Underground—North America—Canada—Tunneling
John Hart Generating Station Replacement Project:
System Solutions for difficult Ground Conditions in an Access Tunnel
The John Hart Generating Station in Campbell River on Vancouver Island in Western Canada has been
operating since 1947. In 2014, a large-scale modernization project was initiated that includes the
construction of an underground powerhouse and associated facilities.
Upon completion, expected in 2018/2019,
the facility will have an increased installed
capacity of 132MW featured by 3 new
turbines. Besides an increase of structural
safety against potential earthquakes, the
visual impact of the hydro station will be
reduced by removing the 3 current surge
towers and wood stave penstock lines.
One key element of the project is the L20 main
access tunnel, which provides truck access
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to the 40m high and 94m long by 20m wide
underground power house.
In May 2015, weak ground was encountered
about half way through the tunnel. As later
confirmed, this zone was part of an ancient
riverbed traversing the previously excavated
basaltic formation likely deposited by an
ancient glacier. These features are sometimes
referred to as buried valleys.
As opposed to the original ground support
concept employed using poly reinforced
shotcrete, lattice girders, and CT-Bolt™
combination rock bolts, excavation and
support of this weak ground zone required
additional measures. Bolstered by technical
support from DSI and various tunnel expert
teams, a contingency excavation and ground
control concept was developed within a short
period of time.