It's a familiar composition to Bay Area commuters, one they've been hearing, watching and paying for as the new eastern span of the Bay Bridge takes shape over eastern Bay's shallows.
That audience the motorists who make 280,000 trips a day across the bridge is unlikely to miss a note as the $5.6 billion symphony conducted by Terpstra, Caltrans' East Span Project Manager, reaches a crescendo at 8 p.m. Friday.
At that hour, the bridge closes for the first time since it was damaged in the 1989 Loma Prieta Earthquake so that workers can demolish and replace the first big piece of it on Yerba Buena Island.
After 3 1/2 days over the Labor Day holiday, the bridge will reopen at 5 a.m. Sept. 4, provided the orchestra doesn't miss a beat.
If there are problems, such as a slow demolition or a hitch in installing the new piece, the closure could throw the Bay Area's workday commute into disarray.
Barring that disaster scenario, motorists will be driving on the first new section of the eastern span, a 6,500-ton slab of post-stressed concrete vast enough to accommodate a Raiders-49ers football game.
``It's going to be a heckuva weekend,'' Terpstra said with a boyish grin at a recent weekly meeting of two dozen Caltrans managers and private consultants responsible for the bridge's various component projects.
Presiding over a campus of several hundred engineers in one-story modular construction offices, Terpstra had just received a positive report on the big move.
C.C. Myers, the Rancho Cordova contractor that wowed the Bay Area by rebuilding the melted Interstate 580 connector ramp in the MacArthur Maze in 18 days, was five days ahead of schedule in its preparations for the big move next weekend. When Friday arrives, they'll be ready.
The impending closure has sharpened the area's focus on the often frustrating 24-year effort to rebuild the Bay Area's 71-year-old primary artery. As the odds of a major earthquake increased with each passing year, the Fates conspired to delay the project.
Engineers argued over retrofitting or replacing the old bridge. Federal, local and state authorities fought over the path of the new bridge. Local officials insisted on a more photogenic span. Caltrans failed to entice competing bids and cost estimates fell well short of reality. Welders warned of shoddy work deep in the skyway's foundations.
As of today, Caltrans engineers estimate the eastern span will be done sometime in 2013. While six years might seem a long time to the uninitiated, it's barely a long vacation in Bay Bridge seismic retrofit years. Time-wise, it means the job is 75 percent finished.
And progress is much more than semantic these days on the new bridge, built by the Caltrans, the state's transportation department, and 60 percent financed by the Bay Area Toll Authority.
The skyway viaducts, east- and westbound, are tangible, visible concrete ribbons for 1.2 miles each, rising up from the Oakland mud flats to meet a yet-to-materialize suspension span.
More than 2,000 feet long and with four conjoined towers rising 525 feet above the water's surface, the bridge's focal point will be the largest self-anchored suspension span in the world.
Columns rising up just south of the old steel-cantilever span on Yerba Buena Island will soon be supporting a $374 million, 2,100-foot-long viaduct that will carry bridge traffic around island construction starting in 2010.
All the project's prior disputes and snafus are what project managers call risk.
Every time it's possible that two contractors will step on each other's toes, whenever it appears that materials might not be available when needed, each likelihood of equipment breakdown is a risk that John Tapping, the East Span Project risk management coordinator, tries to head off.
The odds that an unanticipated breakdown might cause the Labor Day weekend closure to spill into commute days is probably one of the biggest risks he's working to minimize these days.
But in case of emergency, Tapping will have hammers handy.
Mega-move The big risk comes from a relatively small section of the original bridge that feeds vehicles into the upper deck of the Yerba Buena Island Tunnel.
Nearly every transportation official in the Bay Area has mobilized to warn motorists that the bridge will be closed while work is going on.
As soon as the bridge closes, the Oakland-based demolition subcontractor Silverado Contractors, Inc. is to begin sawing pieces of the concrete upper deck, rigging them with cables and lifting them with a giant rotating crane.
Pneumatic hammers on long hydraulic arms will then chip away at anything that can't be lifted out, such as the heavy columns that support the old structure, being careful to avoid the new columns built recently to hold the replacement structure.
In case the tidy cutting and lifting plan doesn't work, explains Caltrans bridge project spokesman Bart Ney, ``We've got a backup plan to bring some more hammers in if we have a problem.''
Demolition should take 43 to 53 hours. By Saturday evening or early Sunday, Dutch moving contractor Mammoet, which lifted the ill-fated Russian nuclear submarine Kursk from arctic waters in 2001, will lay out rails on the reinforced eastbound lanes leading out of the tunnel.
Mammoet is expected to move the slab within 13 to 15 hours.
The actual moving will, to the dismay of photo journalists, probably take place over five hours during the night. The new viaduct will be lifted with jacks from eight temporary concrete pillars, then simultaneously pushed and pulled northward about 100 feet by another set of jacks.
Once in place over eight new columns, the slab will be lowered a few inches onto metal pins atop eight concrete columns. As workers pour a thin strip of concrete to close the three-inch gap at each end of the structure, others will attach utility lines and remove equipment.
