It has been 27 years since the National Independence Historical Park in downtown Philadelphia last moved the Liberty Bell, placing it in a pavilion near Independence Mall. In late September, the bell will find a new home in a museum that is part of a $314-million renovation of the mall.

Preparations to transplant the bell into Liberty Bell Center are currently in the works. "A new building is under construction right now. It will have an expanded exhibition space, as well as new visitor amenities," says Karie Diethorn, the park's chief curator.

WIRED Strain gauges monitored crack during test. (Photo courtesy of National Park Service)

Hill International Inc., Marlton, N.J., is managing the project, now estimated at $314 million, up from the original $160 million reported in 2000. Hill project manager Dan Bozin explains that the renovation has grown in scope. Designed prior to 9/11, the new mall buildings also required added security measures such as special visitor screening areas.

The 3-ft-tall Liberty Bell weighs 2,080 lb. The Pennsylvania Assembly ordered it from London in 1751 for what is now Independence Hall to celebrate the 50th anniversary of William Penn's Charter of Privileges. The bell cracked when first rung on March 10, 1753, and was reforged in Philadelphia. When the crack first appeared in the new bell is lost to history, but the final expansion was in 1846 on George Washington's birthday.

Diethorn says the bell is like "a piece of fruitcake" because of the unsophisticated casting process. It is delicate, forged from a melange of metals including copper, silver, tin, lead, zinc, gold, iron and nickel. Transporting it will not be a typical pick-and-place operation.

George Young Co., a local mechanical contractor, will move the bell. It is no stranger to the bell, having relocated it several times since the firm was founded in 1869. The company's fourth-generation president, George Young, says he is doing the work pro bono to honor "those who perished in 9/11 and the troops who keep us free." Attaching slings to an I-beam, the company will use a 20-ton-capacity, four-point hydraulic gantry to lift the bell by its trunnions, then slowly travel the apparatus three-quarters of a block away into the new building, where a new pintle rest will secure the bell. The new Liberty Bell Center was designed by local architect Bohlin Cywinski-Jackson and will cost $12.9 million.

On March 17, officials conducted a test lift to verify equipment selection and rigging techniques. Scientists from MicroStrain Inc., Williston, Vt., monitored the bell's structural integrity with specially designed strain gauges calibrated to 5 microns installed along the crack's edges. Diethorn says the data is critical for making sure the bell will hold up during the move and future maintenance. When renovations are complete, the new Independence Mall is expected to reopen fully by the end of the year.