Snoqualmie Falls Hydroelectric Plant
| Industry | Hydroelectric power generation |
|---|---|
| Founded | 1899 |
| Headquarters | Snoqualmie , United States |
Area served | Seattle area, Tacoma area |
| Products | Electricity |
| Owner | Puget Sound Energy |
| Website | www |
The Snoqualmie Falls Hydroelectric Plant is situated just to the north of Snoqualmie in King County, Washington, approximately east of Seattle. Located beneath the Snoqualmie Falls, the facility consists of two generating stations: Plant 1 and Plant 2. Plant 1, completed in 1899, holds the distinction of being the world’s first underground hydroelectric power station.[1][2][3] Constructed in 1910, Plant 2 is positioned along the right bank of the Snoqualmie River. Both plants utilize water sourced from a reservoir created by a weir installed atop the falls. Plant 1 has an installed capacity of 13.7 MW, while Plant 2 contributes 40.2 MW, combining for a total output of 53.9 MW—enough electricity to supply roughly 40,000 residences.[1][4]
On April 23, 1976, Plant 1 was recognized on the National Register of Historic Places under the name Snoqualmie Falls Cavity Generating Station.Cite error: The opening <ref> tag is malformed or has a bad name Additionally, in 1981 it received designation as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers.Cite error: The opening <ref> tag is malformed or has a bad name Ownership of the plant is held by Puget Sound Energy. The Snoqualmie Falls Hydroelectric Power Plant Historic District was also added to the National Register in 1992.[5]
History
The concept for this power generation site originated with Charles H. Baker during the 1890s. As an engineer for the Seattle, Lake Shore and Eastern Railway, Baker aimed to harness the vertical drop at Snoqualmie Falls for hydroelectric production, drawing inspiration from New York’s Schoellkopf Power Station at Niagara Falls. After losing his job due to the Panic of 1893, Baker obtained financial backing from his family—most notably his father William T. Baker, a prosperous businessman—to establish the Snoqualmie Falls Power Company and acquire ownership of the falls and adjacent lands in 1897. Construction commenced in 1898 with a cofferdam constructed to block river intake on the left bank of the falls. Steam-driven pneumatic drills were employed to excavate a vertical shaft and horizontal tunnel leading into the cavern designated for Plant 1. To ensure adequate water supply, a weir was erected upstream to elevate river levels. Initially, four Pelton turbines rated at 1.5 MW each were installed along with Westinghouse generators. The first generator began delivering electricity to Seattle on July 31, 1899; by November 1 all units were operational, extending service to Tacoma as well. In 1903, ownership transferred to Seattle Electric Company; that same year Charles Baker’s involvement ceased due to financial setbacks and his father’s passing. A fifth turbine-generator—a horizontal Francis type rated at 5 MW—was added in 1905. Subsequently, in 1908 Seattle-Tacoma Power Company, which later evolved into Puget Sound Energy, acquired Seattle Electric Company.
The penstock was manufactured and installed by Chicago Bridge & Iron Co. Following installation of the fifth generator, engineer W.A. Brackenridge initiated plans for Plant 2. This addition featured a tunnel drawing water from the weir into a forebay that supplied water downstream from the falls. Commissioned in 1910 with one Francis turbine-generator rated at 9 MW, its tunnel and penstock were designed with capacity for up to three generators to accommodate future expansion. Beginning in 1956, Plant 2 underwent enlargement with a second Francis turbine-generator installed in 1957 alongside an upgraded penstock to meet increased demand. At that point, combined capacity reached 44.4 MW. The second turbine was replaced twice—first in 1991 and again in 2004 after damage caused by sediment accumulation. In that same year, Puget Sound Energy obtained a new 40-year operating license from the Federal Energy Regulatory Commission, mandating a minimum continuous discharge of .[6]
Rehabilitation and Modernization
In April 2010, Puget Sound Energy initiated a comprehensive $200 million modernization and rehabilitation effort for the hydroelectric facility. This undertaking included refurbishing the first four generators within Plant 1 and installing a new fifth generator, as well as replacing a turbine-generator unit in Plant 2. To mitigate upstream flooding, the weir was lowered to 16 feet in height, extended by 37 feet in length, and its water intake structure was entirely rebuilt. Enhancements to the penstocks supplying both plants were carried out, alongside the addition of automatic shut-off and bypass valves in Plant 2 to improve emergency handling and ensure continued downstream water flow during outages. To enrich visitor experience and cultural appreciation, new amenities such as visitor centers, hiking paths, a boardwalk, and landscaping upgrades were introduced. Renovations at Plant 2 concluded by April 2013, while the installation of the new 6.5 MW Francis turbine generator in Plant 1 and the overall project wrapped up by mid-2014. These improvements elevated the total installed capacity from 44.4 MW to 53.9 MW.
Design
The water supply system for both Plants 1 and 2 is controlled by a weir that varies between 4 and 16 feet in height, forming a modest reservoir upstream. The intake for Plant 1 is positioned just above the left abutment of the weir, channeling water into a vertical penstock that is 280 feet long and seven feet in diameter. This penstock leads down to a cavern situated approximately 270 feet below ground level and roughly 300 feet behind the waterfall. The cavern itself extends 200 feet in length, spans 40 feet in width, and rises 30 feet high, accommodating four Pelton turbine-generators rated at 1.8 MW each alongside one Francis turbine-generator with a capacity of 6.5 MW. Water discharged at flow rates up to 700 cubic feet per second exits through a tailrace tunnel measuring 650 feet before rejoining the river.
Plant 2’s intake is located near the right abutment of the weir and directs water into a tunnel running along a ridge downstream from the falls. This tunnel leads to a forebay that temporarily holds water before it is released into two penstocks—each approximately 520 feet long—with the larger penstock having a diameter of ten feet. Situated on the right bank of the Snoqualmie River, Plant 2 houses two Francis turbine-generators with capacities of 13.7 MW and 26.5 MW respectively. The plant discharges water at flow rates reaching up to 1800 cubic feet per second directly back into the river.
External links
- Snoqualmie Falls Hydroelectric Project at Puget Sound Energy
- Snoqualmie Falls Hydroelectric Project at SnoqualmieFalls.com
- Snoqualmie Falls Cavity Generating Station at the ASCE
- 1902 Scientific American
- ↑ 1.0 1.1 Cite error: Invalid
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<ref>tag; no text was provided for refs namednrhpdoc - ↑ "About the Snoqualmie Falls Project". Puget Sound Energy.
- Dams in Washington (state)
- Dams completed in 1899
- Weirs
- Hydroelectric power plants in Washington (state)
- Energy infrastructure completed in 1899
- Energy infrastructure completed in 1910
- Dams on the National Register of Historic Places in Washington (state)
- Historic American Engineering Record in Washington (state)
- National Register of Historic Places in King County, Washington
- 1899 establishments in Washington (state)
- 1910 establishments in Washington (state)
- Run-of-the-river power stations
- Buildings and structures in King County, Washington
- Historic Civil Engineering Landmarks
- Underground power stations
- Puget Sound Energy
- Energy infrastructure on the National Register of Historic Places