Sewer Vent (The Obelisk)

  • Number
    4571022
  • Other name
    The Obelisk
  • Primary address

    289, Elizabeth & Bathurst Streets Sydney, . NSW
    LGA: Sydney City
    LGA region: Sydney
    DUAP region: Sydney South

  • Owner
    Sydney Water
  • Current use
    Monument
  • Former use
    Ventilation of Sewer
  • Item type
    Built
  • Item group
    Utilities - Sewerage
  • Item category
    Other - Utilities - Sewerage
  • Curtilage/Boundary
    The curtilage is restricted to the original fabric of the ventshaft and the property upon which it is constructed, as shown on the curtilage plan.
  • AMG easting
    334432719
  • AMG northing
    6250295851
  • Statement of significance
    The Obelisk built in 1857, is an important component of the first planned sewage system in the city of Sydney. It was the first major sewer vent constructed and the only ventshaft constructed partially of sandstone. The Obelisk Vent was an ambitious achievement at the time of construction owing to its utilitarian purpose. It is historically significant as one of the oldest items of infrastructure in the early city sewerage system and the oldest special sewer vent in the Sydney Water system. It has landmark qualities, providing a fitting terminus to the eastern end of Bathurst Street. It is also significant for its contribution to the streetscape of Elizabeth Street, its visual role in the axial vistas of Sydney, and as a significant object within Hyde Park.
  • Endorsed significance
    State
  • Designer
    Public Works Department
  • Builder
    Public Works Department
  • Circa
    Yes
  • Physical description
    A simple masonry shaft consisting of a sandstone base and decorative bronze ventilator apex. The Obelisk was built to ventilate Sydney's first planned sewerage system which was constructed by the Municipal Council. Sydney’s first planned sewerage system consisted of 5 harbour outfalls. It was completed in 1857. Its unique features include a ventilation channel of square profile, measuring 26 by 26 inches (66 by 66cm). The design reflects the high classicism of the 1850s, as evidenced in the pseudo-Egyptian form.
  • Modifications made
    The obelisk has remained largely intact since its construction in 1857, significant changes have included the alteration to the sandstone base to make way for the widening of Elizabeth Street, replacement of the copper vent, various maintenance works and changes to the configuration of the Obelisks surrounds. In 1854, a Hyde Park Improvement Committee was formed to improve the layout and amenity of the park. Improvements to the park included a formal layout, with plantings of Moreton Bay Figs and a stone dwarf wall (1876) surrounding the entire park (which still exists today). Plans of the Obelisk and surrounds, circa 1886 show this dwarf stonewall, with six smaller obelisks surrounding the ventshaft. It is unknown whether these smaller obelisks were constructed as part of Hyde Park improvements or when the obelisk was originally constructed in 1857. In 1889, The Metropolitan Water, Sewerage and Drainage Board took control of the water and sewerage services from the Municipal Council in the City of Sydney; this included the operation and maintenance of the Obelisk. No file records for the maintenance of the Obelisk could be located for works carried out from this time until 1960s. Detailed works were conducted between 1963-1968. Steeple-stack reconstructions were engaged to conduct rehabilitation works on the upper portion of the Obelisk (excluding the sandstone base). Works included installation of a new lightning rod, new concrete topping, restoration to internal stonework and brickwork, replacement of metal top, the spire was cut back to the brickwork and re-rendered, and internal steel work was cleaned. Works were completed on 28th July 1967. The original tender submitted by Steeple-Stack Reconstruction suggested the removal of the Egyptian detailing on the sandstone base; this however, was rejected by the sewerage engineer of the time. In April 1968, negotiations began between the Board and the Sandstone Restoration Company for proposed restoration works on the sandstone base. Works completed on the sandstone base included ilmenite blasting to remove paint from Sphinxes, cornice and ashlar, patching, painting and repointing, resurfacing and re-rendering. Renovations were completed in November 1968. The following additional restoration works were carried out in 2009: - existing defective leadwork was removed and repalced - missing joints repointed, loose mortar was raked out and missing joints repointed - corroding metal bars were repaired insitu - synthetic stone reapirs, six patches were carried out. The sphinx's nose on the north eastern corner and hind legs on the southern elevation was pinned and patched to stop water penetrating into the cracks causing further deterioration. - bronze cap was waxed - lightning protection system inspected.
