Manly Dam - Wall

  • Number
    4573702
  • Primary address

    187, Across Manly Creek, near King Street Manly Vale, 2093. NSW
    LGA: Warringah
    LGA region: Sydney
    DUAP region: Sydney North

  • Alternate Address

    188, Arana Street Manly Vale, 2093. NSW
    LGA: Warringah
    LGA code: WARI
    LGA region: Sydney
    DUAP region: Sydney North

  • Owner
    Sydney Water
  • Current use
    Retains the waters of Manly Reservoir
  • Former use
    Water Supply storage
  • Item type
    Built
  • Item group
    Utilities - Water
  • Item category
    Water Supply Reservoir/ Dam
  • Parcels

    Parcel code: LOT
    Lot number: 10
    Section number:
    Plan code: DP
    Plan number: 840821
    Updated: 17 February 2003

  • Curtilage/Boundary
    The site is located wholly within Lot 10 of DP 840821 as shown in the curtilage plan. The curtilage includes the entire dam wall, spillway apron and natural vegetation to the east of the wall.
  • Map name
    Sydney Heads
  • Map scale
    1 : 25000
  • Latitude
    33 47 00 S
  • Longitude
    151 15 17 E
  • AMG easting
    338527482
  • AMG northing
    6260705291
  • AMG zone
    56H
  • Statement of significance
    Manly Dam Wall is of heritage significance at the state level because of its historical and technical values. The item has historical significance for its role in the development of Sydney’s water supply as it served as an independent water supply scheme. The item was built despite concurrent completion of the first stage of the Upper Nepean Water Supply and its gradual implementation on the north shore. The item provides evidence of the progressive and independent development of former remote suburbs. Manly Dam Wall has technical significance for the “post-tensioning” method pioneered in the late 1970s to strengthen the item. Manly Dam Wall is an important reference site due to this engineering technique. The item is a rare remnant of an independent water supply system. The item is also representative of a medium-sized, concrete gravity dam from the late 19th Century. It is one of the last of its size, designed, built under supervision by the NSW Department of Public Works, and associated with their prominent engineers, E.O Moriaty and C.W. Darley. Manly Dam Wall is of heritage significance at the local level because of its aesthetic and social values. The item has a picturesque setting. The item is also valued by the local community as the construction of the wall has enabled recreational activities to be undertaken within the Manly Warringah War Memorial Park, including fishing, swimming, kayaking, water skiing, bird watching, bushwalking and mountain bike riding. The metal walkway on the top of the dam wall forms an important part of a walking trail around the bushland reserve.
  • Endorsed significance
    State
  • Designer
    Public Works Department
  • Builder
    Public Works Department
  • Circa
    No
  • Physical description
    Manly Dam Wall is a sandstone and mass concrete gravity structure with a maximum height of 19 metres and length of 250 metres. It is located on Curl Curl Creek, approximately 3km north-west of Manly in the Sydney metropolitan area. The dam reservoir behind Manly Dam Wall is one of the largest artificial freshwater dams in the Sydney metropolitan area, with a capacity of 441,000,000 gallons (approximately 2,000 megalitres). Its catchment comprises of approximately 520 hectares and extends to French Forest in the north. The water level behind Manly Dam Wall is maintained at 34.1 metres.
  • Modifications made
    In 1906, a main was installed under Middle Harbour to supplement the water in the dam from a reservoir in Mosman (part of the Upper Nepean Scheme). In 1909, the capacity of dam was increased to 84,000,000 gallons (approximately 381 megalitres) with the excavation of a new enlarged by-wash and building up of the old by-wash, which allowed the Manly Dam Wall to be lengthened. These modifications allowed the Top Water Level to be raised to 28.4 metres above sea level. In 1914, the by-wash was raised, the wall lengthened and the dam wall was raised by 0.6 metres. The spillway height was increased to 29 metres and the capacity increased to 90,500,000 gallons (approximately 411 megalitres). In 1922, the dam wall was increased to its current height of 19 metres. The 1922 modifications