The Dewey lakes project in Alaska has been generating electrity for 113 years

By Glen Martin

The 943-kW Dewey Lakes Hydroelectric Project is located in southeast Alaska, within the Klondike-era gold rush community of Skagway. Situated at the head of Taiya Inlet, off the north end of Lynn Canal, it is 90 miles north of Juneau, 1,000 miles north of Seattle, Wash. and 108 road miles south of Whitehorse, Yukon Territory, Canada. Among its many colorful distinctions, Skagway was Alaska’s first incorporated city, snatching the honor just ahead of the capital city of Juneau by a single day. Its closest neighbor, the town of Haines, population 2,592 is at the opposite end of the deep fjord Taiya Inlet, about 15 miles southwest.

Dewey Lakes Hydro is operated in run-of-river mode. The project first began operations in September 1902 with a 125-kW Pelton turbine/generator. By this time Skagway had shrunk from its 1898 high of about 10,000 people to about 3,000 according to the 1900 U.S. Census. The project shared the water for a time as a fresh water source for the community and as a pressurized water source for firefighting when it was connected to the city main. Later the community went to a well system for their fresh water, leaving the reservoir for hydro operations and fire protection.

Alaska Power & Telephone Company (AP&T) purchased the Skagway power assets in 1957, which included Dewey Lakes Hydro, and the local telephone assets shortly thereafter. AP&T is investor-owned with a lengthy and loyal history of significant employee stock ownership. AP&T has acquired power and telephone assets in 40 Alaskan communities since 1957 and currently owns and operates seven hydroelectric projects in Southeast Alaska; four of which were built by AP&T.

In July 2015, the Dewey Lakes Hydroelectric Project was inducted into Hydro Review’s Hydro Hall of Fame during a ceremony at HydroVision International in Portland, Ore. The Hydro Hall of Fame recognizes hydropower plants across the U.S. that have been in continuous operation for 100 years or more.

Background

Dewey Lakes Hydro contains features that go back to the Klondike Gold Rush between 1896 and 1899. Skagway was the gateway to the Klondike at this time, particularly for those going through White Pass into Canada as well as through the infamous Chilkoot Pass in the neighboring watershed. The community quickly grew to about 10,000 gold seekers in one form or another. Some of these hardy souls decided to make Skagway their home and wanted to have the accoutrements of a modern society, i.e., freshwater, electricity, schools, newspapers, etc. Some of these they already had, including electricity from a two-boiler steam plant that utilized enormous amounts of wood.

In 1898 the Project Forebay Dam was constructed to create a reservoir of fresh water for the gold rush community. To construct the dam, a trail had to be etched from the bedrock cliffs, a steep 500 feet in 0.25 miles, to haul equipment and supplies via manpower and mules. A 1,500-foot tramway was also installed from downtown to the forebay dam to haul up some of these supplies; which is still in operation today. Local rock and timber were used to construct the dam and woodstave pipe was used to transport the water down slope to the community.

In 1902, a hydroelectric project was developed utilizing the city reservoir as its source of water, while still providing water to the city by Home Power Company. A 12-inch steel pipe was used to transport the water to a single turbine in the powerhouse built on Pullen Creek at the base of the slope below the reservoir.

Dewey Lakes Hydro was first turned on Sept.17, 1902, and provided electricity only between the spring thaw and fall freeze up. During the winter the steam power plant was utilized. At an unknown date the city went to a well system for its water supply, eliminating the need for the reservoir as a freshwater source. As more homes and businesses connected to this small grid, the desire for year-round hydropower grew as well. In addition, the power company was struggling with the expense of bringing in firewood for the boilers and so decided to expand the hydro operations to eliminate steam as the primary source of power. During this period steam power was also eliminated in favor of diesel generation as a backup source of electricity because diesel was less labor intensive and thus cheaper.

In 1908, Lower Dewey Lake was developed by installing a dam at an existing small lake to increase the storage capacity. This provided significantly more storage, making the original project reservoir the forebay. Additional features were developed, primarily by diverting other streams and drainages to Lower Dewey Lake, as described previously in Project Features, until about 1939. This completed the present overall design of the project. Construction of these features was not easy if compared to today’s mechanical equipment methods, but men’s strong backs, ingenuity, and the mules they utilized accomplished much.

