​Alberta Transportation says its assessment of the proposed Springbank off-stream reservoir — designed to protect Calgary from major floods — has determined the project will have no significant impact on the environment.

That assessment will now be submitted the provincial Natural Resources Conservation Board and the Canadian Environmental Assessment Agency for approval — the final regulatory steps before construction could begin.

The province has been moving forward with the Springbank reservoir project since 2015, after the previous Progressive Conservative government decided it was the best option to protect Calgary from another major flood like the one that devastated the city in 2013.

"Springbank off-stream reservoir continues to be the best option for a number of reasons," Adam Johnson with Alberta Transportation said Wednesday.

"It's the most cost-effective to build. It has the least impact on the environment. And it would be the quickest to build, so it would provide flood protection the quickest for Calgary and other downstream communities."

This is the location of the proposed Sprinbank Reservoir, which would fill with water during periods of extremely high flow on the Elbow River to protect the City of Calgary from flooding. (The Canadian Press)

Area landowners have been campaigning against the project through a group they call Don't Damn Springbank.

They've been raising concerns about contaminants that could be picked up by floodwaters and left behind in sediment once the reservoir is emptied, and about potential impacts on groundwater.

The Tsuut'ina First Nation is also opposing the project, citing concerns over the fact that Stantec, an engineering services company involved in conducting the environmental assessment, would also be involved in the construction of the project.

"Let me restate for the record that the Tsuut'ina Nation continues to deny consent to this megaproject that will be metres from our Nation — a project that could have potentially disastrous impact on treaty lands, both upstream and downstream of the project," Chief Lee Crowchild wrote on Thursday, in an open letter to Transportation Minister Brian Mason.

Johnson said Stantec would be the "managing engineer" on the project, if it proceeds, and the province would hire "a separate firm to actually go through and do the construction."

Mark Svenson, an environmental co-ordinator with Alberta Transportation, also said any environmental risks from the project would be small and manageable.

"For the most part, the environmental impacts of this project are minimal and nothing that can't be mitigated," he said.

Mark Svenson, an environmental co-ordinator with Alberta Transportation, speaks with reporters about the Springbank reservoir project. (Julien Lecacheur/Radio-Canada)

Some area residents also say the loss of land would affect their way of life, even though they would be compensated for the value of the property.

Johnson said as many as 22 landowners would be affected and the province is offering to buy only the specific land that is required for the reservoir or to buy entire parcels if the owners would prefer not to split their land up.

The reservoir requires a minimum of 1,460 hectares (3,610 acres) to be purchased and the project is estimated to cost $372 million, including the price of land acquisition.

If every landowner wanted to sell every affected parcel in its entirety, that would boost the total land acquisition to 2,750 hectares (6,800 acres) and bring the estimated cost up to $432 million.

Johnson said the province expects it would recoup the additional $60 million by selling the surplus land that isn't needed for the reservoir, itself.

How does the reservoir work?

The project would involve building a temporary diversion that would be activated only during periods of extremely high water flows on the Elbow River.

Svenson said the river's typical high flow is about 23 to 25 cubic metres in June (the highest-flow month of the year) and the diversion would kick in only once the flow rate reaches 160 cubic metres per second.

Any water flow above that level would be directed into the Springbank reservoir.

The remaining flow would continue downstream to the Glenmore reservoir, which Svenson said is designed to handle that level of flow.

Adam Johnson with Alberta Transportation speaks to reporters in Calgary about the Springbank Reservoir project. (Julien Lecacheur/Radio-Canada)

The regulatory approvals are expected to take about a year, although the exact timeframes could vary.

If approvals are granted by October 2018, Johnson said it would take about two years from that point to get to a functional level of completion, at which point some amount of water could be diverted, if necessary.

It's expected it would take until fall 2021 for a full level of completion.

"At that point, we'd be able to take all of the floodwaters that we saw in 2013 between Springbank and the Glenmore reservoir," Johnson said.