RTA Bridge Inspections
Descend Underwater Training Centre recently won a major contract to inspect all of the bridges over the Murray River in N.S.W. The inspections started close to the start of the Murray River at Indi, where you can literally walk across the river, and proceeded downstream to Wentworth on the South Australian border some 1200 kilometres distance. The bridges varied from small wooden structures to the massive thirty-nine span bridge at Mulwala and included historic bridges with cast iron piers and rising centre spans to accommodate paddle steamer traffic.
The terms of the very thick contract called for a penalty of $4400 per week if we exceeded the twelve weeks allowed to finish the job so we were very keen to plan this one right and finish on time. The preparations included a bridge inspection course for everyone involved in the project. This was a one-day event where we got everyone on the same page and talking the same language. This included the standard bridge terminology. Words like piers, piles, columns and beams were to become second nature along with pile caps, corbels, soffits and beams. Two experts from Sydney explained the problems associated with graphitisation in cast iron and alkaline aggregate reaction in concrete and how to grade the various defects so that all reporting would be accurate and consistent. The next part of the planning involved getting the paper work correct. Written policies had to be formulated for environmental protection, anti-discrimination, rehabilitation and record keeping and water traffic management plans formulated. A comprehensive format for bridge inspection reporting was prepared which had to include written reports on each face of each pile along with photos and video footage and water analysis reports. Insurances had to be upgraded and spill kits and channel marker buoys needed to be fitted into our truck and advertisements taken in appropriate newspapers to announce possible disruption to water traffic.  | | After cleaning |  |
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Finally it was time to start the actual inspections. With boats launched, channel markers in place and risk assessment completed the cleaning process started. The contract called for face of each square pile to be cleaned. A 100mm strip on two faces adjacent a corner and two 100mm strips in the centre of each other face. If the pile was round it required a 100mm strip cleaned every two metres and in the case of a column five 100mm strips along the length each side. We started cleaning using a pressure washer however we soon found that it was more efficient to use a hand scrubbing brush. After cleaning the structure had to be visually inspected and photographed. The contract required us to document any faults or cracks to within 1mm and colour, texture and abnormalities all to be described. Finally water samples were taken and analysed by a NATA laboratory and the results included in the report.  | |
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From start to finish the job took us nine weeks and of course it came at a time when we were already committed to other projects. We solved the problem by expanding our operation by running two full time contracting teams. This required a second boat and we had to recommission our tandem trailer to support team two. We even expanded our premises by another 150 square metres to fit it all in and that gave us the opportunity to set up a second classroom for commercial diver training. All in all a very satisfactory operation. For more information contact Descend Underwater Training Centre Shop 1, 826 David Street, Albury. 2640.
Phone 0260411405.
Email dive@descend.com.au or www.descend.com.au.
For more photos of the bridges please select the link below :
http://www.descend.com.au/training/gallery/PhotoGallery.asp?whichcategory=RTA%20Bridge%20Inspections&AreaID=17
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