Media blitz While engineers fret about how to keep the project moving, a small battalion of public relations people from Caltrans, the Metropolitan Transportation Commission (which has the same members as the toll commission) and area transit agencies like BART are busy trying to keep weekend travelers moving in spite of the bridge closure.
The mission is to encourage people to ride ferries and BART, which Caltrans is paying to run hourly overnight service, instead of attempting to use alternate bridges and very likely create gridlock.
But there's one option they won't recommend.
``We will not be directing people to stay home. We will not be directing people to leave early,'' Ney announces at a meeting for Caltrans and local transportation agencies to prepare for the weekend closure.
Terpstra reinforces that notion, saying that as soon as officials start urging people to stay home, not go shopping, not go to events around the Bay Area, ``that's when the phones start ringing off the hook.''
While officials acknowledge that staying home is one obvious alternative to trying to cross the Bay, they say their job is to keep people moving, and telling people to stay home would be frowned upon by Bay Area business interests.
The blitz will include television, radio and newspaper ads, flashing highway signs across the area and full-color brochures explaining the closure, handed out at public places such as dry cleaners, BART fare gates and movie theaters as well as entry points for travelers such as airport rental car counters.
Caltrans public outreach efforts have also extended to Tennessee, where fans of the University of Tennessee Volunteers were warned months ago of the difficulty they would face getting across the Bay for their game against the University of California Bears in Berkeley at 5 p.m. Saturday.
Caltrans has also worked hand-in-hand with brides, bridesmaids and groomsmen to see that Labor Day weekend nuptials aren't ruined by the closure. Many of these types of outreach efforts were made last year, when the eastbound deck of the bridge was closed to allow demolition of a major section of the bridge's western approach in San Francisco.
And then there are the inhabitants and business owners on Treasure Island, to whom Caltrans is handing out special passes to allow them to cross the western span of the bridge.
While the niceties will make some people's lives easier, the primary mission is to avoid headaches for anyone who plans to travel next weekend. ``If we don't reduce the amount of trips regionally, we're going to have gridlock in the area,'' Ney told his colleagues.
Last year, the outreach effort helped cut car trips in the area by an estimated 40 percent below normal traffic for that weekend.
Maintenance work on the bridge is usually accomplished with a lane closure here or there.
As he shouted above the roar of lower-deck traffic on a recent visit, Ney pointed to concrete strips crossing all five lanes.
``Over the past month, we have been closing lanes,'' he said as a down shifting tractor-trailer sputtered by. ``We chipped out the old asphalt and put these runners in here.''
The concrete will serve as a solid base for the steel tracks supporting the viaduct-on-rollers.
Once the bridge is closed, it will be a long-awaited maintenance holiday, allowing Caltrans workers to perform all kinds of routine maintenance and repairs that would have much trickier with traffic blowing by.
The biggest job will be adding and reconfiguring FasTrak lanes to make it easier for users of the electronic toll tags and consequently more difficult for cash toll payers.
Next steps After the next weekend's dust settles, observant motorists may start to notice the beginnings of the self-anchored suspension span atop ruddy steel tubes just north of where the old bridge makes landfall.
That most expensive and controversial piece of the new eastern span is awaiting steel components from factories in China, Japan and South Korea.
In an office on the Port of Oakland's Pier 7, engineers with San Francisco engineering contractor TY Lin International are poring over paper drawings from the factory and comparing them point-by-point with computer-aided-drawings on a PC screen.
The contractor alone employs about 60 engineers in a two-story permanent port building with enough room to house the suspension span's gargantuan steel components. After they are inspected, those sections will be floated on barges to the tower base now under construction and assembled into the central tower that will carry the looped single cable and the weight of the side-by-side bridge decks.
Late in 2012, two years after the bridge has to close yet again to re-route traffic onto the detour structure, that span will be complete enough to open the westbound deck of the bridge. Eastbound travelers will continue to use the old bridge until the rest of the structure is completed during that next year.
Even then, the different sections of Terpstra's orchestra will be competing for his attention.
One of those contracts was awarded this spring for the ``Oakland Touchdown'' project, which will connect the skyway with Interstate 80. The other is for the Yerba Buena Island Transition from the new bridge's two decks to the double-deck configuration that crosses the island.
The two projects could well be competing with each other for the honor of not being the last contractor still working on the seemingly endless bridge project.
On a recent afternoon on Yerba Buena Island, Caltrans Assistant Structural Representative Lalit Mathur shows a visitor from the Metropolitan Transportation Commission staff how the suspension span's concrete decks will be initially held aloft.
A forest of steel tubes 94 feet high support a platform, known to engineers as falsework, that will temporarily support one end of twin 2,047-foot-long concrete decks.
When the 525-foot tower is assembled, and its single suspension cable slung and connected to suspender cables that support the deck _ sometime around 2012 _ they'll be able to remove the columns.
The procedure, apropos to the time that's passed since the earthquake, will work something like an hourglass. Workers will drain fine sand from the bottom of each column, allowing it to drop eight or nine inches and leaving the soaring structure to support itself.
Contact Erik Nelson at firstname.lastname@example.org or (510) 208-6410. Read his Capricious Commuter blog at www.ibabuzz.com/transportation.