Thames Water Ring Main
Encyclopedia
The Thames Water Ring Main (TWRM) (formerly known as the London Water Ring Main/LWRM) is a major part of London's water supply infrastructure that consists of an approximately 80 km system of mostly 2.54 m (100 in) concrete pipelines used to transfer potable water
from water treatment works (WTWs) in the Thames and River Lee
catchments to distribution within London
.
The initial ring was constructed between 1988 and 1993. , two extensions are under construction. There are plans for further extensions through 2025.
, Walton
, Ashford
and Kempton
WTWs clustered on the Thames upstream of Teddington Weir
to central London by a southern branch via Brixton
and northern branch via Kew
and a separate unconnected length from Coppermills WTW
to Stoke Newington
. The pipeline is well below the level of most water mains, being at a depth of between 10 to 60 m below ground level and approximately 10 to 30 m below sealevel (as measured with respect to Ordnance Datum
). It is connected to the water supply zones by some 20 shafts that extend from the ring main to ground level.
and Park Lane pump-out shafts. The loop is not closed for hydraulic reasons but rather to provide the redundancy that allows any segment on the ring to be isolated and drained for maintenance without interrupting the supply to any shaft.
with sections within the overlying alluvium and underlying Lambeth Group
and Thanet Sand. The predominance of the London Clay lengths is by design, as being easily excavated, largely impermeable and somewhat self-supporting (for short periods), it is a near ideal tunnelling material. Where the hydraulics have required entry into the Lambeth Group and Thanet Sand, tunnelling was considerably more difficult. In particular, the Thanet Sand requires a high boring torque, is highly abrasive and, most challengingly, sufficiently permeable to contain a water table continuous with the underlying Chalk and measured at pressures up to 4 bar. An unexpected entry into the Thanet Sand while excavating near Tooting Bec Common
led to the flooding of the tunnel and the temporary abandonment of a Tunnel Boring Machine
(TBM).http://fbe.uwe.ac.uk/public/geocal/SoilMech/water/WATERCAS.htm#THAMES A further consideration of Thanet Sand is the presence of glauconite
which oxidises on contact with air. The resulting de-oxygenated air resulted in two fatalities during the excavation of a pump-out shaft.
projects are being assessed for their environmental sustainability through CEEQUAL
.
works (supply), pumping station
s (demand), and access shafts where no water enters or leaves the ring main.
Drinking water
Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...
from water treatment works (WTWs) in the Thames and River Lee
River Lee (England)
The River Lea in England originates in Marsh Farm , Leagrave, Luton in the Chiltern Hills and flows generally southeast, east, and then south to London where it meets the River Thames , the last section being known as Bow Creek.-Etymology:...
catchments to distribution within London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
.
The initial ring was constructed between 1988 and 1993. , two extensions are under construction. There are plans for further extensions through 2025.
Overview
The average daily flow is approximately 1 gigalitre (thousand millions of litres), out of a total London average day demand of approximately 2.6 gigalitres. The system is not strictly a ring but currently comprises one major loop linking the HamptonHampton, London
Hampton is a suburban area, centred on an old village on the north bank of the River Thames, in the London Borough of Richmond upon Thames in England. Formerly it was in the county of Middlesex, which was formerly also its postal county. The population is about 9,500...
, Walton
Walton-on-Thames
Walton-on-Thames is a town in the Elmbridge borough of Surrey in South East England. The town is located south west of Charing Cross and is between the towns of Weybridge and Molesey. It is situated on the River Thames between Sunbury Lock and Shepperton Lock.- History :The name "Walton" is...
, Ashford
Ashford, Surrey
Ashford is a town almost entirely in the Surrey borough of Spelthorne in England, with a small part falling within Greater London. It is a suburban development situated 15 miles west south-west of Charing Cross in London and forms part of the London commuter belt...
and Kempton
Kempton
Kempton is the name of several places:*Kempton, Shropshire, a village listed in the Domesday Book, located in south Shropshire, England*Kempton, Tasmania, a township in Tasmania, Australia*Kempton, Dublin, an estate in Dublin, Ireland*In the United States:...
