Puntledge River Siren System Tests, Water Flow Tests

April 26, 2016

From BC Hydro:

"Public safety is very important to BC Hydro and we communicate as much as we can when river flows may not be normal. Flood risk management, kayak flows and fish migration flow requirements are common reasons for needing to spill water downstream, but those events are planned operational changes where BC Hydro can provide notice through media and river signage. There are other situations where river flows can adjust quickly and be unplanned either from the powerhouse are diversion dam areas. To test and ensure our siren system is working should such a water flow event take place to warn the public, we will be mimicking significant and actual water flow fluctuations in the Puntledge River on April 28.

Whether planned or unplanned, quick river flow adjustments can be a public safety hazard, so the BC Hydro warning sirens placed along the river from the Comox Dam to Puntledge Park should initiate during these flows tests. Permanent river safety signage is in place, but the siren system provides the real-time flow event in advising people to get out of the river.

We will be manually testing the siren system on April 27, from 8:00 am to 4:00 pm, prior to the actual flow tests on April 28. On the 28th, the first process involves slowly ramping down the generation station from 24 megawatts to 5 megawatts and shifting the water over to the diversion stretch of the river, and increasing that flow from about 6 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 8:00 am, 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.

Unlike other system tests when the sirens are initiated individually, this test is to determine that they work as anticipated during an actual river flow change. Modifications to the system will be undertaken as needed following the test. The water low test is done once a year.

The normal discharge from the Comox Dam is about 32 m3/s. At various times on April 28 the flow release will drop down to 27 m3/s and hit a peak of about 50 m3/s.

The public is advised that on April 27 and 28 you will hear the siren sounds and to not enter the Puntledge River until after 4:00 pm. Temporary caution and danger safety signage will placed along the river from Comox Dam to Condensory Bridge. BC Hydro staff will also be along the river to monitor the warning system.

Enjoy the Puntledge River this summer and please be reminded of general water and river safety considerations, and this information can be found at http://www.redcross.ca/what-we-do/swimming-and-water-safety/swimming-boating-and-water-safety-tips. With the warmer weather, people will begin to gravitate to water to cool off and enjoy the summer. About 500 people have been counted throughout the Puntledge River system at one time. The public is reminded that this is a hydroelectric system where river flows may change quickly.

This spring, we will begin replacing the siren warning system along the Puntledge River. The various water gauges within the watershed, that trigger the communication of water flow rate changes to the sirens, will also be upgraded.

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 5 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 centimetres of fast flowing water is enough to knock a person off their feet."