Poor ground conditions, combined with a high water table, presented main contractor CJL Construction with a significant challenge when it required a foul sewer application for the large residential development on behalf of its client, Permission Homes.
A large number of manholes were required on the project as part of the overall foul sewer system adopted by Wessex Water, and CJL required a solution that reduced the potential for leakage and groundwater contamination.
Traditional concrete manholes often contain more joints than plastic systems and can be more time consuming to install due to their construction and weight. Polypipe CGU approached CJL with the capability to design a bespoke manhole solution to meet the needs of the project.
Working closely with the teams at both CJL and Wessex Water, Polypipe CGU supplied over 70 bespoke sealed manholes in 1200mm diameter for the foul water drainage scheme. Constructed off-site at the Polypipe CGU Fabrications Department in Loughborough, each unit was pre-fabricated so it arrived to site ready to install.
The design developed by Polypipe CGU incorporated a pre-formed and pre-benched manhole with a complete shaft. The lack of joints within the manhole construction significantly reduced the number of potential leakage points, which was a clear benefit to CJL and Wessex Water.
Installed with a concrete bed and surround, each manhole is capable of resisting floatation caused by the high water table.
Robin Milliner, Senior Contracts Manager at CJL Construction, said: “We had worked closely with Polypipe CGU on this project for over two years, so we’ve seen the designs and requirements of the product change significantly to meet the requirements of the project.
“Polypipe CGU’s capability to produce a bespoke product for a particularly demanding site and the off-site construction element of the manholes has certainly been a major benefit at the installation stage.”