WTWs clustered on the Thames upstream of Teddington Weir
Teddington Lock
Teddington Lock is a complex of three locks and a weir on the River Thames in England at Ham in the western suburbs of London. The lock is on the southern Surrey side of the river....
to central London by a southern branch via Brixton
Brixton
Brixton is a district in the London Borough of Lambeth in south London, England. It is south south-east of Charing Cross. The area is identified in the London Plan as one of 35 major centres in Greater London....
and northern branch via Kew
Kew
Kew is a place in the London Borough of Richmond upon Thames in South West London. Kew is best known for being the location of the Royal Botanic Gardens, now a World Heritage Site, which includes Kew Palace...
and a separate unconnected length from Coppermills WTW
Coppermill Stream
The Coppermill Stream is located in the London Borough of Waltham Forest at Walthamstow in an area generally known as the Lea Valley. It is a minor tributary of the River Lea and approximately long. The stream is part of a Site of Metropolitan Importance...
to Stoke Newington
Stoke Newington
Stoke Newington is a district in the London Borough of Hackney. It is north-east of Charing Cross.-Boundaries:In modern terms, Stoke Newington can be roughly defined by the N16 postcode area . Its southern boundary with Dalston is quite ill-defined too...
. The pipeline is well below the level of most water mains, being at a depth of between 10 to 60 m below ground level and approximately 10 to 30 m below sealevel (as measured with respect to Ordnance Datum
Ordnance Datum
In the British Isles, an Ordnance Datum or OD is a vertical datum used by an ordnance survey as the basis for deriving altitudes on maps. A spot height may be expressed as AOD for "above ordnance datum". Usually mean sea level is used for the datum...
). It is connected to the water supply zones by some 20 shafts that extend from the ring main to ground level.
Driver
The ring main serves as a partial alternative transfer system to existing trunk mains which were suffering increasing frequencies and severities of leaks and bursts. Being some of the oldest operational pressure mains in the world (the oldest dates from 1838), the high level trunks have weakened with steady corrosion and concurrently there has been both an increased carrying requirement resulting from increasing water demand and increasing external stresses resulting from higher vehicle weights and frequencies. This has been exacerbated by limited system redundancies which has restricted preventative refurbishment. The ring main has both extended the operational life of the high level trunks by reducing the flow demands placed on them, and, by providing a high degree of redundancy, enables key trunks to be isolated and maintained.Hydraulics
Flow through the main is not pumped but rather flows by gravity under the driving head of the service reservoirs at the source WTWs. By virtue of its depth the pipeline is under some pressure, however, the hydraulic grade line rarely exceeds ground level, and to enter supply, water must be pumped up into the distribution zones at the various pump-out shafts. In some respects, therefore, the ring main can be considered as a reservoir (albeit with negligible capacity), from which supply is drawn as required. An indication of this dynamic variation in demand is that the minimum hydraulic level does move between the BatterseaBattersea
Battersea is an area of the London Borough of Wandsworth, England. It is an inner-city district of South London, situated on the south side of the River Thames, 2.9 miles south-west of Charing Cross. Battersea spans from Fairfield in the west to Queenstown in the east...
and Park Lane pump-out shafts. The loop is not closed for hydraulic reasons but rather to provide the redundancy that allows any segment on the ring to be isolated and drained for maintenance without interrupting the supply to any shaft.
