BC Hydro’s annual siren system test is set to take place along the Puntledge River May 12 and 15.
The test to ensure the public warning system is working as designed heading into the summer season. Whether planned or unplanned, quick river flow adjustments can be a public safety hazard. The BC Hydro warning sirens placed along the river from Comox Dam to Puntledge Park initiate when such events take place.
Permanent river safety signage is in place, though the siren system provides notice of a real-time flow event and for people to move out of the river channel.
The siren system test is done once a year. BC Hydro will be manually testing the siren system on May 12, from about 8 a.m. to 4 p.m., prior to the actual river flow tests on May 15.
On May 12, we advise the public to stay out of the Puntledge River given the flow tests and the siren activations that will be taking place. Temporary caution and danger safety signage will be placed along the river from Comox Dam to Condensory Bridge.
BC Hydro staff will also be along the river to monitor the warning system. Depending on the test results on May 12, there is a chance a siren may be modified and briefly tested again on May 14.
On May 15 the generation station will likely be running at about 20 per cent of capacity, and BC Hydro will shift some water flow through the Nymph Falls and Stotan Falls section of the river, where flows will go from about six cubic metres per second (m3/s) to about 20 m3/s.
This flow redirection is to keep fish habitat fully covered and limit any potential impacts to fish from the test. After 8 a.m., there will be a quick pulse release from the Comox Dam to increase the river flow by an additional 20 m3/s. This flow should then initiate the siren at the dam and as the water surcharge moves downstream, with the other sirens initiating in sequence.
For the last part of the testing, the flow out of the generating station will be increased quite rapidly to test the siren just downstream of the station.
The current discharge from the Comox Dam is about 19 m3/s. At various times on May 15, the Puntledge River flow will increase to 27 m3/s and hit a brief peak of about 50 m3/s.
BC Hydro noted they understand people enjoy the Puntledge River yet this test is also a reminder that this is a hydroelectric system where river flows may change quickly.
The Puntledge River hydroelectric system includes the Comox Dam, which impounds the Comox Lake Reservoir, where the water released travels 3.7 kilometres down to the Puntledge River Diversion Dam.
From there, a minimum fish habitat flow is provided down the river and the majority of water is directed down a five-kilometre penstock to the generating station, where the water is then discharged back into the river.
River flow hydraulics and under-surface currents can be dangerous. Only 15 cm of fast-flowing water is enough to knock a person off their feet.