The Staines Reservoirs are two large pumped storage reservoirs sitting to the east of the King George VI Reservoir near Heathrow Airport in Surrey within the Colne Valley regional park. The village of Stanwell is mainly to the north east, and the town of Staines is to the south. Both adjoin, west, the A3044. The south one adjoins the A30 where the road is bypassed by the intra-M25 motorway network but is a trunk road, maintained by National Highways. They were completed in 1902.
History For reliable and plentiful water supplies, three London water companies resolved to construct and operate two large reservoirs at seasonally waterlogged land partly in the parish of Staines, otherwise in Stanwell. These would be pumped storage reservoirs to hold water abstracted from the Thames receiving it from an aqueduct, then delivering it by another to treatment works for their supply pipes. The three were the New River Company, the Grand Junction Water Company and the West Middlesex Water Company.
To obtain full indemnity and a compulsory purchase mechanism they promoted the Staines Reservoir Bill of 1896. The bill was opposed by some landowners, as well as London County Council and Middlesex County Council. Nevertheless, the bill was enacted, with amendments, as the Staines Reservoirs, &c. Act 1896 (59 & 60 Vict. c.ccxli). The companies formed a joint committee to oversee the construction. The two reservoirs, North and South, are separated by a 1,030-metre embankment dam. The embankments of the two have a 6- to 8-metre-deep puddle clay core having scoured out the surface gravel to the underlying London Clay. They have total capacity of 3,338 million gallons (15.175 million m3) and were completed in 1902. The valve towers are to the west. Later in the same year of building the three companies, and seven others, dissolved into the Metropolitan Water Board – under the Metropolis Water Act 1902.
Operation The reservoirs are filled from the Staines Reservoirs Aqueduct, built as part of the works. Water was originally lifted from the aqueduct to the reservoirs by five steam driven engines, each with a capacity of 16 million gallons per day (72,737 m3/day). The engines were housed in Staines pumping station south-west of the south reservoir. Under the original legal provisions, when the flow of the river at Bell Weir exceeded 265 million gallons a day (1.205 million m3/d) the joint company could abstract any surplus up to 100 million gallons (454,609 m3) of which 35 million gallons (159,113 m3) could be run directly to the filter beds at Hampton and the surplus (295,496 m3/day) pumped into the reservoirs. The top water level in the North Reservoir is 3 m higher than the South reservoir. Water for treatment and use is drawn from the reservoirs through the valve towers and delivered to the aqueduct to flow south-east to several water treatment works. The Metropolitan Water Board operated the reservoirs until the board was abolished in 1974 under the provisions of the Water Act 1973 and ownership and control transferred to the Thames Water Authority, now Thames Water. In 1992, there was a proposal to increase the capacity of the reservoirs by raising the height of the dam walls and removing the dividing embankment. The work was estimated to take up to six years to complete. From April 2020, a sheet pile cut-off wall was installed in two places to prevent leakage of water through the core of the south reservoir's embankment. The area has been designated a Site of Special Scientific Interest (SSSI) as it carries important wintering populations of tufted ducks, pochard, goosander and goldeneye.
Staines Reservoirs Aqueduct
… excerpt ends here. Continue reading the full article.
