IDA issues report on modeling Khamisiyah
"pit" and makes recommendations

Washington, August 4, 1997 (GulfLINK)- Bernard Rostker, special assistant for Gulf War illnesses, released the Institute for Defense Analyses'(IDA) final report on Khamisiyah "pit" releases of nerve agent on July 17, 1997. The study was commissioned by the Department of Defense (DoD) and the Central Intelligence (CIA) in November 1996 to review modeling efforts to date and to explore the uncertainties associated with modeling the "pit" demolitions at Khamisiyah. This southern Iraq location contained a weapons storage facility which was destroyed by U.S. forces on March 10, 1991.

Joint efforts of the DoD, the CIA, and a national panel of technical experts developed a best estimate model to determine who might have been exposed to the nerve agent sarin at Khamisiyah.

The entire modeling effort is part of the comprehensive DoD program to answer two major questions: (1) who may have been exposed to chemical agents at Khamisiyah and (2) to what extent they may have been exposed. Final results of the Khamisiyah plume analysis, including the number of troops who were potentially exposed, were presented on July 24, 1997.

The CIA suspended the pit analysis in September 1996 due to the number of uncertainties, including: information about the number and dates of the demolition event, limited meteorological data, incomplete knowledge about number of rockets, quantity of agent, agent purity and how chemical warfare agents react in an open pit.

"Last year our modeling efforts came to a halt because the uncertainties were so great in the source term, and in the meteorological data that we could proceed no further." explained Robert Walpole, special assistant to the Director of Central Intelligence for Persian Gulf War illnesses issues during the DoD news briefing.

The IDA panel of experts were asked to identify improvements in recent modeling analyses, to reduce modeling uncertainties, and to recommend the best available meteorological, and transport and diffusion models to better understand the Khamisiyah pit release. Their review recommended examining multiple factors associated with the number of rockets and release mechanism to understand reasonable ranges of conditions that prevailed at Khamisiyah.

Additionally, the IDA panel noted that reconstruction of the meteorological conditions at the time would require considerable computer resources, making the simulation of meteorological variations in the meteorology time-consuming and expensive. But, it recommended extending the meteorological reconstructions and running the models at least 72 hours.

The report further explained that additional modeling uncertainties emerged from the differences among the models used. Because models that simulate the same physical phenomena can differ in their outputs because of the use of different mathematical procedures for solving the problem, data gridding, and other factors, the panel also recommended linking dispersion and meteorological models. Integration of models had not been applied during previous modeling activities.

IDA's report also pointed out that the process could be improved by ensuring that models are linked to incorporate all of the elements required for analysis such as meteorological estimates as well as transport and diffusion estimates.

In addition to the advanced methodology suggested by the IDA report, the demolition tests completed at Dugway Proving Grounds in Utah during May 1997 have contributed to reducing source term uncertainties associated with the Khamisiyah demolitions. Source terms are all of the variables involved in analyzing the "pit" demolitions. Testing provided data on critical questions regarding these source terms or variables, such as how much agent aerosolized, how much spilled in the soil, the amount of agent per rocket, and agent purity.

Additional information was obtained through interviews with the soldiers who were at the site. Five soldiers have been interviewed by the DoD and CIA, about half of the soldiers involved in the "pit" demolition. Based on their first-hand descriptions, the total number of rockets at the pit has now been estimated to be about 1,250, of which only some 500 were found to have been damaged by the demolition attempts. Samples taken by the United Nations have recently demonstrated that the agent purity was only about 50%, much lower than previously estimated.

"What we've been able to do is gain a lot of insight into the events at Khamisiyah, and we've applied that insight into the analysis," explained Dr. Rostker. "The analysis is also much advanced by the help we got from IDA in terms of how to put the various models together, as well as some dedicated efforts to find classified and unclassified meteorological patterns."