NB Power opens door to extending Mactaquac life beyond 2030
New technology reveals better structural integrity in dam's concrete than previously understood
NB Power is expressing greater confidence the life of the Mactaquac Generating Station may be able to be extend beyond 2030, avoiding the need to replace or remove the existing dam before that time.
The Crown corporation has been examining its options for Mactaquac with the expectation it would reach its end of life prematurely in 2030 due to expansion in its concrete structures.
- Mactaquac dam life extension through full rebuild on site ruled out
- Mactaquac dam replacement cost could hit $5B, says NB Power
The three end-of-life options under review are to build a new generating station on the opposite site of the St. John River, leave the dam in place without power generation, or remove the dam and generation station and allow the river to return to its natural state.
In an update released Friday, NB Power is now giving greater consideration to a fourth option — to extend the life of the existing generation station beyond 2030 through removing and replacing concrete and equipment in the existing structure.
"In recent months, technology has allowed for more detailed modelling of actual and potential impacts of the concrete expansion at Mactaquac, revealing better structural integrity than was previously understood," said NB Power in a statement.
We've yet to decide whether or not that's the right thing to do.- George Porter, NB Power's Mactaquac project director
"This improved understanding has provided NB Power with greater confidence in the potential for alternative approaches to allow Mactaquac to generate electricity beyond 2030, perhaps even to its original 100-year service life."
Two alternate approaches
The Mactaquac dam opened in 1968 with an expected service life of 100 years. However, an alkali aggregate chemical reaction in the dam's concrete has been causing the dam to expand over the years, resulting in the expected end of life in 2030.
Two alternate approaches are under review in the fourth option for the dam:
- Remove and replace the concrete in the most affected parts of the generating station and replace or repair certain mechanical and electrical equipment.
- Stabilize and replace some concrete in the most affected parts of the generating station, replace or repair certain mechanical and electrical equipment, and periodically change the position of the equipment.
NB Power said some of the the mechanical and electrical equipment involved in those approaches would have been due for replacement due to age and wear.
The costs of removing the dam, replacing it with a new dam and generating station, or maintaining the headpond but without power generation are estimated to range between $2 billion and $5 billion.
Porter could not give a cost estimate for the fourth option.
"I don't have a number right at hand. We're still working at refining the numbers on all the options," he said.
Porter said the fourth option would have a shorter lifespan and lower cost than building a new generating station and dam that would be expected to operate for 100 years.
"We're really still in pre-project phase where we haven't selected the specific project yet," said Porter.
NB Power has scheduled three public meetings for this month for presentations and "community conversation" about the future of the station. Those sessions are scheduled for:
- May 17, Crowne Plaza in Fredericton, 6 p.m.-9 p.m.
- May 18, Riverside Resort at Mactaquac, 6 p.m.-9 p.m.
- May 19, Best Western in Woodstock, 6 p.m.-9 p.m.