Armin F. Koernig Hatchery Dam
The Armin F. Koernig (AFK)
Hatchery Dam provides all of the water supply to the AFK Hatchery. In 2008, NGE
performed a periodic safety inspection of the original dam which was
constructed during the 1930s and expanded in the 1970s. During the inspection
it was determined that the dam had deteriorated significantly and was in need
of repair or replacement. In 2009 NGE-TFT was contracted to perform a
feasibility study for the repair or replacement of the dam. As a result of that
study, the decision was made to replace the dam and 16-mile long above ground
pipeline that provides the hatchery water supply. It was also decided to raise
the normal reservoir level by approximately 5 feet. Design of the new dam began
in 2010 and construction was completed in 2012. The new dam consists of a 23
foot tall post-tensioned concrete dam in the main stream channel with two
sheetpile core earthen berms. The new dam had to be constructed without disrupting
the water supply to the hatchery. Other project constraints include the remote location
in Prince William Sound (air and sea access only) and frequent severe weather. NGE-TFT
provided all of the design services including geotechnical,
hydrologic/hydraulic,and structural as well as construction monitoring and
materials testing.
Lake O’ The Hills
The
Lake O’ the Hills dam is a privately owned dam that impounds a recreational
lake. When the State of Alaska Dam Safety Program determined the existing
corrugated metal pipe spillway was no longer fit for service due to
insufficient capacity and pipe corrosion, NGE-TFT was contracted to design and
construct a new spillway. Because the spillway was the only outlet for the
reservoir, water levels were maintained during construction using a 6-in
diameter siphon. A sheet pile weir and rip-rap protected spillway was designed
to pass a flood flow of approximately 250 cfs.