Construction
The ring main was constructed over two phases, the first comprising the southern leg from Ashford Common WTW to Barrow Hill Shaft and constructed from 1988 to 1991 and the second comprising the northern leg between the same locations and dating from 1991 to 1993. Each phase was in turn divided into a number of 'stages' that were separately contracted and constructed largely simultaneously. The differing contractors involved in each stage is to some degree reflected in the variation in tunnelling and tunnel construction techniques used.Geology
The ring main lies mostly within London ClayLondon Clay
The London Clay Formation is a marine geological formation of Ypresian age which crops out in the southeast of England. The London Clay is well known for the fossils it contains. The fossils from the Lower Eocene indicate a moderately warm climate, the flora being tropical or subtropical...
with sections within the overlying alluvium and underlying Lambeth Group
Lambeth Group
The Lambeth Group is a stratigraphic group, a set of geological rock strata in the London and Hampshire Basins of southern England. It comprises a complex of vertically and laterally varying gravels, sands, silts and clays deposited between 56-55 million years before present during the Ypresian age...
and Thanet Sand. The predominance of the London Clay lengths is by design, as being easily excavated, largely impermeable and somewhat self-supporting (for short periods), it is a near ideal tunnelling material. Where the hydraulics have required entry into the Lambeth Group and Thanet Sand, tunnelling was considerably more difficult. In particular, the Thanet Sand requires a high boring torque, is highly abrasive and, most challengingly, sufficiently permeable to contain a water table continuous with the underlying Chalk and measured at pressures up to 4 bar. An unexpected entry into the Thanet Sand while excavating near Tooting Bec Common
Tooting Commons
The Tooting Commons consist of two adjacent areas of common land lying between Balham, Streatham and Tooting, in south west London: Tooting Bec Common and Tooting Graveney Common....
led to the flooding of the tunnel and the temporary abandonment of a Tunnel Boring Machine
Tunnel boring machine
A tunnel boring machine also known as a "mole", is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through anything from hard rock to sand. Tunnel diameters can range from a metre to almost 16 metres to date...
(TBM).http://fbe.uwe.ac.uk/public/geocal/SoilMech/water/WATERCAS.htm#THAMES A further consideration of Thanet Sand is the presence of glauconite
Glauconite
Glauconite is an iron potassium phyllosilicate mineral of characteristic green color with very low weathering resistance and very friable.It crystallizes with a monoclinic geometry...
which oxidises on contact with air. The resulting de-oxygenated air resulted in two fatalities during the excavation of a pump-out shaft.
Future
The ring main will be extended in a series of stages over the coming decades. Work is currently underway to bridge the gap between the main loop at New River Head and the isolated segment at Stoke Newington and to extend a branch from the Brixton Shaft to Honor Oak reservoir. Both these major civil engineeringCivil engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...
projects are being assessed for their environmental sustainability through CEEQUAL
CEEQUAL
CEEQUAL, is an assessment and awards scheme for improving sustainability in civil engineering and public realm projects, based in the United Kingdom. It is promoted by the Institution of Civil Engineers and a group of civil engineering organisations including CIRIA, CECA and ACE...
.
Shafts
Access shafts are generally divided into those for water treatmentWater treatment
Water treatment describes those processes used to make water more acceptable for a desired end-use. These can include use as drinking water, industrial processes, medical and many other uses. The goal of all water treatment process is to remove existing contaminants in the water, or reduce the...
works (supply), pumping station
Pumping station
Pumping stations are facilities including pumps and equipment for pumping fluids from one place to another. They are used for a variety of infrastructure systems, such as the supply of water to canals, the drainage of low-lying land, and the removal of sewage to processing sites.A pumping station...
s (demand), and access shafts where no water enters or leaves the ring main.
North leg of Ring
- Ashford CommonAshford CommonAshford Common is a village in Surrey, England....
— WTW - Kempton ParkKempton Park, SurreyKempton Park is a locality in the Spelthorne district of Surrey, which is the location of Kempton Park Racecourse.Kempton Park appears on the Middlesex Domesday Map as Chenetone. It was held by Robert, Count of Mortain...
— WTW - Mogden — Access
- KewKewKew is a place in the London Borough of Richmond upon Thames in South West London. Kew is best known for being the location of the Royal Botanic Gardens, now a World Heritage Site, which includes Kew Palace...
— PS - Barnes — balancing storage
- Holland ParkHolland ParkHolland Park is a district and a public park in the Royal Borough of Kensington and Chelsea, in west central London, England.Holland Park has a reputation as an affluent and fashionable area, known for attractive large Victorian townhouses, and high-class shopping and restaurants...
