Exclusive: Inside The Port Of Miami Tunnel Project

MIAMI (CBS4) — It's been three months since television cameras toured the Port of Miami Tunnel project.  The billion dollar underground wonder is on track to open for cargo and cruise traffic in 2014.

"Right now we are entering underneath government cut.  We are 120 feet below sea level right here.  Right above us today are four cruise ships," said Chris Hodgkins, the Vice President of the Miami Tunnel project.

Hodgkins took CBS4 News through the mile and half tunnel that has been carved so far.

Five additional mini tunnels have also been constructed that will act as emergency exits.

"If you are traversing in the tunnel and something should happen you have to have a way to get out.  So what we are doing is creating a cross passage that goes from this tube into the other tube," Hodgkins explained.

The distance between the two tunnels is about 55 feet.

SLIDESHOW: An Inside Look At The Tunnel

The big tunnels were bored with a mega machine named "Harriet".

One of the interesting secrets to digging underwater is using ice. Construction crews are pumping in brine that is 22 degrees below zero, essentially freezing the limestone and surrounding water.  After 30 to 60 days the workers chip away that ice and material eventually creating massive new tunnels.

The digging takes about three weeks.

The other major change happening is what can be seen just driving by the tunnel's outside.

"What we are building right now are the enclosures for 50-ton metal gates on both tubes.  They'll come down and seal off the tunnel to make it water tight," explained Hodgkins.

Water tight entrances are important because of South Florida's threat of hurricanes.  When completed the Miami Tunnel should be able to survive storm surges of any kind.

The plan is to have the tunnel open in May of 2014.