Update on Potential Mustard Agent Release at Ukhaydir Ammunition Storage Depot

4 September 1997

A Brief Review

In April 1997 while at Ukhaydir, UNSCOM inspectors found three 155-mm artillery rounds, which contained mustard, near a bunker that had been bombed during the Gulf war. The three rounds were located near the road in front of the bunker. More significantly, the road had been patched from an apparent bomb impact during the war. We assessed that bombing during the Gulf war could have released some mustard agent from this site.

We have reconstructed the chain of events for the damaged road and bunker at Ukhaydir. The bunker was attacked successfully on the night of 20 January 1991, resulting in a large fire as shown by a massive soot deposit. Because it was obvious to the Iraqis that the Coalition forces were targeting the bunkers, they probably moved all of their mustard rounds into open areas, such as the road along the front fence of the bunker. UNSCOM has never found any mustard rounds in the bunker, after three different inspections. We assess that the rounds on the road were hit, or at least disturbed, by a bomb near midnight on 13/14 February 1991.

Number of Rounds Involved

Through Iraqi declarations and other sources, including UNSCOM inspections, we believe that 6,394 rounds of 155-mm artillery containing mustard were stored at the Ukhaydir Ammunition Storage Depot during the period from mid-January 1991 to as late as May 1991. These rounds were later moved to the Fallujah Proving Ground where 6,380 were counted by UNSCOM inspectors. (They were ultimately destroyed.) Most of the rounds were undamaged and painted gray. Those found at Fallujah included 104 fire- or heat-damaged gray or green rounds, 10 of which still contained mustard; and 117 green rounds, 10 of which contained agent. The Iraqis asserted that the 104 burned rounds were damaged at the Muthanna State Establishment; they did not indicate where or when the green rounds had leaked. This leaves a potential for a maximum of 212 rounds to have been affected by the bombing, including 11 rounds not recovered by UNSCOM (6,394 minus 6,383).

Current Thinking on Agent Release

We have applied multiple transport and diffusion models to this issue, although we have not completed the ensemble modeling with DoD comparable to the Khamisiyah effort. More significantly, so far we have used only one of the two regional-scale meteorological models from the Khamisiyah effort. Once the other model supplies its weather predictions, we will be able to complete the full ensemble and increase our confidence in the overall results.

20 January. Any mustard rounds near the bunker on 20 January would have been severely damaged by the Coalition air attack and subsequent fire, and probably would not have released much agent. The fire could have damaged the 104 rounds observed by the UNSCOM inspectors at the Fallujah Proving Ground. Hence, if the 104 rounds were not damaged at Muthanna as the Iraqis say, they could have been near the bunker on 20 January. Because we do not yet have meteorological data for this date, we have not published a plume. Nevertheless, the direction of the bunker's soot pattern--suggestive of the initial wind direction--is to the southeast, which is parallel to the border 200 km away. Using this initial wind direction, we have modeled the potential release from the 94 rounds that did not contain agent when inspected. The concentration of mustard agent that likely survived the blast and fire would probably not have been above the general population limit beyond about 40 km. Even if the meteorological data change the wind direction, the plume will disperse hundreds of kilometers away from our troops.

13/14 February. For the rounds on the road in front on the bunker, both DoD and CIA believe that some could have released agent when bombed on the night of 13/14 February. The bomb crater did not show any evidence of fire or excessive blast damage. Therefore, we assume the bomb physically hit about 11 rounds before exploding underground. The 11 rounds would have burst and probably aerosolized about 70 percent of their contents--35 kg or 7 gallons. The size of the crater suggests that about 560 of the 700 rounds assessed to have been on that part of the road fell into the crater. (See illustration.) On the basis of US drop tests from a height of 7 feet, perhaps 1 in 40 rounds that dropped into the bomb crater would have leaked, or only 14 of the total of 560. The US drop tests showed that a drop height of 40 feet would increase the ratio to 1 in 8 leaking, or 70 of the 560.

Amount of Agent Released. Although it is possible that no rounds were damaged--the bomb's angle of entry and subsurface detonation may have shielded the rounds from major damage--we modeled a more conservative situation. In fact, we assumed the 11 missing rounds took a direct hit and aerosolized 35 kg of mustard. We also assumed that 107 of the 117 green rounds leaked at Ukhaydir or 396 kg, instead of the more likely 14-70 gray rounds that would leak after falling into the crater, or 63-315 kg. (The 107 showed no signs of damage and could have leaked before any bombing occurred.) The total amount of mustard modeled was 431 kg, or about 90 gallons. The downrange extent of the mustard agent above the general population limit would result in a plume of about 125 km towards the southwest. The maximum width is estimated to have been 10-20 km. (See map.)


Even with these very conservative assumptions, the potential plume from Ukhaydir did not reach Saudi Arabia, much less any of our troops. Indeed, as already indicated, it is possible that there was no agent release on 14 February 1991. As we have stated above, the only other possible mustard agent release was from the bombed bunker on 20 January 1991. And, again, any resulting plume would not have come within hundreds of kilometers of US or other Coalition forces.

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