Lower Dewey Lake Dam was constructed using a flume to transport logs down slope, which were then pulled into place with the help of mules at the site. Mining carts on narrow gauge track were used to provide earthen fill behind the dam and the track is still visible today. Those mining carts did not roll up to the site, but were most likely packed in on the backs of mules. There was plenty of hard work available in Skagway for those willing.

In 1930, the Federal Energy Regulatory Commission (FERC) issued a 50-year license for the project, retroactive to 1927. In 1957, AP&T purchased the local power and telephone utility owning and operating this hydroelectric project. In 1980, a 30-year FERC license was issued retroactive to 1977. Another 30-year license was issued in August 2007.

This project is unique for the time it was constructed in [1902] when few hydropower projects were in existence, even in the lower 48 states. In this remote location in a state that was just beginning to be discovered and its resources assessed, this project reflects its genesis from pioneers of the Klondike Gold Rush. This project epitomizes the self-sufficiency and innovation typifying the Alaska frontier spirit; Skagway residents were “home-sourcing” their energy needs and decreasing dependence on expensive outside fuel, long before “renewable energy” became an industry buzzword. The business model Dewey Lakes pioneered over 100 years ago remains in practice today, through AP&T’s continued development of clean energy in rural Alaska.

Operational description

Dewey Lakes uses a run-of-river mode of operation because of the limited storage available in the project forebay. The water source encompasses 8.13 square miles of drainage that includes Upper Reid Creek, Upper Dewey Lake, Dewey Creek, Devil’s Punchbowl, Snyder Creek, Icy Lake, Icy Creek, and Lower Dewey Lake.

Operationally, water from Reid Falls is diverted into the 0.24-mile-long Reid Falls pipeline, which releases water to Icy Lake. Water from Icy Lake is released to Icy Creek, which drains into Lower Dewey Lake. Also, Dewey Creek drains into Lower Dewey Lake and flow from Snyder Creek is diverted into Lower Dewey Lake. Water from Lower Dewey Lake is transferred to the forebay by a deep, wide ditch or canal. Penstocks move the water from the forebay to the powerhouse. Water from the powerhouse is released to Pullen Creek, which drains into Taiya Inlet.

The project has a maximum hydraulic capacity of 32 cubic feet per second (cfs) and a minimum hydraulic capacity of 0.6 cfs.

AP&T block loads the project turbines at a specific energy output when there is consistent inflow to the reservoir and forebay. This allows AP&T to use other sources of electricity of either hydro or diesel to follow the load swings on the grid. This makes Dewey Lakes Hydro the stable block of power that needs little adjustment throughout the day. The company also checks the water level in the Dewey Lakes Reservoir every 15 minutes to determine if any adjustments need to be made to turbine operation. Average flow adjustments are generally less than 1 cfs and occur on average one to two times per day. During storm events when the reservoir may fill quickly, the boards at the Lower Dewey Lakes Dam spillway are removed to control the lake level.

Once inflow begins to recede, the boards are put back to keep the lake near full. During the summer months, keeping the lake near full is important for recreational users who swim and picnic around the lake and utilize the 5.4-mile trail system. The pioneers of Skagway who hunted, harvested wood and enjoyed recreational opportunities originally developed this trail system. As owner/operator of the hydroelectric project, AP&T helps the community maintain the trail system that is a shared benefit and connects the project features.

In this image, the Forebay Dam is pictured as it appears today.
In this image, the Forebay Dam is pictured as it appears today.

Dewey Lakes provides year round energy to Skagway, contributing about 160 kW to 200 kW of capacity during the winter. The balance of Skagway’s energy needs are met via two additional hydro projects, 4-MW Goat Lake and 3-MW Kasidaya Creek. The nearby community of Haines is also connected to Skagway’s power grid via 15 miles of 34.5-kV submarine cable installed in 1998 and benefits from these renewable energy resources.

