the use of fresh water supplies. During a drought in 1790 three storage tanks were constructed in the sandstone beside the Tank Stream and it is from these that the stream gets its name. One of these was at the present intersection of Pitt and Spring Streets and the other two in Bond Street on the opposite side of the stream. The Tank Stream could not meet the needs of the growing colony and, despite efforts by successive Governors, it became increasingly polluted by runoff from the settlement. It was finally abandoned in 1826, though it had been little more than an open sewer for the preceding decade. Sydney's next supply of water was Busby's Bore, in 1830. In 1850 the swamp feeding the Tank Stream was drained. Starting in 1860, the Tank Stream was progressively covered and is now a storm water channel which is controlled by Sydney Water. In 2007 there were calls from some to see it run above ground again to create a central feature in the city. Over the past century, Tank Stream has remained a part of the stormwater channel within the Sydney system. Changes to the channel have been largely restricted to replacing sections with modern pipe. This has destroyed a number of sections of the channel and is largely tied to post-World War II redevelopment where little regard was paid to the historic value of the Tank Stream. Redevelopment of the GPO site allowed further investigation of Tank Stream and has provided information on the building development of Tank Stream over time. Brick drains, possibly dated pre 1820, were found. A further search revealed soil from the original Tank Stream bed. 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. 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