Sebastian Calderon, Murray Pioneer

Riverlanders are being treated to the rare sight of an emptied lock in the region, with maintenance and repair work being done on the major water infrastructure.

Lock 3, near Overland Corner, was drained earlier this month and is undergoing essential maintenance works, allowing SA Water crews to undertake a detailed inspection and necessary repairs to structural and mechanical components.

Completed in 1925, Lock 3 controls 85km of the Murray River and contains the most diverse range of flow conditions of all the South Australian River weir pools.

SA Water senior manager of River Murray Operations Garry Fyfe said “as part of our maintenance schedule, every decade we have a real strong aim to get into the bottom of the chamber, so we can actually look at the bits and pieces below water”.

“What we found is that corrosion rates are quite high in some locations, leaving us with a loss of metal in the structure, paint disappearing and loss of concrete materials and rubber seals at the bottom of the gates and the valves,” Mr Fyfe said.

“Over time, those components start to shred away with water pressure, so the process we’ve got is to put large coffer dams in place, which block off the upstream and downstream water and seal the chamber.

“We then pump the water out of the chamber and remove all debris from the bottom.”

Mr Fyfe said once the chamber – which allows vessels to travel through the lock – is free of water, the removal process can take between one or two days, before the engineers can really assess the necessary repairs.

“We take some assessments based on what we know,” Mr Fyfe said.

“This time, we knew we had to replace all the valves that actually allow water in and out, so they’ve already been purchased and procured

“From previous assessments, we expected a lot of damage to our valve and gate rubbers from the previous floods. That turned out to be true, which is approximately 700m of valve rubber we need to replace.

“We are now in the process of getting subcontractors and specialists, alongside the concrete company which is already onsite. The concrete has eroded faster than expected due to the damage on the rubber seals.”

The maintenance and refurbishing process of the chamber and its locks can take between 14 to 16 weeks, depending on the weather and other unforeseen circumstances, but according to SA Water, the chamber should be ready in mid-October.

“There is a lot of work going on in a short space of time, because once the works are finished, we have to test the chamber, locks, seals and make sure everything has been done correctly,” Mr Fyfe said.

“We will re-water the chamber by pumping water back in and if it’s all good, we’ll then remove the coffer dams and away we go from there.

“The weather can slow the process, depending if we get more rain during these months. There is a lot of hydraulics that have to be reconnected, so you want to make sure that the right gate opens when you push the button.”

SA Water authorities advise that river traffic in the area may be impacted during the closure, which is expected to last several weeks.

The lock 3 water chambers are essential to allow water flow, using gravity.

This article appeared in Murray Pioneer, 28 May 2025.