CARLA ALLEN
Tri-County Vanguard
An $18-million refurbishment project for a Yarmouth County hydro dam that dates back to 1928 is well underway by Nova Scotia Power.
Work began in the summer of 2017 but came to a standstill following a decision by the Nova Scotia Utility and Review Board that the Crown – a.k.a. the province – did not consult enough with Indigenous communities.
The situation was resolved in February and Nova Scotia Power has outlined a schedule of remaining work.
This summer, water migration issues discovered in 2017 were resolved by constructing a concrete core wall between the Tusket power canal and the new Tusket main dam structure.
Browren Allard, project manager with the NS Power Tusket Dam project, says work on the project is being done without draining Lake Vaughan.
“It’s certainly been challenging,” she said.
“It’s required a lot of effort to leave Lake Vaughan at its current elevation, especially this spring with so much rain in advance when we were trying to get started.”
The first three concrete sections of the new dam are slotted for completion by the end of 2019.
Demolition of the existing Tusket main dam concrete sections (after they have served as a cofferdam for the construction of the new dam) will be one of the last tasks completed, as the existing dam is being used to hold back the waters of Lake Vaughan during construction. It’s estimated that this task will be completed in November/December 2020.
Replacement of the Hurlburt Falls Bridge, which is parallel to the dam over the Tusket River, is scheduled to be completed this fall.
A detour of the bridge was set up in August and will remain in effect until early November.
Allard says the replacement bridge will be higher over the water and close to 30 feet longer, with a wooden deck.
As of early September, the crew was several weeks away from constructing bridge abutments for the new bridge. Weather conditions impact the schedule considerably.
Components for the pre-fabricated bridge are on site. As dismantling and removal of the old structure happens, the new bridge will be constructed on the road, then slid into place.
The new structure will be a big improvement over the old.
“It will actually will be able to pass the same amount of water as the dam,” said Allard.
Twelve to 20 people are working on the project at any one time.
“We try to use as many Nova Scotian-based contractors as we can. There’s a lot of local content here. A lot of money is being spent within the province,” said Allard.
The new dam structure is needed to meet Canadian guidelines that were updated in 2007. Since 2008 Nova Scotia Power has been addressing dam structures throughout the province to bring them in line with the guidelines. There are 178 structures across the province. NS Power began updating high-risk structures first.
Construction on the Tusket project will cease Dec. 31, 2019 to July 1, 2020 as per environmental regulations.
Work scheduled for 2020 includes: refurbishment of various dams that form the power canal (including the Tusket canal embankment, the Tusket powerhouse embankment and the western wing dam), as well as modification of the east embankment dam and Tusket main dam fish bypass.
Upon completion of the project, the four spillway gates will have been replaced with eight and the associated superstructure, hoists, stoplogs, etc., will allow the dam to withstand a one-in-1,000-year flood, while maintaining the level of Lake Vaughan within Nova Scotia Power’s flowage rights.
