Water and Effluent Treatment Magazine
Issue link: https://read.utilityweek.co.uk/i/867569
JUNE 2015 WET NEWS 9 concrete spraying two days behind schedule at one point, requiring weekend working to regain time. Work on the grating was completed in week seven to cover the outlet channel. During the ninth week of the contract, a separate team erected scaffolding and fixed safety net- ting to the internal roof, providing safe internal access to the vents. During this week, steel fabrica- tion contractors also arrived on site to install a series of channel covers inside the reservoir. Because the metal roof would not safely withstand the weight of people working on it, scaffolding was erected in sev- eral places over the top, together with a series of safety lines to provide safe external access to the vents. With the roof vents fixed in place, a Davit Arm and an SS ladder were introduced; and these, together with the scaffolding, provided safe access for the internal steel sur- faces in the roof to be coated. With the concrete spraying nearing completion, work then commenced on the perimeter walls overbanding, applying some 120m of overbanding to seal the joints between the 24 bays. In the final week, all plant and equipment were removed, final tests conducted to ensure the water tightness of the over- banding and the site cleared and cleaned ready for inspec- tion. A new handrail was installed on the top landing area and bracing applied to the newly installed access ladder. The final inspection was con- ducted by UU and the project was deemed completed and handed over. ONSITE INfrastrUctUrE the reservoir acts as a 'staging post' for water flowing from Lake Vyrnwy in North Wales to north-west England fixing mesh across a total area of 1,200m² created a suitable surface for the concrete spray to be applied a total of 55,000 litres of sika 133 gunite concrete spray was applied to the perimeter walls across 24 bays and a total area of 1,200m 2 . Fixing the mesh, which took a total of 15 days, created a suit- able surface for the concrete spray to be applied. In total, 55,000 litres of concrete spray were applied to the perimeter walls. Timber screed rails were then fixed into place and spray- ing of the reservoir walls began in week five, once the mesh had been applied in the first few bays. Safety netting To stay in line with the contract schedule, a target of completing the spraying of one bay a day was set, while mesh fixing con- tinued on the remaining bays. Progress was slowed somewhat with numerous spray pump breakdowns, putting the Stonbury, one of the largest contractors in this sector of the water industry, typically under- takes around 450 refurbishment projects of this nature every year, making the process fairly standard for the company and its supply partners. Financially viable The ageing nature of our water supply infrastructure, and the cost of replacing it, means that retaining the structures that can be refurbished should represent a very worthwhile investment where it is technically feasible and financially viable. Moreover, there is a wealth of knowledge within the sector on the best techniques and materials to use, and considerable experi- ence gained over the years on tackling projects of this nature to anticipate likely problems aŠer work commences and factor these into contract tenders. The Malpas Service Reservoir offered some interesting chal- lenges, not least the issue of safely accessing the metal roof (internally and externally) in order to repair the vents and coat the internal surface. Because of the high specifica- tion, particularly on the finish of perimeter walls, it could undoubtedly have been deliv- ered at a lower cost with a lower specification, but this would have impacted upon the future duration of the reservoir. Stonbury has a legacy of structures within the UK water industry designed and built by our predecessors to last a very long time indeed. With fore- sight, ingenuity and the appli- cation of modern refurbishment techniques, many of these struc- tures can be retained and used for some time to come. ProjEcT SPEcS • refurbish century-old service reservoir • carry out external repairs to the service reservoir • create a new internal wall surface • clean staffordshire blue engineering bricks TEchKNoW • Overbanding was required to cover the 3,849m 2 of flooring • the internal surface of the reservoir walls required mesh to affixed • timber screed rails were used • the walls were grit blasted to prepare them for resurfacing ThE VErDIcT the Malpas service reservoir offered some interesting challenges, not least the issue of safely accessing the metal roof (internally and externally) in order to repair the vents and coat the internal surface. NEED To KNoW 1 Investigations discovered water ingress to the tank the existing brickwork walls were found to be in a poor state 2 staffordshire blue bricks have a hard, impervious surface with high crushing strength and low water absorption 3 a team of 15 full-time engineers were assigned to the project 4 constructing a new service reservoir would have cost an estimated £5M