Ultrasonic Pipe Wall Thickness survey carried out by PMP.

In 1993, PMP were engaged by United Utilities to carry out an ultrasonic pipe wall thickness survey of the cast iron draw-off pipes from New Year's Bridge IR. The '93 survey revealed varying degrees of corrosion throughout the draw-off tower and tunnel but most significantly on the vertical stack at the base of the shaft.

In 2005, PMP were re-engaged to carry out a repeat pipe wall thickness survey of the same cast iron draw-off pipe but this time only to the bottom two pipe sections which had previously been identified as 'at risk' during the '93 survey.

The repeat survey concluded that no significant deterioration had occurred.

The bolt replacement recommended in 1993 was also carried out.