Safety reviews of the Dickson Lake and Cannell Lake dams in the Mission area have turned up multiple issues that need to be addressed within the year.
The reviews of the reservoir structures, which are operated by the Abbotsford Mission Water and Sewer Commission, were mandated by provincial rules requiring once-a-decade safety analyses of dams with a “high failure consequence.” The company that undertook the report, Ecora Engineering & Resource Group, found several items it deemed of “high” or “very high” priority.
But Peter Sparanese, the city’s general manager of engineering and regional utilities, said the reports weren’t particularly surprising, with dams requiring regular maintenance and upgrades.
“These things come about every so often,” he said.
At both dams, a video inspection of the low-level outlet conduits and the setting of an automated alarm to warn officials of hazardous water levels were each identified as “very high” priorities that should be addressed within six months.
Multiple other high-priority issues were identified at both lakes, including the installation of a log boom across the inlet channels, detailed topographical surveys, and the preparation of emergency preparedness and response plans for both lakes.
At Cannell Lake, high-priority items include the restoration of the design crest of the dam and various measures to prevent erosion, while Dickson Lake requires the removal of debris from the downstream channel. Such fixes should be done within one year, the report advised.
Several “medium” priority issues were also identified. They should be fixed within three years, the report recommends.
To address those and other issues identified, the report recommends solutions that would cost the WSC between $290,307 and $405,307.
A staff report prepared for the joint shared services committee envisions addressing the issues through tasks over the next three years. It suggests the safety upgrades will cost $726,500 over the next three years. The largest costs would be $375,000 for engineering assessments and remedial works at the two dams.
The report by staff says its estimates were adjusted upwards from Ecora’s estimates “as deemed prudent for internal admin costs and to correct certain Ecora assumptions, plus adds a minimum 50 per cent contingency.”
While the Ecora report suggests “very high” priority issues should be addressed within the next six months, only staff dam safety training is recommended to be conducted this year. Pipe outlet video inspections and installation of automated alarms are both scheduled in the report for next year. The installation of log booms would also be completed in 2017.
Sparanese said the six-month time frames are guidelines, and that the city is still completing work budgeted for the current year. The report will help planning for the upcoming budget year.