Bullsbrook Wastewater Diversion to Ellenbrook

DMC worked with Water Corporation to offer an alternative design for the pipeline route to minimise vegetation clearing and to increase protection  measures adjacent to the existing live water supply pipeline.

There were strict environmental constraints to be managed including:

• Maximum of 1 hectare of native vegetation clearing;
• Construction adjacent to threatened ecological communities;
• Construction adjacent to Western Swamp Tortoise protected habitat;
• Construction adjacent to protected Banksia habitat;
• Crossing of Ellen Brook;
• Crossing of ARC rail freight line; and
• Significant construction along MRWA operated Great Northern Highway.

The transfer pumping station constructed near the middle of the route between Bullsbrook and Ellenbrook, was a Type 90 (3.0m Diameter) plastic lined wet well approximately 9m deep with 370m3 of emergency storage.  Construction of the pumping station was programmed and completed between January and March when the local groundwater table was predicted to be at its lowest. This minimised the amount of dewatering required for installation of the wet well and storage.

The dual horizontal directional drill (285m of DN400 and DN315) presented additional challenges with the complexity of the works and the environmental constraints around crossing a significant waterway.  On commencing the HDD works, concerns were raised regarding potential fracking of drill mud and its potential to impact the waterway.  DMC, along with its HDD contractor, Kier Contracting, redesigned the profile of the river crossing to complete work without any impact on Ellen Brook.

DMC scheduled and resourced the works such that that the impact to the environment and motorists on Great Northern Highway were minimised and the majority of the high impact works were completed prior to being affected by inclement weather.