Overview:
Location: Byford, Shire of Serpentine-Jarrahdale.
Date: 2009
Design, Documentation, Tender, Contract Administration and Superintendence of approximately 530m of DN600, 1120m of DN500 and 80m of DN400 MSCL Water Distribution Main.
Scope & Challenges:
Design and documentation of this Water Distribution Main including several complex bored crossings of MRWA Road and PTA Railway reserves with custom large diameter MSCL pipe supports. Design included constructability assessments in narrow road verges with existing services (including high pressure gas mains) and street trees, selection of alternate routes to avoid congested portions and service realignments to permit the main to be constructed on a standard alignment.
The construction of this water main also required addressing the concerns of, providing progress updates to, and patiently listening to complaints of affected commercial property owners when the main was constructed their premises. This included explanations of why alternative planning and / or constructability perspectives and subsequently negotiating satisfactory standards of reinstatement with the Shire of Serpentine – Jarrahdale and the property owners without incurring excessive cost to the Water Corporation.
Outcomes:
Although the program struggled due to complex approvals and the unavailability of specialised boring equipment, the construction and installation of pipework proceeded with little difficulty once the site and equipment was accessed.
Amongst the most successful outcomes was that the bored crossings were designed such that they were capable of being constructed using Reinforced Concrete Jacking Pipe Sleeves as requested by Water Corporation as well as through the use of a sacrificial Mild Steel Sleeve with the Reinforced Concrete Jacking Pipe grouted within the sacrificial sleeve.
This was intended to both increase the number of potential boring subcontractors who could be employed in the project, and also allow the sleeves to be installed using either slurry micro tunneling methods or horizontal auger boring methods which were more readily available at the time. When the original boring subcontractor first experienced delays on a project that the machine was employed on, and subsequently lost the machine when it got irretrievably stuck, this allowed another subcontractor to step in and complete the job with a minimum of lost time and extra cost.
The design of this distribution main traversed a Main Roads controlled highway and intersection which was undergoing upgrades at the same time as the distribution main works. This was successfully negotiated with MRWA and works co-ordinated to minimise the disruption to both parties. During the course of this project, we arranged a site visit for members of the Water Corporation, through the contractor, so that they were able to witness the available trenchless installation techniques in action.
