Grand River Conservation Authority (GRCA) officials are hoping a new study will result in a lower cost for a major spillway construction project at the Conestogo Dam.
The authority has been facing a 2015 deadline to address deficiencies to the Conestogo Dam spillway capacity identified in a 1997 dam safety study.
Based on the study, a cost estimate of over $20 million was placed on the spillway project, which would involve constructing a channel around the dam to direct water into the Grand River.
The channel would run under Wellington County Road 11, requiring construction of a bridge, which GRCA communications officer Dave Schultz said would represent the largest single element of the project cost.
“Bridges are very expensive,” he noted.
The $20-million project estimate was based on existing standards. However, in 2011, the Ministry of Natural Resources (MNR) updated the technical guidelines relating to the design criteria of dams in Ontario. Schultz said that could change the size, and the cost, of the spillway.
At its Aug. 25 general meeting, the GRCA authorized a $60,000 inundation analysis project aimed at, among other things, determining the Hazard Potential Classification (HPC) for the dam at Conestogo Lake. The HPC categorizes dams according to the consequences of a failure or mis-operation of a dam.
That information includes the effect on the potential risk to people and property in the event of a large release of water from the reservoir. Estimates provided at a public meeting in 2009, indicated about 240 homes and 800 lives would be at risk from a major dam failure.
Schultz said the spillway would allow for a managed overflow, “If the water ever got so high that we had to get rid of some it to prevent a dam break.”
While the financial impact won’t be known until the inundation study is completed, Schultz said the GRCA is “expecting,” and “hoping” that the new technical requirements will allow the projected cost of the project to be adjusted downward.
When the new technical requirements were implemented, Schultz said the MNR granted the authority an additional year to finish the spillway, pushing the projected completion date back to 2016. However, he noted, funding sources for the project are still not determined.
“Generally speaking, the province, when you’re doing this kind of a project, has a policy of helping out through a fund that will provide 50 per cent,” from a pool of up to $5 million for all 36 conservation authorities in the province.
“The problem is, in this case, this project at 50 per cent would use up all the money in that fund for at least two years.”
Schultz said GRCA directors have been lobbying provincial officials to provide additional funding “for this type of major, multi-year project.” Meanwhile, the spillway project remains in the authority’s five-year capital budget forecast at the original estimate of over $20 million.
“Hopefully it will turn out to be less expensive. Then we will roll that into our five-year forecast,” said Schultz.
