Beneath your tunnel drive is a vast safety system

A dozen high-powered fans, eight industrial drainage pumps the size of washing machines, miles of electric cables and concrete-encased water pipes, and walls of power breakers and transformers.

This is the Chesapeake Bay Bridge-Tunnel drivers never see.

The guts sit behind the tunnel's walls, ceilings and floors and in five-story buildings at each tunnel portal.

It takes 159 staffers working around the clock to run the vast network of machinery.

As with the region's other four tunnels, all of this remains out of sight and out of mind for drivers - unless something goes terribly wrong.

That's what happened July 2 at the Hampton Roads Bridge-Tunnel when a water main burst, spilling more than a million gallons of water under the road, flooding the travel lanes and shutting down the westbound tunnel for most of the day.

Human error caused the closure because tunnel workers failed to respond quickly enough, despite alarms and warnings, Virginia Department of Transportation Commissioner David Ekern said last month.

VDOT does not allow tours of its tunnels and keeps secret the design and operation. Disclosing such information poses a national security risk, VDOT officials say.

The Chesapeake Bay Bridge-Tunnel has less traffic than the Midtown and Downtown tunnels and the Hampton Roads and Monitor- Merrimac Memorial bridge-tunnels, putting it in a lower risk category, officials say.

The Chesapeake Bay Bridge-Tunnel is run by a state entity that's independent of VDOT. Bay-bridge tunnel officials offered a glimpse of the two tunnels' inner workings in a behind-the-scenes tour.

Staff members regularly give tours for groups and individuals. Security-sensitive areas are kept off limits.

Funded entirely by user tolls, the Chesapeake Bay Bridge-Tunnel is a 20-mile-long road consisting of bridges and two one-mile-long tunnels that cross the lower Chesapeake Bay. Its annual operating budget is $12.7 million. After it opened in 1964, it was named one of the "Seven Engineering Wonders of the Modern World."

Executive Director Jeff Holland said the bridge-tunnel is situated "in the harshest marine environment of any facility in the U.S."

The structural design of the Chesapeake Bay differs somewhat from that of other local tunnels.

Still, the elements critical to any tunnel's daily operations are the same - keep air flowing, power humming, water at bay and, of course, traffic moving.

"We're sitting at the mouth of the Chesapeake Bay - all kinds of weather comes at us at any time and we still maintain the facility and the traffic," said Michael Wells, electrical/mechanical superintendent.

The keys: redundancy and maintenance.

Every system or piece of equipment has at least one back up, Wells said.

And maintenance is "constant for us with all the salt air," he said. Workers known as maintainers check every piece of equipment in the tunnel once every two to three hours.

"They put their hands on the equipment," Wells said. "They check, look, listen for any discrepancies in the equipment on all five floors of all four buildings."

The control rooms are the brains of tunnel operations. The facility has two, one at each tunnel. They're perched on the top floor in two of the four ventilation buildings at the ends of the tunnels.

Quiet and spare, the only clue that they control a major transportation facility is the view out of a window of cars and trucks zipping by below at 55 mph.

From these rooms, operators monitor all aspects of the tunnel with 10 cameras at each tunnel, three computers, and a control panel of buttons, lights and alarms.

When water starts collecting somewhere and pumps start running, a light and alarm are activated and stays on until the controller walks around the desk, stands before the panel and turns it off.

"It forces you to come over here and do something so you can't ignore an alarm," Wells said.

The controller then dispatches a maintainer to assess the situation and notes it in a log.

In a hard hat and reflective vest, the maintainer descends to the lower floors of the building to dark, damp equipment rooms that smell like a musty basement.

It's normal for pumps to run in stormy weather. Rainwater runs into roadway grates and collects in sump basements. Float devices, similar to the ball in a toilet tank that monitors water levels, detect pooling water and activate the drainage pumps.

The pump rooms are separated from areas where water collects. There are three pumps at each end of the tunnel and two in the center. Their combined pumping capacity is 7,000 gallons per minute.

"Most of the time, one pump takes care of everything," Wells said. Pumps are used in an alternating fashion so they get even wear and tear, he added.

All the drainage pumps are original to the tunnel and are now being replaced. Wells said that finding parts was becoming difficult for the old models, plus the new ones operate more efficiently.

The pumps, both old and new, are not submersible. VDOT is installing submersible ones in its tunnels so they operate even when inundated.

"We don't plan on being under water," Wells said. The facility has never been closed because of flooding.

In addition to the drainage pumps, each tunnel has two booster pumps, which maintain a flow of water through a network of pipes for fire protection. They each pump 250 gallons of water per minute.

A 150,000 gallon tank holds water for fire suppression and tunnel washing.

"If they come on, I know water is somewhere; I know something is wrong," Frankie Brady, senior tunnel equipment operator, said of the booster pumps.

Like other control room operators, Brady used to work in maintenance at the tunnel and is familiar with the mechanics.

"All our senior operators have been through the ranks," Wells said. "They know what's normal and what's not."

Below Brady's control room is the open and airy fan room.

Each tunnel has a dozen massive fans - six exhaust fans and six intake fans each nearly 15 feet across.

At least two of each run at all times. Their loud whirling sounds similar to airplane propellers. As with the water pumps, they are used in an alternating fashion.

The circulation cleans the air of exhaust fumes and prevents the buildup of potentially deadly carbon monoxide from the 10,000 autos that pass through the tunnel on average each day. It also prevents a build up of moisture that could damage tunnel equipment.

Monitors measure carbon monoxide levels, and operators activate the appropriate number of fans.

Maintenance director Robert Johnson said that if all the fans are operating at their highest speed, the air in a tunnel can be completely recirculated in two minutes.

The blowers push fresh air under the roadway through an air duct. The air moves into the travel lanes through openings on the sides of the roadway.

Exhaust fans suck the air out of the tunnels through flues in the ceiling then into an overhead air duct.

The upper and lower ducts run the length of the tunnels and are nearly pitch black, confining, concrete-encased wind tunnels. Inside, the sound of rumbling cars mixes with the whoosh of wind, making conversation nearly impossible.

The building also houses an electrical floor with breakers, transformers and back-up generators. Electricity comes to the facility from the Virginia Beach side of the Bay.

Another area of the building contains the controls for the tunnel lights. Meters gauge the tunnel's brightness and automatically adjust lighting levels.

Several elements run the entire length of the tunnels, including electric cables and fire mains. The fire mains are encased in concrete in the walls of the tunnel with access hatches at each valve.

All the components of the facility's tunnels and bridges are inspected and rated regularly by an outside firm, many of them on an annual basis, Holland said.

Those findings are reported publicly and are used by the facility's 11-member governing board, who are appointed by the governor, to make decisions about maintenance and capital activities.

"We feel that the more information the better," Holland said.

In that vein, the bridge-tunnel offers audio driving tours for users that can be downloaded to MP3 players that include not only facts and history but also information about ongoing maintenance projects.

Likewise, capital projects are described on the bridge-tunnel's Web site: www.cbbt.com.

As with other complex transportation facilities, Holland said, "It's incredible everything that goes on behind the scenes that make for a seamless operation."

Debbie Messina, (757) 446-2588, debbie.messina@pilotonline.com