provided a concrete arch walkway at the top of the wall and concrete piers spaced 3 metres apart, along the wall. During World War Two, the dam was fortified with machine guns and barbed wire, although there are no known remains of these fortifications. After 1961, as a flood mitigation measure, the draw-down time on the dam wall was reduced from 65 hours to 25 hours through additional scour capacity. From 1979 to 1981, the dam wall was strengthened through pioneering major engineering works, known as “post-tensioning”. The metal walkway on top of the dam wall as added during these works, which replaced the 1922 concrete arch walkway as a means of traversing the dam wall.
  • History
    In 1886 an Act of Parliament to provide a complete water supply for Manly created the catchment reserve. In 1890, tenders were called for the construction of a dam wall. By 1892, Manly Dam Wall was constructed by the NSW Government's Department of Public Works with Manly Waterworks, and officially opened on 4 February. It was one of the only two ‘Independent Water Supply Schemes’ in the Sydney metropolitan area; the other was at Parramatta. The original Manly Water Supply Scheme comprised of a dam, pumping station, rising main, service reservoir (originally on Red Hill) and reticulation. In 1892, the Manly Dam Wall was a mass concrete, gravity structure with an original maximum height of 11.3 metres, 85.3 metres long and a capacity of 68,216,000 gallons (approximately 310 megalitres). The Manly Water Supply Scheme was progressively called on to supply neighbouring suburbs such as Balgowlah and Seaforth and eventually the coastal strip of Warringah Shire to as far north as Mona Vale. Manly Council operated it for ten years. In 1902, operation and ownership of the Manly Waterworks site, including the dam wall, transferred to the Metropolitan Board of Water Supply and Sewerage at its original cost (£37,820), less the amount (£454) that had been paid off by the council. In 1906, it was necessary to supplement the local supply by connecting it with the metropolitan system (supplied by the Upper Nepean Scheme). This was done by installation of a main from Condamine Street connected to a reservoir in Brady Street, Mosman under Middle Harbour, at the Spit. The Board raised the Manly Dam Wall three times: 1909, 1914 and 1922. By 1928, increasing demand for water had overtaken the dam's capacity and in 1929 it was phased out, with supply for Warringah and Manly being provided by pipeline from the main metropolitan system at Pymble Reservoir. In 1930, the Manly Warringah Water Scheme was officially opened, to cater for the growing population. Water from the artificial freshwater dam created by Manly Dam Wall was used only to supplement supply to a small local area nearby until 1933. In 1936, the use of the artificial freshwater dam as a potable water supply ceased, and the pumping plant was subsequently dismantled. In 1939, the Reserve was dedicated as the Manly Warringah War Memorial Park. When the general water storage position became critical during the 1934-42 drought, Manly Dam was re-commissioned as a temporary potable water supply. This involved the transfer of the lower set of pumps from Engadine that were no longer required for the Sutherland water supply. After 10 months of use at the Manly Dam site, these pumps were removed to Pipe Head in October 1942. During World War II, the dam was fortified with machine guns and barbed wire. After WWII, the public reserve was used for recreational purposes. The Board ‘retained ownership of the dam and its land downstream of it where it has built an hydraulic model-testing station, and has carried out extensive investigations in connection with the design of its major works’ (Aird 1961: 82).The dam wall was strengthened in 1979-81 using ‘post-tensioning’ to bring the dam up to current safety standards. This technique was considered revolutionary at the time and gained world recognition when a paper was presented by Sydney Water Board engineers to the 14th Congress of the International Commission on Large Dams in Rio de Janeiro in 1982.
  • National
    Economy
  • State
    Technology
  • Local
    (none)
  • National
    Settlement
  • State
    Utilities
  • Local
    Water Supply
  • Local description
    Relates to the planning, development, expansion and provision of water supply.
