PROVIDENCE, R.I. (AP) — Rhode Island's governor is going deep underground below Providence to check on work to build a tunnel to protect Narragansett Bay from sewage contamination.

Gov. Lincoln Chafee is scheduled to tour the tunnel being built by the Narragansett Bay Commission on Tuesday.

The tunnel is part of a more than $1 billion effort that will be the largest public works project in the state's history when completed.

The three-mile long tunnel is 26 feet in diameter. It runs deep under Providence and is designed to divert storm water that otherwise would overwhelm local sewage treatment plants, causing significant pollution into Narragansett Bay.

The project's cost is expected to reach $1.3 billion when the work is completed around 2017.

Shutterstock/Stephen B. Goodwin