Technical Summary

On 31 March 2026, construction workers along Tanah Merah Coast Road in the Changi East development area alerted the Singapore Police Force (SPF) to a war relic at approximately 04:55 hrs local time. The site falls within the construction zone for Changi Airport’s Terminal 5 (T5). The Singapore Armed Forces (SAF) Chemical, Biological, Radiological and Explosives Defence Group (CBRE DG) deployed an Explosive Ordnance Disposal (EOD) team to assess the item.

The SAF EOD team identified the item as a WWII-era aerial bomb with a total mass of approximately 250 kg. The bomb was assessed as unsafe to move, necessitating controlled on-site disposal. The decision not to transport the item is consistent with standard EOD doctrine: when fuze condition is unknown or degraded, and when energetic fill stability cannot be assured after 80+ years of burial, movement introduces unacceptable initiation risk. The principle of As Low As Reasonably Practicable (ALARP) dictates in-situ disposal over transport in such cases.

The Defence Science and Technology Agency (DSTA) applied advanced numerical modelling techniques to determine the blast leakage effects of the fortified protective structure on the surrounding area. This informed the establishment of safety zones and the multi-agency coordination required to maintain airport operations during the disposal window.

Analysis of Effects and Protective Works

The CBRE DG constructed protective works comprising compacted sandbag overhead cover and reinforced concrete barriers around the Unexploded Ordnance (UXO) to contain blast overpressure and fragmentation effects. This approach is consistent with established blast mitigation practice for items that cannot be moved to a remote demolition site.

For a 250 kg aerial bomb with an estimated Net Explosive Quantity (NEQ) of 75–125 kg, unmitigated high-order detonation would produce lethal blast overpressure (>35 kPa) at approximately 30–40 m, with a Casualty Radius (CR) at the 7 kPa threshold extending to approximately 80–120 m. Fragment Dangerous Distance (FDD) for natural fragmentation from the bomb casing could extend to 600–800 m. The protective structure was designed to attenuate these effects to acceptable levels at the safety zone boundary.

The controlled detonation was executed between 02:30 and 04:30 hrs on 2 April 2026, a window selected to minimise disruption to airport flight operations and public exposure. Changi Airport Group confirmed no impact on flight operations.

Personnel and Safety Considerations

The operation required multi-agency coordination between the SAF CBRE DG, the SPF, DSTA, the Civil Aviation Authority of Singapore (CAAS), and Changi Airport Group. The use of numerical blast modelling by DSTA to determine blast leakage effects represents a sophisticated approach to risk quantification — moving beyond standard Quantity Distance (QD) tables to site-specific modelling that accounts for the geometry of the protective structure, the surrounding terrain, and the proximity of critical infrastructure.

Standard Cordon and Evacuation Distance (CED) for HD 1.1 items at 100 kg NEQ under unmitigated conditions would typically require 400–600 m. The use of engineered blast mitigation structures permitted a reduced safety zone, enabling continued airport operations. This is a textbook application of ALARP principles: accepting the residual risk of blast leakage through a designed structure rather than imposing the disproportionate consequence of airport closure.

Data Gaps

DATA GAP: Bomb designation — The specific bomb type (e.g., US AN-M57, Japanese Type 97, or British MC 250 lb) has not been publicly identified. This determines the exact explosive fill composition, fuze type, and fragmentation characteristics. Singapore was bombed by both Japanese and Allied forces during WWII, making origin assessment difficult without physical examination markings.

DATA GAP: Net Explosive Quantity — The reported 250 kg is the total mass (All-Up Round). NEQ has not been confirmed. The 75–125 kg estimate is based on typical WWII aerial bomb fill ratios and carries medium confidence.

DATA GAP: Fuze type and condition — The fuze type, arming state, and degree of degradation have not been disclosed. The “unsafe to move” assessment implies either an armed or indeterminate fuze state, or degraded energetic fill that could sensitise the item to mechanical stimuli.

DATA GAP: Cordon distance — The actual safety zone distances established for this operation have not been published. DSTA’s numerical modelling informed the decision, but the specific overpressure thresholds and fragment distances used are not in the public domain.