500,000-pound sigh of relief
The grand old dome of the Emporium gets a lift -- and now waits for its new home atop Bloomingdale's
Dan Levy, San Francisco Chronicle Staff Writer
Wednesday, May 19, 2004
In a spectacular engineering feat, the 250-ton, glass-and-steel dome of the old Emporium was lifted 60 feet in the air.
The crown jewel of the old Emporium will top the new Bloomingdale's, shown here from the rear.
They raised the roof Tuesday at the old Emporium.
Well, it wasn't the roof. It was the dome -- a 500,000-pound relic of San Francisco's early 20th century excitement and excess.
Thanks to a custom-designed hydraulic lifting system, the beloved glass- and-steel structure 100 feet in diameter made a safe climb to its new height of 170 feet above Market and Mission streets as a crowd of hard hats and real estate suits looked on.
Nobody on hand had witnessed quite such a dome-raising before.
"We did not really have knowledge for a project like this," said Archie Schachle, vice president for Sheedy Drayage Co., the San Francisco engineering firm that pulled off the feat.
The closest thing anyone could think of was the dismantling of the City of Paris department store dome back in 1981 and its reassembly in the then-new Neiman Marcus store on Union Square.
But that was a relatively simple matter of screwdrivers and chisels.
Tuesday's show was about lifting, whole hog, a fragile and bulky century- old structure.
When the Bloomingdale's department story and retail center, being built on the site of the 108-year-old Emporium store, opens in fall 2006, the dome will be the visual and spiritual centerpiece of the 1.5-million-square-foot, mixed-use behemoth.
"People love light, and there is going to be a lot of light streaming through those lunettes," said project architect John Tindall, looking up at the arched windows at the base of the dome structure.
Incredibly, a 1920s addition to the Emporium building had covered up the lunettes, which are small windows, robbing shoppers of the feeling that they were buying perfume in St. Peter's. During its decades-long heyday, the Emporium dome was where San Franciscans met, supped and canoodled.
Planners decided not only to remove the offending blockage -- and whatever else was left of the guts of the old Emporium -- but also to raise the dome 60 feet and restore it to its former glory.
Accomplishing this required a stabilizing concrete pad, a 120-foot steel- beam tower to support the dome and four hydraulic jacks to do the heavy lifting.
As assembled visitors looked on, an engineer flipped the switch on the jacks, which were positioned on massive horizontal beams that supported the weight of the dome. Ever so slowly, the giant dome was lifted inch by weighty inch.
It was impressive to bystanders. But foreman Don Vick, watching the 94- year-old structure rise slowly and steadily, said the job wasn't too different from adding a deck to a bridge or lifting a floor into an office building.
"It's just like putting a floor together one piece at a time," Vick said.
Workers and engineers stationed under the jacks watched the progress of the lift by eyeing tape measures that dangled from the beams. The lifting had to be done in unison on all four sides.
"It's got to go up at the same level, and you want to make sure you don't get hung up on something you don't see," Vick said.
By 4 p.m. the lift was done, and the first phase of the Bloomingdale's construction project was complete.
The dome will stay perched on the steel tower for 10 months while the Emporium structure is demolished and a new steel structure is erected around the dome. Then the dome will be lowered 2 feet to rest atop the new frame.
For those scoring at home, that makes a total lift of 58 feet.
The next phase will be construction of 200 stores, cafes and restaurants, a nine-screen cinema and 235,000 square feet of office space, the priciest of which will look out onto the newly restored dome.
One point of history: Developers Forest City and Westfield America were required by the city to save the dome if they wanted to build the project, which is expected to cost $410 million by the time it opens in two years.
And if you listen to them today, nothing to the contrary ever crossed their minds.
"Carrying through the quality of the architecture is going to make a statement," said Westfield executive Steve Eimer.
The dome of the former Emporium department store, built in 1908, was lifted 60 feet using hydraulic jacks.
The structure under the dome -- except for the original beams and supports -- had already been removed, a process that took several months.
Next, contractors built a reinforced horizontal base for the dome. A lifting tower, with the hydraulic jacks at the top, was erected under the dome and connected to the horizontal support.
On Tuesday, the dome was raised 60 feet in four hours.
During the next 10 months, the dome will remain on the hydraulic lifting tower until a new building is completed underneath it.
When the work is complete, the dome will be lowered 2 feet to rest on the new structure and the hydraulic lifting tower will be removed.
Lifting the Emporium dome
The historic dome of the old Emporium building, a 500,000-pound structure built almost a century ago, has been lifted 60 feet to crown the center of the new Bloomingdale's project in downtown San Francisco. The dome will sit on a supporting tower for nearly a year while a new structure is built underneath it to house shops and restaurants.
1) The structure under the dome - except for the original beams and supports - was removed, a process that took several months.
2) Next, contractors built a 4-foot-thick reinforced-concrete footing as a base on which to mount the steel tower.
3) After erection of the tower, a lifting frame was constructed extending beyond the tower to lift the dome from its base. Hydraulic strand jacks were mounted at the top of the tower.
4) Hydraulic strand jacks (controlled by hoses and cables connected to four hydraulic jacks and to the operator's console on the second floor) pulled on steel strand wires connected to the lift frame. All four jacks were operated simultaneously.
Earlier this month the dome was raised 30 feet and secured while the tower was extended in height by 30 feet. On Tuesday, the dome was raised the second 30 feet.
Source: Sheedy Drayage Co.
E-mail Dan Levy at firstname.lastname@example.org