Tom Estrem starts work a little differently from most construction workers. He is working on, or rather under, Pier 15 in San Francisco.
Two years from now, the pier will be the new home of the Exploratorium -- a state of the art museum full of green features and innovative science exhibits.
But first the old pier, built in 1915, is getting a retrofit to withstand an earthquake up to an 8.2.
David Mik with Power Engineering took an ABC7 crew on a tour below the deck.
The project is a massive undertaking. Work on the deck and pilings alone will cost $50 million.
The crew scrambles to do as much as possible at low tide.
"Probably the one thing that impacts us most is the waves out here," Mik said.
There's a cave-like feeling under the pier, with more than 100 workers climbing around the site. They are stationed in teams, some on top of the deck, some underneath. Many have been partners for years.
"You need someone you can trust and depend on because they might need to save your life," pile driver Otho Middleton said.
Right now they are reinforcing old pilings. First the pilings are wrapped in rebar, then they are covered with a fiberglass shell. Finally, concrete is pumped in through a port which is closed off when the job is done.
Divers make all that happen underwater in very murky conditions.
"A lot of times you can't even see your hand in front of your face, so just turn your light off, close your eyes and kind of go to work, feel around," Estrem said.
The dive helmets weigh 30 pounds, but underwater they feel much lighter.
Oxygen tanks for the divers provide them with air as they go down and work on the piers below and tubes provide not just oxygen, but also warm water to circulate through their wetsuits, because of the cold temperature of the bay water.
The divers' helmets have microphones so they are in constant communication with a supervisor.
Meanwhile, high overhead, a giant crane is lowering new pilings. They are six feet wide and as long as 135 feet. On top of the pilings there is a huge concrete block to support the pier deck.
The public will never see all this, but divers say sometimes there is an audience.
"Every once in a while you feel a little crab or fish or something like that, once in awhile a sea lion will come by," Estrem said.
The entire project will cost about $300 million. The Exploratorium is leasing two piers from the city. Part of the deal is that the museum pays for all the improvements. They are still working to raise the money. During construction, the original Exploratorium at the Palace of Fine Arts is still open.
The new Exploratorium is scheduled to open in 2013.
Written and produced by Jennifer Olney
