Remediation of degraded wharf structures can be both very costly and very risky. Corroded steel, timber and delaminated and spalling concrete can be very difficult to remove and repair while still maintaining the existing wharf’s structural capacity.
Access below the structure in the tidal zone can also be limited, often requiring the additional cost of divers and floating access platforms.
Generally the type of repairs that need to be carried will be determined based on the useful life, current structural capacity and future structural capacity based on the loadings and use of the structure in the future. The useful life along with the structural capacity and maintenance regime (time between repairs) required by the owner will determine the level of repairs. For example, 10 year repairs on a concrete wharf may only involve patch repair of damaged/spalling concrete, where as a 30 year repair may include patch repair and a cathodic protection system. Costings can be completed on various options to determine a best for project outcome taking into account the pre-determined useful life and the maintenance regime that will be required for the wharf to reach its useful life.
One of the largest risks when undertaking a wharf remediation project is accurately determining the scope of works prior to procuring the works. The normal process is to engage an engineer to test and inspect the structure. This involves cleaning, taking measurements, completing testing cores and measuring the components. This can either be completed by sampling parts of the structure or testing and inspecting the whole structure. The main difference here is that if a sample is taken you have to apply the sample to the whole structure to estimate the works, whereas if the whole structure tested and inspected you can more accurately determine the total scope. The main cost restraint is that the testing and inspection can be extremely expensive task, but by not completing full testing and inspection the total scope cannot be determined and a provisional sum type contract will have to be entered into in lieu of a lump sum contract.
WT Partnership has been involved in a number of these projects and has the following advice when procuring/constructing Wharf Remediation:
- Ensure you accurately determine the useful life and apply the correct load criteria based on the use
- Test and inspect as much of the structure as possible to reduce the cost risks of additional remediation post contract procurement
- Minimise if possible the below deck repairs or look at time efficient installation options that minimise the cost
- Complete life cycle costs and options to ensure the most cost effective solutions are achieved for the structure’s life
- If the contract is completed on a provisional sum basis have an experienced remediation engineer to assess the repairs before works begin to validate the correct quantum of repairs is being undertaken
Richard Deed, Associate
T: +61 3 9867 3677