FOUNDATION AND Exploration Services has carried out an investigation for a jetty retaining wall for Associated British Ports' new container terminal at Dibden Bay, Southampton Water.
Four cable percussion boreholes were put down to 35m below seabed along the line of the steel sheet piled retaining wall for the berth face. Work was carried out from an eightsection pontoon to cope with the 5m tidal range.
Ground conditions were assessed between the proposed jetty and existing deepwater shipping channels, where some 12M. m 3dredging will be carried out.A further five,15m deep boreholes were drilled in water depths of up to 10m, in this area.
Differential GPS survey equipment was used to accurately position the pontoon over each borehole position within 0.5m. Effective stress tests and contamination analyses were also carried out at the firm's laboratories.
FES had already undertaken an onshore borehole and trial pit survey to determine the settlement characteristics of dredged fill and alluvium and to assess potential soil and groundwater contamination.
A contamination survey of the seabed on the foreshore ensured that dredged material could be disposed of at sea.