East Toba & Montrose Hydroelectric

LOCATION:  Powell River, British Columbia   |   OWNER:  Alterra Power Corporation
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This run-of-river hydroelectric development project is located about 100 kilometers (62 mi) north of Powell River, British Columbia. Owned and operated by Alterra Power Corporation, it consists of two hydroelectric generating facilities: the 146 MW East Toba Hydroelectric Generation facility and the 88 MW Montrose facility.

The 146 MW East Toba facility operates at up to 30.7 m3/s (1084 ft3/s) and 581 meters (1,906 feet) of gross head. The integrated dam and intake structure is a reinforced concrete structure with spillway, control weir, earth/rock embankment abutments, trashracks, stoplog gates, inflatable spillway control gate, and associated controls. The 5.5-kilometer (3.4 mile) buried penstock includes a short reach of 3-meter-diameter (9.8 feet) high density polyethylene pipeline, and 4.9 kilometers (3 mile) of 2.7-meter-diameter (8.9 feet) thin-walled welded steel pipeline.

The 88 MW Montrose Creek Hydroelectric Generation facility is in service and operating at up to 22.8 m3/s (805 ft3/s) and 466 meters (1,529 feet) of gross head. The integrated dam and intake structure is a reinforced concrete structure with a Coanda screen spillway and collector channel, earth/rock embankment abutments, and associated controls. The 4.2-kilometer (2.6 mile) penstock includes approximately 3.8 kilometers (2.4 mile) of 2.7-meter-diameter thin-walled welded steel buried pipeline, and 283 meters (928 feet) of 2.1-meter-diameter (6.9 feet) thin-walled welded steel surface pipeline on an 88% grade.

As a sub-consultant, McMillen Jacobs Associates provided independent design review of the two dam/intake structures and penstocks for this $660 million USD hydroelectric project. Our review included the diversion dam stability and intake hydraulic steel structure design and operations. We also reviewed the penstock alignments, hydraulics, transients, structural analysis and design, bends, fabrication, welding, soil restraint systems, backfill and compaction, penstock linings and coatings, and geologic/geotechnical considerations. In addition, McMillen Jacobs Associates provided selected construction monitoring services during construction of the intake structures and penstocks.

Both facilities were constructed using the engineer-procure-construct method and were commissioned in 2010.