Draining of Murray lock allows for essential upgrade

In a rare and unique event, Overland Corner's Lock Three stands empty of its usual eight-million-litres of water, while SA Water carries out a major refurbishment of the River Murray structure.

Lock Three opened to river travel in 1925, as part of the Murray Waters Agreement of 1914 and the River Murray Act of 1915. The agreements provided for the construction of permanent navigation to allow the safe travel of boats and other river users moving up or downstream, during all types of flow events.

SA Water's Senior Manager of River Murray Operations Garry Fyfe said going through a lock may seem like a simple process, but the empty lock chamber reveals there's a lot more going on beneath the surface.

"Within the 60-metre-long, 20-metre-wide and five-metre-deep chamber, there are a number of different components, and you might be surprised to know, this includes a series of tunnels," Garry said.

"When the lock's valves are open, water can flow to and from the lock chamber through these tunnels to alter the water level. The level is raised and lowered entirely by gravity - there are no pumps used.

"The lock also contains hydraulic-powered arms and butterfly valves used to open the large gates at either end."

The $700,000 refurbishment began in mid-June and is expected to take up to 14 weeks to complete. Works being undertaken include repainting the lock gates; replacing gate seals and bottom fenders; rehabilitating upstream and downstream valves and tunnels; and replacing all cathodic protection works.

"We used a range of expertise, equipment and technology to prepare for the emptying of the lock, such as divers and a mini un-crewed submarine equipped with a camera," Garry said.

"The ROV, or Remote Operated Vehicle, used high-definition images and video to help us see the condition of the lock and determine the priority of maintenance."

Another unique aspect of this project is the use of a four-person crew, aboard SA Water's travelling work barge the Maratala, to carry out the bulk of construction.

"The Maratala has been used for various maintenance works along the River Murray for almost 50 years," Garry said.

"When she's required for work more than an hour away from home-base in Berri, the crew can also live on board - sleeping quarters, a galley kitchen, laundry, bathroom, workshop, office and common meeting area are all contained within the 34 by 10 metre barge."

Around 4000 people on vessels ranging from small tinnies to huge paddle steamers pass through Lock Three every year.

"It's very important we maintain the lock, to ensure its longevity and continued safe and efficient operation," Garry said.

The lock will be closed to river users during the project, and public access to the nearby riverbank will be changed.

For more information, people can call Lock Three on (08) 8588 7005 or SA Water's River Murray Operations Berri office on (08) 8595 2222.

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