Work is nearing completion on the first half of a massive project to rebuild the toughest 15 miles of I-90 east of Snoqualmie Pass.

Part of the $551 million project includes the state’s first animal “overcrossing,” a better and safer way for animals to cross the interstate. The crossing will link habitats on the north and south side of the freeway.

Also see | 'Cascade Crossroads' chronicling I-90 wildlife bridge

The “overcrossing” is designed to simulate a natural environment allowing animals to move from one side of the freeway to the other.

Not only will the crossing have trees and natural vegetation but also high walls to keep animals from seeing the traffic and headlights below.

If you’ve driven through those strange concrete “tunnels” east of Snoqualmie Pass, those are part of this project.

Several “underpasses” were built into early construction where Washington State Department of Transportation cameras are picking up animals moving under the freeway.

The project is scheduled to be completed in the fall of 2018.

WATCH: Video shows need for I-90 wildlife bridge at Snoqualmie Pass