D.  Modeling Efforts

After the Intelligence Community assessed that it was possible that mustard agent could have been released from Ukhaydir during the air campaign, in 1997, the Office of the Special Assistant and the CIA modeled the potential extent of any resulting hazard areas to see if the possible mustard agent releases could have reached US troops.

The CIA and DoD conducted separate modeling efforts. The CIA conducted preliminary modeling in the spring of 1997 for presentation at the September 1997 meeting of the Presidential Advisory Committee on Gulf War Veterans’ Illnesses in Washington, DC. The modeling presented to the Committee was preliminary because it used incomplete weather data and only one model to produce the hazard area.[38] In late 1997, DoD conducted a more detailed, follow-on modeling of the potential mustard releases at Ukhaydir. This effort used several models and incorporated more comprehensive weather data.

The CIA developed the source characteristics[39] for both its own and DoD’s modeling in the spring of 1997 based on UNSCOM’s discoveries at both the Fallujah Proving Ground in 1991 and Ukhaydir in 1997. The modelers always chose the more conservative path, that is, they always assumed the highest possible amount of agent was released, consistent with UNSCOM discoveries up to that point.

1. CIA’s Analysis of January 20, 1991, Storage Bunker Fire

In 1997, when it developed the source characteristics for the potential release on January 20th, the CIA assessed that the bunker fire started by the Coalition airstrike could have caused 94 mustard-filled 155mm rounds to release their agent.[40] However, an examination of the soot deposit indicated that the fire was quite extensive. Therefore, most of the mustard probably burned immediately, releasing very little agent into the atmosphere.[41]

Extensive weather data was not available when the CIA conducted its preliminary modeling, so it used an analysis of the direction of the bunker’s soot pattern, which suggested that the "initial wind direction [was] to the southeast."[42] This meant the wind was blowing parallel to the Saudi border and parallel to the US forces located there. According to CIA testimony before the Presidential Advisory Committee:

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 [emphasis added] have been above the general population limit [see glossary for definition] beyond about 40 [kilometers]. Even if the meteorological data change the wind direction, the plume [hazard area] will disperse hundreds of kilometers away from our troops.[43]

Due to the absence of extensive meteorological data, the CIA did not produce a representation of the simulated hazard area showing the extent of any potential exposures.[44] However, on January 20th, US forces were located south of the Saudi border, over 300 kilometers from Ukhaydir and far beyond the 40 kilometer radius shown in Figure 13. Because CIA’s modeling showed such a small potential hazard area,[45] DoD did not model this strike.

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Figure 13.  Map showing 40 kilometers radius around Ukhaydir and the locations of US forces on January 20, 1991

2. CIA’s Analysis of February 13/14, 1991, Strike of Munitions Stored on the Road

The CIA developed source characteristics for the February 13/14, 1991, strike in the spring of 1997 from UNSCOM inspection data before UNSCOM discovered the fourth round at Ukhaydir. After their first inspection of Ukhaydir, UNSCOM had accounted for all but 11 of the 6,394 mustard-filled 155mm rounds declared by Iraq (6,380 at the Fallujah Proving Ground plus 3 at Ukhaydir). The CIA assumed that the direct impact on the 11 rounds caused them to burst and aerosolize 70 percent of their contents (seven gallons of mustard agent).[46]

In addition to the 11 rounds potentially destroyed by the impact, the CIA determined that as many as 560 rounds fell into the crater after the bomb exploded underground. According to the CIA, "on the basis of US drop tests from a height of 7 feet, approximately 1 in 40 rounds that dropped into the bomb crater would have leaked, or only 14 of the total 560." Additional US drop tests from a height of 40 feet would "increase the ratio to 1 in 8 leaking, or 70 of the 560."[47] Although these tests showed that fewer than 107 rounds would have leaked after falling into the bomb crater, the CIA followed the more conservative path and assumed all 107 of the empty, green rounds inspected at the Fallujah Proving Ground leaked, releasing approximately 83 gallons of mustard agent. After adding the seven gallons from the 11 rounds, the CIA assumed a total of 90 gallons of mustard agent was released as a result of the February strike.[48]

The CIA presented its preliminary modeling results for the February strike at a hearing of the Presidential Advisory Committee on Gulf War Veterans’ Illnesses on September 4, 1997. Given the source characteristics and the weather conditions at the time of the release, the CIA’s modeling produced a hazard area of contamination above the general population limit extending approximately 125 kilometers toward the southwest. The modeling showed the hazard area’s maximum width would have been between 10 and 20 kilometers.[49] (See Figure 14.)

