15/04/2025
Australia: Rob Carr carries out construction work on the Eleventh Road sewer collector in Armadale
Rob Carr was awarded the construction of the DN600, DN450 & DN375 Collection Sewer Eleventh Road Project in Armadale in late October 2024 by the developer for the adjacent property development. The works involve the construction of 1,239 m of sewer which is required to enable the servicing of housing in the fast-growing southeast corridor of Perth.
The work carried out
The project consists of the installation of the following pipe sizes via tunnelling:
- 356 m of DN600 Glass Reinforced Plastic (GRP)
- 517 m of DN450 GRP
- 277 m of DN375 GRP
- 37 m of DN225 PVC
Additional works include:
- 52 m of open trench pipe laying for connections;
- 13 plastic lined concrete access chambers up to 5.5 m deep;
- Connections to the existing DN600 and DN225 sewer.
Rob Carr is utilising its fleet of Iseki Tunnel Boring Machines to carry out the majority of the work. The longest drive is 186m long involving the installation of a DN600 GRP jacking pipe.
The technique selected
Slurry pressure balanced micro tunnelling was selected in lieu of other techniques due to the proximity of the new sewer alignment to Eleventh Rd, a busy local thoroughfare. With the new sewer also parallel and below a DN1400 high pressure water main for the entire length, the more traditional method of open excavation was considered too high risk.
The geotechnical conditions
The geotechnical conditions expected were a mix of silty sand and clay. The groundwater level in the area is high and is expected to be near surface level during winter. Rob Carr is undertaking daily monitoring of the groundwater discharge rate and quality to ensure compliance with the Department of Water and Environmental Regulation approved Dewatering Management Plan. To date the ground conditions encountered have been favourable with consistent clay ground conditions and a lower-than-expected water table.
Road traffic management
Gaining approval of the traffic management plan from the Local Authority proved significantly more difficult than anticipated due to the volume of heavy vehicles utilising Eleventh Road to service the adjacent development works, which made diversions unsuitable, there was also significant other infrastructure installation works in the area with existing Traffic Management Plans in place which had to be taken into consideration. However, with close consultation with the stakeholders involved and a revised methodology this issue was resolved in time to ensure no delay to the commencement of the works.
Works commenced on 06/01/2025, with the required date of completion in August 2025.
