again prohibited obligation of construction funds until the completion of the second review (P.L. 112-10). The scope for both the 2010 SSRA and the 2012 uSSRA addressed accidental release of pathogens from the NBAF in Manhattan, Kansas, and excluded terrorist acts and malicious threats from its risk assessments.

The NRC convened a committee of experts to evaluate the adequacy and validity of the uSSRA. This report is the committee’s evaluation of the final uSSRA.

OVERALL ASSESSMENT

The committee evaluated the uSSRA provided by DHS in February 2012 and finds that it is a substantial improvement over the original 2010 SSRA. DHS and its contractors should be commended for this effort. Many of the shortcomings identified by the previous committee have been addressed in the uSSRA, and this has resulted in a more quantitative and transparent analysis. The uSSRA uses more conventional risk assessment methods and better complies with standard practice than did the 2010 SSRA. In general, the descriptions of the approaches are clear, and the uSSRA uses appropriate conceptual models and methods.

The quantitative conclusions of the uSSRA differ dramatically from those of the 2010 SSRA. Data and methods of the previous risk assessment led to a conclusion that for the two scenarios with the greatest risk of FMDv release (fomite and worker without respiratory protection), there would be a 70% probability that FMDv release would cause an infection resulting in an outbreak during the 50-year life span of the NBAF in Manhattan, Kansas. In contrast, the uSSRA concludes that the cumulative probability for 142 risk events (including catastrophic events such as tornadoes and earthquakes) leading to an accidental release of FMDv over 50 years is about 0.11% (or 1 in 46,000 per year), which is orders of magnitude lower than the first estimate. Improvements in the 65% design phase documents for the facility compared with the earlier and less complete design documents on which the 2010 SSRA was based may explain some of the risk reduction. However, the committee believes that questionable and inappropriate assumptions were used in the uSSRA that led to artificially lower estimates of the probabilities and amounts of pathogen released.

In contrast with the 2010 SSRA, which cited fomites and lack of respiratory protection as the most likely pathways of accidental FMDv release, the uSSRA concludes that the most likely release mechanisms are those associated with natural hazards, specifically earthquakes and tornadoes. The uSSRA concludes that these are about 20 times more likely than operational pathways.

Despite improvements, the committee finds that the uSSRA under-



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement