William Girling Reservoir

and the William Girling Reservoir in background The reservoir was conceived as part of an overall plan for the Lea Valley and laid before the Royal Commission on Water Supply (Balfour Committee) in 1893. At the time the responsible authority was the East London Waterworks Company. However, under the provisions of the Metropolis Water Act 1902, the undertakings of this and seven other companies were transferred to the Metropolitan Water Board (MWB). Work began in 1936 when the tender of John Mowlem (for £682,156) was accepted. The project was led by civil engineer, Robert Wynne-Edwards. Due to the use of mechanical scrapers and bulldozers, which were being used for the first time in British dam construction, progress was rapid. The design, by Sir Jonathan Roberts Davidson, As part of the 2012 Summer Olympics security exercise, the reservoir was identified as suitable for the deployment of Rapier surface-to-air missiles. == Description ==

The geology of the site is alluvium underlain by river terrace gravels and in turn overlying the London Clay formation. The reservoir is formed by a continuous earthen embankment that encloses the basin. The embankments consist of a central puddle clay core with a selected material adjacent to the core forming a filter. The core is a maximum of wide at the base and tapers to wide at the crest. The core typically extends into the London Clay to form a watertight cut off. The embankment shoulders consist of zones of ballast and filling material. The upper embankments slopes are 1 in 2.5 externally, whilst the lower slopes to the berm were constructed at a bank slope of 1 in 8. It was considered necessary to reinforce the NW corner (Ponders End) with sheet-piling which was driven, suspended from a Weldex crane (see photo) ending in 2020 == Inflow ==

Water is pumped from the River Lee Diversion through five inlet pumps with a maximum of 600 ML/d, though normal operation is 250 ML/d. In addition there are two 200 mm diameter inlets from the North London Artificial Recharge borehole scheme. == Outflow ==

The outlet tower consists of a granite faced dry shaft that houses a diameter vertical pipe, with draw-off pipes at four different levels. The lower end of the standpipe is connected to a diameter steel outlet conduit. The water is conveyed to the Coppermills Water Treatment Works for treatment, with the facility for bulk transfer to Essex and Suffolk Water. == Ecology ==

The water is part of the Chingford Reservoirs Site of Special Scientific Interest (SSSI). It is a major wintering ground for wildfowl and wetland birds, including nationally important numbers of some species. The water also forms a moult refuge for a large population of wildfowl during the late summer months. A total of 85 wetland species have been recorded here in recent years. == Gallery ==

File:Weldex 24 9 20.jpg| Weldex crane below embankment. File:Crane Girling Reservoir 1 k.jpg| Weldex carrying out sheet piling work NW corner of reservoir. File:William Girling Reservoir, K.jpg| View west towards Ponders End ==See also==