The National Institute of Standards and Technology on Friday released a final report into the technical investigation of the May 22, 2011, tornado that struck Joplin — the deadliest tornado in the United States in the 64 years that official records have been kept.
Marc Levitan, lead investigator for NIST, said the final report is strengthened by clarifications and supplemental text suggested by organizations and individuals from across the nation in response to the request for comments on the draft report that was released on Nov. 21 in Joplin.
Levitan said NIST received about 13 comments, some of them long and detailed, in the 45-day comment period.
Levitan said the revisions did not alter any of the investigation’s major findings or its 16 recommendations.
The report calls for nationally accepted standards for building design and construction, and public shelters and emergency communications that can significantly reduce deaths and the steep economic costs of property damage caused by tornadoes.
The study was the first to scientifically examine a tornado in terms of four key aspects: storm characteristics, building performance, human behavior and emergency communication — and then assess the impact of each on preventing injury or death.
It also is the first to recommend that standards and model codes be developed and adopted for designing buildings to better resist tornadoes.
Levitan said NIST has already started the “long and arduous process’’ of converting the recommendations into new codes and standards for building tornado-resistant structures.
“New codes are adopted in three- to six-year cycles,’’ he said. “You propose the changes. It’s reviewed by a committee and from there goes out for public comment. We have to be inclusive and make sure that people have the chance to comment on things that affect everybody.’’
The city of Joplin did not officially comment on the report, but it did release a statement on some of the conclusions that NIST reached and how they relate to the city.
The NIST study recommends “the development and implementation of uniform national guidelines that enable communities to create the safest and most effective public sheltering strategies. The guidelines should address planning for, siting, designing, installing, and operating public tornado shelters within the community.”
The city’s response to that recommendation: “While the city supports efforts to shelter the public in the location where they are currently located, there is a constraint placed upon the city that is not well addressed in the report. Simply put, this restraint is time.
“The average response time for a tornado approaching the city, from when it is spotted to when it first touches down, averages about 10 minutes. This is hardly enough time to: receive the warning; understand it; believe it; personalize it; seek other input; decide to act; and act appropriately. It is only enough time to seek shelter immediately, in place. There is little, if any, time to seek shelter by traveling to another location as is often the case when public shelters are built and advertised as such. To encourage the citizens to travel to a public shelter is to encourage them to be out in the open where they would be subject to the wind and debris produced by a tornado, resulting in possible injury or death.’’
The city, instead, is encouraging the building of shelters for personal protection, regardless of the facility — be it home, business, work, school, place of worship or public venue.
The city said it also has approved amendments to the International Residential Code to improve the ability of a home to survive a tornado. These amendments include:
• Foundation anchorage to be spaced a maximum of 4 feet on center on the wood sole plate at all exterior walls on monolithic slabs and wood sill plates.
• Block cells shall be filled with concrete from the footing up.
• Masonry foundation walls shall have a minimum of one No. 4 reinforcing bar a maximum of every 4 feet on center.
• Trusses shall be connected to wall plates by use of connectors commonly known as “hurricane clips.”
NIST also recommended the development of national codes and standards and uniform guidance for clear, consistent and accurate emergency communications.
To ensure accurate and consistent emergency alerts and warnings, the city said it has provided 4,000 NOAA Weather Radios to its residents; upgraded its outdoor siren warning system, and reworked the siren testing policy to reduce the number of yearly activations, among other things.
The complete text of the final report, Technical Investigation of the May 22, 2011, Tornado in Joplin, Missouri, is available at: www.nist.gov/manuscript-publication-search.cfm?pub_id=915628.
The public comments are available through the NIST Joplin Tornado web page www.nist.gov/el/disasterstudies/weather/joplin_tornado_2011.cfm.