Rehabilitation of the John Hart dam

The largest and most recent rehabilitation project undertaken by British Columbia Hydro involves the John Hart Dam on the Campbell River on Vancouver Island. This area has the potential for large earthquake events, with an earthquake with a 7.3 rating on the Richter scale occurring as construction was underway in 1946. Investigation showed that the dam and foundations were liable to liquify under low seismic loading, and the area downstream is now well developed and inhabited. Taking the 120 MW power plant out of operation would jeopardize the power supply to northern Vancouver Island, so it was decided to take immediate steps to stabilize the most sensitive areas and then to rehabilitate the dam to an acceptable level of earthquake resistance while maintaining the reservoir at normal level with the power plant in operation. Using innovative engineering techniques and careful monitoring, the project, which included foundation improvement under existing structures and virtual rebuilding of the earthdam, was completed without lowering the reservoir. In spite of the very restrictive environmental constraints, the work was done without unacceptable environmental impact or adverse public reaction. Costs were $24 million, slightly under budget. All instrumentation has been monitored on a regular basis and the performance of the dam is satisfactory. 7 figs