wheeled through another utility’s transmission system to an interconnection with Public Service Company of Colorado’s transmission system. The generator also provides needed voltage support, is black-start capable and can produce enough generation in an emergency to power critical facilities in the area for many weeks should normal transmission be lost.

The project operates today primarily as a peaking operation, providing generation during the periods of greatest demand. The project is monitored and remotely operated from Xcel’s Cabin Creek Pumped Storage Hydro, with a small operations/maintenance staff on site Monday through Friday. Capital improvements to all areas of the operation are planned over the next decade as the plant is prepared for another century of operation.

Despite the claim to fame of being the first AC hydroelectric generating plant, literally changing the future of mankind and influencing the greater usage of AC, even more amazing is how Ames stands as testament to the reliability and longevity of hydro as a source of clean, renewable energy.


Alfred Hughes is superintendent of the Ames, Tacoma, and Salida hydro plants for Xcel Energy. Richard Rudolph is a licensed engineer with RR Engineering Consulting.

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