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Figure 14.  CIA's preliminary modeling results for the February airstrike

3. DoD’s Analysis of February 13/14, 1991, Strike of Munitions Stored on the Road

a. DoD’s Modeling Methodology

The DoD also modeled the February strike, but employed more detailed weather information and additional models than the CIA’s preliminary modeling.

DoD used two types of models to determine the extent of the hazard created by the possible mustard agent release: weather prediction models and transport/diffusion models. Weather prediction models reconstruct the weather conditions in an area of potential release. Transport/diffusion models use the source characterization and data (e.g., wind and temperature) generated by weather prediction models to simulate how an agent released into the atmosphere might disperse, and to define the extent of any subsequent contamination. Using a union of the results from several independent weather and dispersion models develops an "ensemble" potential hazard area. This ensemble approach provides an array of "credible predicted concentrations for use in determining the area where service personnel might have been exposed"[50] and increases the confidence in the resulting hazard area. More information about DoD’s modeling is provided in Tab D.

b. DoD’s Modeling Results

During the first 24 hours—when the rounds would have released the most agent, the weather models predicted low-level winds out of the north/northwest, producing a southerly to southeasterly hazard area. The hazard area extended the farthest from Ukhaydir and closest to US troop locations during this initial 24-hour period. Nevertheless, the hazard area was still 275 kilometers from US units at its closest point. (See Figure 15.[51])

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Figure 15.  DoD's modeling results for the February 13/14th airstrike, Day 1

On the second day, the winds were initially from the west and then generally calm in the vicinity of Ukhaydir, with wide shifts in direction from north/northeast to south/southwest. Overall, the winds were lighter than on the first day. The calm weather, combined with a significantly reduced rate of agent evaporation, produced a hazard area emanating from the crater and directed to the east. The hazard area for the second day did not extend as far south as that for the first day, so it also did not reach US troop locations. (See Figure 16.)

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Figure 16.  DoD's modeling results for the February 13/14th airstrike, Day 2

Lower evaporation rates from the crater and calm winds slowed dispersion further on the third day. That day’s winds were out of the southeast and pushed the hazard area approximately 20 kilometers to the northwest, away from US troops. (See Figure 17.)

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Figure 17.  DoD's modeling results for the February 13/14th airstrike, Day 3

After the third day, the models predicted that the level of mustard agent did not exceed the general population limit anywhere, and therefore no longer presented a threat to US troops. DoD completed this modeling of the February airstrike in early 1998. All the modeled hazard areas fell hundreds of kilometers short of reaching US troops.

E. UNSCOM’s 1998 Ukhaydir Inspection

While the DoD modeling progressed, UNSCOM continued its work in Iraq. In the spring of 1998, Iraq told UNSCOM that it had unilaterally excavated the area around the bomb crater at Ukhaydir and discovered 12 additional mustard-filled 155mm rounds. Consequently, in the summer of 1998, UNSCOM inspectors returned to Ukhaydir to ensure the site was cleared of chemical weapons, investigate Iraq’s excavation and perform a geophysical survey of the area around the bomb crater using ground-penetrating radar.[52]

According to Iraq, it found five of the rounds under the repaired crater in the roadway in front of the bunker. Iraq also claimed that the remaining seven rounds were found in the area around the roadway, near where UNSCOM had discovered the four intact mustard-filled rounds in 1997. Like those rounds, the 12 rounds excavated by Iraq were intact and painted grey, with no sign of burn damage. The inspectors examined the contents of two of the twelve rounds and found them consistent with mustard. The other shells were examined and all were found to contain liquid. UNSCOM transported all the rounds it found during these inspections of the Ukhaydir Ammunition Storage Depot to the Muthanna State Establishment where they were destroyed under UNSCOM supervision.[53]

During its geophysical survey, UNSCOM used ground-penetrating radar to search an area around the repaired bomb crater in the road. They did not discover any additional intact munitions during this survey. Moreover, inspectors found no evidence of significant munitions debris or other evidence of chemical munitions destruction at the site. The only metal inspectors found in the survey was a piece of angle iron. They detected no mustard contamination in the area they surveyed. Iraq continues to state that no chemical rounds were destroyed at Ukhaydir during the Gulf War.[54]

F. CIA’s Reassessments

Although both DoD’s and CIA’s modeling showed that it was unlikely any mustard agent reached US forces in Saudi Arabia, the new information obtained from UNSCOM’s 1998 inspection caused CIA to re-evaluate its original assessment of a likely release from Ukhaydir during the Gulf War.