  • History
    There are two types of sewer vents within the Sydney Water system; educt and induct. Induct vents draw air into a sewerage system to aerate the pipelines. Educt vents allow gases to escape when the gas is lighter than air. The shape of the cowling on the older types of vents were set to produce either eduction or induction whenever there is a natural breeze. This is an educt shaft, a simple masonry shaft modelled on Cleopatra's Needle (now situated on the Thames Embankment, London) and erected in 1857 during the period of George Thornton as Mayor of Sydney. Vents are for the safety of personnel as well as to prevent corrosion by chemical decay. The ventilation of sewers is a very important facet of continued operation of a sewerage system. Poor ventilation can result in serious odour problems and breakdown in fabric. Little primary material exists regarding the construction of the Obelisk. The Vent shaft was proposed by the City Commissioners and was completed under the regime of the newly formed Municipal Council in 1857. Plans for the ventilation shaft and Bathurst street sewer were signed by the City Engineer, Edward Bell, on 17th March 1857 and were then endorsed by the City Commissioners, prior to the reinstalment of the City Council, on 7th April 1857. The proposal for the ventilation shaft was presented in the second meeting of the City Council’s Sewers Committee meeting on the 27th May 1857. It was resolved that the City Engineer would forward plans and specifications for “the construction of a small sewer in Bathurst street and ventilating shaft to be constructed at the Eastern end of that street in the purpose of ventilating the sewers”. On the 1st of June 1857, the newly formed Council approved the Sewer’s Committee report. This was about 35 years before J. M. Smail, (Water Board’s Engineer for Sewerage 1889-1893 and Chief Engineer 1894-1920), began presenting his argumentation in favour of ventilation of sewers in the Water Board’s Annual Reports of the 1890s. Further to implementation of Smail’s ideas and proposals, sewer ventilation became a standard part of the sewerage process, and series of standard and special sewer vents were created. The purpose built special vent shafts of the late 19th century were elaborate masonry masterworks, designed as local landmarks and often featuring decorative capping and bonding of bricks. The construction of special ventshafts was site and case specific, and each item features unique characteristics. Most special vents were created as masonry structures, and majority were built between the 1890s and the 1920s. Later materialisation varied from fine examples of brickwork craftsmanship around the turn of the 20th century to the Interwar concrete structures. The Obelisk is the oldest special ventilation shaft erected in Sydney. It is also the only ventilation shaft built partly in sandstone, and with a decorative bronze ventilator apex.
  • 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 Obelisk was created as part of Sydney’s first sewerage system. The ventshaft was built to replace the street gratings that had been used to eliminate noxious gases from the sewer system. The Obelisk is the first special sewer ventilating shaft built in Sydney and NSW and the predecessor of a complex network of special sewer vents subsequently created. The item meets this Criterion on State level.
  • b) Association
    The ventshaft was created by, or under supervision of, the City Engineer Edward Bell. The sandstone basis commemorates the name of George Thornton, Mayor of Sydney when the Ventshaft was erected. The item meets this Criterion on local level.
  • c) Aesthetic
    The Obelisk is a sandstone ventshaft which displays the classical architecture and technology of the late 19th century. It is a landmark feature within Hyde Park and Sydney, which is visible as a major feature at the end of Bathurst Street. The Obelisk is the first special ventshaft in Sydney, and the only one in the system that was created in sandstone. The item demonstrates, through its dimensions and its surviving original fabric, the high level of elaboration of classical architecture’s aesthetic principles and construction technology of the mid-nineteenth century in NSW.
  • d) Social
    The Obelisk ventshaft has been used as a sewer ventilating shaft since the date of its creation, indicating it does not feature associations with a particular identifiable community or cultural group for spiritual, cultural or social reasons. The vent stack however is a relatively prominent local landmark, recognisable from a distance, and a popular meeting place in CBD. The significance of the item has been confirmed through the listing on the SWC S.170 Register, the State Heritage Register, the Register of the National Estate and the Register of the National Trust Australia (NSW). The item meets this Criterion on Local level.
