Provision of UXO risk mitigation services prior to bridge construction at Springhead Park, Ebbsfleet Valley

Part of one of the largest multi-million-pound regeneration schemes in the south-east, Springhead Park is a new housing development at Ebbsfleet Valley. Here, the newly established Ebbsfleet Garden City will cover over 1,000 acres with business, retail, leisure and community space as well as up to 10,000 new homes.

With Springhead Park set to feature an 87 metre-long bridge connecting residents with Ebbsfleet International station across the River Ebbsfleet, Balfour Beatty commissioned Fellows to survey the construction site for unexploded ordnance (UXO). The work was vital to identify and mitigate the risks as the site lies on a flight path used by the Luftwaffe to attack London during World War II.

Solution

As the site is alongside the Thames estuary, it was regularly overflown by German bombers on World War II air raids and the area itself was a target as various factories supporting the war effort were in the vicinity. Untouched for decades, both the land and water surrounding the development site could easily conceal bombs which failed to detonate on initial impact.

On site, Fellows constructed a floating pontoon to enable access for the team to manoeuvre and utilise intrusive survey equipment. A Cone Penetration Test (CPT) rig was used for deep magnetometer probe work as the depth of water and the geology of the
riverbed and surrounding land meant UXO could be lying far beyond the capability of non-intrusive detection techniques and equipment.

With the planned bridge construction requiring some 300 piles to be driven, Fellows not only had to probe the precise location for each of these but also investigate the surrounding areas for any UXO that could be disturbed by the vibrations and land movement that would be caused by the construction work.

Outcome

After 20 days of meticulous survey work on site, Fellows had collected and analysed data from each pile location, checking for any magnetic signatures resulting from ferrous objects in the ground. On discovery of any anomalies, Fellows can then conduct any further probe work to aid decisions on dealing with individual risks. Once all of these were established and mitigated, Fellows were able to submit its final report.

Groundworks are now underway and Springhead Bridge is set to open in early 2020 with access for all vehicles across two lanes as well as pedestrian footpaths and a cycle path.