Successful outcomes for a unique project

April 2018

The replacement of a 70-year-old timber bridge over the Oaklands Main Drain on Gossage Road, Cardup was a small yet unique project compared to other conventional Water Corporation infrastructure projects we have completed. This showcased DM Civil’s wide spectrum of civil construction capabilities including demolition, remediation, earthworks, concrete works, culvert installation, traffic management, environment management and community liaison.

The scope of works encompassed demolishing the old timber bridge structure, installation of a new box-culvert drainage crossing, restoring the road pavement, installation of road safety barriers and associated minor earthworks. The demolition of the old timber bridge was considered a high-risk construction activity and was vigorously scrutinised by the Principal. A comprehensive Demolition Safe Work Method Statement was developed which ensured that the demolition works were carried out safely, and in an environmentally-friendly manner.

The construction works required a 6-week full road closure of Gossage Road between Kargotich Road and Hopkinson Road. This road closure involved considerable planning and consultation with the Shire of Serpentine – Jarrahdale and local residents, notifying road users and emergency services.

One of the biggest challenges working in open drainage channel is the diversion of stream flow around the construction site. Although it had been anticipated that the drain would be dry during the construction period in the months of February-March, there was still a possibility of a summer storm which could have generated significant flow through the bridge location. Coffer dams and bypass pumping facilities were put in place as preparation for such potential storm events. The construction program also incorporated some flexibility to adjust the timing of critical construction activities such as casting of base/apron slabs to avoid such wet weather conditions. This was achieved through closely monitoring the weather forecast outlook leading to these critical construction activities.

The Lifting Procedure which was developed in-house had been put to the test on this project whereby DM Civil-owned excavators were used to lift precast concrete units up to 4 tonnes. Skilful operation of the excavators enabled the precast box-culverts, link slabs, wing/head walls to be safely lifted and placed into position with precision.

Working in a relatively pristine rural environment like Gossage Road, environment and safety had been important aspects of the project. The construction site was fenced up and isolated from the public and extensive traffic management measures were implemented to enforce the full road closure to the project site. Disturbance to the environment was kept to a minimum and disturbed areas were reinstated or improved from the original condition. We provided a safer route for a busy road used by commuters, heavy trucks and the local community.

The new bridge was completed successfully with satisfied stakeholders, namely, Water Corporation and Shire of Serpentine/Jarrahdale. This project demonstrates the diversity of DM Civil’s capabilities and reiterates our ability to provide comprehensive civil solutions. Our focus is to work closely with clients to achieve their strategic goals in the most cost-