The John Hart Generating Station Replacement Project is progressing well, and this includes the tailrace rock excavation adjacent to the existing John Hart generating station.
InPower BC, the project contractor, is excavating downward into the rock and is now encountering conditions that require more sensitive controlled rock blast areas near the operating and aged John Hart generating station. To be cautious during this work and with the goal of always protecting downstream fish habitat, BC Hydro is transferring some flow from the generating station to Elk Falls Canyon during this blast, BC Hydro spokesperson Stephen Watson says. The operational redirection of flow will ensure that fish habitat in the lower Campbell River remains fully covered with water.
“We are providing a public safety notice of increased Elk Falls Canyon flows on the Campbell River system from Tuesday evening through to mid-afternoon on Wednesday this week,” Watson says. “People are advised to stay away from the river upstream of Elk Falls and obey the safety signs along the trails systems.”
The increased flows in the canyon over a short duration of time is to protect fish habitat downstream of the generating station during a potentially higher vibration blast to start the next level of rock excavation of the tailrace water outlet. The tailrace water outlet facility requires about a 20 metre deep excavation through the rock adjacent to the river. This is being excavated in layers. The initial controlled blast for the start of each layer may have higher levels of rock vibration.
Water flows in the canyon were increased from 10 m3/s to about 80 m3/s overnight on Tuesday and will be reduced back to 10 m3/s by early afternoon today. Water flow coming from the generating station will be adjusted by an equal and opposite amount. The normal canyon base flow for this time of year is 7 m3/s but BC Hydro is providing the last of its springtime two-day steelhead migration and spawning flows in the canyon.
The short duration flow increase should have no significant effect on fish in the canyon. Water flows downstream of the John Hart generating station should remain fairly constant as the operators incrementally shift flow from the powerhouse to the canyon and back.
InPower BC, the project contractor, is doing controlled drilling and blasting very close the 68-year-old generating station. The new water discharge outlet or tailrace is being constructed just upstream of the existing station, and there is very good communication with construction crews and powerhouse facility staff. This is where water that has come from the John Hart reservoir and traveled the new power tunnel and underground powerhouse re-enters the Campbell River. Vibration monitors and contingency operational plans are in place for each blast to protect and respond to the six operating turbines and generators. Given the sensitivity of the old equipment that’s in poor condition, units have occasionally been operationally affected since the work started in October 2015, Watson says. Quick response by crews to re-start the unit or increase the capacity of other units has resulted in minimal to no impacts to fish habitat.
The Campbell River flow below the powerhouse before, during and after this morning’s controlled blast will be about 125 m3/s. The discharge rate out the generating station for this tailrace blast will only be about 45 m3/s with the remaining 80 m3/s flowing down the Elk Falls Canyon. All six units will be running at low capacity. A Campbell River flow of about 80 m3/s keeps the fish habitat fully covered with water. The proactive spill down the canyon will protect downstream fish habitat should one or more of the six powerhouse generators be temporarily affected.
This type of sensitive blast and a short duration spill event may happen again in the future.
The John Hart project is building a water bypass facility within the new underground powerhouse so that if one or more of the new units are forced offline, the bypass facility will automatically re-direct the water and maintain downstream river flow continuity. Maintaining downstream river flows for fish is one of the three reasons for the project.