In early 2008, the contiguous pile shoring wall supporting a deep basement excavation in Botany Road, Alexandria moved significantly; as a consequence:
- the nearby large [450 mm dia] 100 year old water main under the major traffic artery burst, and caused a large volume of water to flood the basement excavation and adjoining streets;
- Botany Road was closed to traffic for more than 3 months;
- there was extensive damage to the nearby building structures, water main and roadway.
Following the incident, SCE were engaged by Sydney Water to advise on the cause(s) of the shoring wall movement / failure, and the related technical issues.
The SCE investigations subsequently revealed that:
- Prior to the large movement / water main burst event, significant movements of the shoring wall had taken place, with consequential cracking & damage to two heritage listed hotels adjoining the excavation, and a large boarding house.
- The survey monitoring the shoring wall movement, as well as the inspection & testing regime for the ground anchors supporting the shoring wall, was fundamentally flawed and incorrect.
- The shoring wall and anchor design was incorrect, with the design errors, in combination with the lift pit excavations adjacent to the wall, being the cause of the movement / failure.
In the subsequent litigation process, including an extensive expert conclave that ran over 4 days, SCE’s opinions as to the cause of the shoring wall movement were accepted by 5 of the 6 experts. As a consequence, parties other than Sydney Water became responsible for the damaged buildings, roads & water main burst.