The deepest cut

A redundant water intake tower is currently being reduced in height by half at the Mardi Dam in New South Wales, Australia, using concrete cutting techniques carried out from barges moored alongside the 20 m (66 ft) structure. A new intake tower was constructed in 2010 to transfer water from the Dam to the Mardi Treatment Plant in a Aus$57 million (US$50.1 million) upgrade as part of a long term strategy developed by Gosford City and Wyong Shire Councils to secure the water supply and protect the environment known as WaterPlan 2050.

In a statement, manager of headworks Garry Casement said of the demolition: “We wanted to find the best and most economical way to carry out the demolition works without compromising water quality. We consulted a number of engineering and demolition companies and came up with a plan to remove the tower in a safe and cost effective way.”

“Over the past few weeks a number of barges have been assembled to form working platforms. The demolition equipment, including concrete saws and a diamond wire saw, will sit on these barge platforms to complete the work. We will progressively cut away the top 10 m of the 20 m tower and use the rubble to fill in and stabilise the remaining part of the tower,” he said.

As the work progresses, the water level in the dam will be dropped to 40% through normal usage or transfers through the Mardi-Mangrove Link.

“Careful attention has been placed on choosing demolition and waste management methods that will not affect the dam’s water quality. Council staff will conduct regular inspections of the site and take extra water quality samples during demolition to ensure water quality remains high,” said Garry. The work is expected to be completed by the end of January 2014 and represents an investment of Aus$270,000 (US$241,000) into the water supply system.