During the 1950s and 1960s, at the height of the cold war, Americans had a deep fear of a nuclear attack. Buildings were designated with black and yellow signs indicating "Fallout Shelter," and some families built underground shelters in their back yards. School children routinely practiced drills in which they took cover under their desks or in school basements until the air-raid signals were silent and all was clear.
After President Kennedy persuaded the Soviet Union to turn back missiles headed for Cuba, and nuclear bombs never dropped, fears eased, and many residential shelters were abandoned or converted to other uses. The "Fallout Shelter" signs often seen in cities and towns have become fewer and fewer.
Today, the threat that has caught the attention of many Americans is not from a foreign country: It is Mother Nature herself. 2010 and 2011 may go down as two of the most destructive years in our recent history: The Haiti earthquake; the Icelandic volcanoes; the Japan earthquake and tsunami; flooding along the Missouri and Mississippi rivers; wildfires raging in Texas. And, a deadly string of tornadoes in Alabama and Missouri that struck in spring 2011. These catastrophes were a grim reminder to education institutions that tornadoes are a continual threat and need to be addressed in building design.
The threat of tornadoes in Alabama is not new. On Thursday, March 1, 2007, a tornado struck Enterprise High School in Enterprise, Ala., destroying the school and killing eight students. In contrast, when a tornado touched down in Atoka County, Okla., April 14, 2011, nearly 200 men, women, children and firefighters survived 165-miles-per-hour winds by taking shelter in a safe room in Tushka Public School.
Alabama lawmakers reacted to the Enterprise tragedy with legislation to make safe rooms mandatory in public schools. Any new public school construction contract awarded on or after July 1, 2010, must include an Alabama Building Commission-approved safe space or hallway. Alabama’s Building Commission adopted the International Code Council/National Storm Shelter Association (ICC/NSSA) Standard for the Design and Construction of Storm Shelters (ICC 500-2008) as the minimum building code for safe spaces.
After the devastating tornado in Joplin, Mo., on May 22 and the barrage of 326 confirmed tornadoes throughout Alabama, Mississippi, Tennessee, Georgia and Virginia from April 25 to 28, other states are likely to adopt tornado safe room legislation. Six Alabama schools received catastrophic damage from the April tornadoes and must be replaced, and at least three other Alabama schools had extensive roof damage. Those schools had dismissed students prior to the storms, or we may have seen a repeat of the Enterprise tragedy. The state’s school architect’s office indicated that, had tornadoes taken a different path through Tuscaloosa and Birmingham, more than 50 schools could have been damaged.
Why ICC 500?
ICC 500 provides standards for hurricane and tornado storm shelters. Hurricane storm shelters are designed for sustained storms of longer duration and are designed for longer terms of occupancy, providing people with places to sleep and cook. For tornado shelters, the standards call for structures to withstand winds up to 250 miles an hour and are designed to be occupied for shorter durations.
Currently, Alabama’s legislation applies only to tornado storm shelters and is limited to new public school construction. The reasoning in requiring a tornado storm shelter but not a hurricane storm shelter has to do with the warning time.
"With a tornado, you have a very short warning," says Katherine Lynn, director of the Alabama Building Commission. "You don’t have time to load students on buses and get them home; with a hurricane, the affected schools usually have several days advance warning."
The legislation applies only to new construction because of the difficulty upgrading an existing school. However, after this year’s tornadoes, many institutions may want to reconsider their level of protection. In Alabama, the Emergency Management Association will help evaluate existing schools or public facilities and advise school officials on the safest place in that facility to take shelter. Architects and engineers who are asked to renovate existing school facilities can contact FEMA and should rely on FEMA 431: Tornado Protection: Selecting Refuge Areas in Buildings.
It would be ideal if ICC 500 could be applied to other community or municipal buildings where large groups of people gather, but for now, lawmakers are concentrating on protecting education facilities.
"With children being in school for the amount of time they are, they represent the greatest risk," says Lynn. "The number of children in school on a given day usually far exceeds the number of people who may be in a public library or city hall, for example."
The 2009 International Building Code includes the ICC 500 standards for storm-shelter design. However, it does not mandate that buildings include a storm shelter, only that if a storm shelter is included, it should comply with the ICC 500. Fourteen states have adopted the 2009 International Building Code statewide (as of April 2011), but Alabama was the only state with legislation mandating the ICC 500 standard for storm shelters in new, public school construction.
