Late in 2023 Sweet Structures contacted us with a very interesting challenge.
On 26th February 2021, whilst constructing a new block of student accommodation, a main contractor unearthed a 1000kg WWII German ‘Hermann’ bomb. It was dropped in the Baedeker raids in 1942 and they were named as such after a well known German travel guide of that era. They were a reprisal for the RAF bombing of Lubeck. Exeter was the first city to be bombed in these raids. In the first raid on the night of 25-26th April, 80 people were killed and 55 wounded. In a further attack in early May, 90 aircraft dropped high explosives, parachute mines and incendiaries. Fires devastated the city's shopping centre and the raids left 163 people dead and 131 badly injured.
This discovery of the unexploded bomb in 2021 forced the immediate evacuation of 2600 properties in the area and also highlighted that all future building projects must require an explosive ordnance survey as a matter of course. Royal Navy Bomb Disposal teams covered the device with steel sheets and over 400 tons of sand to absorb the explosion.
Location:
Exeter, Devon
Client:
Admiral Insurance
Type:
Commercial
Completed:
July 2024
Sector
Commercial Insurance
Designer
Sweet Structures
On Saturday 27th the device was detonated with the effect of sending 400 tons of sand and steel sheets high into the air, created a crater the size of a double decker bus and threw debris up to 250 metres away. However, more critically the sand dampening caused a seismic event which travelled up to a mile distant through weaknesses in the geology of the surrounding and wider area.
The house at the centre of our project was only a third of a mile from the blast site and has been the subject of an insurance case. This property was significantly damaged throughout:
- Lintels in window openings shifted back in the walls
- Windows and doors were buckled and required replacing
- In situ concrete retaining walls were split and elements of the garden liquified and flowed down through the site
- Paving sub-bases split
- Balconies were structurally damaged and left dangerously precarious
Sweet Structures assessed the damage and designed a sympathetic scheme to remediate the entire garden damaged by the blast with new retaining structures with engineered footings and new steel balconies clad in Millboard Smoked Oak with laminated glass balustrades to meet modern best practice.
Due to the tight site access we had to utilise cranes, four wheel drive compact loaders and concrete pumps. Unique Projects worked with the homeowners, the design team and the insurance company throughout to deliver a truly unique project, and all parties gained a wealth of knowledge and experience on blast damage and seismic events.
46 St. Lukes Road, Newton Abbot, Devon, TQ12 4ND
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Unique Projects (Devon) Ltd is a company registered in England & Wales. Registered number: 14221838. Registered office: 38 Elizabeth Road, Seaton, Devon, EX12 2DR.