(Above) A concrete restoration technician, Juan, steps from a balcony railing on the 37th floor of Marina City’s east tower to a scaffold suspended alongside on October 22, 2010. (Click on images to view larger versions.)

For a short time in the 1960s, Marina City was the world’s tallest structure made of reinforced concrete. The cost to maintain the concrete has never been cheap. In the early 1990s, Marina Towers Condominium Association spent $1.7 million over three years to repair the concrete and repaint balconies and vertical surfaces.

The cost was $2 million in 2008 when the condo association needed to repair problem areas identified in 2006 and 2007 by the structural engineering firm Wiss, Janney, Elstner Associates, Inc.

Over the next three years, weakened concrete would be cut open down to the rebar, sandblasted, sealed with epoxy, then covered with concrete in which adhesive had been mixed. Railings would be repaired, too, and unit owners had an option of a polyurethane membrane that would cover the concrete slab on their balcony. (Left) Rebar is exposed after concrete is cut away on an east tower balcony.

The membrane would cost the unit owner $1,250 for a full balcony and $900 for a half-balcony. All apartments at Marina City have a full balcony. One-bedroom units have an additional half-balcony and two-bedroom units have one and a half additional balconies. (Right) On the west side of the west tower of Marina City on October 5, 2009, brothers Cruz (left) and Hernando (right) Gonzales work from a “swing stage” scaffold suspended approximately 260 feet above Dearborn Street.

While waterproof, the membrane would not level the balcony floor and prevent “ponding,” the accumulation of small pools of water and an ongoing issue at Marina City. According to property manager David Gantt, when the concrete was finished in the early 1960s, an error with how floor drains were placed resulted in uneven balcony surfaces. Marina City architect Bertrand Goldberg, he suspects, “must have had a fit.”

Gantt said that in more recent years, experiments had been done to see how the ponding could be fixed. “We tried to see if it would be possible to create a little [water collection] trench to the drain but the engineers determined that the rebar would be too close to the...trench. The rebar would then rust. We tried lightweight concrete and determined that...was not entirely acceptable as the drains were still too high. The cost would be over $12,000 per balcony...That’s $12,000 times 1,248 balconies.” (Left) Marina City’s concrete when it was new, during construction of the west tower in 1962, photographed by Portland Cement Association.

Repair of the massive concrete exterior of both towers began during the week of September 20, 2009, starting with the west tower. With sidewalk canopy barricades (right) protecting pedestrians on Dearborn Street from any falling debris, workers moved up and down the towers from four “swing stage” suspension scaffolds.

Suspended hundreds of feet above Dearborn Street, workers for Quality Restorations, Inc., would visit 16 balconies on each of 44 residential floors in two towers between October 2009 and December 2010. The first step in preparing old concrete for repair is to cut around the problem area. This provides a retaining boundary for the repair material. (Left) A circular saw is used to remove concrete from a balcony on the 30th floor of the west tower.

(Above) Hernando Gonzales inspects the work.	A hairline crack is being enlarged so that it can be adequately repaired. They will also drill into weakened concrete, down to the rebar. The steel bars that reinforce the concrete will then be sandblasted, sealed with epoxy, and covered with a specialized adhesive-added concrete.

(Right) Suspended just beyond the 29th floor of the west tower, Cruz and Hernando prepare to move on to the next balcony. In the upper left frame, you can see where nails have been hammered into the old concrete and areas cut around concrete that will be repaired. Photos by Steven Dahlman except where noted.