A statutory inspection was completed by the All Reservoir Panel Engineer in January 2007 during which the Panel Engineer recommended that works be carried out to the concrete face of the dam and that additional measures be implemented to prevent further deterioration of the concrete. Following this recommendation,
United Utilities commissioned
MWH to undertake works to improve the condition of the existing concrete dams and to help to implement recommendations to ensure that the reservoir would meet the requirements for a Category A reservoir. Work began in 2010, when the downstream face of the main dam was cleaned and loose concrete,
efflorescence and other surface deposits were removed. The concrete face was then protected from further deterioration by using a cementitious repair mortar and
siloxane waterproofer. The remedial works on the upstream face included the installation of a
PVC geocomposite membrane,
geonet drainage layer and associated drainage system to the upstream face of the main dam and the auxiliary overflow. The
geomembrane is sealed on the concrete face along the foundation line and on the
parapet wall 300 mm above the crest level to cover the joint between the upstream face and the parapet wall. The geomembrane covers a total surface area of 1,100m2. A Geomembrane drainage system was incorporated into the design to discharge water through 3 holes in the dam. Joints and cracks in the concrete were treated with an
acrylic resin where the perimeter seal crosses the joint to prevent reservoir water bypassing the perimeter seal. A reinforced concrete wave wall was constructed to the same dimensions and levels as the existing but it extended into the high ground at the left and right ends of the dam. Finally,
riprap erosion protection was laid at the left hand end of the dam to arrest erosion of the embankment. The material for the erosion protection was sourced from the reservoir basin. ==References==