The first internal inspection was carried out in 2004 and revealed an 8% loss in strength. Findings from the second inspection, which was carried out earlier this year, indicate that the cables have now lost about 10% of their strength, but Faber Maunsell is optimistic that the rate of deterioration is at the slower end of expectations.
Hardwood wedges were driven in to open up the cables and allow engineers to assess the condition of a representative sample of the 11,618 individual wires that make up each bundle. The condition of each wire was recorded and samples were taken for laboratory testing.
A third inspection will be carried out in 2011/12 to verify the effectiveness of dehumidification.
If efforts to halt the corrosion fail, it is now thought that weight restrictions might require to be considered some time between 2017 and 2021, rather than the previous estimate of 2014 to 2020.
FETA has announced that Flint & Neill Partnership is to be commissioned to carry out an independent check of Faber Maunsell's findings.
