William Girling Reservoir

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William Girling Reservoir
The reservoir viewed from Chingford
Location	London Borough of Enfield
Coordinates	51.6316° N 0.0244° WCoordinates: 51.6316° N 0.0244° W
Lake type	reservoir
Primary inflows	River Lee Diversion
Basin countries	United Kingdom
Surface area	135 ha (330 acres)
Max. depth	12.5 m
Water volume	16500 ML

The William Girling Reservoir is located in the London Borough of Enfield and is part of the Lee Valley Reservoir Chain that supply London with drinking water. It is named after William Girling OBE a chairman of the Metropolitan Water Board (MWB). Together with the King George V Reservoir they are known collectively as the Chingford Reservoirs. The storage reservoir is owned by Thames Water and is bordered by Chingford to the east and Ponders End and Edmonton to the west, and covers 334 acres (135 HA) with a perimeter of 3.5 miles. There is no public access.

1 History
2 Description
3 Inflow
4 Outflow
5 Ecology
6 References
7 External links

[edit] History

The reservoir was conceived as part of an overall plan for the Lee 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 of 1902, the undertakings of this and seven other companies was transferred to the Metropolitan Water Board.

Work began in 1936 when the tender of John Mowlem (for £682,156) was accepted. 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 Davidson (President of the Institution of Civil Engineers 1948/49) attracted widespread technical interest when a major slip in 1937 occurred in the partly formed embankment at the north-west corner. When the embankment fill had reached 23 ft a 66 ft width had dropped 2 ft 4 in. and moved forward 13 ft. Fortunately, the dam failed before any water had been stored. Investigations were under way when a second slip occurred in December 1937. Two independent soil mechanics experts were called in; Dr.Herbert Chatley and Professor Karl Terzaghi, who both made recommendations. In July 1938 the (MWB) made important modifications to the original design. Subsequent investigations into this land slip can be regarded as the birth of modern soil mechanics in Britain. The reservoir was redesigned to increase its capacity by 11.3%.

Construction was further delayed by the outbreak of the Second World War and the reservoir was finally completed in 1951 and officially opened on the 4th September by William Girling ^[1].

[edit] 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 which 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 12 ft wide at the base and tapers to 5 ft wide at the crest. The core typically extends 3 ft 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.

[edit] 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 200mm diameter inlets from the North London Artificial Recharge borehole scheme.

[edit] Outflow

The outlet tower consists of a granite faced dry shaft that houses a 54” diameter vertical pipe, with draw off pipes at four different levels. The lower end of the standpipe is connected to a 50” 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 .

[edit] Ecology

The water is a Site of Special Scientific Interest(SSSI) ^[2], and is a major wintering ground for wildfowl and wetland birds and include nationally important numbers of some species. The water also form a moult refuge to large population of wildfowl during the late summer months. A total of 85 wetland species have been recorded here in recent years.