  • a) Historical
    Manly Dam Wall is the largest example of an independent water supply system within the Sydney metropolitan area. The item played an important role as an independent water supply scheme for the northern beaches area of Sydney. The item is a remainder from the period when the northern beaches were remote from the major areas of settlement in Sydney, prior to the opening of the Sydney Harbour Bridge. The item is an early example of the Government initiative of the early 1890s, allowing local councils to raise loans for water supply purposes. The item was designed and built under supervision by the NSW Department of Public Works and is associated with the prominent engineers in this department at this time, particularly, E.O. Moriarty and C.W. Darley. The dam is one of the last of its size and type designed by the NSW Department of Public Works as a gravity wall, prior to the general adoption of curved concrete walls for small dams. Manly Dam Wall is of heritage significance at the state level because of its historical values.
  • c) Aesthetic
    Manly Dam Wall is a simple and attractive construction, located in a picturesque setting. The item is a good example of a basic concrete-walled gravity dam. It is an impressive structure, with its relatively thin wall standing between the water body of the reservoir on the west and the void and valley floor on the east. Manly Dam Wall is of heritage significance at the local level because of its aesthetic values.
  • d) Social
    The Manly Dam Wall is highly regarded by the local community. The metal walkway on the top of the dam wall forms an important part of a walking trail around the bushland reserve. Construction of Manly Dam Wall also enables recreational activities to be undertaken within the Manly Warringah War Memorial Park. Manly Dam Wall is of heritage significance at the local level because of its social values.
  • e) Research
    Manly Dam Wall is important for the pioneering “post-tensioning” method used in the late 1970s to strengthen it. “Post-tensioning” involved forty-six vertical steel tendons anchored through the dam wall, into the rock foundations and to the top of the dam wall, to pull the dam wall down harder onto the bedrock. This makes it an important reference site. These works included the addition of the metal walkway on top of the dam wall. The item is a century-old, mass-concrete gravity dam that has no operational imperative, making it an ideal facility for a range of experimental and research activities. The item is the site of on-going testing and monitoring of the wall-strengthening methodology pioneered at this dam. Manly Dam is of technical significance at a state level for its association with the Hydraulics Laboratories in the former water treatment plant and its continuing role in the provision of experimental facilities. Manly Dam Wall is of heritage significance at the state level because of its technical values.
  • f) Rarity
    Manly Dam Wall is a key part of the largest and most developed of the surviving regional independent water supply schemes in Sydney. The item is one of the very few substantial dam structures located within the suburbs of Sydney. The item was subject to a dam strengthening program which pioneered a world-first technology and which has subsequently become an accepted procedure for this purpose. The item is one of the last of its size and type designed by the NSW Department of Public Works between the 1890s and 1930s as a gravity wall, prior to the general adoption of curved concrete walls for small dams. Manly Dam Wall is of heritage significance at the state level due to its rarity.
  • g) Representative
    The Manly Dam Wall is a representative example of a small concrete gravity dam structure from the late 19th century erected for water supply purposes by the NSW Department of Public Works between the 1890s and 1930s. Manly Dam Wall is of heritage significance at the state level due to its representativeness.
  • Integrity assessment
    Manly Dam Wall and its associated features within heritage curtilage appear to be in good condition and are intact. The Dam Wall is subject to daily visual inspections
  • List name
    Register of the National Estate
  • Name
    Manly Dam and surrounds
  • Reference number
    Database # 019904
  • Date listing listed
