What Lies Beneath: A Board Replaces a 94-Year-Old Vault Below a Sidewalk

Unfortunately, a rift developed between the engineer, from Rand Engineering & Architecture, and the contractor, from Technical Construction Services. By the time the job was half-complete, the two weren't talking to each other. "The end product was satisfactory," recalls board president Joel Butnick, "but the condo board had to make a choice. Since the job was the engineer's baby, we decided to seek a different contractor for phase two."

Just Conduit

The board hired Central Construction Management. James LaTerza took over as structural engineer when the original engineer left Rand, and he knew to expect the unexpected. "In projects like this," he says, "you always encounter conditions you hadn't foreseen. For instance, there were Verizon fiber-optic conduits buried in the outer foundation wall of the sidewalk vault under Worth Street." The condo would be responsible for any damage to them. LaTerza contacted Empire City Subway, a Verizon subsidiary, to obtain drawings of the conduits and specs for protecting them. That set the work schedule back a couple of weeks.

The next surprise was a massive piece of iron embedded in cement that had not been detected by the engineer's original borings of the site. The metal had to be cut up, then removed by a crane, which required permits from the city and the temporary closing of busy Worth Street. Other cranes lowered 20-foot I-beams through tight openings between boilers and water heaters and snaking bundles of conduit.

The condo's property manager, Paul Brensilber, president of Jordan Cooper & Associates, shepherded the meetings with businesses and city agencies from Verizon to the Department of Transportation, the Metropolitan Transit Authority, Con Edison and the Department of Environmental Protection. He also served as project manager, the daily liaison among the engineer, the contractor, the residents, the commercial tenants and the board.

"The key to success was being able to bring people together to work in unison," says board president Butnick "He's the single reason the whole thing came together."

Construction Communication

Another reason is that the friction between the original engineer and the original contractor gave way to a smooth working relationship between their successors. "We follow the direction of the engineer and the architect," says Michael DiFonzo, president of Central Construction. "We over-communicate. It makes for a better project. If there's a change order, we like to submit shop drawings, using CAD (Computer-Aided Design) software, so there won't be any misunderstandings."

After overcoming all these obstacles, the board decided not to cut corners as the job neared completion. DiFonzo suggested using a liquid, roll-on substance, manufactured by Carlisle, to waterproof the structural concrete slabs. But rather than the conventional "flood test" to check for leaks, the board opted for the more sophisticated and expensive "vector mapping," which uses electrical currents to pinpoint even the tiniest of leaks. Five small leakages were discovered and repaired before the sidewalk slab was poured on top of the membrane.

For using the vector mapping, the condo received a 20-year warranty from Carlisle. "That was not in the original plans," says Butnick, "but, on the recommendation of the engineer, we decided to do the upgrade. It wasn't excessively expensive and it made every bit of sense. Now nobody will have to worry about that sidewalk for 50, maybe 100 years." 

Even so, regular maintenance will be critical, says LaTerza. "If the waterproof membrane is compromised, water gets inside the vault and the steel framing can rust, the concrete will spall and crack. … Proactive, preventive maintenance is critical to the life of vaults, and all structures. If there's a problem, you should respond quickly."

Of lessons the board drew, says Butnick, chief is that your engineer should provide different options, "from the merely adequate to the 50-year job. Decisions should not always be made strictly on the basis of cost but rather on the long-term benefits to the building. As a board member you have a fiduciary responsibility to do what's best for the property in the long term. Another thing — the board must set the strictest limits on the engineering costs. Those things can fly away terribly. They have to be negotiated very, very carefully, with an absolute ceiling put on these costs, if possible."

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Photo by Jennifer Wu. Click to enlarge.