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Iowa Army Ammunition Plant Firing Site (FS) Area

The Firing Site (FS) Area was developed for the testing of explosives and ammunition. The South and North Test Fire Areas, now collectively termed the FS Area, were apparently originally established to support BAECP operations. In addition to the perimeter fence surrounding IAAAP to limit unauthorized access to the site, the FS Area is also fenced to further restrict access. There is also a locked gate blocking vehicular traffic to FS-12. Operations at the South Firing Site centered around FS-6, and at the North Firing Site Area at FS-12.

FS-6 was constructed in 1948 and this FS is still used for ordnance testing. Quality control testing of explosives (plane-wave testing) was conducted at this site until these test-shot procedures were moved to FS-14 in 1972. Apparently, most of the explosives testing at FS-6 did not contain any radioactive elements, however, some explosives may have contained a thin sheet of DU. This DU would have been pulverized or fragmented upon detonation of the shot. During a walk-over conducted by the COE, DU was discovered in the earthen berm at FS-6. However, the source of this DU is unclear. Little is known of the testing activities conducted at FS-14, but information gathered in interviews indicate that testing of small amounts of conventional explosives occurred there.

DU or other radiologic contaminants were not detected in the FS-6 area by the October 2002 airborne survey. Based upon the available evidence, ATSDR concluded that the opportunity for human exposure to infrequent and minor environmental releases of DU at FS-6 was extremely limited and does not represent a health threat.

FS-12 was constructed in 1964. Both TNA and COE report that during the interval between December 1965 and December 1973, a series of specialized tests called "hydroshots" were conducted exclusively at FS-12. Hydroshots tests were conducted to test the hydrodynamic performance of the shaped explosives used in the ordnance produced at BAECP.

The explosive device used in the hydroshot testing was assembled in FS-5 and comprised of an explosive charge shaped as a hemisphere, about half the size of a basketball and weighing from 1-3 kg (2.2 to 6.6 lb). The explosive charge was surrounded by a DU ring about 1-2 inches in height and weighing about 22 kg (48.5 lb). The purpose of the DU ring was to simulate the hydrodynamic conditions in a fully spherical weapon.

The records indicate that a total of 701 hydroshot tests were performed between 1965 and 1973. These tests reportedly dispersed about 4,000 kg (8,820 lb) of DU that was scattered as far as several hundred feet from the FS-12 firing point. Detonation of the shaped charge pulverized the containing ring of DU, yielding DU-debris ranging in size from coarse fragments to very fine particles.

The standing operation procedure was to collect DU fragments after each test and dispose of them as radioactive waste. Because fine particles of DU were also produced during the test detonation, the AEC conducted air monitoring during some of the tests. A concentration of radioactive material of 5.3E-13 microcuries per milliliter (Ci/ml)2 was measured at FS-12. Because DU is very dense and will settle to the ground more rapidly than other particulate material, the air monitoring did not detect any DU-radioactivity at the IAAAP boundaries.

In 1975 the AEC performed a fairly limited site clean-up at FS-12 by excavating a few inches of soil in an area which encompassed the area immediately surrounding the firing site and a "couple hundred square meters" around the periphery of the site. The removed soil was tested and disposed of as radioactive waste in an offsite facility in Illinois. Although testing results did not find radioactive contamination at that time, numerous DU fragments have been found recently at FS-12.

The site was turned over to the Army in 1975 for testing of conventional weapons, not including DU. Then, in 2000, DU fragments were discovered and the Army discontinued use of the site. It is theorized that larger fragments of DU penetrated the surface soils a few inches, shielding them from previous detection or site remediation. Subsequent site maintenance, or the natural process of frost-heave, then exposed the DU fragments now found on the surface of the FS-12 site. There is a limited potential for incidental, inhalation exposure to DU for workers involved in munitions testing or site maintenance at FS-12 during the interval from 1975 until 2000. Because DU fragments are so dense, the potential for re-suspension of those fragments or particles is low. Therefore, the potential for incidental, inhalation exposure during the 1975-2000 interval is limited.

The conditions created by the detonation of a hydroshot are far less severe than those created by the penetration of hard armor by a DU penetrator. Thus, it is likely that little if any DU-oxide aerosols were created during the detonation of a hydroshot. Additionally, surface soil disturbance during remediation activities or subsequent maintenance operations conducted at FS-12 had, and have, the potential to result in incidental inhalation exposure.

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Page last modified: 05-07-2011 02:42:02 ZULU