Cranbrook voters are casting ballots Saturday on a plan to double the city's size. (Courtesy of Citizens for a Livable Cranbrook Society)

Voters in Cranbrook are heading to the polls Saturday to decide whether to double the size of the city in B.C.'s southeastern Interior.

The so-called Eastern Boundary Expansion plan would add about 3,640 hectares by incorporating some private and Crown land east of town, effectively doubling the size of the city.

All but one member of council wants to expand the city into the rolling hills overlooking the Rocky Mountains.

The pro-expansion group, called Yes for Opportunity, is made up largely of the Cranbrook business community, including the Chamber of Commerce, and most city councillors.

They say the city should have some say in how the land is developed.

"This is private land. It's going to be developed anyway and we should have control over the nature and pace of that development," said proponent Courtney Magro.

However, opponents say the community is already too big and unwieldy, and that spreading out farther across the valley would push development in the wrong direction.

"This is the future of our community and it's a huge issue, and I think we need to fix the Cranbrook we have and there is a lot to fix," said opponent Sharon Cross, who runs Citizens For a Livable Cranbrook Society, a grassroots organization formed to fight the expansion.

Polls for the referendum are open 8 a.m. to 8 p.m. local time Saturday.