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wwtonline.co.uk | JUNE 2018 WET NEWS 15 pipes between 375mm and 450mm diameter require a 1,350mm diameter chamber, pipes between 500mm and 700mm diameter require a 1,500mm diameter chamber; and pipes between 750mm and 900mm diameter require a 1,800mm diameter chamber. Precast manhole systems offer great versatility and are designed to accommodate all standard pipe materials and sizes. Existing precast manholes can even be retrofitted with new connections from future devel- opment without the need to replace the entire manhole. 6. Minimise the need for granular backfill The robust design and wide chamber walls of the factory manufactured precast concrete manhole base system means that the use of granular or con- crete backfill can be eliminated, unless it is specifically required by the client. Using a precast concrete manhole base system enables the construction to be com- pleted quicker. The excavation can be backfilled sooner using the soil that was excavated, thus making the installation safer and faster whilst simultane- ously reducing the cost of back- fill and disposal of the exca- vated material. 7. Save on carbon emissions A big advantage of the factory manufactured precast concrete manhole base system is that it offers a significant saving in embodied carbon for the instal- lation. The BPDA estimates that carbon savings could be as much as 43 per cent per man- hole compared with traditional in-situ construction. A notable part of this carbon saving is the avoidance of concrete or granu- lar backfill and the use of exca- vated soil. The environmental creden- tials of a precast concrete solu- tion are further enhanced by the responsible local sourcing of raw materials and the appropri- ate use of recycled materials. This ensures cradle-to-site miles are low and helps keep the product's environmental impacts to a minimum. The BPDA estimates that 15,000 tonnes of CO2 equivalent of embodied carbon would be saved annually if all manholes manufactured by the Associa- tion's members changed from in-situ construction to the circu- lar precast base system. 8. Consider durability The precast manhole base sys- tem is manufactured under factory conditions by quality assured processes. This ensures the finish and quality is to a higher and to a more consistent standard than could have been achieved on site. The combination of dura- ble precast concrete and qual- ity controlled offsite manufac- turing process will ensure that a precast manhole system has a long service life. Their self-weight is an advantage in situations with high groundwater or in flood- ing where they can have a nat- ural resistance to floatation and where additional anchor- age is not required. A major benefit of concrete drainage systems is that they have a long, proven service life, typically in excess of 120 years. This helps to keep down whole life and carbon costs. 9. Listen to what other users have to say Natta Building opted to use the precast manhole base sys- tem from BDPA member Mar- shalls CPM to save time on site at its redevelopment of New Covent Garden Plaza project. The scheme forms part of the regeneration of Nine Elms in South West London. "We chose to use the Marshalls CPM Perfect Manhole system as the integral cost-in, high performance seals maintain water tightness and decrease the time taken to install the manholes," James Hidderd of Natta Building said. "Because the bespoke inlet and outlet benching is made off-site, the manhole construction is closed quicker on site." For more information on precast concrete manholes, go to www.precastdrainage.co.uk Precast manhole solutions have the benefit of swift installation For details visit: precastdrainage.co.uk/heavyweight T: 01179 814500 E: sales@cpm-group.com W: www.cpm-group.com Concrete's performance is a matter of record. Concrete pipelines are at the heart of drainage infrastructure in many of the UK's biggest cities. They are tough enough to cope with construction traffic and deeper cover depths. They don't lose shape or strength over their service life. They are the strong, stable and sustainable choice. Why pick a lightweight? t. 0800 8046 062 www.atiuk.com Modular, multi- parameter water quality monitors for networks

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