Before the FERC Application for New License for the Annex Creek ...

A-7
3.0 SALMON CREEK COMPONENT DESCRIPTION
3.1 GENERAL
The Sa 1 mon Creek Component is 1 oca ted wi thi n the Juneau Towns i te
Boundary. Salmon Creek Reservoir, located approximately 3 miles north of
downtown Juneau, is formed by a concrete-arch dam. The spillway is located in
the right abutment of the dam. An intake structure is built into the base of
the dam wh i ch connects to the Sa 1 mon Creek Upper Pens tock and Upper Powerhouse.
The Upper Powerhouse contains two turbine-generator units for a total
of 3,500 kVA. Power generated at the Upper Powerhouse is transmi tted via a
transmi s s ion 1 i ne to the old lower swi tchyard 1 oca ted near the Lower Powerhouse.
Immedi ate 1 y above the Upper Powerhouse, the Upper Penstock bi furcates,
permitting water to be diverted to the Upper Powerhouse or into the
Lower Penstock leading to the Lower Powerhouse. The flow of water to either
powerhouse is controlled by two butterfly valves located at the bifurcation.
Due to Upper Penstock flow capacity and existing water rights, both
powerhouses cannot be operated simultaneously. The Lower Penstock is of
welded steel construction and is buried except where it crosses Salmon Creek.
The new Lower Powerhouse is located on Gastineau Channel adjacent to the old
Lower Powerhouse, now retired, approximately 3 miles northwest of downtown
Juneau. The Lower Powerhouse contai ns one turbi ne-generator uni t rated at
10,500 kVA. The nameplate capacity of the Lower Powerhouse Unit is 8.4 MW and
was installed for future expansion. The licensed capacity of the unit is
6.7 MW and is the maximum capacity the unit can presently operate. The power
generated is transmitted via a short section (450 feet) of intertie to the new
lower switchyard, where interconnection is made with AELp·s distribution
system.
When the Salmon Creek Component was originally constructed, an
arbi trary e 1 evati on datum was used wi th the dam spi 11 way crest at E1 1172.
This arbitrary datum is 26.29 feet below Mean Lower Low Water Datum (MLLW).
Throughout thi s exhi bi t thi s arbi trary datum wi 11 be referred to as the Upper
Salmon Creek Datum (USCD).
The Lower Penstock and Lower Powerhouse, which were built in 1984,
used another arbitrary elevation datum which is 4.79 feet below MLLW. This
arbitrary datum will be referred to as the Lower Salmon Creek Datum (LSCD).
3.2 PROJECT STRUCTURES
Salmon Creek Dam. The Salmon Creek Dam is a concrete arch dam 170 feet
high with a crest length of 648 feet. The dam crest is at E1 1175 (USCD).
The spillway crest elevation is 1172 feet (USCD) with 3 feet of freeboard provided
by the dam. An intake structure is built into the base of the dam. At