Tag Archives: Geotechnical Risks

Canvey Island Sea Wall Erosion, should be the Real Focus of CPBC’s Attention. Residents again being kept in the Dark?

The condition of the Canvey Sea Wall, or Sea Defence system, is causing serious concern, despite the lack of news or information.

The cause, which should not be too surprising, is currently under investigation.

Further inland on Canvey a large Green Belt site, identified as being deliverable and developable by Castle Point borough council, was the subject of a pre-development Ground Investigation Report, probably the first, and most thorough investigations of its type on Canvey Island, to be made public via the cpbc planning portal.

The Ground Investigation Report indicated what should be serious concerns to the cpbc development committee and planning officers, should they refer to it and give it the respect it warrants.

We suspect, however, committee members are unaware of its existence!

Despite this site being a full Kilometre from the Estuary, the effects of tidal water which surrounds Canvey Island have been found!

The Ground Investigation Report was carried out to consider what Risk the subsoil and water table might have on development structures, such as Housing.

It found;

Geotechnical Risks*
Poor bearing capacities of the low strength / loose soils;
Aggressive ground and groundwater conditions
Shallow groundwater (possibly under tidal influence)

The High Water table found on Canvey Island is well known to residents, however what was surprising is that this water consisted of a level of saline, or sea water, content!

In effect our Sea Defence is incapable of stopping Tidal Water from penetrating UNDER the sea wall.

If these influences can be found 1 kilometre from the sea wall, how much more damaging are they to the Sea Defence itself?

The constant changes via the ground water saturation and drying processes, and the less than stable subsoil beneath the Sea Defence foundations will over time, challenge the longevity of the structure. Whilst the effects of the Tide itself is more obvious!

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The effects of the more frequent passing of larger and larger transport vessels along the Thames, requires monitoring, as does the constant dredging.

As recently as September 2017 we were reassured that these Sea Defences are “well maintained”, and whilst these images probably indicate superficial damage we have learnt that the Environment Agency have identified some areas of the Sea Defence causing them serious concerns!

The Environment Agency are known to have carried out surveying inspection works and are considering what steps are required to maintain the integrity of the Canvey Island Sea Defence.

*Geotechnical engineering is the branch of civil engineering concerned with the engineering behaviour of earth materials

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