Salmon Creek Dam Background
Salmon Creek Dam is a concrete arch dam constructed in 1914 to provide water for hydroelectric power generation. The reservoir also provides drinking water to Juneau, water for a salmon hatchery, and is a popular hiking destination. The dam, located about three miles up the Salmon Creek valley, is 47-feet thick at the base, and six-feet thick at the top. It is regulated by the Federal Energy Regulatory Commission (FERC) which has very specific requirements for public safety and dams.
AEL&P Safety Activities
AEL&P monitors the level of Salmon Creek Reservoir, the flow from the dam in the penstock, and the flow in the lower part of Salmon Creek in real time, 24-hours-a-day. Alarms sound in AEL&P's main control room if any of these parameters exceed normal values. AEL&P crews inspect the dam each month. The inspection includes physical verification of the reservoir level, measurement of dam deflection (any movement of the structure), and visual inspection for any cracking, erosion, seepage, or other deterioration. FERC personnel inspect Salmon Creek Dam annually. FERC also requires a thorough inspection and investigation by a qualified independent engineer every five years. Engineers from AEL&P also perform an inspection as soon as possible after any earthquake felt in the Juneau area.
Safety of Salmon Creek Dam
To ensure the safety of Salmon Creek Dam, FERC requires AEL&P to keep the reservoir level below elevation 1,140. Should the water level in the reservoir reach elevation 1,140, AEL&P is required to open a valve at the base of the dam releasing water into Salmon Creek until the reservoir falls below 1,140.
The flood plain
The flood plain map represents the approximate high-water line under the worst possible conditions. Assumptions used in the flood study include a reservoir elevation of 1,167 (its level during a 10,000-year flood), and a disaster that would cause the complete and immediate failure of the dam. AEL&P maintains an Emergency Action Plan for Salmon Creek Dam. For more information about what to do in an emergency, or about the Emergency Plan, contact our Consumer Affairs Department at (907) 780-2222.