During the design and appraisal stage, a major risk to the construction process was the issue of unexploded ordnance. The docks at Tilbury were, not unexpectedly, a target for bombs during the Second World War, as well as the resting place for unexploded anti-aircraft shells.
Tilbury Hotel - after which the Hotel Gardens outfall is named - was destroyed by direct hit in February 1941.
The team commissioned a report from specialist company Bactec, which goes into incredible detail about the number, size and location of bombs that fell in the area, and confirmed that measures should be taken on site to ensure that there were none on the line of the cofferdam.
As a result, Bactec has carried out an intrusive survey using a probe fitted with a magnetometer. 'They probed down to 14m, which is the predicted depth that a bomb would go down to, ' explains Ian Lock, Jackson's site agent.
'The probe is effectively a metal detector that equates the readings to mass, and from that it can work out the size of the bomb.' Probing was done ahead of each 10m run of piling, with the equipment suspended from a crane sitting on the platform behind. Readings were taken at 750mm centres on the line of both sides of the cofferdam.
Fortunately, no ordnance was found, and the team is now confident that the excavation can go ahead without danger.