LOS ANGELES (CBSLA.com) — Almost 100 feet under the surface of Los Angeles, a new network of massive rail tunnels is being built.

CBS2 News got an exclusive look at the new light-rail line nearly 9 miles long being built in the southwest part of the city.

It’s that olive-green line running from the Expo Line in Crenshaw through Inglewood and down to Los Angeles International Airport.

Metro says this area has more mass-transit riders than anywhere else in LA.

The starting point at Exposition Boulevard and Crenshaw right now is a massive pit and underground city of workers.

Charles Beauvoir is the project director and talked about progress of the tunnels.

“All the boring with the tunnel-boring machine” is done, he said. “But some of the tunnels that don’t use the tunnel-boring machine are still under construction.”

Tunneling is not a quick process. Just to drill a half-mile portion took about three months.

“The maximum speed we’ve ever achieved was about 150 feet per day,” Beauvior said. “We were concerned we might get a ticket from the police!”

Over in Hyde Park, the tunnels are much shallower. Workers call this a “cut and cover,” cutting through the street and covering it up.

The other end of the rail line crosses the busy 405 Freeway. Workers used an old railroad bridge to support the form for the new one in a major operation.

This process took “19 hours, 150 trucks of concrete for one of the pours,” Beauvior said.

The rail line will run right into LAX and the Green Line. A smaller people mover will get travelers in and out terminals.

It’s expected to be finished in about a year and a half.

“I think the rail system is the way of the future for Los Angeles to mitigate all the congestion,” Beauvior said.

The new line comes with a $2 billion dollar price tag. It’s been costing each taxpayer about $25 per year, part of Measure R that took effect eight years ago.