Adding years to the life of a century old asset

Service reservoirs play a key if sometimes unsung role, in the supply of clean water within the UK The refurbishment of one such service reservoir dating back over a century has given it an additional 30-year lease of life at a fraction of the cost of building a new one. Undertaking this project did not come without its technical challenges. Project background In common with a large number of service reservoirs, Malpas Service Reservoir, owned and operated by United Utilities, dates back many years. The 20.5ML balancing reservoir was built in 1913 close to the village which gave it its name and lies close to the southern border of Cheshire, a few miles from the border with Wales. Then, as now, it formed an important ‘staging post’ for water flowing from Lake Vyrnwy in North Wales into the North West. Lake Vyrnwy was constructed in the 1880s with a capacity of 59.7GL, originally to supply water to Liverpool via a 68-mile aqueduct constructed by Liverpool Corporation. Other pipelines were subsequently added, and the water from Lake Vyrnwy now forms part of a network of sources supplying a much wider area. Today, the Malpas Reservoir helps service a population across a wide area of Cheshire. And while originally it was built as an open tank for clean water storage, after regulations changed, the circular tank was enclosed with a steel-clad roof. Having served its purpose well for over a hundred years, time has now taken its toll on Malpas. Recent investigations discovered water ingress to the tank and the existing brickwork walls were found to be in a poor state. Stonbury, specialist contractors to the water industry, were commissioned to undertake a comprehensive internal refurbishment together with some external repairs. The roof vents to the service reservoir were found to be allowing in rainwater, and so works to the roof were to be carried out internally and externally. This required erecting scaffolding and an extensive area of safety netting. External access to the roof also posed safety risks as the roof had a low load bearing capacity. In addition, the contract came with a tight deadline of just 12 weeks because of the need to get the reservoir back into use to meet the higher customer demand of water in late spring. A very high quality surface internal finish was required, to ensure that the reservoir will provide the maximum service length after completion.  Stonbury assigned a team of 15 full time personnel to the project, including specialist contractors for the steel fabrication and construction of new stainless steel stairs within the reservoir. Work commenced in November 2016 and was completed in early April 2017. Scope of works - Internal & External Removal of flume from centre of tank Grit blasting to walls and surfaces Cleaning of Staffordshire blue engineering bricks Preparation work to floors, before complete overbanding towards floor centre (spider-web effect) Mesh fixture to all wall surfaces Concrete spray over the mesh creating a new wall surface Installation of scaffolding and safety netting to roof internal (for safe external works) Refurbishment of roof vents Project progress The project commenced with overbanding to the floor joints, applying the longer lengths first while keeping the joints clean ready for the welding. Ultimately, some 3804 metres of overbanding were required to cover the 3849m2 of flooring creating a spider web effect in the circular-shaped reservoir. Priority was given to completing the joints near the flume first, so it could be fixed back into position. At the same time, another team commenced grit blasting the walls to prepare them for resurfacing, as well as cleaning the other surfaces; including the steelwork within the reservoir. Work started first on the walls at the lower section, allowing regular checks on the profile to ascertain if the amount being removed was adequate and even. Specialist engineers then undertook a detailed survey of the roof vents (which had been allowing in rain water) and the grating to the floor channel to determine the scope of work required, while the blasting grit was removed from the reservoir floor by another team. By week 6 of the project, the overbanding to the floor of the reservoir had been successfully completed, and the internal surface of the reservoir walls, comprising Staffordshire blue engineering bricks, had been sufficiently prepared for mesh to be fixed to the walls across 24 bays and a total area of 1200m2. Fixing the mesh, which ultimately took a total of 15 days, created a suitable 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 spraying of the reservoir walls began in week 5, once the mesh had been applied in the first few bays. To stay in line with the contract schedule, a target of completing the spraying of one bay a day was set, while mesh fixing continued on the remaining bays. Progress was slowed somewhat with numerous spray pump breakdowns, putting the concrete spraying two days behind schedule at one point, requiring weekend working to regain time. Work on the grating was completed in week 7 to cover the outlet channel. During week 9 of the contract, a separate team erected scaffolding and fixed safety netting to the internal roof, providing safe internal access to the vents. During this week, steel fabrication contractors also came 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 several 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 surfaces 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 overbanding and the site cleared and cleaned ready for inspection. A new handrail was installed on the top landing area and bracing applied to the newly installed access ladder. The final inspection was conducted by the client and the project was deemed completed and handed over. Conclusion Stonbury, one of the largest contractors in this sector of the water industry, typically undertakes around 450 refurbishment projects of this nature every year, making the process fairly standard for Stonbury and their supply partners. 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 experience gained over the years on tackling projects of this nature to anticipate likely problems after work commences and factor these into contract tenders.  

Stonbury sponsors the Institute of Water South East Area

Stonbury are pleased to sponsor the Institute of Water, South East Area with Platinum Sponsorship As specialist contractors to the water industry, we are pleased for this year to be Headline Sponsors at the Area’s highly anticipated Weekend School, now in its 7th year. We look forward participating in the Area’s programme of events over the next year and meeting the committee and members of the South East. 

