Lessons learnt from the 2011 Christchurch earthquakes led the Tasman District Council to upgrade its three key concrete water storage reservoirs in Richmond. The work stemmed from a desire to minimise the risk to Council assets located in a fault zone. Initially, the project started with the installation of flow control valves linked to flow meters.
Flow control valves prevent reservoirs from emptying in the event of a major pipe failure. The key success criteria for the Council were ensuring a continuous water supply to its customers and minimising shutdowns during the construction works.
During a review of the existing as-built drawings however, it was discovered that the wall to floor connections of these concrete reservoirs were likely to fail during a seismic event. The review highlighted a connection deficiency which was common in concrete tanks that were constructed before the mid 1970’s. For some circular precast reservoirs the base of the precast wall panels simply rested in a slot with no reinforcement connecting the components together. Due to this deficiency, the scope of the original project was extended and a structural analysis of the three reservoirs undertaken.
This paper highlights the key issues and describes the lessons learnt from both the installation of the flow control valves and the completion of structural strengthening works at each of the reservoirs.