Heritage

Bondi Sewage Treatment Plant

Item details

Name of item: Bondi Sewage Treatment Plant
Other name/s: Bondi STP
Type of item: Built
Group/Collection: Utilities - Sewerage
Category: Other - Utilities - Sewerage
Location: Lat: 33 53 11 S Long: 151 16 58 E
Primary address: Blair Street, North Bondi, NSW 2026
Local govt. area: Waverley

Boundary:

At ground surface level, the Bondi Treatment plant boundary is the property boundaries of the two component areas of the plant. The western area is bound by Blair St, Military Road, O'Donnell St and the adjoining property to the west. The east area is bound by Military Road, the southern boundary of the Hugh Bamford Reserve, the Pacific Ocean shoreline and the northern boundary of Williams Park.
All addresses
Street AddressSuburb/townLGAParishCountyType
Blair StreetNorth BondiWaverley  Primary Address
Military RoadNorth BondiWaverley  Alternate Address

Owner/s

Organisation NameOwner CategoryDate Ownership Updated
Sydney WaterState Government 

Statement of significance:

The Bondi Sewage Treatment Plant was the first sewage treatment plant attached to a major ocean outfall sewer in NSW and the first connected to a deep ocean outfall in Australia. It was the largest sewage treatment plant in Australia at the time of its construction and was comparable in size with large overseas plants. It was the first treatment plant located underground in tunnels and chambers excavated from solid sandstone. The underground works are impressive and a rare example of the installation of extensive processing facilities in an excavated underground situation. The Bondi plant contains a representative set of sewage treatment equipment and processes related to deep water ocean disposal and its continued evolution illustrates the continual development and expansion of those treatment processes in the latter half of the twentieth century. The Bondi Sewage Treatment Plant is associated with the continued evolution of the Sydney sewage system overall and is closely associated with earlier sewerage works such as the Bondi Sewer, which were a major step in the nineteenth century to improve the standard of public health in central Sydney. The Bondi Sewage Treatment Plant, owing to its association with Bondi Beach, is symbolic of sewage treatment in Sydney.
Date significance updated: 23 Jun 00
Note: There are incomplete details for a number of items listed in NSW. The Heritage Branch intends to develop or upgrade statements of significance and other information for these items as resources become available.

