The Swift Creek Hydroelectric Project FERC No. 1651, is located in Bridger – Teton National Forest, on Swift Creek, in Lincoln County, Wyoming. The project is located approximately 1 mile east of Afton, Wyoming in Lincoln County, Wyoming.
|Project Name||Swift Creek|
|LIHI Certificate Number||103|
|LIHI Effective and Expiration Dates||August 16, 2012
August 16, 2017
|Owner||Lower Valley Energy|
|Location||Located in Bridger – Teton National Forest, on Swift Creek, in Lincoln County, Wyoming.|
|Installed Capacity||1.445 MW|
|Average Annual Generation||Approximately 7 GWh|
The Swift Creek facilities were originally built in the early 1940’s and licensed on November 30, 1942 with a 50 year license. The project consists of two independent hydroelectric systems commonly referred to as Upper and Lower Swift Creek. In 1968 the plants were decommissioned due to a snow avalanche that crushed the upper penstock. The lower project was decommissioned due to needs for upgrading the existing equipment.
On November 29, 1990 the Swift Creek Power Company filed an application for new FERC License. The project has undergone a complete construction and rehabilitation effort and is currently operating under a new 50 year FERC License No. 1651 issued December 19, 1997.
Diversions: The upper reservoir, located about 3.5 miles east of Afton, consists of a dam 25 feet high and 100 feet long. The dam is a gravity concrete dam constructed between two prominent rock formations. The original dam had an impoundment of approximately 22 acre-feet. Due to being decommissioned in 1968 and with none to little maintenance on the existing sluice gates, the reservoir has silted in. In 1984 there was a large debris (mud) flow approximately 2 miles up stream from the upper diversion dam. This debris flow is located on United States Forest Service Property. When the mud entered Swift Creek, it was eroded away and was deposited in both the upper and lower reservoirs. This is why the upper reservoir has currently approximately 1 to 2 acre-feet of water storage.
The lower reservoir, located approximately 1.5 miles east of Afton, Wyoming, is a 30 feet high and 360 feet long, earth filled-concrete core dam. The original impoundment (adjudication) was approximately 48.45 acre-feet. Due to being decommissioned and with none to little maintenance on the existing spillway, the reservoir has silted in. As described above, the debris flow contributed to the siltation of the reservoir. The reservoir currently has approximately 10 acre-feet of water storage.
Penstocks: The upper project has a steel penstock 36 inches in diameter and 7,000 feet long.
The lower project penstock has been removed. The land that the penstock was constructed on was originally owned by Lower Valley Power & Light but since has been sold to a private individual.
Powerhouses: The upper project’s powerhouse is a concrete building with a native rock face. The powerhouse houses two (2) 400 kW turbines and generators.
The lower project’s powerhouse was sold with Lower Valley Power & Light’s property. The same person owns the powerhouse that owns the property where the penstock went.
Transmission Line Lower Valley Power & Light owns the existing lines into Swift Creek. There is a 13.5 KV line that comes off the Afton substation and runs to the existing upper powerhouse.
Project Components After Rehabilitation
Diversions: The upper reservoir has been cleaned out in front of the dam and outlet works. There is a 48” slide gate that is at the bottom of the dam. The gate has been cleaned and repaired to be functional in order to sluice out material as it is deposited in the reservoir. A new 48” inlet control valve has been installed. The dam has been refurbished and reinforced with steel and concrete. The cleaning of the reservoir did not bring the water storage back to the original 22 acre-feet. There is no reason for additional storage because the reservoir will only be used as a diversion structure. Additional dredging would only be done to enhance the local fishery. The material from the cleaning of the reservoir has been hauled off the USFS property and dumped at Peavler’s Mountain Star Excavating “fill pit”. The fill pit is located approximately 1.5 miles from the lower powerhouse.
The lower reservoir has been cleaned out to approximately 20 acre-feet of storage. The existing outlet has been cleaned and made functional. The existing spillway has been cleaned and new stop logs along with a flow monitoring weir have been installed in the spillway to regulate the flow. The cleaning of the reservoir has been limited to the area around the intake structure and spillway. There is no reason for additional cleaning for power production. There is not enough water for peaking power. The reservoir will only be used as a diversion structure after cleaning for the production of power. Additional dredging would only be done to enhance the local fishery. The material removed from the reservoir will be disposed of at Peavler’s fill pit. Some of the material has been dried and used on the down stream face of the dam as top soil. The down stream face of the dam has been restored and brought back to a 3 to 1 pitch with material imported from the Afton Lagoon site. Additionally, riprap has been placed around the spillway and new toe drains installed to prevent future erosion of the downstream face of the dam. The dam has been seeded with a USFS approved seed mixture and vegetation has begun to grow.
Penstock: The upper project’s 36” diameter, 7,000 foot long penstock was removed and replaced with a new 43.5”diameter, 7,000 foot long penstock. The new penstock was installed in the same location as the existing, above ground, 36” penstock line. The installation included new concrete pipe support pedestals, stream crossings, game crossings, and in locations where the penstock is susceptible to erosion from Swift Creek, mud and snow slides and/or falling rocks, gabions have been used to protect the penstock or it has been buried. The ground disturbance from the upper penstock line has been seeded with a USFS approved seed mixture and vegetation has begun to grow. The lower project has a new 49.5” diameter penstock that is approximately 1,800 feet long. The penstock is buried from the outlet works of the reservoir to the powerhouse. The entire line has been bedded in 1.5” minus washed rock and compacted. Gabions were used in steep sections of the penstock line to prevent erosion. A new sluice bypass has been installed on the penstock near the downstream face of the dam and will release flows into the existing spillway periodically to flush rocks and debris that enter the penstock. The lower penstock line has been seeded with a USFS approved seed mixture and vegetation has begun to grow.
Powerhouses: The upper powerhouse is equipped with a new Francis Turbine and 940kW generator. New controls and switchgear have been installed. The building has been cleaned, re-roofed, stucco applied, painted, new doors, new windows and air vents, new inside office, new access bridge and the surrounding area has been cleaned, landscaped, re-vegetated and brought back to original standards.
The lower powerhouse is all new construction and located on the property that Lower Valley Energy owns. The property is between the existing USFS\County road leading into the canyon, and the existing Brog road, and Swift Creek. The lower powerhouse is equipped with a new Kaplan turbine and a 597kW generator.
March 12, 2013: The Swift Creek Hydroelectric project has been certified as low impact for a five year term, effective August 16, 2012 and expiring August 16, 2017.
February 27, 2013: The LIHI Governing Board reviewed the application for certification, as well as the Application Reviewer’s Report. The vote to certify Swift Creek was unanimous.