Underwater Inspections on EA Flood Barriers

Case Study Overview

Underwater condition assessments of flood barrier structures on River Thames & Thames Estuary including hydrographic survey techniques in support of periodic diving inspections

Diving contractor responsible for all health & safety planning, provision of full surface supply diving equipment and team for underwater inspections from vessel using R7M in house engineer divers.

Diving inspection of assets to check for likely defect/obstruction to operation of flood barriers, provision of condition assessment reports. Management and supervision of hydrogrpahic surveying specialist – interpretation of digital 3D survey data to supplement/enhance physical dive inspections and aid reporting.

At a glance

  • Location: Tilbury, East Haven, Fobbing, Colne Barrier (hydrographic survey only)
  • Project Value: Current Outturn Approx. £30,000 – NB on going commission with EA East Div
  • Programme Duration: Typically 1 day per site with reporting time back in office, today approx. 1 months work inclusive of all site/office time plus all mod/demob.
  • In-House resources Work: Provision of 4 man R7M team with surface demand diving equipment to carry out physical inspections. All H&S preparation carried out by R7M for approval by EA including provision of Divesafe 4 documentation
  • Subcontractor Work: Port of London Authority (PLA) for hydrographic survey of structures 3rd party charter for dive vessel

The Solution

All scheduled inspection/survey work executed in a safe manner and delivered on time and within agreed budget. Full liaison/approval with EA and other controlling authorities on Thames (PLA, Port of Tilbury) for dive planning, permits etc. Diving programme based around slack water neap tides to maximise diveable windows in fast flowing River Thames. Requests made to EA Operations to open gates at low water to sluice away silt deposits ahead of R7M mob to site to aid inspections.

Use of high resolution multi beam echo sounder techniques by PLA to image structures from bed level to superstructure to image structures, highlight any defect, identify scour patterns , build up of materials that could compromise barrier closure operations during flood events.

Value Added
Careful programming to make best and safest use of tides. Recommendation to EA to use PLA MBES capability to fully image structures to aid condition assessment/monitoring. PLA able to carryout work on back of other schedule work – cost saving. Use of nearby R7M wharf facilities on Thames to assist in mob/demob of kit and equipment on board dive vessel – cost saving.

Colne Barrier at low waterUnderwater Inspections

Multi Beam data of Colne Barrier
Underwater Inspections




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