Description

Designer/Maker: Metropolitan Water, Sewerage and Drainage Board of NSW
Builder/Maker: Metropolitan Water, Sewerage and Drainage Board of NSW
Construction years: 1936-1968
Physical description: The Bondi plant is a primary sewage treatment plant, i.e. the treatment process is a physical one, employing screening and settlement to treat the flow of liquid sewage before discharge to the ocean. These works are particularly noteworthy in that the greater part of the works are situated nearly 40m underground in large caverns excavated out of solid rock. The main underground installation covers an area approximately 120m x 55m with some of the chambers being up to 14m high.
The plant provides what is known as full primary treatment with sludge digestion, the components of the latter process being located on the surface. The main treatment processes, in order, are:
(i) Grit Removal
Removes sludge and screenings as well as sand sized particles (mainly inorganic 'heavy' particles), collectively called ‘grit,’ from the screened sewage, in specially designed channels. At Bondi, this process will be upgraded after 2010.
(ii) Fine Screening
In the Bondi Sewage Treatment Plant, fine drum screens (with 5mm apertures) have been inserted between the grit channels and the sedimentation tanks to remove additional solid material finer than that removed by the coarse bar screens. This process is also to be upgraded after 2010.
(iii) Primary Sedimentation
This takes place in large, long tanks, where the velocity of flow is greatly reduced allowing the heavier organic materials to settle out to become raw sludge and the lighter organic material, oil and grease to float to the surface to become scum. These tanks are larger and longer in Bondi Sewerage Treatment Works than normal. The sludge and scum are then transferred to the surface to the Sludge Digestion Tanks. The ongoing flow of treated effluent is then pumped 2.2km out to sea through the submarine ocean outfall tunnel, commissioned in 1991.
(iv) Sludge Digestion
The raw sludge and scum from the sedimentation process are pumped up to four large steel tanks, lined externally in brick, located on the surface (just to the north of the Bondi Golf Course) where they undergo anaerobic digestion (i.e. in the absence of air) by various micro-organisms. This process produces two main end products:
1. Digested Sludge which is converted to sludge cake in centrifuges for biosolid production. This material is relatively inert and is utilised for a range of commercial and industrial uses such as a soil conditioner; and
2. Methane Gas, which can be used for stirring the tanks by recirculating it through them, or be reticulated throughout the works and used for heating. This gas can also be used, with the addition of diesel fuel, as fuel for powering ‘dual fuel’ internal combustion engines.
After the digestion is complete, the digested sludge is sent for dewatering. The dewatering plant comprises two centrifuges and is currently located in the former engine room of the decommissioned electricity generating plant. The dewatered sludge is referred to as sludge cake.
At Bondi STP, most of the present equipment is not original but consists of improved modern replacement equipment undertaking the same treatment processes.
The size of the Bondi Sewer where it enters the treatment plant is about 2.1m x 1.8m. The flow is then divided into four main streams to pass through four identical sets of screens, grit channels and sedimentation tanks before being re-united in a common channel for discharge to the submarine ocean outfall pumping station (previously, it discharged directly to the submerged cliff face outfall). This system is licensed to give full primary treatment for up to about 450 megalitres per day of raw sewage, with the average dry weather flow of about 130 megalitres per day. However, wet weather flows can reach 700 megalitres per day and, to provide for this, there are two extra flow lines which can accept the surplus of 180 megalitres per day but provide only coarse screening and grit removal.
In the 1960s, the methane gas from the sludge digestion process was used as fuel for three dual fuel engines (previously mentioned), each of 450 HP and coupled to a 312 KW alternator, located in a building on the western side of the Digesters. These provided sufficient electric energy to operate the auxiliary machinery of the whole treatment works. This arrangement attempted to make the plant self-sufficient but, unfortunately, the operating and depreciation costs of the engines were greater than the cost of electricity purchased from the State grid, so the dual fuel engines were phased out in the late 1970s.
Above ground, the Bondi STP has two areas of structures, one on the east side of Military Road and one on the west, between Blair and O'Donnell Street. The eastern area contains four circular Digesters and their ancillary equipment, with a two storey concrete post and beam building between these and Military Road. Below this building is the inclined tunnel entrance to the underground works, which is a vehicular road from the surface which spirals down to the underground areas. South of this, connected to the underground works but located above ground in the adjacent golf course, is the Ben Buckler Ventilation Stack (separately listed). On the western side of Military Road are the administration offices for the treatment plant, housed in a two-storey brick building dating from the 1960s. It is a plain, functional building. Two electric passenger lifts and stairs connect vertically from this building (and its gatehouse) to the underground works. The treatment plant, particularly the eastern section, is one of the most easterly structures on the coastline and the setting for the treatment plant is spectacularly scenic, with views down the coast across Bondi Beach. The old ventilation stack is a local landmark on the coast.
The physical curtilage is defined by the property boundary of the site.
Physical condition and/or
Archaeological potential:
The Bondi Sewerage Treatment Plant is operational, utilising equipment ranging in age from zero to approximately fifty years. A significant proportion of the older equipment is in poor condition and is planned to be replaced. The Plant has an ongoing program of upgrading and replacement of equipment in line with a proposed upgrade to full primary treatment.
Date condition updated:28 Aug 00
Modifications and dates: 1889 - Ocean outfall sewer at Bondi initiated
1910 - The original ventilation shaft is demolished and replaced
1936 - Construction commenced on an underground sewage treatment works at Bondi to treat sewage prior to discharge into the ocean (completed in the late 1960's)
1953 - Plant begins partial operation
late 1980's - An underground pumping station and related works built.
1991 - 2.2 km long submarine ocean outfall commissioned
1990's - The plant has undergone a constant stream of modifications due to continue for another fifteen years.
Current use: Sewerage Treatment Plant

History

Historical notes: In 1859 Sydney had a rudimentary system of five sewers which serviced an area just beyond today's central business district and drained directly into the Harbour.
By 1889, the system had grown to some 10km of main sewers and 130km of subsidiary sewers, serving the city and the suburbs of Darlington, Paddington and Redfern. This amplified system continued to discharge into the Harbour, posing a serious threat to public health, as the Harbour was the centre of Sydney's activities at the time. In 1889, two major projects were commissioned (built by the Government and subsequently transferred to the Board of Water Supply and Sewerage). These were:
(i) an ocean outfall sewer discharging to the ocean near Bondi; and
(ii) a main southern sewer, draining to a sewage farm near Botany.
These two sewers intercepted most of the discharges to the Harbour and were a major advance for Sydney. These gravitational sewers were unable to take in areas below their own level, thus leaving some localities still discharging into the harbour. To cope with this problem, the government constructed pumping stations at various locations to lift waste to the gravitational sewer before going to the outfalls. The first pumping station to be connected to the Bondi system was the Double Bay Ejector in 1898. Power was provided from the Rushcutters Bay t
ramway Power House. The total project was completed by the Public Works Department and handed over to the Board in 1904, with more pumping stations subsequently built and connected to the system. Today these sewers and outfalls are still in operation as important components of Sydney’s overall sewerage system, although the sewage farm on the Southern and Western Sewer has long since been replaced by the Malabar Ocean Outfall.
The Bondi sewer originally discharged its flow of raw sewage at a cliff face outfall just above minimum sea level and, in 1936, 47 years after its commissioning, the then Water Board decided that a predominantly underground plant should be constructed to provide primary treatment and discharge would be into the ocean approximately 7m below sea level. Construction of the new treatment plant was commenced in 1936 and completed in the late 1960s, although partial operation of the plant began in December 1953. The greater part of the works are situated nearly 40m underground in large caverns excavated out of solid rock. The total amount of spoil removed was approximately 53,000 cu metres. The main underground installation covers an area approximately 120m x 55m with some of the chambers up to 14m high. An additional underground pumping station and related works were built in the late 1980s as part of a 2.2km long submarine ocean outfall which was commissioned in 1991 to improve water conditions along the coast.

