Victoria Wharf is used daily by thousands of commuters and leisure travellers catching ferries to and from Devonport.
In accordance with engineering reports, pillars and bracing under the wharf were due for their 50 year upgrade. This work was required to ensure the integrity of the structure, and public safety.
As part of the $6m Victoria Wharf renewal project, Intergroup performed hydrodemolition on the pillars, bracings and deck.
Over time, the concrete pillars and bracings that support Victoria Wharf have deteriorated in the harsh maritime environment. To assess the extent of the damage an engineer must inspect the steel reinforcing within each structure, requiring removal of several centimetres of concrete to expose the steel.
Depending what the inspection reveals, further concrete may need to be removed to determine the full extent of the deterioration, and to prepare the structure for repair.
Intergroup pioneered hydrodemolition in New Zealand – using high pressure water jetting to partially remove concrete. This innovative technique is ideal for the type of work required at Victoria Wharf. The process is faster than using jack-hammers, and avoids the risk of unintentional damage to adjacent areas of concrete. It also prepares the steel reinforcing bars for the subsequent repair.
Having performed hydrodemolition for many other wharf repair projects, we were uniquely qualified to deliver this work. We carefully removed the concrete – never more than needed or expected – from areas marked by the engineer on each pillar and brace. We also exfoliated areas of the wharf deck where the concrete had started to flake, so that the extent of any damage could be assessed.
Time and Tide
The times we were able to work under the wharf were limited by the tide and weather (swell) conditions. Each day we could work a maximum of between four and six hours in a window around low tide.
This challenge was compounded by another issue that arose on site. Because the hydrodemolition work temporarily weakened the wharf structure, we were unable to park our trucks on the wharf. This meant we had to run 120m hoses from the vehicle-mounted 20,000psi pump to the work area. The resulting reduction in water pressure at the work site meant preparing each pillar and brace took slightly longer than usual.
We also had to share the under-wharf work area with the repair team. This required daily coordination on site to ensure all works could be progressed within the short work-time window.
In combination, the factors described above presented a significant challenge. Fortunately we had the equipment, highly skilled operators, and planning capability to manage the situation. Our flexibility in working with the conditions and other contractors contributed significantly to the successful project outcomes.
At all times while we were working under the wharf we operated a safety watch with direct line of sight to the hydrodemolition operator(s), prepared to take action in the event of any safety incident in the hazardous area.
We completed all hydrodemolition work at Victoria Wharf to the standard required by our client BBR Contech, and within budget.