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

B-2
2.0 ANNEX CREEK COMPONENT
Annex Creek Lake Reservoi r is 1 oca ted 10 mi 1 e s northeas t of downtown
Juneau. Annex Creek has a dra; nage area of approx i ma te 1 y 6.2 square
m; 1 es above the dam site. The Annex Creek bas in conta ins two 1 akes, Upper
Annex Lake Reservoi r and Lower Annex Lake. Upper Annex Lake Reservoi r has a
water surface area of 264 acres at the maximum water surface El 844 Mean Sea
Level (MSL). Lower Annex Lake, which is located less than 0.25 mile downstream
of the Upper Lake, has a natural water surface area of approximately
25 acres at water surface El 620 (MSL). Lower Annex Lake is approximately
0.5 mile from the mouth of Annex Creek at Taku Inlet.
The Annex Creek drainage basin varies in elevation from sea level
to 4170 feet at Annex Peak. Unlike the Salmon Creek basin, the Annex Creek
basin is not covered by glaciers.
2.1 PROJECT OPERATION - PROCEDURES AND CONSTRAINTS
The Applicant proposes to continue overall operation of the Annex
Creek Component as in the past, providing maximum power generation during the
peak winter load months of December through April. The Annex Creek Powerhouse
is remotely operated and the facility is currently staffed by an operator/
watchman. All control alarms and indications are telemetered to the Thane
Operations Center which controls all generation for the Juneau area. The
plant factor of the Annex Creek Component is estimated to be 76%, based on the
4,050-kVA rated capacity and the average annual energy generation.
Under all flow conditions, the Annex Creek power facility is opera
ted to ma i nta in the reservoi r 1 eve 1 between E1 705 MSL and E1 844 MSL, max i­
mi zi ng generation duri ng the peak wi nter months. Under norma 1 condi tions,
flow through the powerhouse varies from 44 cfs in early spring to 73 cfs in
the August-November period. Wi th a full reservoi r, the operati ng procedure
calls for a maximum controlled release of 76.8 cfs, the hydraulic capacity of
the Annex plant, in addition to uncontrolled spill. When the reservoir level
falls to the minimum pool, El 705 MSL, no releases are made.
2.2 ANALYSIS OF ESTIMATED DEPENDABLE
CAPACITY AND AVERAGE ANNUAL ENERGY
General Methodology. The Applicant has performed reservoir operations
studies to determine the average annual generation and dependable capacity of
the Project. Input data used in the operations studies included monthly average
reservoir inflows; minimum reservoir releases; reservoir area-capacity
curves; turbine and generator flow/efficiency characteristics; and hydraulic
head losses ; n the water conveyance systems. The average annua 1 energy and
dependable capacity were estimated separately for each Project component.
Dependable capacity was calculated based on the average power output during
the peak load months of December through April for the worst year of record.