Condition of in situ unexploded ordnance

Area of Science:

• Environmental Science
• Geochemistry
• Soil Science

Background:

• Unexploded ordnance (UXO) poses environmental risks as casings degrade, releasing explosive compounds.
• Understanding UXO failure modes is crucial for assessing and mitigating soil contamination on military training ranges.

Purpose of the Study:

• To investigate the failure mechanisms of unexploded ordnance (UXO) in situ.
• To identify the primary routes of explosive release from UXO into surrounding soils.
• To differentiate between recent and historical explosive contamination.

Main Methods:

• Documented the physical condition of 42 unexploded ordnance (UXO) samples on military training ranges.
• Collected and analyzed soil samples from beneath the UXO to detect explosives and their transformation products.
• Estimated UXO surface density.

Main Results:

• Oxidation was identified as the primary cause of metal UXO casing failure, leading to catastrophic swelling and rupture.
• Pitting corrosion was not a significant pathway for explosive release.
• Eight of 42 UXO were found to be leaking explosives, with identified causes including cracked/perforated casings, corrosion, and partial detonation.
• Estimated UXO surface density was 74 per hectare in the sampled subset.
• Analysis of explosive and transformation product concentrations helped distinguish recent from past contamination.

Conclusions:

• Catastrophic casing failure due to oxidation is a major mechanism for explosive release from UXO.
• Soil analysis can effectively identify leaking UXO and differentiate contamination sources.
• Findings inform environmental risk assessments and remediation strategies for contaminated military sites.