As with any new code adoption, there is uncertainty about the requirements and how they will be interpreted. Some general guidelines and questions may help designers and education administrators set up storm shelters:
•Before designing a school storm shelter, institutions must first determine the governing authority and applicable codes. Some local authorities also may require community storm shelters to be combination facilities, providing shelter from both tornadoes and hurricanes.
•Form follows function. Next, determine the size and population the storm shelter will serve. For schools, the storm shelters must be designed to adequately house the school population and situated with easy access from all areas, generally within a 15-minute travel distance. A campus with more than one school or multiple buildings may require multiple storm shelters, and a shelter may need to be closest to the youngest group of students. For community storm shelters, the number of people it should accommodate is established by the population within a predetermined distance. The travel time must include the time to enter and secure the storm shelter. The designer also must be aware of other site-specific influences, including whether it is situated in a floodplain or seismic zone, urban or rural areas, or if it is integrated into the structure or independent.
•Consider operational issues.If a storm shelter is for school use only, it will be used primarily between 7:30 a.m. and 3:30 p.m. However, community storm shelters will need to be available 24 hours a day; this raises operational and access issues.
For example, if a tornado strikes at night, who will be in charge of unlocking the door to let people in? What will be the policy if local residents show up at the shelter with pets? Will the community personnel operate the shelter, or will a local authority such as the emergency management agency or the fire department operate the storm shelter? Who will ensure the storm shelter remains in operational condition with functional safety features and mechanical-electrical systems? All of these issues must be worked out in advance to ensure the most effective design.
•Design and construction considerations:
-Siting and designing for collapse. When situating a storm shelter, schools need to consider the possibility that other portions of the building may collapse around or on top of the storm shelter. If a storm shelter will be next to a two-story portion of a building, a shelter will need a roof that can withstand a collapse, in addition to a 250-miles-an-hour wind load. Utility towers, adjacent buildings and trees also must be considered when choosing a site for the storm shelter.
-Emergency operations. ICC 500 assumes that electrical and HVAC systems may not be operational, so fresh airshafts and backup electrical must be provided. Other emergency provisions include temporary toilet facilities and first-aid kits. Emergency communication, other than cell phones, also should be considered—most cell phone communication is limited during and after a storm event.
-Single use vs. multiuse facilities. Designers must consider whether a storm shelter will be a single-use facility. The most cost-effective designs incorporate storm shelters into the daily use of the facility. Both single-use and multiuse facilities must be designed and maintained so that they can be used for storm shelters when the need arises and they do not become storage rooms. At Selma High School, the first high school in Alabama to conform to the new code, the storm shelter is integrated into the academic wing of the school, so students can exit classrooms and be in the storm shelter/corridor. Men’s and women’s toilet facilities are in the storm shelter/corridor, which is constructed of poured-in-place concrete reinforced walls and roof.
Most schools in Alabama are built with concrete masonry unit (CMU, or block) walls, so storm shelters with CMUs blend in well with the adjacent construction. However, because the safe room/corridor at Selma is two stories, poured-in-place concrete was used to achieve the requisite strength and lateral resistance. In other settings, steel plates or buried structures on a sloping site also can provide the design strength required.
-Selection of materials. The issue of whether to use concrete masonry units or poured-in-place concrete highlights the difficulty designers and engineers have in determining which materials meet ICC 500 standards. This is similar to the struggles designers initially had in meeting LEED requirements, the U.S. Green Building Council’s standard for energy-efficient and environmentally friendly design. There was a general lack of information on which products which had been tested and were readily available to meet the LEED standards. Therefore contractors and architects expected higher cost in projects required to meet those standards. Now it is easier to build to LEED standards without increasing costs because of the availability of "green building" products. Eventually, it will be easier to determine which products meet ICC 500 standards, and more products and systems will be tested and certified.
With each new project, designers will determine what worked well, what didn’t and what was most cost-effective. The greater availability of products will enable contractors and designers to become more comfortable with incorporating storm shelters into their designs. Until the entire construction industry catches up, the sharing of knowledge is the greatest tool in the designer’s toolkit.
Percival-Young, AIA, is project manager with the firm. She can be reached at [email protected].
About the Panel Discussion at the Safer Alabama Summit: