Manly Dam | NSW Environment & Heritage

Culture and heritage


Manly Dam

Item details

Name of item: Manly Dam
Type of item: Complex / Group
Group/Collection: Utilities - Water
Category: Water Supply Reservoir/ Dam
Location: Lat: -33.7814024885 Long: 151.2546274220
Primary address: King Street (near), Manly Vale, NSW 2093
Local govt. area: Warringah
Local Aboriginal Land Council: Metropolitan
Property description
Lot/Volume CodeLot/Volume NumberSection NumberPlan/Folio CodePlan/Folio Number
LOT10 DP840821
All addresses
Street AddressSuburb/townLGAParishCountyType
King Street (near)Manly ValeWarringah  Primary Address
Arana StreetManly ValeWarringah  Alternate Address


Organisation NameOwner CategoryDate Ownership Updated
Sydney WaterState Government27 Nov 98

Statement of significance:

Manly Dam is a representative example of a medium-sized, concrete gravity dam of the late nineteenth century, as regards both design and construction. It has historical significance for its role in the historical development of Sydney’s water supply, in particular as being an independent scheme, built despite the fact that the renowned first stage of the Upper Nepean Water Supply, a comprehensive, long-term scheme with capacity for progressive augmentation by the successive construction of major dams on the contributing rivers, had recently been completed. It has technical significance as a representative example of its type and for the pioneering strengthening methodology which was developed for this dam. The dam is a rare remnant of an independent water supply system within the Sydney Metropolitan Area, providing evidence of the progressive and independent development of Sydney's suburbs, and has local aesthetic value. The former treatment plant and pumping station buildings are also significant but are not owned by the Sydney Water Corporation
Date significance updated: 09 May 05
Note: The State Heritage Inventory provides information about heritage items listed by local and State government agencies. The State Heritage Inventory is continually being updated by local and State agencies as new information becomes available. Read the OEH copyright and disclaimer.


Designer/Maker: Public Works Department
Builder/Maker: Public Works Department
Construction years: 1892-1892
Physical description: It is a mass concrete gravity structure with a maximum height of 19 metres and a length of 250 metres. It is located on Curl Curl Creek (and therefore dams Curl Curl Creek) some 3 kilometres north west of Manly with a catchment area of about 520 hectares extending to Frenchs Forest in the North. The Catchment area and stored water of the Dam are now used primarily for public recreation. The stored water is also utilised as a supply for the adjoining hydraulic investigation laboratories of Sydney Water, the Public Works Department, and the University of New South Wales.
Modifications and dates: Between 1979 and 1981, it was strengthened using a new method of vertical steel tendons anchored onto rock foundations and the crest of the dam (A.K.A. post-tensioning).
Current use: Retains the waters of Manly Reservoir
Former use: Water Supply storage


Historical notes: Manly Dam was built in 1892 by the Public Department Works as a water supply dam for the Manly area, which 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. The dam was constructed as a mass concrete, gravity structure with a maximum height of 19 metres and length of 250 metres. Its catchment area extended 520 hectares to Frenchs Forest. The dam was constructed by the NSW Government's Department of Public Works for the local council under a special Act of Parliament as part of a complete water supply scheme for Manly. It consisted of a dam, pumping station, rising main, service reservoir and reticulation. It was operated by the council for ten years until it was resumed by the Metropolitan Water Sewerage and Drainage Board in January 1902, at its original cost (37 820 pounds), less the amount the council had paid off already. The concrete dam was designed to hold 68,216,000 gallons but was upgraded in 1909 with an enlarged by-wash being excavated on the eastern side and the old by-wash built up, thus enabling the top level of the reservoir to be raised and the storage capacity increased to 84,000,000 gallons. In 1914, the capacity was raised further to 90.5 million gallons and then in 1922 to 441 million gallons with the top water level being 115 feet above sea level. In 1920, a filtration plant was installed, consisting of a settling and coagulating basin, gravel and sand filter beds, inspection chambers and a clear water basin. 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 1936, the pumping installation was dismantled, following the commissioning of an amplified connection to the main metropolitan system, the completion of a 10 million gallon reservoir at Rocky Hill and the progressive development of the Upper Nepean Scheme. Despite this, during an extensive drought period from 1934-1942, the dam was again brought into service, with pumps transferred from Engadine. During a nine and a half month period up to October 1942, 975 megalitres of water were drawn to supplement Sydney's supply. From 1942, parts of the former water treatment plant downstream of the dam were reused in association with a hydraulics laboratory set up by the Department of Water Conservation and Irrigation. The Department of Public Works set up similar facilities in 1944. The MWS & DB also established water hydraulics experimental facilities and in 1955, the University of Technology (now the University of NSW) also established hydraulics laboratories. These facilities remain in use, although ownership and administration has varied between departments at times. The dam wall was strengthened in 1979-81 to bring the dam up to current safety standards. The methods used involved the sinking of long, vertical, steel tendons into the rock foundations but free in the dam wall itself, to permit future load monitoring and adjustment, and then anchored in heads specially designed for these tests on the crest of the dam. 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 Janero in 1982.

