Northern Suburbs Ocean Outfall Sewer (NSOOS)

  • Number
    4570286
  • Primary address

    181, Flushcome Road, Blacktown to Ocean Outfall at North Head Northern Suburbs of Sydney, . NSW
    LGA: Manly
    LGA region: Sydney
    DUAP region: Sydney North

  • Owner
    Sydney Water
  • Current use
    Sewerage Disposal
  • Former use
    Sewerage Disposal
  • Item type
    Built
  • Item group
    Utilities - Sewerage
  • Item category
    Other - Utilities - Sewerage
  • Curtilage/Boundary
    The curtilage of NSOOS is difined by the structure plus three meters from the outer edge of the structure. .
  • Statement of significance
    The Northern Suburbs Ocean Outfall Sewer (NSOOS) is of considerable significance, being the third major sewerage system built to service Sydney's growing wastewater needs. The primary significance of the system is embodied in the function it serves to the community of the northern and western areas of Sydney by channelling and managing its effluent, and in the careful and precise methods of achieving this. NSOOS is culturally significant as evidence of the growth of Sydney's sewerage system, the rapid development of the northern suburbs, and the substantial improvement in sanitary conditions for Sydney's inhabitants. Collectively the different components which make up NSOOS provide excellent examples of the major public works construction techniques of the early 1920's. The NSOOS system contains components which are in themselves highly significant items. The two major syphons associated with the system are fine examples of engineering methods. The Middle Harbour Syphon, in particular, is individually possibly the best example in the State of an inverted syphon on such a scale. The Lane Cove Syphon is a good example of the engineering tunnelling methods of the time. The architectural styles and engineering qualities of the associated pumping stations, aqueducts, vent stacks, syphons and surface fittings make a contribution to the city's streetscape. In particular, the valvehouse structures attached to the syphons have aesthetic significance. These structures are of architectural interest as early examples of the Art Deco style, displaying influence of Egyptian Architecture in civic industrial utility buildings. The various aqueducts located in the system display superior utilitarian design and detailing. The scale, colour, texture and detail of these structures make an effective contribution to the parks and tree covered slopes in which they are situated. The boundary and curtilage of NSOOS is to include all original fabric from 1933 from Parramatta to North Head outfall with a 2 metre buffer zone parallel to the existing structures. The curtilage is to include all overpasses, access points and settings along the existing alignment of the NSOOS.
  • Endorsed significance
    Local
  • Designer
    Public Works Department
  • Builder
    Public Works Department and the Water Board
  • Year started
    1916
  • Year completed
    1933
  • Circa
    No
  • Physical description
    NSOOS is a large main sewer servicing an area of 416 sq. km. The system has its upstream end near Wentworthville Station (Holroyd municipality) and discharges into the ocean at Blue Fish Point, near North Head. It crosses beneath Middle Harbour and Lane Cove River, and passes through Manly, Mosman, North Sydney, Lane Cove, Hunter's Hill, Ryde, Ermington, Rydalmere, Dundas, Parramatta, Baulkam Hills and Blacktown. The following main branches extend from the NSOOS: (a) West Middle Harbour submain - this branch was constructed by the PWD and transferred to the Board in 1927. It extends from the main sewer at Cammeray Park to Rocky Creek, Gordon. Four aqueducts were constructed along the line of this sewer. (b) East Lane Cove submain - constructed by the PWD and transferred to the Board in 1928. It extends from Lane Cove River Syphon north to Stringy Bark Creek, Lane Cove. (c) West Lane Cove submain - this branch sewer junctions with the main sewer near the western extremity of the Lane Cove River Syphon and from there extends to the intersection of Strand and Pittwater Road. Five aqueducts were built to span gullies, while both Middle Harbour and Lane Cove River were crossed by inverted syphons. A total length of 26.5km was constructed in tunnel through ridges 60m - 90m high, the tunnel being lined with concrete averaging 0.20m thick. The size of the concrete sewer at the ocean outfall at Blue Fish Point is 4.1m x 2.6m, and diminishes to 3.7m x 2.5m opposite the Spit at Clontarf. The syphon under Middle Harbour is 358m in length and consists of duplicate pipes, 1.8m in diameter, laid on the bed of the harbour from near the Spit to Clontarf, the depth