Upper Orwell Crossings ground investigations

About the ground investigations starting on 15 January 2018 in the River Orwell, Ipswich to inform the design of the Upper Orwell Crossings.

TUOC + Strap

Starting on 15 January 2018, the ground investigations (GI) will investigate the geology that will support the foundations of the proposed bridges and inform the design for the Upper Orwell Crossings.

The scope for the GI work has been developed by Geotechnical Engineers who will analyse the information and use it to design the foundations on which the bridges will sit. 

The works will also help to determine the extent and detail of existing buried structures e.g. quay walls and anchors. This information is essential for the ongoing design of the bridges.

Further information

Ground investigations map

C1568 Uruguay 5 Skate 3CEven though we know the type of geology for the area, the depths and strength of the material can vary considerably, therefore we need to collect and test samples.

To obtain this information boreholes, which are deep narrow holes in the ground, will be used to bring up a core of the underlying material. Boreholes will be drilled overwater and on land.

To drill overwater, the machinery will sit on a jack up barge. Once the cores have been brought to surface they will be inspected by a geotechnical engineer at the site compound and then sent off for testing.

There are two types of drilling that will be used during the investigations to obtain boreholes:

  1. Cable percussion drilling A weight to drive a casing and sampling tubes into the relatively soft materials found close to the surface.
  2. Rotary drilling Used for sampling harder materials such as the chalk at greater depths.

We will also undertake:

  • Cone Penetration Testing (CPT) A cone is pushed into soils to test the resistance to enable the load bearing capacity of soils to be estimated.
  • Mechanically excavated trial pits These enable the geology to be visually assessed at shallow depths, usually up to 4m deep. This method also enables larger soils samples to be taken.

Some of the works will be noisy, particularly the cable percussion drilling.

The likely noise effects have been modelled and this has informed the permitted time for working.

Land based investigations

  • Monday to Friday: 7am to 7pm
  • Saturday: 7am to 1pm

River based investigations

  • Monday to Sunday: 24 hours
  • Cable percussion drilling is limited to 7am to11pm, with the exception of the New Cut (Ground Investigation, Location B) which is 7am to 7pm.

Acoustic barriers will be used to minimise noise levels. As shown in the picture below, the specially developed sound absorbing barrier is attached to fencing panels around the works and can achieve up to 30 decibel noise reduction.

Example Drilling Compound Setup 24m x 4m

Noise levels will be monitored throughout the works.

Fugro GeoServices Ltd and WSP are carrying out the works on behalf of Suffolk County Council. Fugro Geoservices Ltd are experts in geo-intelligence and have years of experience in marine drilling. 

They have performed numerous site investigations for bridge projects around the world.

No ground investigation or construction works are proposed in the compound area.

The compound’s principle purposes are to:

  • provide staff welfare and meeting facilities.
  • provide for the secure storage and occasional maintenance of equipment, plant, and materials.
  • undertake logging and photographing of borehole cores collected during the ground investigation works, prior to it being sent for laboratory analysis.

Planning permission for the compound site was granted by the Suffolk County Council Development Control Committee on the 18 January 2017.

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