Aging Tanks Do Have Value – the Arcadia Vale Water Tank Strengthening Story

Abstract

As critical water infrastructure ages, conditions deteriorating and with a need to maintain community service with minimal disruption, how do we rehabilitate and strengthen structures in a seismically active region? This is the challenge facing a 35m diameter by 10m high 9-megalitre (ML) prestressed concrete water tank, constructed in the 1960’s, in Newcastle, NSW. This paper explores the historic deficiencies, field investigation findings, outcomes from a global literature review, and arrangements investigated that can achieve a full operating level reinstatement to meet the key project criteria in an economic and timely manner. Previous studies concluded that the rubber bearing wall to floor connection may no longer be performing as designed, causing a redistribution of wall stresses. The original design did not allow for earthquake loadings and with the current wall to floor connection arrangement, there is potential risk for structural damage or failure in the event of an earthquake, with the decision to operate the tank at reduced levels limiting community supply availability. This led to the need to further investigate cost effective and innovative solutions to strengthen the tanks that can maximize operating levels and protect against failure from an earthquake event, rather than the costly alternative of demolition and installation of a new tank in a constrained location, within a high-value vegetation area. This paper aims to highlight the strengthening options available and value it brings to protect our most critical asset, water.