Crews are upgrading and building onto a 1950s-era pier without disturbing three buoyant caissons supported by timber piles. The pier is designated as a nationally historic structure and will be home to Google offices this fall.

A team of RXR Realty and Youngwoo & Associates is redeveloping Pier 57, off Manhattan’s West Side Highway, under a 97-year lease from landlord Hudson River Park Trust. The team will create 425,000 sq ft of retail and office space and a new 100,000-sq-ft rooftop park. “The trust let a RFP in 2007,” says Michael Rem, RXR project executive. “Young Woo & Associates submitted the winning proposal and spent a few years rezoning the property and getting environmental approvals. We joined in 2014 and started construction in March 2016.”

The $350-million renovation of the abandoned pier, designed by Emil H. Praeger to handle military transport vehicles and based on World War II pontoons (ENR 1/11/51 p. 46), includes mitigating corrosion to concrete elements, including prestressed, precast girders that sit atop three buoyant hollow boxes. Two 360-ft-long, 127-ft-wide, 33-ft-high caissons each weigh 27,000 tons. A smaller caisson, 367 ft x 80 ft, forms the top of the “T” to support the perpendicular head house at the front. At the bulkhead, the piles extend to bedrock, but “farther west off the coast, the rock drops off,” notes Peter Koklanos, senior structural engineer with McLaren Engineering Group. “The caissons are supported partially off buoyancy and partially off silt several feet below the water.”

McLaren designed repairs to the corroded concrete elements, dry chambers to accommodate new elevators and utilities, and elements to support future commercial live loads.

In order to preserve the historic integrity, crews are building a high-performance curtain wall that is “a high-rise lying on its side,” says Frank Fusaro, partner with Handel Architects. “That meant understanding how much the pier potentially would move and rotate around the existing joints. In the curtain wall, we integrated flexible joints to allow for that.”

McLaren also specified a two-layer system to protect against floods of 50- and 100-year return periods, says Koklanos. The primary system is a cast-in-place curb. To protect against another Superstorm Sandy, “we specified a temporary flood-barrier system, called Aquafence,” he says. “It looks like a folding chair made out of a series of steel parts and a plastic membrane. Braces keep it open. Water hits the vertical surface, and struts keep it rigid. We’ll preinstall anchors at the toe of the folding gate into the deck.”

The barrier elements will be stored within the building.