Eagle Pond is a 40,000m3 reservoir retained by a 4m high dam in east London, built prior to 1745. Being in an urban area, the reservoir is considered to be high risk in terms of consequence of failure.
The project was to implement a recommendation in the interests of safety, from a Section 10 inspection report under the Reservoirs Act 1975, to increase the spillway capacity to pass the Probable Maximum Flood. The project is complicated as the dam is in an area of woodland in Snaresbrook conservation area, and in the grounds of a crown court well used by the public. The reservoir is owned by the Cooperation of London.
The scheme comprised installation of a line of sheetpiles along the upstream face of the dam crest and raising the side walls of the existing concrete spillway. The size of spillway enlargement required was mitigated by utilising an existing sheetpile wall along the side of the reservoir as an auxiliary spillway, designed to spill onto a road pavement for floods in excess of 1 in 1000 chance per year. The new sheetpiles were clad in timber with coir rolls at the normal waterline to encourage a vegetation screen along the upstream face.