Dewey Lakes Hydro inspired AP&T to change its business model and commit to stabilizing rates and displacing diesel generation of electricity with renewable hydropower. Since 1991 AP&T’s employee-owners have worked to convert from 95% diesel-based generation to 75% renewable; predominantly hydropower. The company now owns 7 hydropower projects, and is in the process of constructing its 8th and 9th. Reduced dependency upon diesel fuel, a volatile commodity with ever-increasing costs, has allowed AP&T to serve its customers with more affordable, predictably priced energy.

However, because this is Alaska, which is not connected to either Canada or the lower 48 states, there are almost as many utilities as there are communities. Each community is often its own micro-grid, due to Alaska’s size, which is larger than Texas, and rugged terrain. AP&T’s Haines power plant has diesel generators as backup for maintenance, as does the Skagway power plant. During the winter months, the Dewey Lakes project generates very little electricity, about enough to keep a 200-kW generator online. During the winter, Goat Lake Hydro, which is a storage project, provides most of the electricity to this two-community grid.

The electric load demand is highest in Haines during the winter because of its larger population. Conversely, the load demand during the summer is highest in Skagway – population 920 – because of the tourism industry. Up to five cruise ships per day visit Skagway during the summer. The Klondike Highway also provides vehicle access to and from Skagway via Canada, which interconnects with the Alaska Marine Highway, an extensive ferry system that includes Skagway as a port-of-call. Skagway can receive an influx of up to 10,000 visitors per day, having a significant impact on the electric load.

Rehabilitation and maintenance

Over time, the 113-year-old Dewey Lakes hydropower project’s features have been modified, rehabilitated, and replaced as necessary to ensure continued safe, efficient service to AP&T’s ratepayers. This project was constructed from the local rock and timber, which eventually required repairs. This project has had many facelifts to repair damage caused by the harsh climate, wearing effects of water in motion and many years of use. For example, the upstream face of the log-cribbed Forebay Dam was covered with geotextile fabric and riprap in 1996. Previous repairs to the upstream face had used earthen fill and log cribbing. The downstream side of Forebay Dam was ultimately covered with concrete. The facility’s four turbine-generator sets have received typical and timely overhauls in conjunction with generation upgrades and wear (i.e., the 1909 unit, a horizontal-shaft twin runner with a single nozzle per runner, originally had a capacity of 200 kW but was rebuilt in 1980 and uprated to 400 kW, but still uses the original 1909 casing).

AP&T’s goal is to keep this legacy low-cost provider of electricity to Skagway running for many years to come as a testament of hydropower’s emission-free reliability and long dedicated service.

Project features

  • A powerhouse with four units: No. 1 (400-kW Pelton), No. 2 (93-kW Pelton), No. 3 (250-kW Pelton) and No. 4 (200-kW Cornell centrifugal pump) for a total nameplate of 943 kW. The attached diesel plant structure houses three backup generators with a total capacity of 2.495 MW. An alternative source of electricity has been used alongside hydropower since the original hydro development because hydropower was not always available year round;
  • Steel and high-density polyethylene penstocks were used that have varying lengths and diameters;
  • Steel cable tramway from base of hill to Forebay Dam (reservoir);
  • Project forebay (reservoir) with a masonry and rock dam (132 feet long and 30 feet high, forms a 2.71-acre reservoir that has about 16 acre-feet of gross storage);
  • Canal that connects Lower Dewey Lake with the forebay;
  • Lower Dewey Lake Dam is an earth and rock-filled timber-crib dam was constructed in 1908 (629 feet long by 28 feet high, with a 3-foot-deep wood-plank spillway, creating a reservoir with a surface area of 32.8 acres and gross storage of about 410 acre-feet);
  • Snyder Creek diversion dam, a rock and fabric structure constructed after 1908 to divert water to the lake;
  • Icy Lake Dam, an earth and rock-filled dam, was constructed in 1911 to divert water to the lake;
  • Upper Dewey Lake Dam was a small log-crib structure, constructed in 1913 to add additional storage for the project; and
  • Reid Falls Dam, built in 1939, diverts water to Icy Lake.

Glen Martin is manager permitting, licensing, and compliance of hydropower projects.

More HR Current Issue Articles
More HR Archives Issue Articles
Previous articleDeveloping 2,400+ MW of Hydro in North America
Next articleTVA Employs PMP Models Developed Using Updated Data

No posts to display