Boisdale Tunnel: Maffra, VIC, Australia
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Boisdale Tunnel, an 80 year old concrete structure, which serves as an irrigation channel for the local farming community, was suffering from scouring. Southern Rural Water contracted National Concrete Solutions to further extend the service life of the concrete tunnel by treating the damaged areas during the 2011 winter irrigation shut down period. Extending the life was critical to Southern Rural Water as the replacement cost is over $13 million. The original structure was constructed by using corrugated iron as formwork, and shaped into a oval shape at approximately 1.8m diameter. After 80 years of the abrasive effect of water and water born particulate through the tunnel, much of the concrete internal surface has suffered from scouring up to 10-15mm and exposing the large aggregate. Some areas were scoured as much as 300mm. The work entailed the setting up on site of an office, regular OH&S Tool Box meetings serving the 7 + on site technicians who complied with SRW's strict compliance to the submitted OH&S Management Plan. The tunnel itself was treated as confined space throughout the duration of the project. To meet the needs of Southern Rural Water a specially manufactured render incorporating Xypex Crystalline Technology was applied to the wall after the extensive preparation of grinding and water blasting on the affected areas. In addition to compliment the specialty render, Xypex Megamix II was utilised in the heavily damaged areas requiring a high build mortar to bring back to contour and reinstate the durability of the internal concrete.
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