Main Outfall Sewer - Engineering Heritage Marker Yarralumla, Australian Capital Territory, Australia
By Team MavEtJu on 22-Oct-15. Waypoint GA7688

Main Outfall Sewer - Engineering Heritage Marker

Main Outfall Sewer Canberra Canberra's first main sewer runs underground past Lennox Gardens for about eight kilometres, from Canberra Avenue to the site of the former sewage treatment works at Weston Creek (formerly called Western Creek).

Construction of the main outfall sewer commenced in 1915, working to a plan prepared by the Department of Home Affairs. But Walter Burley Griffin, who had been excluded from the design process for engineering services, argued for an alternate design which he claimed would lower costs. A Royal Commission into the controversy was held during WW1, with much debate regarding the best type of treatment plant. After further advice from the US Rockefeller Institute, the layout proposed by the Department of Home Affairs was endorsed and approval given for a revised treatment works at Weston Creek. This allowed excavation of the sewer to recommence in 1922. The system was completed in 1926 in time for the opening of the original Parliament House. The sewer is still in use today.

The egg shaped tunnel allows waste to flow by gravity from North and South Canberra to the treatment works. Here in Lennox Gardens, the tunnel is 15 m below the surface, and is deepest where it passes 44 m under Stirling Ridge. The concrete lined tunnel is 1.68 m high by 1.12 m wide. It comes to the surface once, crossing Yarralumla Creek near the Woolshed as a small concrete weir.

Three work camps were established along the route — near the treatment works at Weston Creek, near Westbourne Woods and in a part of Stirling Park then known as Westlake. Hundreds of unmarried workmen lived in tents, while married men were sometimes accommodated in timber and galvanised iron huts. Three original brick ventilator shafts still exist along the route — one near the decommissioned incinerator at the Royal Canberra Golf Club and another at Weston Creek. Sewer Vent No 3 is at Stirling Ridge, 200 m west of the intersection of Empire Circuit and Forster Crescent in Yarralumla.

Unassuming as it may seem, the main outfall sewer is an important part of our heritage. With roads, water supply and electricity, it is a key element of the original engineering infrastructure that enabled the building of the national capital and the transfer of Federal Parliament to Canberra. After more than 85 years it still performs its original function, safeguarding public health while Canberra's population has grown from 5,000 to more than 350,000.

When logging this virtual, please add a photo of yourself or your GPSr at the plaque.

For more information, please see the nomination PDF at the Heritage Register at the Engineers Australia website: https://www.engineersaustralia.org.au/portal/heritage/main-outfall-sewer-canberra-1926