Condition of in situ unexploded ordnance

Unexploded ordnance (UXO) become point contamination sources when their casings fail and their explosive fill dissolve. To determine the modes of failure, we documented the condition of UXO found on military training ranges and sampled soils for explosives beneath 42 in situ UXO. We found that oxidation caused the metal UXO casings to swell and fail catastrophically. Unlike previous work, pitting of the metal casings was not found to be an important release route for explosives. Of the 42 UXO sampled, eight were leaking explosives into the soil and of these, four had perforated or cracked casings, three were corroded and one was a partially detonated round. We estimated a surface density of 74 UXO per hectare for a subset of UXO sampled. We used the relative concentrations of explosives and their transformation products in the soil to determine if the explosives had recently dissolved or were from past military training.