SUB SANDWICH. Low, steel-framed ceiling, exposed concrete walls and structurally expressed concrete buttresses give underground exhibit an oppressive, German "sub-pen" look and feel. (Photo courtesy of the museum of science and industry)

Engineers working for a Chicago museum knew it would be difficult enough to move a 700-ton Nazi submarine 1,000 ft and squeeze it into a 42-ft-deep, underground exhibit, but they first had to figure out how to shore up a historic, 111-year-old brick structure adjacent to the excavation. And nearby road work gave the engineers little room to breathe as they planned around Chicago Dept. of Transportation’s $162-million rehab of Lake Shore Drive, now in final punchlisting.

Tim S. Kaye, the museum’s structural engineer and principal of Chicago-based design firm Halvorson Kaye, calls the team’s multifaceted solution of steel sheeting, jet-grout walls, post-tensioned concrete beams, friction micropiles and hand-dug underpinning pits a "catalog" of foundation engineering. "The unusual nature of this project really brought the whole team together," says Kaye, who likens the old-and-new techniques to the artifacts that will occupy the $35-million exhibit, set to open next spring.

The underground sub "sandwich" at Chicago’s Museum of Science and Industry centers around the restoration of the WWII submarine U-505. The U.S. Navy captured the sub off the coast of Africa in 1944. In 1954, U-505 was sent across Lake Michigan to the museum’s lawn, where curators spent $250,000 on a dry-dock exhibit.

Over the years, the elements took their toll. In 1998, the owner began raising funds to restore and relocate the sub. Working since 2001, designers have planned an underground "sub pen," replete with Das Boot-like German grit.

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The facility has canted walls and wandering ramps of exposed concrete. An acoustically lined steel roof will reverberate sonar sounds. The result will be a "foreboding industrial sense of construction" that is aesthetically and geotechnically functional, says architect Michael Kaufman, a principal of Lohan Caprile Goettsch, Chicago.

The structure forms an L-shape in plan. A main, 25,000 sq-ft hall houses the sub while a 10,000-sq ft corridor directs visitors out through the museum’s East Pavilion, a historic brick-and-stone building originally designed and built for the World’s Columbian Exposition of 1893.

The team broke ground in February 2003, but was halted for several months after an old sewer line flooded the site. Nearby CDOT engineers, who were driving an exposed-steel cutoff wall for Lake Shore Drive, coordinated a water prevention effort that benefitted both parties. The city agency installed an extra acre’s worth of unexposed steel that saved the project $500,000 in cladding costs.

"Enlarging the area of the cutoff wall to encompass the museum’s excavation made economic sense," says Chris Wuellner, CDOT project manager.

Museum crews then removed part of the East Pavilion’s original 1893 foundation to make room for an elevator shaft and stairs. "With load-bearing masonry, the...