Various proposals have been introduced to use the dam as a flood mitigation tool or have the levee removed to improve river flow and the ecosystem. The energy facility is planned to be decommissioned in 2025 and water rights given to the city of Centralia.
History
The Skookumchuck Dam was built under ownership of Pacific Power & Light Company on the Skookumchuck River beginning in May 1969. Completed in October 1970, the earthen embankment was built by Lockheed Shipbuilding and Construction Company of Seattle at a cost of $6million.[1] The damming of the waterway created the 4-mile (6.4km)-long Skookumchuck Reservoir.[2] Its primary use is to provide water for the TransAlta coal plant and is not used for local or community water needs.[a] The dam is an earthen bank structure measuring 190 feet (57.9m) tall and spans 1,340 feet (408.4m).[3]
With low water levels in the reservoir, the system provides some flood protection to communities downstream, such as Bucoda, however, the dam was not built for flood prevention.[3] The earthen dam has been part of several flood mitigation proposals to protect the Centralia and Chehalis communities from continuing overflow events.[4][5] The embankment contains a trap system in which mature steelhead are caught and transported over the spillway but existing fish passages prevent young salmon from migrating.[3]
The dam and reservoir is overseen by TransAlta and, by contract, will continue in their oversight role after the coal plant is closed at the end of 2025. At that time, water rights will revert to the city of Centralia for public consumption.[6]
Dam removal
Studies focusing on certain aspects on removing the dam were begun with a first phase in 2020 under the Office of Chehalis Basin (OCB) and connected agencies and organizations.[7] An OCB study released in 2022 estimated a removal cost up to $35million, with a potential high of $80million when factors are added for the loss of downstream water rights. The study concluded the best options were improvements to the dam to include fish passages, as well as to use the dam for flood control purposes.[8]
In June 2024, a petition to remove the dam at the termination of the Centralia Steam Generation Plant operations was filed by the Quinault Indian Nation. Requesting the removal by at least the end of 2025, the Quinault expects immediate, natural restoration of the river's flow and salmon habitat.[8]
As of 2025[update], the dam is no longer being considered for removal.[7]
Geography
The dam is located on the Skookumchuck River in Hanaford Valley. The embankment is approximately 11 miles (18km) east of Centralia and east of Bucoda and the ghost town of Tono.[1]
Technical aspects
The embankment contains 2,200,000 cubic yards (1,700,000m3) of earthen fill that was taken from the surrounding hills in the valley. A concrete spillway, a control outlet, and a fish passage were added at construction. The dam contained an intake pipe that could extract water from the reservoir at different levels, supplying cooler or warmer water as needed for the steam plant. A 12-mile (19km)-long pipeline connected to a 3 foot (0.91 metres)-wide, 3-mile (4.8km)-long pipe that transferred the supply to the energy facility. The surface of the reservoir was reported to cover 550 acres (220ha) and contain up to 38,800 acre-feet of storage capacity.[1]
↑ Although the reservoir's purpose was not as a water supply for the local region, in the year after construction, the city of Centralia had access to 2,000,000 US gallons (7,600,000L; 1,700,000impgal) per day if necessary.[1]
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