Long range survey | Mudflats, London Gateway

London Gateway

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Did You Know…?

London Gateway is the UK’s newest deep-sea container port, combined with Europe’s largest logistics park, located 25 miles east of central London. Construction on the site began in 2010, with dredging and new land creation taking place alongside the development of key infrastructure.

Still with plots to lease, London Gateway will enable the world’s largest container ships to call at the heart of the UK’s economic and population centre. The port’s highly efficient road, rail and sea links offer a quicker, cheaper and more environmentally friendly way to transport goods to their destination.

Met Consultancy Group provided specialist survey services on the London Gateway project for an engineering consultancy client.

Project Overview

Met Consultancy Group’s Land and Building survey team were contacted by Cullen Grummitt & Roe (an international engineering consultancy who specialise in port and harbour engineering, cold storage and mining infrastructure projects) to advise on a mudflat survey solution on the River Thames.

The 28 hectare site is part of the London Gateway project, but was considered too dangerous for conventional topographical survey as pedestrian access was impossible. The area is within the tidal zone of the Thames Estuary and a number of watercourses outfall into this area. Between the high and low water tidal lines the site consists of thick silty mud and was known to be subject to constant movement from erosion and deposition.

The client required the site surveying by remote methods and then to be monitored over 12 months at quarterly intervals so the effects of tidal and river movement on the silt deposits could be observed. Met suggested setting up a control network using Global Navigation Satellite System (GNSS) over permanent ground anchors. This would be followed by laser scanning to give a grid of levels across the site with a fully contoured 3D digital plan. The Point Cloud data would also be available for the client to undertake his own interrogation if required.

The site posed a number of problems besides accessibility. The survey could only be carried out during a limited period of time; when it was low ebb tide, but before standing water would restrict observations of the silt levels. The working day revolved around tide times and the surveyors were on site at dawn and dusk for some visits. The ground water levels and hence the ground levels and station positions could theoretically rise and fall with the tide.

Survey Station locations were observed by GNSS several times during each visit to obtain a mean level. The scanning was undertaken using specialist long range Riegl scanners as some observations were over 500m. To minimise survey time the surveyors were able to ensure the scan target area was kept to a minimum horizon and the scanner was set up and measured from several locations around the site periphery to ensure maximum coverage was achieved.

Standing water did prove to be an issue but this was detected by the scanner and indicated on the final plan. The client could then make their comparisons over the 12 month period to provide the base data for an engineering design.

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