Hazelmere dam suffered a major flood event that resulted in the spilling of the dam on 10th April 2022. This developed into a sustained deluge of water and debris cascading over the Piano Key Weir (PKW) and into the anchor recesses before continuing downstream over a period of four days. It is noteworthy that at the spillway location, four unstressed anchor tendons protruded from the boreholes in separate blocks in preparation for load cell installations before stressing, testing and lock-off.
Before the spilling of the dam, the protruding tendons were subjected to a corrosion inspection (carried out by GGL in February 2022 and reported on by GGL in March 2022). Following this inspection work, the exposed tendons were coated in corrosion-inhibiting compound (CIC), protected by lengths of HDPE sheathing, and then collectively bound and covered in heavy-duty plastic sheeting. However, the effect of the flood was so severe that these protective measures were destroyed, and the strands were completely exposed to the environment with just a residual coating of CIC retained on the surfaces of the steel strands.
Before carrying out the stressing of the spillway anchors, it was considered crucial to undertake another inspection of the tendons to assess whether the flood event, described above, had any adverse effects on the protruding strands that could potentially affect the stressing operation.
A total of 320No. individual strands were inspected and found to be satisfactory.