The CNSC moved the meeting to Ajax, given the interest in the community on the refurbishment.
While OPG has filed an environmental assessment (EA) with the commission on the refurbishment, the company has not yet made a decision on whether the work will be done. The Province has asked OPG to look into refurbishing Units 5, 6, 7 and 8.
In addition to the EA, OPG is also conducting a business case on whether the project can be financially viable.
The EA completed by OPG found there would be "no significant adverse environmental impacts" with a refurbishment, Pat McNeil, senior vice-president of generation development for OPG, said to the commission.
OPG considered several factors in the EA, including the effect the work would have on air, land and water, effects on humans and wildlife, socio-economic considerations and Aboriginal interests.
In a press conference prior to the start of the hearing, groups opposed to the work outlined where they think the EA is lacking.
"We're here to tell the CNSC not to approve the EA as it is today," said Shawn-Patrick Stensil of Greenpeace.
The EA is "flawed" and "it shouldn't be used as an excuse to rebuild," Mr. Stensil said. "Let's state the obvious. Pickering 'B' should be shutdown and replaced with green energy. The CNSC has refused to look at alternatives to Pickering 'B'."
Mark Mattson of the Lake Ontario Waterkeeper said one million fish are killed each year when water is drawn from the lake.
"The EA doesn't consider mitigating effects," Mr. Mattson said.
During the hearing, Paul Pasquet, the senior vice-president of Pickering 'B', said the company has two options to mitigate the impacts on fish, including putting in a net near the intake or use sonar to keep fish away.
"The assessment should look at options and this assessment doesn't look at that," said Cherise Burda of the Pembina Institute.
There's a "cap" on the amount of green energy that can be produced in Ontario and that has to be removed, she said.
"There's very little space for green energy to grow. If Ontario is serious about getting more green energy on the grid, there needs to be less of something else. Obviously, where they need to do less is less nuclear energy," Ms. Burda said.
A poll showed Ontarians would prefer to replace old nuclear stations with green energy, Ms. Burda said.
"As nuclear comes off line, we can start ramping up the green portfolio," she added.
Creating "2,000 megawatts of green energy is very easy to achieve," Ms. Burda said.
Mr. McNeil outlined the public consultation undertaken by OPG during the EA.
"Overall, we feel confident in saying that there is not a high level of public concern regarding potential refurbishment, given the overall level of interest in the project," he said.
"The effects of the project are considered to be minor and are already managed and understood," Mr. McNeil said. "The project is not expected to change the local community's use and enjoyment of private property or neighbourhoods.
"The positive effects are broad and regional in scope," he said.
If the refurbishment is done, work would start around 2012 and take about two and a half years for each reactor. The units would then operate until 2060.
CNSC staff reviewed the EA and agreed with the recommendation that there would be no significant environmental effects.
The CNSC is expected to announce a decision in about six to eight weeks.