Water and Effluent Treatment Magazine
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Out of site • Affinity Water is using offsite innovation as it takes a new approach to major asset upgrades using traditional on-site techniques. Off-site approach Affinity Water awarded spe- cialist contractor Nomenca the design and build contract for the new plant. Nomenca pro- posed an innovative technical approach to the project, employing its Skilled Assem- bly Factory Environment (SAFE) modular construction. Moving the building pro- cess away from the physical site and into a controlled off- site environment can have many benefits, from improved health and safety to lower costs. While offsite construction is yet to become the norm for the water industry, it is growing in popularity. Nomenca has already brought its SAFE approach to a number of pro- jects but Affinity Water's Essex pumping station was the most ambitious project yet. Gavin Stonard, Engineering Director at Nomenca, said: "Offsite construction tech- niques are in a growth period worldwide – and already deliv- ering efficiency savings in the UK water industry, as well as helping to overcome safety and operational challenges." BIM technology was intrin- sic to project delivery from the outset. Nomenca and Affinity Water shared a virtual view of the site and collaborated online to develop a detailed job scope – reducing the need for the 500-mile round trip to the site. A 3D laser scan using a FARO focus scanner captured the dimensions and positions of all assets on the site. Buried services were then mapped with ground-penetrating radar, and the results brought together to produce a 3D Auto- CAD model. With the extent of the works reviewed, next came a detailed, working 3D design model built within a multi-dis- ciplined Common Data Envi- ronment. The model incorpo- rated all the major and minor components and their various interconnections. It featured the chemical treatment plant and borehole pumping kiosks with their pipework, steelwork and electrical installations, the diesel generator and fill point kiosk, and the chemical delivery area along with its drainage, valve chambers and blind tank. Nomenca's in-house virtual reality so™ware enabled Affin- ity Water to walk through the proposed design. The virtual modelling was also used by construction teams, as well as for community engagement with local residents and coun- cil planning application meetings. The technology meant almost every design detail ONSITE OFFSITE INNOVATION Inside the pump station kiosk. The project realised a 5% saving on the original project capex T aking a pioneering new approach to a borehole pumping station upgrade in Essex, Affinity Water mini- mised asset downtime and costs using a strategic offsite build programme. The ambitious project com- bined virtual design technol- ogy with modular offsite man- ufacturing, shi™ing the mainstay of the construction work to a controlled factory environment. The challenge The borehole pumping station and water treatment works supplies 120,000 houses in Saffron Walden and surround- ing villages via a nearby reser- voir. Rated at 14Ml/day, water is disinfected using hypochlo- rite dosing and a contact tank then boosted to 9 bar into sup- ply and to a remote reservoir. To ensure the plant contin- ued to operate at full capacity for the area, Affinity Water needed to replace existing equipment with a new and effi- cient installation. Due to limited shutdowns being feasible at the facility, the existing plant would ide- ally need to remain opera- tional right up until the new equipment had been commis- sioned and tested – something that would be hard to achieve 10 WET NEWS FEBRUARY 2018 could be checked right at the outset, from the tie-ins to existing service mains and drainage to the location and dimensions of cable ducts and draw pits. The building process With detailed designs approved, the AutoCAD model of the upgrade work was laid over the site survey model – ensuring equipment built off- site would fit perfectly once in position. This process immedi- ately highlighted where small design tweaks were needed. Dealing with these onsite – as would normally be the case – would have inevitably caused delays and increased costs. The offsite build took place at Nomenca's specialist facili- ties in Warrington. An SR4- rated kiosk was developed to house the UV and hypochlorite dosing systems, through which raw water from the boreholes would be pumped at mains supply pressure. It holds an additional booster pump to an auxiliary reservoir too in case of a network shortage along with other ancillary equip- ment, building services and the heating and ventilation systems. The kiosk also includes the new main site Motor Control Centre that powers not only the skid equipment, but also the new borehole pumps and existing surge vessel. Consid- ering the breadth of services it contains, the 20m-long, 4.2m-wide and 3.4m-tall skid is "Offsite construction techniques are in a growth period worldwide – and already delivering efficiency savings in the UK water industry, as well as helping to overcome safety and operational challenges." Gavin Stonard, Nomenca