Water Corporation Tunnels
Tunnels seem all the go these days, whether it is the 1.6 km Graham Farmer Freeway tunnel or the 8 km Forrestfield railway tunnel, and most know that before the Farmer tunnel was built only tunnel of note in Perth was the 1895 built, 340 m long Swan View tunnel on the old Eastern Railway line in John Forrest National Park – or was it?
In fact, the main “tunnel” utility in WA remains the Water Corporation. Our first tunnels were the 1,000 m network of water supply tunnels built under Fremantle prison from 1888 (great tour by the way).
When the 351 of our staff members went off to the First World War, they were mainly posted to the Corps of Engineers, primarily in tunnelling companies (as many of them had worked on the Goldfields). In fact, our Chief Engineer, Fredrick Lawson, served in both the 4th and 5th Tunnelling Companies. While mostly they were engaged building pumping stations and laying water mains for the 1st Australian Corps (110,000 men, 80,000 horses) there was a lot of tunnelling done as well. The movie Hill 60 accurately captures this.
Our post World War I program of work reflects this as well. In 1924/1925 alone we build the 81 m tunnel and shaft up Mt Eliza, the 3.5 km Subiaco Main Sewer/Drain Outfall tunnel and the 3 km Herdsman Main Drain tunnel. This work continued into the 1930’s with the 685 m Claremont Main Sewer tunnel.
These were done by traditional hand digging and timber propping, with the pipe (generally 42” or 48” in diameter) being laid in the tunnel and then the tunnel being backfilled with sand or concrete.
Post-World War II there was a bit of a hiatus, until the demand for more water necessitated either trebling the capacity of the Canning Contour Channel (as designed) or building a whole new outlet for Canning Dam. For a number of reasons (not the least of which was water quality) it was decided to do a 5.5k m long hard rock tunnel from Canning Dam to Roleystone straight through the Darling Range.
This was so successful that a similar scheme was used at the new Wungong Dam in 1982, this tunnel being “only” 4.9 km long. Both these tunnels are in the majority unlined and around 2.6 m in size. Don’t even think of breaking in as they are full of water all the time and are used “in reverse” to store Desal water during winter months.
At the same time, we were doing major upgrades to our Sewer System and in 1982/1983 the Water Corporation built the 4.9 km long Beenyup Ocean outfall tunnel and the 1.9 km Bibra Lake Main sewer tunnel, of a similar size, finishing up in 2002 with the 1.3 km Perth Main Sewer tunnel in Wembley. (these may not run full, but access is even more dangerous and smellier)
Since then, we have thrust bored a considerable number of main sewers and large diameter water mains including the of 960 m DN1800 Perth Main Sewer alongside the JTWC in 2006. As these are relatively short discrete sections (~150m) between pits we don’t really record them as tunnels.
In an interesting sideline, ICA (Shenton Park) developed a specialised machine to inspect the Canning and Wungong tunnels to ascertain their suitability for “reverse” flow. When the Greymouth disaster occurred in New Zealand in 2010, we had the only machine available in the world at short notice which could travel the 3.5 km down the mine and allow any trapped miners to contact rescuers. We advised the New Zealand authorities of its availability at 17:00 on the Monday and by 15:00 the next day; the machine, supporting equipment and crew were in a RAAF C130 Hercules flying direct to New Zealand.
Author: Perry Beor, Water Corporation, September 2022