Avenue — PS - Barrow Hill — PS
South leg of Ring
- Ashford Common — WTW
- WaltonWalton-on-ThamesWalton-on-Thames is a town in the Elmbridge borough of Surrey in South East England. The town is located south west of Charing Cross and is between the towns of Weybridge and Molesey. It is situated on the River Thames between Sunbury Lock and Shepperton Lock.- History :The name "Walton" is...
— WTW - HamptonHampton, LondonHampton is a suburban area, centred on an old village on the north bank of the River Thames, in the London Borough of Richmond upon Thames in England. Formerly it was in the county of Middlesex, which was formerly also its postal county. The population is about 9,500...
— WTW - SurbitonSurbitonSurbiton, a suburban area of London in the Royal Borough of Kingston upon Thames, is situated next to the River Thames, with a mixture of Art-Deco courts, more recent residential blocks and grand, spacious 19th century townhouses blending into a sea of semi-detached 20th century housing estates...
— PS - HogsmillHogsmillThe Hogsmill River in Surrey is one of the tributaries of the River Thames; it rises in Ewell and flows into the Thames at Kingston upon Thames on the reach above Teddington Lock.-Course:...
— Access - Raynes ParkRaynes ParkRaynes Park is a suburb within the London Borough of Merton south-west London, centred around Raynes Park station and situated between Wimbledon and New Malden. It is 8.2 miles south-west of Charing Cross. The area is effectively divided into two by the Waterloo - Southampton mainline railway...
— Access - MertonMerton (historic parish)Merton was an ancient parish in the Brixton hundred of Surrey, England. It was bounded by Wimbledon to the north, Mitcham to the east, Morden to the south and Kingston upon Thames to the west. The 1871 Ordnance Survey map records its area as . The parish was centred around the 12th century parish...
— PS - StreathamStreathamStreatham is a district in Surrey, England, located in the London Borough of Lambeth. It is situated south of Charing Cross. The area is identified in the London Plan as one of 35 major centres in Greater London.-History:...
— PS - BrixtonBrixtonBrixton is a district in the London Borough of Lambeth in south London, England. It is south south-east of Charing Cross. The area is identified in the London Plan as one of 35 major centres in Greater London....
— PS - BatterseaBatterseaBattersea is an area of the London Borough of Wandsworth, England. It is an inner-city district of South London, situated on the south side of the River Thames, 2.9 miles south-west of Charing Cross. Battersea spans from Fairfield in the west to Queenstown in the east...
— PS - Park Lane — PS
- Barrow Hill — PS
North extension
- Barrow Hill — PS
- New RiverNew River (England)The New River is an artificial waterway in England, opened in 1613 to supply London with fresh drinking water taken from the River Lea and from Amwell Springs , and other springs and wells along its course....
Head — PS
Segment under construction - Stoke NewingtonStoke NewingtonStoke Newington is a district in the London Borough of Hackney. It is north-east of Charing Cross.-Boundaries:In modern terms, Stoke Newington can be roughly defined by the N16 postcode area . Its southern boundary with Dalston is quite ill-defined too...
— PS - CoppermillsCoppermill StreamThe Coppermill Stream is located in the London Borough of Waltham Forest at Walthamstow in an area generally known as the Lea Valley. It is a minor tributary of the River Lea and approximately long. The stream is part of a Site of Metropolitan Importance...
— WTW
South extension
- Brixton — PS
Segment under construction - Honor OakHonor OakHonor Oak is an inner suburban area principally of the London Borough of Lewisham, with part in The London Borough of Southwark. The name originates from Oak of Honor Hill, or One Tree Hill. The legend is that on 1 May 1602, Elizabeth I picnicked with Sir Richard Bulkeley of Beaumaris in the...
— Underground Storage
External links
- History of the Thames Water Ring Main, Thames Water Utilities
- Thames Water Tunnels Mott Macdonald, contractor for the current extensions.