AEL&P will conduct the annual test of the Salmon
Creek emergency evacuation sirens on Thursday, Oct. 20, 2011, at
9:00 a.m. The sirens will remain on for no more than five
minutes during the test. We apologize for any inconvenience this
may cause residents and businesses in the Salmon Creek area.
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, as
well as a popular recreation spot.
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 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&Pís main
control room if any of these parameters exceed normal
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
To ensure the safety
of Salmon Creek Dam, FERC requires AEL&P to keep the
reservoir level below elevation 1140. Should the water level
in the reservoir reach elevation 1140, AEL&P is required to
open a valve at the base of the dam releasing water into
Salmon Creek until the reservoir falls below 1140.
The flood plain
The flood plain shown
below represents the approximate high-water line under the
worst possible conditions. Assumptions used in the flood
study include a reservoir elevation of 1167 (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.