of the water being 22m near the centre. The Lane Cove Syphon is 266 m in length. A tunnel 4m x 2.1m was driven through sandstone from shaft to shaft. Duplicate 1.35m diameter reinforced concrete pipes were laid in the tunnel with a fall towards the downstream end, and the intervening spaces between the tunnel lining and the pipes were filled with concrete. Five aqueducts were constructed to cross gullies. These were: 1) Quakers Hat Bay Aqueduct - located adjacent to Carrington Avenue at Quakers Hat Bay, Middle Harbour. The aqueduct consists of a 13.7m long single span reinforced concrete rectangular section measuring 3.5m by 2.6m with a splayed concrete overflow weir located on both sides of the structure. It was completed in 1927. 2) Brightmore Reserve (Willoughby Bay) Aqueduct - designed in 1925. This structure is located in Brightmore Reserve at the head of Willoughby Bay. It consists of reinforced concrete sections measuring 3.5m by 2.6m and supported on four concrete columns. 3) Tunks Park (Long Bay) Aqueduct - built in 1927. The structure is predominantly located in Tunks Park adjacent to Long, Middle Harbour. The aqueduct consists of an 85m long reinforced concrete haunched beam and column structure. 4) Scotts Creek (Sugarloaf Bay) Aqueduct - this aqueduct is associated with the West Middle Harbour submain, and is located in Harold Reid Reserve adjacent to the north arm of Sugarloaf Bay, Middle Harbour. The aqueduct is situated in dense bushland and is not easily visible to public view. The structure is approximately 46m long and is similar, except for span length and height, to the Tunks Park Aqueduct in appearance. 5) Buried Box section (below Manly CBD) - located in the first section of NSOOS. This item consists of a concrete sewer built mostly in trench construction and is located under Darley Road, Manly. Sewage from Parramatta and parts of Harris Park, Merrylands, Guildford, Auburn, Lidcombe and the whole of the Duck River drainage area either gravitates to, or is pumped to Camellia Pumping Station (No.67), and is lifted from there into the outfall sewer at a point near Dundas Railway Station. The NSOOS continued to develop as the population of the suburbs increased.
  • Modifications made
    Between 1933 and c.1970 the areas between Parramatta and Blacktown were constructed.
  • History
    The history of NSOOS is intricately linked to the earlier smaller council systems it replaced. The systems that were present prior to their replacement by the NSOOS included North Sydney, Mosman, Manly, Chatswood-Willoughby and Parramatta. Later, the Hornsby system, which had been transferred to the Board's control in 1911, was also diverted to the NSOOS. The supervising engineer for the scheme was W.G. Hudson later to be Sir William Hudson, the first Commissioner of the Snowy Mountains Scheme. After the NSOOS, he also worked at Nepean Dam, Woronora Dam and as Engineer-in-Chief at Warragamba Dam. By 1912 it was obvious to the Board that the various North Shore Sewerage Works were approaching their limit due to the increasing number of services and limited land for plant expansion. A comprehensive scheme was proposed which would involve the closure of North Sydney (Willoughby Bay/Follys Point), Chatswood, Balmoral and Parramatta Sewerage Treatment Plants. It also involved an ocean outfall system for the suburbs along the Milson Point - Hornsby Railway line, plus capacity for the far western suburbs. The proposed scheme was prepared by the Public Works Department (PWD) in 1914 and comprised a large main sewer with several branches, the upstream end being at Wentworthville Station. The scheme was submitted by the Joint Parliamentary Standing Committee on Public Works in September 1915, however it was not until September 1916 that the scheme was approved by Parliament. The approved scheme now involved the replacement of all sewerage works on the North Shore, with the exception of Hornsby. In addition a large pumping station at Camellia would replace the existing Parramatta Sewerage Works. Construction of the sewer was carried out by PWD from 1916 until 1928. The work was then transferred to the Board for completion under the provisions of the 'Metropolitan Water, Sewerage and Drainage Act of 1924'. At the time of transfer four sections of the main outfall had been completed, enabling the interception of sewerage previously discharged into the treatment works at North Sydney (Willoughby Bay) and Mosman (Balmoral). Of the 13 sections in the NSOOS, the first 7 sections were initially built by PWD and then transferred to the Board for completion by 1930. The remaining sections including those reaching Blacktown in the 1970's were built solely by the Board.