  • e) Research
    The design and placement of The Obelisk was used to understand the behaviour of gases within the sewerage system and how to best design vents to help eliminate the gases safely. The ventshaft was also to relieve the gaseous pressure that built up within the sewer system. The surviving original fabric of the Obelisk sewer vent is important in demonstrating the principal characteristics of the earliest period of design of ventilating stacks and chimneys, as the ventstack is the only one such item built in the 1850s and has preceded the development of elements of its class in NSW for almost 40 years. The related technical documentation is important in demonstrating differences between design styles, aesthetic principles and architectural detailing of different periods. It is believed that the experience with the design and placement of the Obelisk was used to understand the behaviour of gases within the sewerage system and applied in subsequent design of vents. It is considered that the Ventshaft meets this criterion on Local level.
  • f) Rarity
    The Obelisk is unique in NSW. It is one of the oldest items of infrastructure in the early city sewerage system. It was the first ventshaft built to eliminate noxious gases from the city's sewer system. The Obelisk ventstack is unique in NSW as an example of a large-scale special ventstack from the 1850s, unique in NSW for its sandstone structure, and rare in NSW terms as a special ventstack with features of Classicist architectural style. Like other special ventilating shafts, it was built to a unique design (dissimilar to any other ventshaft), and is a rare item of its class that survives in Sydney and NSW. The Obelisk is a rare example of the neo-Egyptian style of architecture popular in the 1850s, and is one of the few remaining structures within the city of Sydney to carry this style. It is unique in that it is the only Ventshaft constructed to take the shape of an Obelisk. The item meets this Criterion on State level.
  • g) Representative
    The Obelisk sewer ventshaft is the only example of a sewer ventshaft constructed of sandstone within the Sydney Water system and is representative of sewer ventilation methods. The sewer vent is demonstrative of an important stage in development of sewer ventilation in the Sydney area, and demonstrative of the earliest stage of ventilating stacks design style. Other Notable Obelisks in Sydney include the Obelisk in Macquarie Place (1818), the Anzac Parade Obelisk (1917), and Obelisk at Captain Cook’s Landing, Kurnell (1870).
  • Integrity assessment
    Considerably intact apart from alterations to its base. Continues to function as a vent although now for the storm water system.
  • List name
    Register of the National Estate
  • Name
    Obelisk, Sydney NSW
  • Reference number
    DB No. 001801
  • Date listing listed
    21 March 1978
  • List name
    Heritage Act - s.170 NSW State agency heritage register
  • Reference number
    285160
  • Date listing listed
    01 January 2000
  • List name
    National Trust of Australia register
  • Date listing listed
    25 May 1975
  • List name
    Heritage Act - State Heritage Register
  • Name
    State Heritage Register
  • Reference number
    01642
  • Gazette number
    220
  • Gazette page
    9709
  • Date listing listed
    15 November 2002
  • Title
    Sydney Water Heritage Study
  • Author
    Graham Brooks and Associates Pty Ltd
  • Published
    1996
  • Item reference number in study
    285160
  • Title
    The Obelisk Conservation Management Plan
  • Author
    Sydney Water
  • Published
    2005
  • Item reference number in study
  • View of Obelisk showing copper cowling after restoration works in 2009.
    View of Obelisk showing copper cowling after restoration works in 2009.
    Created by: Sydney Water
    Creation date: 28 October 2009
  • The Obelisk after conservation works were carried out in 2009.
    The Obelisk after conservation works were carried out in 2009.
    Created by: Sydney Water
    Creation date: 28 October 2009
  • The physical curtilage plan for The Obelisk Sewer Vent.
    The physical curtilage plan for The Obelisk Sewer Vent.
    Created by: Sydney Water
    Creation date: 13 July 2006
  • View of Obelisk Ventshaft on the corner of Elizabeth and Bathurst St''s Sydney, erected 1857.
    View of Obelisk Ventshaft on the corner of Elizabeth and Bathurst St''s Sydney, erected 1857.
    Created by: Sydney Water
    Creation date: 22 June 2000
  • Data entry status
    Basic
  • Entered
    03 June 1998
  • Updated
    01 November 2016