    27 March 2001
  • List name
    Local Environmental Plan
  • Name
    Manly Dam
  • Reference number
    Conservation area under Locality G3
  • Date listing listed
    05 December 2000
  • List name
    Heritage Act - s.170 NSW State agency heritage register
  • Name
    Sydney Water Heritage and Conservation Register
  • Reference number
    4573702
  • Date listing listed
    30 June 2002
  • List name
    National Parks and Wildlife Register
  • Name
    AHIMS registered listing
  • Reference number
    45-6-2085
  • Date listing listed
    01 April 1990
  • List name
    National Trust of Australia register
  • Name
    Manly Dam and Old Water Treatment Works
  • Date listing listed
    20 July 1987
  • List name
    Heritage Act - State Heritage Register
  • Name
    Manly Dam
  • Reference number
    01327
  • Date listing listed
    18 November 1999
  • Title
    Manly Dam and Old Water Treatment Works Register Classification card
  • Author
    Clark S. & Collocott J. M.
  • Published
    1987
  • Title
    The Sweat of their Brows - 100 Years of the Sydney Water Board 1888 - 1988
  • Author
    Beasley M.
  • Published
    1988
  • Title
    The Water Supply, Sewerage and Drainage of Sydney
  • Author
    Aird W. V.
  • Published
    1961
  • Title
    National Trust of Australia Listing Card
  • Author
    J.M Collocott
  • Published
    1987
  • Item reference number in study
  • Title
    Sydney Water Heritage Study
  • Author
    Graham Brooks & Associates
  • Published
    1996
  • Item reference number in study
  • Title
    Manly Dam Wall Conservation Management Strategy
  • Author
    Urbis
  • Published
    2009
  • Item reference number in study
  • Title
    The Sweat of their Brows - 100 Years of the Sydney Water Board 1888-1988
  • Author
    Beasley M.
  • Published
    1988
  • Item reference number in study
  • Title
    Manly Dam and Old Water Treatment Works Register Classification card
  • Author
    Clark S. & Collocott J. M.
  • Published
    1987
  • Item reference number in study
  • Title
    The Water Supply, Sewerage and Drainage of Sydney (1788 -1960)
  • Author
    Aird W V
  • Published
    1961
  • Item reference number in study
  • Downstream face of Manly Dam Wall, 2008.
    Downstream face of Manly Dam Wall, 2008.
    Created by: Sydney Water
    Creation date: 10 August 2008
  • Downstream face of Manly Dam Wall, 2008.
    Downstream face of Manly Dam Wall, 2008.
    Created by: Sydney Water
    Creation date: 10 August 2008
  • Downstream face of Manly Dam Wall and swales, 2008.
    Downstream face of Manly Dam Wall and swales, 2008.
    Created by: Sydney Water
    Creation date: 10 August 2008
  • Manly Dam Wall Walkway showing the post-tensioning technology, 2008.
    Manly Dam Wall Walkway showing the post-tensioning technology, 2008.
    Created by: Sydney Water
    Creation date: 10 August 2008
  • Manly Dam Wall Walkway showing the post -tensioning technology, 2008.
    Manly Dam Wall Walkway showing the post -tensioning technology, 2008.
    Created by: Sydney Water
    Creation date: 20 October 2008
  • Construction of Manly Dam Wall, c 1892.
    Construction of Manly Dam Wall, c 1892.
    Created by: Sydney Water
    Creation date: 09 November 2009
  • Manly Dam Wall shortly after construction, 1890s.
    Manly Dam Wall shortly after construction, 1890s.
    Created by: Sydnay Water
    Creation date: 09 November 2009
  • Manly Dam Wall shortly after construction, 1890s.
    Manly Dam Wall shortly after construction, 1890s.
    Created by: Sydney Water
    Creation date: 09 November 2009
  • Manly Dam Wall shortly after construction, 1890s.
    Manly Dam Wall shortly after construction, 1890s.
    Created by: Sydney Water
    Creation date: 09 November 2009
  • Manly Dam Wall cross section showing additions, 1920.
    Manly Dam Wall cross section showing additions, 1920.
    Created by: Sydney Water
    Creation date: 01 January 2020
  • Raising Manly Dam Wall, c1921.
    Raising Manly Dam Wall, c1921.
    Created by: Sydney Water
    Creation date: 01 January 2021
  • The physical curtilage plan for Manly Dam Wall.
    The physical curtilage plan for Manly Dam Wall.
    Created by: Sydney Water
    Creation date: 12 October 2009
  • Data entry status
    Basic
  • Entered
    01 December 2000
  • Updated
    21 February 2014