CASE STUDY
Concrete solids are captured in the bags, crushed and then reincorporated into the project as fill material for beneath hard standings, car parks and pathways
Siltbuster – Airbus RCW case study
The past ten years have seen unprecedented changes in the way that construction activities are undertaken. This is reflected not only in new technology but also in the way that construction projects are procured and managed. Environmental best practice has gradually come out of the shadows and is now seen by many as a key deliverable in construction projects of all sizes.
By combining process improvement and environmental best practice, companies can increase profitability, improve customer and employee satisfaction, enhance safety and productivity, and reduce their environmental impact.
The following case study demonstrates the benefits that can be achieved when environmental best practice is adopted from the outset of a construction project.
Background Construction work is currently underway on a multi- million pound project to build a new wing manufacturing unit at Airbus Operation Ltd UK’s factory site in Flintshire, North Wales. The facility is seen as pivotal in the development of the UK aviation industry. Morgan Sindall, the principal contractor on the project, has responsibility to ensure that all activities on-site use best practice, minimise the environmental impact of the build during construction and comply with environmental legislation.
In 2008, Airbus UK started construction works on its new manufacturing unit for wings of the new A350 family of planes. The company appointed Morgan Sindall as principal contractor to undertake the construction of a 52,000m2 manufacturing unit. Structurally, the facility will comprise a steel frame structure in a three bay configuration. To support this vast structure, highly- complex machine bases and concrete floors supported by 8,000 piles have been designed and installed.
The North Factory construction site has high-level groundwater issues and is within a permitted site regulated by the Environment Agency, therefore allowing high pH water to seep into the ground would pollute the groundwater system. With an average of 60 deliveries of concrete per day and over 53,000m3 of concrete
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required, there was a considerable volume of concrete wash-water that had to be dealt with on-site.
From the outset of conceptual design, environmental characteristics of the building and the use of best practice were included within the client’s brief. As an example, it was apparent that the usual construction site practice of using plastic-lined skips for crude concrete washout facilities was inadequate and that an alternative solution was required. For a project of this size, the number of skips required would also have implications in terms of available space on-site.
Solution Following research into the different solutions to treat concrete wash-water currently available on the market, the project team approached Siltbuster Limited, specialists in total water management solutions, for advice. UK based Siltbuster Limited had developed the RCW - Roadside Concrete Wash-water Treatment system - an innovative system designed specifically to treat high pH concrete and wash-water from concrete truck chutes, making it ideal for this sort of task.
The first Siltbuster RCW unit was introduced to the North Factory site in March 2009. Two more were soon in place to control and treat wash-water generated on-site and a further two more made available for use when required during larger concrete pours. An average of 60 concrete trucks deliver material to the site each day but during the pouring of the machine bases this peaked at 283 concrete trucks over the course of just one weekend, which necessitated the use of four RCW units.
Treatment of the wash-water is a straightforward operation. When the concrete has been offloaded, each truck reverses up to the RCW and washes off the rear end of the truck directly into the front end of the RCW unit which contains two de-watering bags. The concrete solids are captured in the bags, which are porous, so the water filters through into the main treatment unit. Once the water has reached a preset level, it is then treated using an innovative, automated process whereby carbon dioxide (CO²) is pumped into the water, adjusting its pH level from highly alkaline (circa. pH 13) to neutral (circa. pH 6 - 8) and any precipitated solids are then removed.
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