With the granting of a permit by Heritage Victoria and the commencement of implementation works, the long-running challenge to determine the future of the Barwon River Sewer Aqueduct, and restore public access to the Barwon River, has been resolved.
The eye-catching, but decaying, de-commissioned concrete structure has been the subject of many investigations over the years — most recently by Lovell Chen in association with structural engineer Arup.
[ Barwon River Ovoid Sewer Aqueduct, date unknown, photo : courtesy Barwon Water ]
The 756m heritage-listed aqueduct crosses the Barwon River flood plain in 14 spans. Its striking form — inspired by the Forth Rail Bridge in Scotland (completed 1890, Sir John Fowler and Sir Benjamin Baker) — is an interpretation of a steel cantilevered structure in reinforced concrete. Each of the aqueduct’s 14 piers is the central support for a double-cantilevered concrete truss. The trusses are joined by the precast concrete sewer pipe, with a walkway on top, that runs through the centre of the structure, as the railway does at the Forth Bridge. The sewer pipe is ovoid in section, chosen for maximum hydraulic efficiency.
[ Construction of the concrete trusses, 1914, photo : courtesy Barwon Water ]
Constructed in 1912-15 to the design of Sydney engineer Edward Giles Stone, for the Geelong Waterworks and Sewerage Trust, the aqueduct was part of the system delivering waste water to an ocean outfall on Bass Strait at Black Rock, east of Breamlea. To maintain gravity flow through the sewer, the route had to overfly the broad flood plain of the river, which was too slow-flowing to disperse the output of a sewage farm.
[ Workers pose on the construction site, photo : courtesy Barwon Water ]
For the structure of the aqueduct, Stone used the Considere reinforcing system, a rarity in Australia. Maintenance was a concern from the start, reflecting issues with the quality of the concrete and the structural solution, plus the paucity of concrete cover over the steel reinforcing of the aqueduct’s thin structural members. These factors accelerated the corrosive effects of the Lower Barwon River’s damp and saline environment. Requiring increasingly untenable repairs and presenting operational risks, the aqueduct was decommissioned in 1992. The ongoing prospect of falling concrete forced closure of the river in the area in 1995.
[ The aqueduct as it appears today, photo : Lovell Chen ]
Balancing the many overlapping cultural values, public interests, heritage and environmental considerations, and practical and economic realities, has been the challenge. Nevertheless, the quarter-century closure of the river needed resolution: there was growing interest in restoring access to recreational water users and traditional owners. To support the decision-making process, we undertook a thorough appraisal study, looking at the history, heritage significance, technical development, structural condition, cost, and public amenity and safety of the aqueduct, and at a series of options for conservation, managed and unmanaged decay, and partial or full demolition.
Barwon Water determined that it would proceed with demolition of four spans that cross the river and with managed decay for the remaining ten, a proposal that Heritage Victoria has supported with conditions. The remaining structure will be stabilised, and the present safety fence removed and replaced at a greater distance. A heritage interpretation plan will be developed, engaging the community, Wadawurrung Traditional Owners and other stakeholders. Removal of the river spans will allow the Barwon to open once again.