FLEXIBLE DRY FLOOD PROOFING CASE STUDY

Photos courtesy of Smart Vent Products, Inc.

Facility: Underground subway stations
Location: New York City
Flood mitigation strategy: Flexible dry flood proofing

The risk: When Superstorm Sandy hit New York City in October of 2012, it revealed a number of vulnerabilities for this dense urban center. Among them was the severe flooding that filled the subway stations and portions of tunnels in lower Manhattan, causing a shutdown of the subway system and widespread power outages.

The mitigation approach: The local authorities, learning from this situation, put out a request for a solution to meet the following key criteria.

• Mitigation solution must be stored at the point of use to allow the subway system to stay open until the last minute, provide a return to normal operations faster, and assure components are not misplaced between events.
• Withstand up to 14 feet of water head pressure given the updated FEMA flood maps
• Must not put any inward loads on the concrete structure of the stairwell (i.e., the system needs to react to all inward flooding loads)
• Use common concrete, mechanical, and electrical construction techniques and equipment
• Do not encroach on the stairwell (i.e., along the sides, at the top step, or at the header)
• Withstand vandalism
• Be deployed by subway station personnel in under 30 minutes
• Deploy mechanically rather than rely on power, which may not be available during a major storm event

The solution: To achieve these goals, technology was employed based on NASA programs that used high-performance soft goods such as the spacesuits that walked on the moon, the impact bags on the Mars Pathfinder landing, and inflatable Space Habitats. Based on carefully designed textile tension fabric membranes, this solution includes:

• Storage in small volumes: 6-foot-wide by 12-foot-long stairwell cover fits on a 13-inch-diameter spool inside a 15-inch-wide storage container
• Ability to withstand high loads at significantly lower weights: a 6-foot by 12-foot cover tested to withstand 16 feet of water weighed only 72 pounds
• Scalability to meet various hydrostatic and hydrodynamic loads: Accomplished by selecting different structural webbings to meet challenges to 30 feet of head pressure and more

The resulting product functions similarly to a window shade or rollup storefront security door. When the notice to deploy is given, the tamper proof cover plates on the gate guides are released and the top step is opened. The cover is deployed by retrieving a T-bar from the storage container and turning a drive spool that allows integral cables to pull the cover through the gate guides toward the top step mechanism. Once fully deployed, the cover is bolted in place via a seal bar that is integral to the cover. The seal is accomplished at the gate guides and top step seal bar when challenged with water.

Results: To date, 24 systems have been installed at New York City Subway entrances and are at the ready for the next major storm event.

FLOOD BARRIER CASE STUDY

Photos courtesy of Walz & Krenzer, Inc.

Case study courtesy of Cooper Robertson based on “White Paper: Flood Mitigation in Museum Design”

Facility: Whitney Museum of American Art
Location: New York City
Architect: Renzo Piano Building Workshop in collaboration with Cooper Robertson Flood mitigation strategy: Hinged watertight doors and removable flood barrier wall

The risk: The location of the new Whitney Museum of American Art adjacent to the Hudson River is particularly sensitive to water level rise and storm surge, which could threaten the artwork as well as the people in the museum.

The mitigation approach: The design of the building by Renzo Piano Building Workshop in collaboration with Cooper Robertson anticipates the effects of climate change and protects 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 feet to over 10 feet. All galleries begin on the fifth floor and extend upward with no permanent gallery or art storage below level five.

The trial: 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 actually withstand a serious flooding event. The structure withstood the storm well, but unprecedented water levels brought over 6 million gallons of river water into the building’s 30-foot-deep basement. Following the storm, FEMA revised its flood zone maps, recommending a 13.5-foot elevation for building on the Whitney site. With the sense that that elevation still seemed too conservative, the Whitney team selected WTM Engineers of Hamburg, Germany, and their partner, the Franzius Institute for Hydraulic, Waterways, and Coastal Engineering of the Leibniz University of Hanover, for further analysis. They undertook an 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 together to devise modifications, both temporary and permanent, for the Whitney’s structure to protect it against future storm events.

The new solution: Reinforced concrete walls surround the basement and protect the building on four sides, but the truck and staff entry points on the west side of the building are at street grade, a 6-foot elevation. To protect this possible water entry point, the design team called for manufactured floodgates that would prevent water from entering through these portals. The floodgates consist of 8-inch-thick stiffened steel components with a hinged door, operated by a turning wheel that seals water out against steel plates embedded into reinforced liner walls. Two Whitney facilities staff members can together close the gates in case of emergency.

Fully prepared: 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. The team also devised temporary protective elements to be deployed in anticipation of flooding. In the hours before a weather event, museum maintenance staff will bring the Whitney’s temporary barriers from local storage and assemble them on site. A continuous concrete curb on the building’s plaza bolsters aluminum posts that are bolted into the ground to hold stacked aluminum logs. Heavy beams hidden from view and below ground were designed to withstand the significant loads that are transferred to the aluminum posts. The temporary barriers will protect the lobby’s large expanses of glass wall that could be vulnerable to pressurized water. To this end, extensive additional structure was added to the plaza design to accommodate the additional weight.

