Bridge may be required for Garnet Dam access road

SUMMERLAND — While keeping a close eye on the snowpack, District of Summerland staff have identified the need for a bridge along the Garnet Dam access road.

Monday evening, council approved the expenditure of $100,000 from the water capital reserve fund for the bridge, which will be located where the road crosses the spillway.

The probable maximum flood volume is 10 times the capacity of the existing culvert.

Staff reported there isn’t enough space to install 10 culverts and that renting a bridge used by logging companies was not feasible.

“Without this improvement (new bridge), there is risk of the access road being washed out, resulting in no access to the dam,” said director of works and utilities Kris Johnson.

During the past few months, inflow volumes into the Garnet Reservoir have been higher than volumes seen since tracking began in 2012.

This past summer’s wildfires, which burned a portion of the catchment area, is most likely a contributing factor to the increased runoff.

“Although many of the trees are still standing in this area, most of the underbrush no longer exists, which allows water on the surface to reach the reservoir more quickly,” Johnson said.

Eventual widening of the spillway and installation of slope protection on the face of the dam are planned to be completed in 2021.

The Garnet reservoir and dam are associated with the Eneas watershed system, a relatively small portion of Summerland’s overall watershed.

The risk of uncontrolled spilling is less in the much larger Trout Creek system because of the increased capacity of Thirsk Dam and the ability of Trout Creek to handle significant variations in flow volumes.

However, the intake at the Trout Creek flume requires upgrades to alleviate the possibility of additional water entering the Summerland Reservoir.

“Since this reservoir has no spillway to release water if needed, the risk of flooding increases if the flume flow is not controlled,” Johnson explained.

Snowpack measurement at Headwaters at the upper end of the Trout Creek system is at 148 per cent above historical average and 159 per cent at Isintok at the southern end.

Although snowpack levels were not measured in the Eneas system, the Trout Creek measurements give staff an indication of levels throughout the watershed, Johnson said.