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        shipped from this location every two to three weeks. Stocks are
        at their highest just prior to the arrival of the ship.


                   3) Anhydrous ammonia is a toxic gas. It is colorless
        with a pungent, characteristic odor. The IDtH concentration,
        i.e., the concentration from which one could escape within 30
        minutes without escape-impairing symptoms or irreversible health
        effects is 500 ppm for ammonia. Exposure even to lower
        concentrations of the gas produces a prompt and violent
        irritation of the eyes and respiratory tract. Additional
        information concerning the toxicity of ammonia can be found in
        Appendix A.

                   4) More significantly, it is unknown if the Ml7Al gas
        masks are effective against ammonia. The MOP? suits, however, are
        known to be effective against ammonia provided saturation of the
        air does not occur.

                   5) The toxicity of ammonia and the unknown
        effectiveness of the gas masks against this chemical make it
        desirable to determine the threat of its release to various
        locations in the Al Jubayl area. Computer simulation were
        performed to determine this threat. Two scenarios were
        considered:  in the first, the gas escapes instantaneously, and in
        t:he second a puddle of ammonia is formed. The instantaneous
        release-scenario is intended to represent a high-speed misssile
-       striking the tank. Obviously, such a hit would scatter the tank
        and its contents in all directions. However, this event is
        difficult to model mathematically. Thus, the next worse-case
        scenario is cnsidered,  i.e., the entire contents of the tank are
        released at once. While this specific event may not occur with
        great frequency,  it closely approximates the effects of a high-
        speed missile. The puddle is created when the tank ruptures and
        the ammonia, which is stored at cryog~enic temperatures,  leaks out
        of the tank.

                   6) The results of the computer simulations are
         summarized below. The discussion focuses primarily on the threat
        to the camp areas and the commercial port because these sites are
         critical to military operations. In addition, the results are
        highly dependent on wind direction. Wind direction in Eastern
         Saudi Arabia varies greatly during certain months of the year.
         For example, for January through March, the wind is from a single
         direction (north-northwest)  less than half. the time. The wind
         comes from a variety of directions the rest of the time. Appendix
         B provides additional information concerning wind behavior in
         this region. Appendix C provides additional details about the
         simulations.

                    7) The following results were obtained for the tanks
         located in the industrial city. If an instantaneous release of
         ammonia occurred during the day from these tanks, a lethal cloud
         (concentration 500 ppm or greater)  of the gas, 1.6 km in

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