Occupational Health and Wellbeing

We are pleased to announce we have engaged Probitas Occupational Health, who will be working with us to deliver an extended and enhanced Occupational Health and Wellbeing programme for all our employees We have always provided occupational health to meet our legal duty of care, however, we recognise the added value that wellbeing brings to both our staff, both personally and to the company as a whole. To date our programme with Probitas includes: Health surveillance - early detection of illness associated with workplace exposures or environments. Health screening Support and advice during sickness absence, working with management to ensure your safe rehabilitation back to work Health promotion – various initiatives aimed at improving your physical health and mental wellbeing We hope to see this develop even further over the coming months and years to enhance the wellbeing of all our employees. 

Stonbury acquires Kingcombe Aquacare

Stonbury are thrilled to announce the acquisition of Kingcombe Aquacare Limited Kingcombe Aquacare, based in Crewkerne, Somerset, have been in business for over 30 years and specialise in all aspects of water maintenance, construction, restoration and management. The company operates throughout the South-west and also further afield throughout the UK. It will be business as usual in the short term for Kingcombe, moving forward the business will fully integrate into the wider Stonbury group. The acquisition fits ideally with Stonbury’s long-term business strategy, as leading water industry specialist contractors across the UK and Ireland. The move also allows Stonbury’s existing services to be expanded into the South West of England, providing an excellent geographical base, experienced resource and new skill sets, complimenting our existing capabilities.

Stonbury is seizing its opportunities

The introduction of a regional structure is helping Stonbury to deal with the tremendous growth experienced in the past year or two Read the full article with Managing Director, James Stonor in this years annual edition of The Leaders 2017  

Our Year in Numbers

Stonbury have just completed the financial year, for the period 1st July 2016 to 30th June 2017. Here’s a brief overview of our year in numbers: It has been a extremely busy, but enjoyable year for Stonbury and along the way, we have faced various success and challenges, that we hope will strengthen us as company going into the future. Over the last year we have achieved new goals and milestones, including our first new build reservoir, that wouldn’t be possible without the trust and collaborative approach to partnership that we embrace with our framework clients. Thank you to all our clients, staff and suppliers for a great year of opportunity and growth!

Slow Sand Filters Floor Replacement

In October 2016, Stonbury as framework contractors to the Northumbrian Water Group and Essex and Suffolk Water, were asked for their involvement with an Investigation and Design (I&D) project, aimed at understanding the poor performing slow sand filters at the Layer Water Treatment works in the Essex supply area With both the expertise in civil engineering and operational structures within the water supply network, Stonbury were suitably selected to provide an added value solution for these challenges. For the initial investigation and design, Stonbury employed Amec Foster Wheeler who work extensively with NWG (Northumbrian Water Group), to review the particular issues around the slow sand filters, whilst providing a full market appraisal. The scope of the project required understanding the issues with the slow sand filters, to develop a solution that would increase the overall output of the WTWs. With the information from the investigation reports, Stonbury, leading the constructability element of the project, whilst also developing budgetary and programme options, were able to provide NWG and E&SW with the best options for delivering the programme. The Solution After on-site investigatory work, it was apparent that the existing brick floors, common to many slow sand filters of this age, had silted up, causing the output of the filters to be limited. This ultimately led to the conclusion that the slow sand filter floors were in need of a replacement, with a like-for-like brick floor. The concerns with this solution, included a high risk repeat of performance issues. Instead, a solution was considered for the installation of an alternative ‘brick’ floor. This method would require the lifting of the original bricks, to be replaced with an accepted market flooring system for slow sand filters. Stonbury proposed the use of a ‘U’ block by Plasmor, which met the design parameters and most importantly, DWI approved for installation within the water supply system. With the decision confirmed on the preferred solution, and using the progress from the I&D stages, Stonbury officially tendered for the construction phases of the project, achieving an approved final costed solution for the initial 4No. filters of 2500m2 each. At the end of January 2017, we were delighted to be informed by the NWG board and Essex and Suffolk Water, the award had been approved to Stonbury. The Works The NWG operational site team at Layer WTWs were responsible for removing the media and once completed, works begun in earnest to remove the existing brick floors. The old brick ‘waste’ was subsequently re-used by a third party as infill material, substantially reducing landfill waste volumes. During the brick removal process, it was noticed that the central collection channel cover slabs, had received damage over the years and were also in need of replacement. Due to the necessity for structural capacity of plant movement, we opted to design and construct the slabs on site in a specially made formwork arrangement, reducing both transport and procurement costs and manufacturing time. Each slow sand filter of 2500m2 required the laying of approximately 48,000 new ‘U’ blocks. With a singular block weighing 14kgs and at 140mm x 240mm x 215mm deep, the dedicated Stonbury operatives laid just over 2500 tonne of blocks by hand. With the commitment of all our stakeholders involved in the programme and the greatly efficient methodology developed in the early stages of the scheme, Stonbury are pleased to report that all 4No. slow sand filters were successfully completed ahead of schedule, completing almost one month ahead of programme. For any further information on the project or slow sand filter refurbishment schemes, please contact