Historic themes

Australian theme (abbrev)New South Wales themeLocal theme
4. Settlement-Building settlements, towns and cities Utilities-Activities associated with the provision of services, especially on a communal basis (none)-

Assessment of significance

SHR Criteria a)
[Historical significance]
The dam is the largest example of an independent water supply system within the Sydney Metropolitan Area. The dam played an important role as an independent water supply scheme for the northern beaches area of Sydney. The dam is a relic of 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 dam was designed and built 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 an early example of the government initiative of the early 1890s, allowing local councils to raise loans for water supply purposes The dam is one of the last of its size and type designed by the NSW Dept of Public Works as a gravity wall, prior to the general adoption of curved concrete walls for small dams.
SHR Criteria c)
[Aesthetic significance]
The Manly Dam is a simple and attractive construction, located in a picturesque setting. -The dam is a good example of a basic concrete-walled gravity dam. -The dam 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.
SHR Criteria d)
[Social significance]
The Manly Dam is highly regarded by the public as represented by the National Trust of Australia (NSW), as evidenced by its identification in the National Trust Register.
SHR Criteria e)
[Research potential]
Manly Dam is a century-old, mass-concrete gravity dam which has no operational imperative, making it an ideal facility for a range of experimental and research activities. -Manly Dam is of technical significance for its association with the Hydraulics Laboratories in the former water treatment plant and its continuing role in the provision of experimental facilities. -The dam is the site of on-going testing and monitoring of the wall-strengthening methodology pioneered at this dam.
SHR Criteria f)
Manly Dam is the largest and most developed of the surviving Sydney regional independent water supply schemes. Manly Dam is one of the very few substantial dam structures located within the suburbs of Sydney. Manly Dam was the site of a dam strengthening program which pioneered a world-first technology and which has subsequently become an accepted procedure for this purpose.
SHR Criteria g)
The Manly Dam is a representative example of of a small concrete gravity dam structure of the late nineteenth century -Manly Dam is representative of a range of small dams erected for water supply purposes in NSW by the NSW Department of Public Works between the 1890s and 1930s
Integrity/Intactness: The dam wall and its associated features appear to be in good condition and intact
Assessment criteria: Items are assessed against the PDF State Heritage Register (SHR) Criteria to determine the level of significance. Refer to the Listings below for the level of statutory protection.

Procedures /Exemptions

Section of actDescriptionTitleCommentsAction date
57(2)Exemption to allow workStandard Exemptions SCHEDULE OF STANDARD EXEMPTIONS
Notice of Order Under Section 57 (2) of the Heritage Act 1977

I, the Minister for Planning, pursuant to subsection 57(2) of the Heritage Act 1977, on the recommendation of the Heritage Council of New South Wales, do by this Order:

1. revoke the Schedule of Exemptions to subsection 57(1) of the Heritage Act made under subsection 57(2) and published in the Government Gazette on 22 February 2008; and

2. grant standard exemptions from subsection 57(1) of the Heritage Act 1977, described in the Schedule attached.

Minister for Planning
Sydney, 11 July 2008

To view the schedule click on the Standard Exemptions for Works Requiring Heritage Council Approval link below.
Sep 5 2008

PDF Standard exemptions for works requiring Heritage Council approval


Heritage ListingListing TitleListing NumberGazette DateGazette NumberGazette Page
Heritage Act - State Heritage Register 0132718 Nov 99   
Heritage Act - s.170 NSW State agency heritage register 122431   
National Trust of Australia register      
Register of the National Estate     

Study details

TitleYearNumberAuthorInspected byGuidelines used
Sydney Water Heritage Study1996122431Graham Brooks and Associates Pty LtdGRAHAM BROOKS AND ASSOCIATES PTY LTD 1 July 1996 Yes

References, internet links & images


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Data source

The information for this entry comes from the following source:
Name: Heritage Office
Database number: 5051428
File number: H00/00225

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