Loch Drunkie: Underwater lining of a 150-year-old cast iron outlet pipe

Loch Drunkie is retained by two earth dams built in 1859. The outlet pipe is a 24 in dia. cast iron pipe through the highest part of the east dam with downstream control only. Although no record drawings exist, it is considered that the pipe is laid directly within the foundation or embankment fill and the presence of any concrete surround is unlikely. The pipe is over 160 years old and, due to the valve arrangement, is always subject to internal pressure from the reservoir. The east dam was inaccessible with no vehicular access to within 500 m. In the 2014 Statutory Report, a recommendation in the interest of safety was made to ascertain the condition of the outlet pipe and carry out any works deemed to be required to reduce any potential threats posed to the safety of the dam. This paper describes the series of investigations and subsequent pipe lining works that were carried out at the reservoir. Due to concerns regarding the integrity of the pipe, all investigations and pipe lining works had to be carried out with the reservoir at top water level to ensure the internal pressure to the pipe was maintained throughout.