Youngs Creek Hydro Power Project, United States of America

The Youngs Creek hydro power project is a run-of-river hydroelectric power plant being constructed on Young Creek, Washington, US. Youngs Creek is a branch of Elwell Creek, a tributary to Skykomish River, which is four miles from Sultan, Washington. The plant, currently owned and managed by Snohomish Public Utility District (SNOPUD), was formerly owned by Hydro West Group.

EES Consulting is the project designer. The plant design will incorporate best management practices to reduce pollution of the state waters, the company says. The power plant project broke ground in February 2010 and is intended to be completed in 2011.

Youngs Creek hydro power project

The Youngs Creek hydro power project is being undertaken to utilise smaller water resources and increase renewable power production in the US. The Federal Energy Regulatory Commission (FERC) issued the licence for the construction of the power plant to Hydro West Group in May 1992.

The project received section 401 water quality certification in February 1992 and was revised in November 18, 1993. Plant construction began during 1993-94 but was put on hold due to the unstable energy market.

In October 2008, the project was acquired by SNOPUD. Following the acquisition, the project's property, along with FERC licence, permissions and certifications, was transferred to SNOPUD.

SNOPUD proposed to resume the construction of the facility in September 2008. The construction was reinitiated by considering the increasing needs of renewable power in the north-west of the US.

Youngs Creek project contracts

Following its appointment by the district in 2008, the project was designed by EES Consulting.

The construction contract, which involves building the dam, intake structure, powerhouse, switchyard and penstock pipe, was awarded to TEK Construction (TEK) in February 2010. In addition, TEK will install the equipment supplied by the district, and will start and test the power plant's operations.

Strider Construction was subcontracted to undertake the majority of the site work. Apart from the installation of penstock pipe, Strider is also responsible for erosion and sediment control, access road improvements and excavation for powerhouse, dam and intake structures.

Whitewater Engineering Corporation (now known as Tollhouse Energy Company) was subcontracted to deliver the machinery installation services.

Hydro power plant details

The facility is estimated to generate about 7.5MW of power, with an annual generating capacity of 20,000MW/h. The plant is referred to as a "run-of-the-river", which includes a low dam to divert and intake water.

The hydro power plant will be located above a natural impassable barrier on Youngs Creek. It will include a concrete weir, an intake structure, a penstock and a short tail race. It also incorporates a masonry power station, which will be fitted with a turbine-generator set.

Power plant construction

The construction work being carried out by TEK Construction involves a concrete 65ft × 12ft (length × width) weir and an intake structure with a crest elevation of 1,520 mean sea level (msl). The dam is being constructed to divert the water stream. A small impoundment, with a surface area of about 0.21 acres at the normal pool elevation of 1,530ft, will be created by the diversion weir.

The project includes the construction of a penstock – 14,300ft long with a 48in-51in diameter – as well as a masonry power station – 65ft long and 48ft wide – and a short tailrace. A turbine-generator set will also be installed, in addition to the construction of a switchyard.

Transmission-line installation activities within all drainage and wetland areas should be avoided, with lines that have been designed according to the plans made. Underground transmission lines will be laid where no overhead lines exist.

Construction activities within drainage or wetland seeps will be carried out by isolating the surface water. A cofferdam that isolates surface water was constructed in agreement with Hydraulic Project Approval (HPA), which was issued by the Washington Department of Fish and Wild Life (WDFW). The water leakages from the cofferdam will be captured by sump pumps. The cofferdams are temporary and will be removed once construction is complete.

Culverts or bypass pipes will also be fixed to control the water flow and continue the construction work on Youngs Creek. These pipes will maintain the flow and keep the penstock's excavation dry. The outlet of the bypass pipes will be positioned at about 50ft downstream from the work place and a rock armour will be laid in order to prevent them from erosion and scour. The culvert will be fixed below the penstock and the trench will be backfilled.

Hydro power plant transmission and distribution

A new 12.5kV transmission line will be used by the power station. The power generated by the powerhouse will be supplied to the Sultan substation via a 8.2-mile long new transmission line. SNOPUD's existing system will distribute power to its customers.

Local environmental impact

The plant's diversion dam, intake structure and powerhouse tailrace channel are all located upstream of the natural barrier to anadromous fish and therefore should not have an impact on their safety.

The resident fish may, however, be affected during the construction and operation of the power plant.

Barriers for the resident fish are in the vicinity of the plant's site. The passage that precludes the falls is around 200ft upstream from the project's intake structure and diversion dam. Intake screens will be installed to protect fish populations during the plant's operation.