  • National
    Economy
  • State
    Technology
  • Local
    (none)
  • National
    Economy
  • State
    Health
  • Local
    Water Supply
  • National
    Economy
  • State
    Environment - cultural landscape
  • Local
    (none)
  • National
    Settlement
  • State
    Utilities
  • Local
    Sewerage
  • Local description
    Relates to the planning, development, expansion and provision of sewerage services.
  • National
    Phases of Life
  • State
    Events
  • Local
    (none)
  • a) Historical
    The Northern Suburbs Ocean Outfall (NSOOS) was the third major sewerage system to be built to service Sydney's rapidly growing wastewater needs. It has been a major historical event in the development of the north shore, and inner and north western suburbs of Sydney.
  • c) Aesthetic
    The system is predominantly underground. However, the aesthetic significance is evident in the range of styles, design, details and materials used in its construction. The architectural styles and engineering qualities of the associated pumping stations, aqueducts, vent stacks, syphons and surface fittings make a contribution to Sydney suburban townscapes. In particular, the syphons at Middle Harbour and Lane Cove have aesthetic significance. The valve house structures attached to these items are of architectural interest, as early examples of the Art Deco style, displaying influence of Egyptian Architecture in civic industrial utility buildings. There are only a limited number of similar styled structures within the current Sydney Water system, for example, those associated with the Avon, Nepean and Woronora Dams. In the case of the Middle Harbour, these valve house structures are prominent well known foreshore landmarks. In addition, the design and detailing of the five aqueduct structures make an effective contribution to the parks in which they are situated.
  • d) Social
    Collectively the different components which make up NSOOS are culturally significant as evidence of the growth of Sydney's sewerage system, the rapid development of the northern suburbs, and the substantial improvement of sanitary conditions for Sydney's inhabitants for which it is likely to be held in high regard by the broad community.
  • e) Research
    Sewerage systems demonstrate a variety of construction techniques ranging from sandstone blocks, solid rock and reinforced concrete. The construction of these systems contributed to our understanding of the development and use of these materials in Australia and reflects the technological change in construction to meet the increasing population of Sydney. The Lane Cove Syphon is a fine example of the engineering tunnelling methods of the time. The passage under the river required considerable judgement and understanding of the nature and behaviour of the rock strata. The Middle Harbour Syphon is possibly the best example in the state of an inverted syphon on such a scale. Both syphons also provide an excellent example of major engineering public works techniques of the 1920's. Innovative engineering techniques were required so that the sewer line was able to cross Middle Harbour. The five aqueducts are significant examples of the superior use of reinforced concrete construction in the 1920's. They provide good examples of major public works and bridge works of the time incorporating sophisticated construction detailing.
  • f) Rarity
    The third major sewerage system built to service Sydney.
  • g) Representative
    Representative of Sydney's sewerage system. Contains components which are excellent representations of public works engineering including; syphons, aqueducts, pumping stations and sewer vents.
  • Integrity assessment
    Substantially intact and operational overall.
  • List name
    Heritage Act - s.170 NSW State agency heritage register
  • Reference number
    001303
  • Date listing listed
    01 January 2000
  • Title
    Sydney Water Heritage Study
  • Author
    Graham Brooks and Associates Pty Ltd
  • Published
    1996
  • Item reference number in study
  • Northern Suburbs Ocean Outfall Sewer Construction, Timbered Tunnel 1929.
    Northern Suburbs Ocean Outfall Sewer Construction, Timbered Tunnel 1929.
    Created by: Sydney Water
    Creation date: 01 January 2000
  • Northern Suburbs Ocean Outfall Sewer Construction
    Northern Suburbs Ocean Outfall Sewer Construction
    Created by: Sydney Water
    Creation date: 01 January 2000
  • Underground Northern Suburbs Ocean Outfall Sewer Construction.
    Underground Northern Suburbs Ocean Outfall Sewer Construction.
    Created by: Sydney Water
    Creation date: 29 November 2029
  • Tunnelling showing timbered supports of roof,  Northern Suburbs Ocean Outfall Sewer 1929.
    Tunnelling showing timbered supports of roof, Northern Suburbs Ocean Outfall Sewer 1929.
    Created by: Sydney Water
    Creation date: 29 November 2029
  • Map showing the route of the NSOOS system.
    Map showing the route of the NSOOS system.
    Created by: Sydney Water Borad Journal, April 1963.
    Creation date: 01 April 2063
  • Data entry status
    Basic
  • Entered
    03 June 1998
  • Updated
    19 June 2015