Historic themes

Australian theme (abbrev)New South Wales themeLocal theme
3. Economy-Developing local, regional and national economies Health-Activities associated with preparing and providing medical assistance and/or promoting or maintaining the well being of humans (none)-
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 Bondi Sewage Treatment Plant was the first to be built to treat sewage discharged from one of Sydney’s three major ocean outfall sewers. It was the largest sewage treatment plant in Australia at the time of its construction.
The Bondi Sewage Treatment Plant was connected in 1991 to a 2.2km long submarine pipeline (tunnelled in rock below the ocean floor) to discharge at a depth of 60m below the ocean surface under sea conditions such that, for some 7 months of the year (the period covering the summer swimming season), the greatly diluted sewage field does not reach the surface.
Its underground location in tunnels and chambers excavated in solid sandstone some 40m below the surface was matched by few, if any, other plants of comparable size. The underground works are impressive and a rare example of the installation of extensive processing facilities in an excavated underground situation.
The Bondi Sewage Treatment Plant is associated with the continued evolution of the Sydney sewage system as it has been expanded to service growing populations.
The Bondi Sewage Treatment Plant is associated with earlier sewerage works such as the Bondi Sewer, which were a major attempt to improve the standard of public health in central Sydney.
The Bondi Sewage Treatment plant is associated with a period of Sydney's history where public recreation and the use of beaches became increasingly popular, ultimately requiring the development of more sophisticated sewage treatment facilities at the ocean outfalls.
SHR Criteria c)
[Aesthetic significance]
Bondi Sewage Treatment Plant is the best known of the Sydney ocean outfall sewage plants and is a symbolic representative for all of the other outfall treatment plants.
SHR Criteria d)
[Social significance]
The Bondi Sewage Treatment is listed on the Register of the National Trust of Australia (NSW), which is indicative of its importance to a significant section of the community.
SHR Criteria e)
[Research potential]
The Bondi Sewage Treatment Plant contains a set of representative equipment and processes of varying ages associated with sewage treatment of the late twentieth century. The range of equipment in use demonstrates the development of sewage treatment equipment as used in Sydney over time. The situation and activities of the Plant provide opportunities for scientific investigation and experimentation regarding sewage and its disposal.
SHR Criteria f)
[Rarity]
The Bondi Sewage Treatment Plant is the oldest primary sewage treatment plant attached to an ocean outfall operating in NSW and was the first to be built with the works located underground in an excavation. It is associated with the first of the deep ocean outfalls developed in Australia in the 1980s.
SHR Criteria g)
[Representativeness]
The Bondi Sewage Treatment Plant contains a representative set of equipment and processes associated with sewage treatment related to deep water ocean disposal of the late twentieth century.
Integrity/Intactness: The basis of the 1930's design is still intact but the plant has and is undergoing constant modification to improve its performance and efficiency.
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.

Recommended management:

Manage the place and its significant components in accordance with the State Owned Heritage Asset Management Guidelines. Where no Conservation Management Plan, Heritage Assessment or Statement of Heritage Impact is in place, or where works are outside the scope existing heritage documentation, assess heritage impacts of proposed works in accordance with Sydney Water Environment Impact Assessment procedures. Undertake a Heritage Assessment and/or Statement of Heritage Impact as required by EIA procedures. Where the item is listed in a Local Environmental Plan Schedule of Heritage items, determine if works are exempt from approval under the LEP provisions. Where works are not exempt, obtain necessary approvals from the local council, in accordance with SWC EIA Guidelines. Undertake archival and photographic recording before major changes, in accordance with Heritage Council guidelines. Lodge copies of the archival record with the Sydney Water Archives and the NSW Heritage Office.

Listings

Heritage ListingListing TitleListing NumberGazette DateGazette NumberGazette Page
Heritage Act - s.170 NSW State agency heritage register  01 Jan 00   

References, internet links & images

None

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Data source

The information for this entry comes from the following source:
Name: State Government
Database number: 4573707


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