Environmentalists are calling for a federal environmental assessment of a billion-dollar oil exploration project in Nova Scotia on top of the provincial one.

Shell Canada is proposing a major offshore Nova Scotia exploration of seven oil wells beginning in 2015.

Armed with geological information it gathered from seismic vessels last summer, Shell plans to drill in much deeper water than the existing gas wells near Sable Island.

Environmentalists worry about the risk of a disaster that could threaten marine life such as whales, swordfish and tuna.

“The probability is low, but as we saw in the Gulf of Mexico, the impacts can be enormous,” said Mark Butler of the Ecology Action Centre.

He referred to BP's 2010 Deepwater Horizon explosion that killed 11 workers on the rig and caused massive damage.

“Right now of course we are excited about jobs and revenues accruing to provincial coffers, but should it go badly wrong out there, we will all be asking ourselves was it worth it,” he said.

The province's offshore regulator will carry out an assessment for the project. There could be a second assessment required as well.

The EAC wants an in-depth federal review on top of those. Ottawa can choose to review the project or not.

Seeking public comments

Stuart Pinks of the Canada-Nova Scotia Offshore Petroleum Board said the goal is to make it as safe as possible.

“The intention is to meld the two environmental assessments into one so there is a single assessment done that satisfies both sets of legislation. Even if it wasn't required under the federal [Canadian Environmental Assessment] Act, we would still require it to be done anyway,” he said.

The Canadian Environmental Assessment Agency is accepting public comments until Dec. 23. Next year, it will decide if there will be an environmental assessment and if it will be by written submission or a full panel review.