Flood Mitigation at the Whitney Museum
When Superstorm Sandy hit New York City in October 2012, it revealed weakness’s in the city’s infrastructure. Since then, resilience has been a high priority on any project being built or considered near the water. The Whitney Museum of American Art (completed in 2015) had the unique benefit of being under construction when Sandy hit, giving the design team an opportunity to see — and fix — weaknesses in its resiliencey systems. Learn how the project design team ramped up resiliencey features during construction and what we can learn from the process.
Forewarned is forearmed
The location of the Whitney Museum of American Art adjacent to the Hudson River is particularly sensitive to water level rise and storm surge, so the design needed to anticipate the effects of climate change and protect the museum's staff and collection from water level rise. In the original design, the team elevated the lobby above the FEMA recommendation of 9 to 10 feet, and all galleries begin on the fifth floor and extend upward with no permanent gallery or art storage below level five.
When Superstorm Sandy hit New York City in October 2012, the museum was well under construction and basic elements of the building's design were already in place to protect the structure in the case of flood. The timing of the storm enabled the team to see how the building could withstand a serious flooding event. The structure withstood the storm well, but unprecedented water levels brought over six million gallons of river water into the building's 30-foot-deep basement. The devastating effects of the storm on New York City's infrastructure inspired a transformation in the practice of flood mitigation, and the timing of the Whitney Museum project put the project team at the forefront of addressing future resilience.
Following the storm, FEMA revised its flood zone maps, recommending a 13.5 foot elevation for a building on the Whitney site. With the sense that that elevation still seemed too conservative, the Whitney team conducted an international search for an advisor to assist in developing a revised flood elevation recommendation. They selected WTM Engineers of Hamburg, Germany, and their partner, the Franzius Institute for Hydraulic, Waterways, and Coastal Engineering of the Leibniz University of Hanover, two organizations well versed in protecting an urban environment from floods. The Franzius Institute undertook extensive study of New York Harbor and its environmental history and advised that the building should be protected up to a 16.5 foot elevation. Based on these studies, the design team worked with WTM to devise modifications, both temporary and permanent, for the Whitney's structure that will protect it against future storm events.
Recalibrating after the storm
In the case of flooding, the main goal is to preserve the ground floor as effectively as possible, which ensures that the entire building is safeguarded. To do this, the team examined all possible water infiltration points within and above the 16.5 foot protected elevation. Reinforced concrete walls surround the basement and protect the building on four sides, but truck and staff entry points on the west side of the building are at street grade, a six-foot elevation. To protect this possible entry point, the team enlisted Walz and Krenzer, manufacturers of watertight doors for navy vessels, to manufacture floodgates that would prevent water from entering through these portals. The floodgates consist of a 8-inch thick aluminum plate with a hinged door, operated by a turning wheel that seals water out against steel plates embedded into reinforced liner walls. In case of emergency, the gates only require two people to close.
To incorporate the floodgates into the design of the building, the team redesigned the surrounding structure. The reconstruction on the west side of the building required the removal of pre-cast concrete from the already-constructed stair tower. During this removal, the pre-cast concrete on the levels above it had to be temporarily secured in place while the new section incorporating the floodgate could be installed.
A crucial element in the Whitney's flood mitigation strategy is continuity: the floodgates only work if the rest of the building is continuously sealed. Waterproof membranes behind the secondary reinforced concrete walls shield the structure from flooding. Aqua-seal is used to seal 3D concrete penetrations created for electrical conduits, gas, electrical service, and piping, maintaining the structure's integrity during a storm surge.
The team also devised temporary protective elements to be deployed in anticipation of flooding. In the hours before a weather event, a contractor will bring the Whitney's temporary barriers from a nearby warehouse and assemble them on site. A continuous concrete curb on the building's plaza bolsters aluminum posts that are bolted into the ground to then hold stacked aluminum logs. The temporary barriers protect the lobby's large expanses of glass wall that could be vulnerable to pressurized water. Extensive additional structure was added to the plaza design to accommodate the additional weight of the temporary barrier system. The plaza's drainage system was also reconceptualized by engineers Jaros, Baum & Bolles so that any leakage or splashover drains away from the dry area.
Considering worst case scenarios
An additional change to the original building design included reworking the building's emergency energy sources. Instead of the 1,000-gallon fuel tank originally planned for the museum, the Whitney's insurance advisors suggested accommodating the largest tank possible. Therefore, the building has a 4,000 gallon tank in order to provide with as much energy as possible in an emergency in order to keep the building's systems — particularly the pump system — running. The team did precise calculations to account for all possible flood scenarios, including the failure of these or other functions. For example, if the pumps should fail, it was determined that 14 inches of water would then flood the basement. Therefore, all placement of electrical equipment was adjusted to sit above a 14-inch elevation. In cases where this was not possible, a concrete barrier provides protection.
In the worst case scenario of water levels above 16.5 feet, the structure is designed to survive flooding of the lobby level, to deflect the force of any debris impact load, and to prevent any stray building materials from blowing off the structure and causing damage or injury. The severe impact of a flood of this magnitude on the city trumps the concern for resuming building operations as quickly as possible. Instead, the design gives the Whitney staff peace of mind that the building will not cause harm to its community during any future unprecedented weather events.
