Interim Radiological Scoping and Characterization Survey Report, 1963 Igloo 572 Accident (Former Medina Base), Lackland Training Annex, Lackland AFB, Texas

On 13 November 1963, 50,000 kg of chemical high explosives detonated and destroyed igloo 572 on Medina Base, Texas now Lackland Training Annex, Lackland AFB TX. The result of the blast was a vaporization of the contents, a sizeable crater, removal of some rock strata below the igloo, with adjacent igloos unimpacted. The only known radioactive material dispersed as a result of the explosion was uranium metal that was comprised of both depleted and natural isotopic compositions. This report documents historical environmental data collected immediately after the accident and an evaluation of current site conditions based on survey guidelines in the radiological scoping and characterization workplan IERA-SD-BR-SR-2000-0013. The current site conditions exhibited the same general pattern of contamination as that described by the historical documents, except that the activity concentrations are presently lower than that of 1963. Among the samples collected and analyzed for total uranium activity concentration, the highest was about 100 pCig. Among the monitored areas, those with uranium activity concentration above 50 pCig was limited, with most of the contaminated area having lower concentrations. Isotopic analyses of samples indicated that both depleted and natural isotopic compositions exist. Most of the areas surveyed are encompassed by a secured munitions storage complex, where access is restricted to personnel involved with munitions storage activities and those completing maintenance i.e. structure repairs, lawn care, etc. For these uses, the uranium activity concentrations existing in surface soils does not present significant health risks to personnel. The residual radioactivity may be below concentrations acceptable for residential occupancy.