Construction on a major transit project that has been planned for the City of Calgary for decades has been halted because of environmental concerns.

Groups have filed an appeal over the southwest ring road project, saying that the diversion of the Elbow River will end up negatively impacting beavers and waterfowl in four surrounding wetlands.

City and provincial officials say that the environmental impact to the area by the $1.4B, 30 km highway is unavoidable.

The appeal is concerned over a small stretch, where it crosses the Elbow River Valley.

Currently, the river runs through the area but the plan is to divert it along a different path and reduce the effort required to build a series of highway bridges.

Planners say mitigation measures, including culverts and water pumps, will be enough to keep water flowing to the impacted areas and prevent any flooding.

The appeal could end up delaying the whole project for an indeterminate period of time.

“Plans will be made in accordance with whatever the EAB rules and, of course, we’ll respect any decision that they come to. KGL Constructors remains confident in their design and in the mitigation measures that have been taken in order to maintain water flow in the area,” said Adam Johnson with Alberta Transportation.

A hearing will be held in October to decide the appeal.

Construction of the southwest ring road has been on the books for decades and only went ahead when a deal was signed with the Tsuu T’ina First Nation in 2013.

The province has set a project completion date of May 2022.