Inside the Devil's Slide tunnels, men were calf-deep in wet concrete the texture of split pea soup on Thursday. They used vibrating poles to dispel air pockets in the mixture. When visited by reporters, they were 10 days into pouring concrete roadways for the north- and southbound tunnels, and an hour, 60 feet and five truckloads of concrete away from completing a symbolic step in the massive project.
They are now more than three-quarters of the way through the project and pouring the concrete marks a big step for the tunnel project slated to open later this year.
More than 20 years in the making, Devil's Slide tunnel aims to get drivers from Pacifica to Montara safely. It's the first tunnel job in California since 1964.
The project has been a formidable feat: The expected December 2012 opening is about two years later than originally thought. Likewise, Caltrans has run roughly $30 million over the state transportation agency's expected budget due to change orders from the project contractor Kiewit. The latest estimate on the total cost stands at $342 million.
On a morning last week, Caltrans invited regional media in for a tour to commemorate pouring the roadways.
Concrete pouring is an exercise in teamwork. Imagine 15 men (no women were there on the day reporters visited) operating a contraption comparable to a pasta-making machine the size of a San Francisco trolley car.
Once the soupy concrete mixture is funneled from the truck, men paddle it even. Then, a nearly 30-foot-wide machine rolls in on wooden tracks. Large sweepers move back and forth to even out the mixture. Scooting along inch by inch, a long spinning corkscrew etches the layer of wet concrete to assure balanced distribution. Following the corkscrew, a ridged roller pads out the mixture. Then comes a smoother that is similar to a giant rolling pin.
"I could watch them make concrete all day," said Jeff Kraus, a safety manager consultant for Caltrans. Wearing a hardhat, plastic goggles, a bright reflector vest and an emergency oxygen tank, Kraus leans against the tunnel wall to look on at the men.
Finally, another trolley sprays a white curing agent that helps slow down the drying process. The agent leaves a film on the pancake-flat concrete that looks like powdered sugar. When the concrete dries it shrinks and is therefore prone to cracking. Later in the process, crews will cut lines in the concrete to prevent nascent cracks from growing.
A man pushing the trolley that sprays the curing mixture smiles when asked if he or other crew members have added their mark to the still-wet cement. He laughed and shook his head no.