Page last updated at 14:33 GMT, Friday, 15 January 2010

Boreholes drilled below Clifton Suspension Bridge

Clifton Suspension Bridge
The bridge is nearly 150 years old

Boreholes of up to 100m (328ft) are being drilled below Bristol's Clifton Suspension Bridge to check the geology of the supporting rock.

Cores of rock of 10cm (4in) will be extracted and sent for analysis.

Although similar tests have been carried out before, some of the new boreholes will be significantly deeper.

The six holes will not all be drilled vertically but at shallow angles to go through the vertical joints of the rock to allow samples to be taken.

The 145-year-old bridge is run by a trust and all costs of the work will be met from vehicle tolls.

Bridge master Dave Anderson said boreholes were sunk into the rock on the Clifton side of the bridge in the 1990s, and on the Leigh Woods side 20 years earlier.

'Complex geology'

"We are not expecting to find any problems but we have to go through the process of checking every part of the bridge.

"This time we expect to gain a clearer grasp of the complex geology on both sides of the Avon Gorge, as well as confirmation that the rock mass supporting the bridge is in good condition.

"[Engineers] will be able to advise us whether the rock which supports the bridge is strong enough to do that in the future."

The £145,000 project is expected to take between five and eight weeks.

"Some footpath closures are planned but traffic is not expected to be significantly disrupted while the work takes place," Mr Anderson added.

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