ROOFING CASE STUDY

Photos courtesy of Carlisle SynTec Systems

Project locations: Livermore Falls and Augusta, Maine
Building owners: Livermore Falls Building and Cives Steel Paint Shop
Resilient roofing system: EPDM

Background: There have been many studies conducted on the performance and physical properties of EPDM membranes, but nothing proves quality and longevity like time-tested performance in the real world. A recent long-term weathering study cited by the EPDM Roofing Association (ERA) examined five roofing systems, all with 28 to 32 years of in-field service. In addition to testing 30-year-old EPDM membranes, the ERA study heat aged the 30-year-old samples to simulate another 10 years of rooftop exposure; then, the heat-aged EPDM samples were retested for tensile strength, thickness, and factory seam strength. These studies concluded that the systems were not only performing up to industry standards but in some cases performing with physical properties that exceeded those of newly produced EPDM membranes. The heat aged testing found that in all categories, the majority of the samples exceeded the minimum property characteristics of aged EPDM and in some cases exceeded the minimum properties for new EPDM membrane. Two specific in-field examples are discussed further as follows.

34-year-old EPDM roofing: Back in December 1980, the Livermore Falls Building in Livermore Falls, Maine, was in desperate need of a new roof. The existing built-up roofing system was nearly 30 years old and failing rapidly. At the time (1980s), built-up roofs were one of the most popular commercial roofing systems, and EPDM was just coming to the forefront of the industry. Though EPDM was a newer product, testing had already shown that it would be an extremely durable membrane, and the decision was made to reroof the 8,000-square-foot building with a heavy-duty EPDM membrane. The roofing contractor began by tearing off the existing built-up roof down to the metal deck. The next step was to install two layers of 1-inch perlite insulation board before rolling out the 45-foot by 100-foot sheets of EPDM membrane and spreading 1.5 inches of stone ballast. The rectangular rooftop featured numerous obstructions, including a chimney and three HVAC units, which the team detailed using field-fabricated EPDM accessories (pressure-sensitive and prefabricated accessories had not yet been invented). The entire installation was completed during the winter months and was awarded a 10-year total system warranty as well as a 15-year material-only warranty. The roofing was inspected after 34 years in continuous service and found to be still performing well.

31-year-old EPDM roofing: In October 1981, the same contractor was awarded another reroofing project at the Cives Steel Paint Shop in Augusta, Maine. Having successfully installed the EPDM roof months earlier on the Livermore Falls Building, the decision was made to use the same membrane on this 9,600-square-foot rooftop. The EPDM had proven to be flexible and easy to install on the previous project, and the contractor knew this would enable it to finish this project quickly while providing the building owner with a high-quality roofing system. Once the existing smooth-surface built-up roofing system was removed, 5 inches of expanded polystyrene (EPS) insulation were loose laid directly onto the metal deck. Then the EPDM membrane was installed in 20-foot by 100-foot and 45-foot by 50-foot sheets. Field-fabricated accessories were used to complete the roof details, and the ballasted system was finished with 1.5 inches of stone loose-laid on top of the membrane. This roof was completed in a record time of three days, which the contractor attributed to the ease of installation provided by the EPDM membrane’s flexibility and convenient roll sizes. This roof has stood the test of time, requiring only minor repairs, the most recent of which occurred in May 2014, when edge metal and drain details were upgraded with pressure-sensitive flashings.

Assessment: These two projects provide an undeniable exhibit of the strength and long-term durability of EPDM membranes, making it an excellent choice for resilient building design. However, longevity is not the only benefit of this membrane since EPDM also has extremely low life-cycle costs plus excellent hail and puncture resistance. EPDM remains repairable throughout its long life, another important attribute that speaks to the sustainability and resiliency of this roofing system. Considering the overwhelming evidence from physical property testing and real-world performance of 30-year-old membrane, it would seem that EPDM, one of commercial roofing’s oldest technologies, is still one of the most sustainable and resilient systems, providing significant value to the building owner and the environment.

SEISMIC EXPANSION JOINT CASE STUDY

Photos courtesy of Construction Specialties

Expansion joint moat covers surround Zuckerberg San Francisco General Hospital and Trauma Center and work in conjunction with the base-isolated building for safe egress in the event of an earthquake.

Project: Zuckerberg San Francisco General Hospital and Trauma Center
Location: San Francisco
Architect: Fong & Chan Architects

The project: The Zuckerberg San Francisco General Hospital and Trauma Center, commonly referred to as ‘The General’, has been serving the city and Northern San Mateo counties for decades. As a top medical training and research facility as well as the area’s only Level 1 Trauma Center, the hospital serves more than 100,000 patients annually. Construction of the nine-story acute-care hospital began in 2009 and was completed in 2015, due in large part to a significant donation from Facebook Founder Mark Zuckerberg and his wife, Priscilla Chan.

Design goals: Located on the San Andreas Fault line, the California Building Standards Code mandates that strict seismic resiliency is included in new construction to ensure the hospital remains operational should an earthquake occur. Additionally, the project had the goal of obtaining LEED Gold certification, meaning that environmentally responsible products needed to be selected.

Solution: With the most advanced seismic designs available, The General is now one of the largest base-isolated hospitals constructed in the United States. The building is able to glide 30 inches in every direction during a seismic event. To allow this movement, multi-axial expansion joint covers were chosen by Fong & Chan Architects in San Francisco and installed by Van-Mulder Sheet Metal Inc. of Hayward, California. This carefully designed system seamlessly connects the new hospital tower to the existing structure, while the exterior moat covers visually unite the landscape and sidewalk with the structure. Nuno Lopes, AIA, principal at Fong & Chan Architects, comments, “The biggest draw from our standpoint was to be able to design a base-isolation system and still be able to accomplish the aesthetics that we’ve always been accustomed to. We were able to embed specific materials into the moat covers so that they would match the surrounding context and still perform as intended. It brings the aesthetics and functionality together into one product.”

Photos courtesy of Construction Specialties

An expansion joint cover runs through the emergency department at Zuckerberg San Francisco General Hospital and Trauma Center. Because ambulances cross over it on a daily basis, this cover is designed to withstand these types of heavy rolling loads.