Big Bar landslide response information bulletin
May 1, 2020
Ongoing onsite operations
Earlier this week, work onsite was impacted by the high freshet flows from the region’s rapidly melting snow packs. During this time, crews readjusted to make progress in other areas such as the installation of anchors that will suspend the tubes for the pneumatic fish pump.
Water levels have since dropped and construction has resumed on the concrete fish ladder, which will guide fish to the pneumatic fish pump system. Efforts are now focused on fully completing the base of the fish ladder while the river remains in check.
Big Bar ferry operations have been suspended since last week as a result of the high water. Work onsite continues to be supported by river boats and crews, who provide site transport and are responsible for swift water rescue.
Prime contractor Peter Kiewit Sons ULC continues to face weather challenges with high winds slowing renewed rock scaling and the spring thaw impacting road conditions.
What do high water levels mean for fish?
Fish should be able to migrate upriver naturally during moderate flows from approximately 1,700 to 3,200 cubic metres per second (cms). Work completed this winter is expected to significantly increase the time during which these levels exist. Higher volumes will be tempered, improving the ability of fish to pass through the slide area on their own.
The cooler spring temperatures delayed the onset of freshet but the Fraser River flow now exceeds 3,200 cms. These elevated volumes mean the “nature-like” fishway will not be viable until the return of more moderate conditions.
The pneumatic fish pump system is expected to be in use by the end of May, when fish usually arrive at the Big Bar landslide site. This system will transport migrating fish when water levels are too high for them to use the “nature-like” fishway.
Finally, fish migration and hydrological monitoring programs throughout the spring and summer will help provide accurate information about fish migration to support further planning.
Installation of anchors that will suspend the tubes for the pneumatic fish transport system.
Construction of the concrete fish ladder was hampered this week by rising water levels, as seen at the bottom of this photo.
http://www.pac.dfo-mpo.gc.ca/pacifi...lide-eboulement/bulletins/2020-05-01-eng.html