1. February 1999 Letter

After UNSCOM returned from its 1998 inspection of Ukhaydir, the CIA re-evaluated its assessment of whether the airstrikes on January 20, 1991, and February 13/14, 1991, caused any releases of mustard agent at Ukhaydir. In February 1999, the CIA’s Special Assistant to the Director of Central Intelligence for Persian Gulf War Illnesses Issues sent a letter to DoD’s Special Assistant for Gulf War Illnesses providing the CIA’s revised assessment. Both the CIA and UNSCOM continue to assess that the rounds inspected at the Fallujah Proving Ground in 1991 were at Ukhaydir during the air campaign. However, the CIA stated in its letter that it now believes a release from Ukhaydir as a result of either airstrike is unlikely.

For the January 20, 1991, bunker fire and the burned rounds at the Fallujah Proving Ground, the CIA stated, "There was no direct evidence the bunker fire actually burned any rounds. [Therefore, it] is no longer considered to be a case for a release."[55] The CIA’s letter did discuss a trailer fire at an unknown time about 20 miles away from Ukhaydir as an alternate explanation for the burn damage discovered at the Fallujah Proving Ground.[56]

For the February airstrike and the missing and empty rounds from the Fallujah Proving Ground, the CIA stated that "Damage to the 11 rounds from direct impact of the bomb against the stack is now considered to be unlikely … [and] it is … unlikely that the empty green rounds—107 in all—modeled previously are involved in the Coalition bombing." This assessment was based on these facts:

[N]o metal fragments from damaged rounds were found … and no chemical contamination was identified …. Also, as shown in [Figure 12] the center of the crater was just to the side of the stack … indicating the bomb did not fly over the stack but landed just in front of the stack …. Finally, the 11 round figure was also based on 11 missing rounds; since that time, Iraq [has] found an additional 12 rounds—more than enough to compensate for the missing rounds.

… [Also,] ninety-eight percent of the 6,395 rounds found … were gray in color, including all 16 rounds found [at Ukhaydir]. We do not know why the green-colored rounds were empty. UNSCOM found no evidence of leakage or damage when they were inspected in 1991—unusual if the rounds were truly damaged in a fall into the crater.

… [For the 107 empty green rounds,] it is unlikely that the rounds were damaged when they fell into the crater given the absence of leaking rounds in 1991, contamination and shell fragments near the road in 1998, or leaking or damage to the 16 rounds found [at Ukhaydir] in 1997 and 1998 …. In addition, we assess—because of the separation of the stack and the crater—that the rounds more likely slid into the crater or fell a short distance onto soft earth as opposed to having a long damaging fall.

… [Finally,] the Iraqis indicated that no rounds were damaged at Ukhaydir even though they had motivation to falsely declare damaged rounds there.[57]

2. October 1999 Letter

In October, 1999, the CIA’s Special Assistant for Persian Gulf War Illnesses Issues sent a second letter to DoD’s Special Assistant for Gulf War Illnesses, again discussing possible explanations for the damage discovered at the Fallujah Proving Ground in 1991.

Although the letter stated that an "[i]ntense fire [would be] required to burst [the] rounds," it did not mention the January 20, 1991, bunker fire at Ukhaydir. The letter stated that the CIA now believes the burned rounds inspected at the Fallujah Proving Ground in 1991 definitely released their agent and discussed five possible locations and times for this release:

The CIA based these possible locations and times on "various declarations to UNSCOM [the first, fourth, and fifth locations] and informed speculation [the second and third locations]. [The second and third locations are] based on the fact that, along with the burned rounds [at the Fallujah Proving Ground,] the inspectors found completely dry obsolete green rounds[,] indicating that Iraq may have cleaned … old rounds out of Ukhaydir, a C[hemical] W[eapons] site since the mid-80’s."[59]

This second letter characterized the February strike as an "unlikely release, based on [the] lack of evidence of damage seen during [the] 1998 UNSCOM inspection." The letter did not specifically address how the empty, green rounds from UNSCOM’s inspection at the Fallujah Proving Ground might have leaked.[60]

G. Lessons Learned

Because this narrative does not review the training, techniques, or procedures used by Coalition forces during the Gulf War, there are no doctrinal lessons to be learned from events at Ukhaydir. Ukhaydir was a legitimate target of the Coalition air campaign. As such, it was struck on several occasions. It is an unfortunate fact of war that aerial bombs, through no fault of the operator, occasionally miss their intended targets, in this case the bunkers believed to store chemical weapons. This review of events at Ukhaydir provided no insight into improving the manner in which the US military conducts war.


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