Atlin Hydro Lower Powerhouse Expansion, British Columbia

Location: Atlin, British Columbia
Owner/Operator: Atlin Tlingit Economic Limited Partnership and Tlingit Homeland Energy Limited Partnership

The Taku River Tlingit First Nation are the band government of the Inland Tlingit located in far north British Columbia, Canada, in the small remote community of Atlin, with a population of approximately 400 people.

For decades this community near the BC/Yukon border, relied on a diesel power plant to sustain their energy needs. Taku River Tlingit First Nation leaders recognized the need to offset diesel power with clean, renewable energy in the long term. With this in mind, the Atlin hydroelectric power station was built in 2009, saving the community from burning more than 1 million litres of diesel fuel every year. A new expansion project promises to further help reduce the amount of diesel burned in the local community. The new project, which is still in the technical review stage, is slated to expand the existing two-megawatt hydropower facility in Atlin, to a 10.5 megawatt facility, and export the additional power to the local energy grid through a new transmission line. The Atlin Hydro Expansion Project would be separate from the existing upper hydro-power facility on Surprise Lake, which currently supplies most of Atlin’s power. The new lower power plant would be constructed just inland from Pine Creek Beach on Atlin Lake.

When complete in 2024 at a cost of about C$206 million, the Expansion Project will eliminate the need for four rental diesel generators and generate about 31 GWh of electricity each winter.

Noise Impact Assessment of the proposed Hydroelectric Generating Station

HGC Engineering was retained by Atlin Tlingit Economic Limited Partnership (“ATELP”) and Tlingit Homeland Energy Limited Partnership to undertake a Noise Impact Assessment of the proposed new hydroelectric generating station. This assessment had been requested to address noise concerns raised by local residents of the nearby town of Atlin. HGC Engineering personnel conducted baseline sound level monitoring near the site to establish existing sound levels, for comparison with the potential future impact of the lower powerhouse.

The facility will utilize a single Pelton turbine generating unit with a nominal capacity of 11 MW. A high voltage switchyard will be located adjacent to the lower powerhouse with an associated step-up transformer. The turbine and generator will be housed within a steel metal clad building placed on a reinforced concrete substructure. The potential sources of steady sound associated with the proposed facility will be building ventilation openings, the tailrace discharge opening, and the transformer within the switchyard.

Computational Acoustical Model of the proposed Hydro Powerhouse

Using a computational acoustical model of the facility, (assembled using sound levels measured at the Box Canyon Powerhouse, a very similar hydroelectric site southwest of Squamish, BC)  the potential sound level impact of the proposed powerhouse was predicted at sensitive receptors located within 750 metres of the site. The results of the acoustic modelling were used to provide input to the project team, to mitigate noise and minimize the potential for adverse impact.

Acoustical Engineering Services Included:

• Noise Impact Assessment of the proposed Hydroelectric Generating Station
• Baseline Noise Monitoring
• Employed predictive analysis to determine the anticipated offsite sound levels in the neighbouring residential communities, resulting from the future operations of the Powerhouse.
• Evaluated the anticipated sound levels with respect to the environmental noise assessment criteria set by the British Columbia Noise Control Best Practices Guideline and Health Canada Guidance.