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myREHAU | AWASHAFT Case Study: Hunter Water - Hamilton NSW

Posted on 30 July 2021

AWASHAFT DN1000 Maintenance Hole 

Case Study: Engineered Solution for 7.2m Deep Class D Installation in Water Charged Ground



Hunter Water required a 7.2m deep Sewer Maintenance Hole solution to replace a failed concrete Maintenance Hole to help reduce the installation time in water charged ground, withstand vehicle loads on a road, and provide a minimum 100-year design life.


REHAU AWASHAFT is a light weight modular system consisting of DN1000 Maintenance Hole, DN800/600 Maintenance Chamber and DN400 Maintenance Shaft. AWASHAFT is 95% lighter than concrete, 100% effective at preventing infiltration and exfiltration. It also comes with a 10-YEAR WARRANTY and 100-YEAR DESIGN LIFE. These attributes on top of the engineering support provided by REHAU made it the perfect solution for this project.


The REHAU base was lowered into place, connected to the existing cast iron pipes using pipe joining couplers, and prepared for the installation of the risers.  Two risers were installed in order to re-connect the external drop structure. The external drop was simply cut into one of the risers using the REHAU hole saw, AWADOCK fittings installed and pipework connected. A precautionary concrete anti-floatation base was poured around the circumference of the base, to provide additional assurance that the structure would not move under 5.0m of water charged ground.  As the backfill was raised and compacted, 6 additional 1000mm risers were installed, the dewatering equipment removed, and shoring boxes raised.  The final 600mm was backfilled with compacted road base material and a REHAU Class D concrete access cover was used to the required Finished Surface Level.



“We were looking for a quick and cost effective solution as we were installing a new MH into an existing live sewer system, and water charged ground where the water level was approx. 5.0m above the pipe invert.  The installation was complex as it was 7.2m deep and in the middle of a road, so the ease and speed of installation were critical.  We were able to install the REHAU base as well as several risers to the REHAU Engineers specifications, and be able to re-connect all the pipes and external drops to allow the system to be operational within 2 hours.  Significant cost savings were made on the sheet piles, shoring boxes & dewatering equipment during construction.  On top of that, REHAU provided support onsite throughout the project”

For more information, please contact your REHAU representative or call our Sydney Office on 1300 768 033 or email us on

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