Sea Defences, Holland-on-Sea, Essex

A ground investigation was carried out on the beach and promenade at York Road in Holland-on-Sea. The purpose of the investigation was to determine the underlying ground conditions and aid the design of a steel sheet pile retaining wall.

The investigation was carried out under the directions of Haydn Evans Consulting, the engineers for the project, acting on behalf of the client, Tendring District Council.

At the time of the fieldwork the beach which was approximately 3.0 to 3.5m below the level of the promenade. The fieldwork comprised the drilling of a single exploratory borehole using conventional light-cable percussive methods through the existing promenade. The fieldwork also included percussive windowless sampling at four locations on the beach and dynamic probing was also carried out at nine locations on the beach using the super heavy (SHDP) method.

The percussive windowless sampling and dynamic probing was carried out using a small track mounted soil sampling rig which utilised a sliding hammer to drive the windowless sampling tubes and dynamic probes into the ground and hydraulic rams to extract them. Each of the windowless samples recovered a core of soil from the ground approximately 1m in length. A single row of dynamic probes was carried out at approximately 8.5m centres and 3.0m away from the promenade’s edge.

The tracked window sampling/dynamic probe rig was craned on and off the beach each day using a lorry mounted crane (Hi-ab) positioned on the promenade. The fieldwork was carried out during a period of spring tides, when the tidal range was at its maximum, allowing the fieldwork crew the maximum amount of time on the beach.

The sea wall was in poor condition due to low beach levels. A void in an access ramp meant vehicles were banned restricting access for maintenance and to boat and beach hut owners. The wall was degrading further as time passed. The existing groynes were left intact to assist in maintaining the beach sand deposits. Granite rock was used to strengthen the defences creating a natural feature in keeping with the area. Residents and business owners, whose properties would have been affected by further erosion, are now assured of the long-term stability of the sea wall.

The project was awarded an exceptional merit in the 2010 East of England ICE Merit Awards.