Editing Tank Stream (section)

== Description ==
The surviving fabric of the Tank Stream is extant from King Street in the south at a point between Pitt and George Streets to [[Circular Quay]] in the north.<ref name=nswshr-636/>

The Stream has been blocked at a point just south of King Street and for 13 metres north of this point represents the 1866 open sewer, which was covered in 1876. The dimensions are 810mm broad by 1220mm high. Between King Street and [[Martin Place]] (163 metres) there are three phases of construction, beginning with a modern concrete pipe (750mm diameter), the section approaching the GPO is part of the historic oviform sewer (810 by 1220mm) and lastly a stainless steel box-profile pipe (1070 by 750mm). The section between Martin and Angel Places returns to the 1866 brick open drains enclosed in 1876. This form continues between Angel Place and Hunter Street for 95 metres before being interrupted by a 36-metre section of modern cement lined pipe laid in 1962 and a steel section laid in 1958 and 1978 (both are 1350mm).<ref name=nswshr-636/>

From Hunter to Bond Street the Stream is a semi-circular stone arch with a shallow V-shaped floor for 35 metres (1500 by 3000mm). The 1790 cut tanks were originally located in this area, but are not thought to have survived. For the following 86 metres, below Australia Square, the original sewer has been replaced with concrete box-profile pipe (1220 by 1830mm), inserted during the construction of the Square in 1962. The Australia Square Tower basement houses the access to Tank Stream for public tours and as an inspection point for Sydney Water.<ref name=nswshr-636/>

The boxed concrete section (1220 by 1830mm) continues from Bond Street to Abercrombie Lane, a distance of 60 metres. Tank Stream between Abercrombie Lane and Bridge Street, a length of 40 metres, is of c.1860 semi-circular stone arch (1500 by 3000mm). From Bridge Street Tank Stream diverts to run under Pitt Street to Circular Quay, a length of 185 metres. Beginning with a stone oviform sewer of 810mm by 1220mm, constructed in c.1878, the shape changes to a semi-elliptic stone arch of 3000mm and varying between 1100 and 1400mm.<ref name=nswshr-636/>

=== Modifications and dates ===
Major modification include the following:<ref>Sydney Water CMP 2005, pp. 32–33</ref>
*1788-1826: Clearing of vegetation within the vicinity of stream, construction of dwellings, grazing and watering of animals.
*1790: Cutting of tanks for water storage
*1790: Chiselling of stone and inset of additional slabs into base of stream to improve flow in a shallow V profile.
*1791: Enclosure within a fence against livestock and trespass.
*1792: First bridge crossing.
*1810: Cut-off drains alongside of Tank Stream channel to reduce inflow of polluted stormwater
*1826: Tank Stream disallowed for drinking by Governor Brisbane. Governor Darling arranged for seven wells to be dug in the city. Governor Darling employed people to repair existing sewers.
*1832: Construction of sewers seriously discussed.
*1833: Water from partly built Busby's Bore used to pipe water to ships.
*1842: City Council incorporated.
*c.1850: Semi Circular Quay was formed which necessitated the extension of the Tank Stream for the area north of Bridge St.
*1855: Brickworks at Newtown was purchased, along with vitreous clay pipes and Roman Cement.
*1857: Work completed on first part of the Bennelong Sewer to discharge sewage as far out as possible into the harbour. This would service the more elevated areas, whereas the Tank Stream in Hunter St and King St as a bolted cast iron oviform aqueduct. This sewer (and possibly stormwater) network had the effect of draining the swamp area that had previously supplied some water to the Tank Stream, making the Tank stream more polluted by being less "cleansed".
*The section of the Tank Stream from the Sydney Cove to the Interception Chamber in Pitt St was completed, approx. 200m. The section at the mouth (approx. 5m has been strengthened with concrete in the two filleted corners. The next 10 m is [[sandstone]] arch. The next 15m section has the original stone floor overlaid with concrete, date unknown. The remaining section up to the Interception Champer (approx. 170m) is sandstone arch.
*1858: Independent outfalls also completed at Woolloomooloo, Hay Street and Black Wattle Bay. Over the next 20 years, approx 10 other minor outlets were also opened.
*1860: The sandstone arch between Bridge St and Hunter St was constructed. This was done to reduce odours from the previously open sewer/stormwater that up until that time had been more of a slops line.
*1866: Section from south of Hunter St to Martin Place was formed as an open stone channel. In late 1870s was converted by roofing with an arch to oviform, whereas more southerly section was oviform invert with a [[flat roof]], where it passes under Challis House...<ref name=nswshr-636-636-2>With northerly section, there were minor alterations in 1878</ref><ref name=nswshr-636-636-3>The whole of this was replaced by a concrete pipe in 1962 and a steel pipe in 1958</ref> (Other parts were replaced in 2001 as part of the Angel Place project).
*Two sections were laid as oviform through the future GPO.
*To the south, two sections were laid as brick oviform and with some amendments in 1878.
*1878: The brick oviform section from the Interception Chamber to Bridge St was constructed by contract for the City council. This was built to replace the open section that ran through private property. At the southern end there is a transition section (reducer), which leads to the sandstone arch, which is in Tank Stream Way (formerly Hamilton St.).
*1879: The section from Bridge St to Hunter St, with its sandstone arch roof in place has its floor slabs lifted and re-instated with mortar [[Foundation (engineering)|foundations]] to water proof the floor for its use as a sewer. In addition a terra cotta "scouring channel" was cut into the centre of the floor
*The section immediately upstream of Hunter St was built as oviform. This included a terra cotta flow channel.
*The next section upstream was also constructed. It was a bottom only oviform, and part of it was built underneath an existing stone arch bridge.<ref name=nswshr-636-636-4>The whole of this section, including the stone arch bridge, seems to have been removed in c.1960</ref>
*1880: Brick oviform was constructed for the full width of King St and terminating.
*1898: SPS [Sewerage Pumping Station] 16 constructed. the section immediately downstream of the interception chamber, has an interception pipe leading to SPS 16 form the tidal weir.
*1940: Section just upstream of Martin Place was replaced with concrete pipe under the GPO in 1940. This replaced 1866 brick oviform.
*1951: Stormwater drainages charges were introduced for parts of the City of Sydney from 16 November 1951.
*1958: Replacement, at the rear of 105-107 Pitt St.
*1962: Replacement, at rear of Commercial Union House [south end of Pitt St.]
*1965: Replacement within Australia Square. Construction of Tank Stream visitor access space.
*1975: Replacement within basement of New Zealand Insurance Building [North of Bond St.]
*2001: Replacement in Former GPO site.
*2002: Replacement within Angel Place project.<ref name=nswshr-636/>