Sweeping around the bends of Gorge Road as it rises above Kangaroo Creek Reservoir towards historic Cudlee Creek, it’s easy to assume the route was established long ago by Adelaide’s early European settlers.
But Gorge Road’s current alignment was only opened in 1966, after a new road was built higher into the mountain side, allowing 4.8 kilometres of the original road to be abandoned below the waterline of the forthcoming Kangaroo Creek Reservoir.
Now – for only the second time in its history – the reservoir’s water level has been reduced to zero per cent of its capacity, revealing the original road and its River Torrens crossings.
Among these is the 28.8 metre long Batchelor’s Bridge, which can now be seen nestled just behind the 61 metre high dam wall.
SA Water's General Manager of Asset Operations and Delivery Mark Gobbie said it was a rare sight arising from upgrades currently underway on the dam wall and spillway.
"We’ve gradually lowered the reservoir’s water level over the past few months, with releases supporting dilution flows into the Torrens, or fed into the Hope Valley Reservoir for drinking water supply," Mark said.
"The reservoir will be kept at zero for around six weeks, while we install approximately 1000 metres of external seals on the upstream face joints of the dam embankment.
"Natural inflows will likely fill the reservoir again over the next year or two, while work continues on the other side of the embankment, widening its base with 180 000 of the 300 000 cubic metres of rock blasted from the spillway."
Crews are halfway through the $94 million project which is on track for completion in late 2019, and will align the dam with updated safety guidelines set by the Australian National Committee on Large Dams (ANCOLD) to better withstand major flood events or earthquakes.
"Kangaroo Creek is always an impressive project site because of its scale and the beauty of the location, but we’ve been counting down to the moment we also get the rare opportunity to see this part of Adelaide’s history."
On 26 May 1922 a ‘Chain of Ponds correspondent’ recounted in The Register – South Australia’s first newspaper – that the newly completed Torrens Gorge Road featured ‘magnificent bridges of reinforced concrete’ in ‘beautiful situations’ that cut down travel time and haulage costs for the region’s market gardeners.
Batchelor’s Bridge was one of six built between 1912 and 1925 to convey Gorge Road’s users across the Torrens, which had only been passable at fords or during dry periods when the water was low.
"There are two other old Gorge Road bridges within the reservoir: Crouch’s Bridge which is still intact and breaks through the water’s surface when the dam dips below 60 per cent, and the remains of Prairie Bridge which wasn’t often submerged but was damaged by floods in the ‘90s," Mark said.
Construction of Kangaroo Creek dam started in July 1966 – only three months after the new Gorge Road opened – and was completed in October 1969, with the reservoir beginning to fill one month earlier.
The first on-stream storage on the River Torrens, Kangaroo Creek Reservoir added around 19,000 megalitres of capacity to service Adelaide’s water demand, which was growing by seven per cent per annum when it was conceived in the late 1950s.
"Given it’s been under water for almost 50 years now, Batchelor’s Bridge still looks to be in relatively good nick," Mark said.
With the reservoir unlikely to be emptied again in the foreseeable future, anyone interested in seeing Batchelor’s Bridge should plan a trip to the public lookout on Gorge Road before the end of April.
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