Innovation - Concrete Manholes
Concrete drainage manufacturers continuously innovate as the industry strives for improved construction quality and operational performance. Recent advances have led to reduced waste, lower costs, faster build times and minimised environmental impacts.
Advances in production techniques and the use of modern logistics systems ensure excellent product quality and reliable service.
Responsible sourcing of raw materials from local suppliers ensures that cradle to site “pipe miles” is low. High use of recycled materials keeps embodied impacts to a minimum.
The use of modern, integrally cast high performance seals helps maintain water tightness and integrity of joints.
The design flexibility of concrete drainage systems means that many special features can be incorporated in the factory and simply placed into position on site. These “offsite solutions” can replace lengthy in-situ operations, thus improving site safety and product quality, reducing waste, speeding up installation and reducing costs.
An excellent offsite example is a precast concrete manhole system with benefits that satisfy designers, contractors and asset owners.
The new manhole design offers:
- Reduced construction time
- Decreased installation costs
- Improved safety on site
- Superior quality
- Watertight system
- Reduced carbon footprint
Concrete Manhole Construction
Traditionally, manhole construction has required the base to be formed in-situ where building of the channel, connections and benching occurs in the trench. This often takes place in confined, wet and unpleasant conditions. The process can take around 40 hours per manhole and is not always successful. Construction quality defects may occur in terms of leakage where egress of waste water can lead to contaminated groundwater. Similarly, water ingress can contribute to overloaded sewer networks plus increased energy usage and pumping running costs.
Concrete Manhole Design
The new concrete manhole design comprises a precast concrete monolithic base unit, complete with channel and benching with predetermined combinations of inlet(s) and outlet. It also has a new thicker walled chamber ring with watertight joints and no lifting holes, removing points of possible leakage.
Both base units and chamber rings are made with thicker, stronger walls. The robust design means that the requirement for a concrete surround is eliminated in most cases. The excavation is backfilled sooner and there is less need for men to work in confined spaces. This reduces time spent in the excavation, further improving site safety and reducing installation costs.
Concrete Manhole Installation
Installation of the precast manhole system is speedy and efficient. Wet trades are eliminated; formation of benching on site and sealing of lifting holes is avoided and follow-up operations can start immediately. Time savings of over 30% can easily be achieved and construction costs reduced by well over 10%. Demonstration videos are available for the CPM Group's Perfect Base, F P McCann's Easi-base and Stanton Bonna's Watertight Manhole System .
The system yields environmental advantages. Less concrete is used, there is less waste and less excavated material is disposed to landfill. An annual saving of over 22,000 tonnes of CO2e is estimated if manholes changed to the new precast base system.
The quality of material and finish is well above that normally achieved on site. The full system is manufactured under factory conditions to ISO 9001 quality management system. Products are Kitemarked to BS EN 1917:2002 and BS 5911-3:2010+A1:2014 Concrete Manholes and Inspection Chambers and tested under laboratory conditions.
The new precast manhole system complies with Sewers for Adoption requirements.