Supply Chain - Civil Engineering - Reinforcement

Usk is a large raised reservoir formed by an earth embankment dam, which completed constructed in 1955 with an approximate capacity of 12,268,000m3. The dam is 480m in length, with a maximum height of 31m, and supplies raw water to Bryngwyn Water Treatment Works and as well as providing compensation water to the River Usk, which is classified as a Special Area of Conservation (SAC) and a Site of Special Scientific Interest (SSSI). The project focuses on the replacement of the reservoir draw-off pipework within the dam’s outlet tunnel. Project drivers Welsh Water appointed Mott MacDonald Bentley (MMB), who form part of the Capital Delivery Alliance, to design and construct the replacement of both historic 18-inch scour mains in the tunnel to improve emergency drawdown capacity and to provide facility for enhanced releases to the River Usk. The works will improve drawdown capacity and as such form part of the works required to address a statutory measure in the interest of safety (MITIOS) under the ambit of the Reservoirs Act 1975. Works to provide ‘enhanced releases’ allow a range of discharges from the reservoir, with the aim of providing benefits to the River Usk and its habitats, which is in line with the European Habitats Directive. Furthermore, the works provide enhanced releases to contribute to the United Nation’s Sustainable Development Goal (SDG) 6. In particular, it contributes to achieve the target of 6.6: ‘By 2020, the aim is to protect and restore water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers and lakes’. Optioneering The historic pipework and tunnel characteristics caused a variety of constraints on the new system that needed to be considered when finalising the desired pipework arrangement. The project aimed to safely maximise the potential drawdown capacity whilst working within these constraints, some of which are described below. The historic arrangement did not allow for easy inspection or maintenance. At the upstream end of the tunnel, the historic 18-inch pipes pass through a concrete plug, which cannot be replaced without a full drawdown of the reservoir. Emptying the reservoir was not feasible due to Usk Reservoir supplying large volumes of raw water for supply and compensation purposes. As a result, the historic 18-inch pipe section formed a constraint on the design and construction of the permanent works. Pipework and valve arrangement within the valve chamber – Courtesy of MMB Pipework and valve arrangement within the valve chamber - Courtesy of MMB The tunnel cross-section is a 2.4m diameter horseshoe shape. Access to the upstream end of the dry side of the tunnel is necessary to operate, inspect and maintain the new pipework and valve arrangement. The pipework arrangement and diameter needed to consider the ability to remove sections of pipework if required at a later date. A long list of options were developed, however the chosen solution was to replace the twin 18-inch pipework with a single larger diameter pipe, offset to one side of the tunnel. This option maximised the outflow from the reservoir and maximised space for access, inspection and maintenance. To merge the two 18-inch pipe sections from the tunnel plug, an asymmetric manifold was designed to combine the flow, with guard and duty valves upstream of this. Enhanced releases are provided by two flow control valves installed offline to the new drawdown pipework, that could be remotely operated using a telemetry system located in a new control kiosk. Other options considered during the optioneering included: Increase diameter of one 18-inch diameter pipe downstream of plug, with the other 18-inch diameter pipe to discharge into tunnel downstream of plug. Larger single pipe solutions, up to 1200mm diameter. Twin 600mm diameter pipes. Moving valve house upstream 50m to immediately upstream of a bend in the tunnel. Design considerations Another consideration in the pipework design, was to limit the flow velocity through the twin 18-inch sections of pipework and valves. If the system was operated for a prolonged duration with excessive velocities, there would be a risk of causing damage to the system through cavitation and excessive wear. (left) Gate valve transportation and (right) bulkhead valves with concrete encapsulation - Courtesy of MMB (left) Gate valve transportation and (right) bulkhead valves with concrete encapsulation - Courtesy of MMB Following the feasibility stage, the pipework system was further optimised to improve hydraulic efficiency whilst maintaining velocities to a suitable level. The manifold was optimised to achieve balanced flows between both legs, to prevent significantly higher velocities within a single leg. The results of the optimisations enabled the diameter of the larger pipework to be reduced from the initial proposal at the feasibility stage, leading to a reduction in material costs and embodied carbon by approximate 10%. The diameter of the larger pipework was 800mm, and the flow rate measured in the commissioning phase was approximately 5m3/s. Concrete tunnel investigation As some cracking had been observed to the tunnel soffit, a condition assessment of the concrete tunnel was completed. Intrusive investigations were undertaken to obtain cores to determine the cause and depth of cracking, mechanical properties, and petrographical assessment of the concrete and the section thickness. Several crack monitoring locations were monitored over a period of 21 months to determine ongoing and potential future movement. The results suggested that limited future movement will take place. Some of the intrusive investigations also showed evidence of alkali silica reaction (ASR). Following a suite of expansion testing, the results showed that future effects of ASR would be limited and unlikely to cause significant deterioration. To help mitigate the risk of deterioration due to water ingress into the cracks, a proactive repair to the cracks was undertaken, and long-term monitoring of the cracks was established. Usk Reservoir: Supply chain - key participants Principal Designer: MMB Principal Contractor: MMB FRC works: Doohan Civil Engineering Electrical & control: Bridges Electrical Engineers Ltd Diving works: Edwards Diving Services Metalwork: D Hughes Welding & Fabrication HPPE siphon pipe: Aliaxis - GPS PE Pipesystems Pipework supplier: UTS Engineering Ltd Submersible pumps: Selwood Valves: Glenfield Invicta Flow meters: Siemens Concrete repairs: RAM Services Concrete cutting & drilling: Gnat UK Ltd Concrete supply: Hanson UK Siphon and over pumping intakes - Courtesy of MMB Siphon and over pumping intakes - Courtesy of MMB Key temporary works To maintain mandatory water compensation from the reservoir to the River Usk once the historic pipework removal had commenced, a twin siphon system was installed from the reservoir basin to the spillway’s stilling basin. Each siphon consisted of 280m long, 400mm OD HDPE welded pipework, with ductile iron fittings. The siphon was designed to operate down to -4m below top water level, which was typical for Usk Reservoir during the summer as the water level fluctuates. It used a pump to prime the siphon, and the pump could also be used in the event the siphon loses prime to discharge the minimum compensation requirement. The siphon was found to be reliable, and throughout the construction phase, saved approximately 260,000 litres of diesel, and 700 tonnes of CO2, when compared to over-pumping. Construction phase and commissioning Scope of work: Temporary siphon for compensation releases. De-commission of existing Portis supply main (including diving works). Demolition/re-construction of the valve house. Construction of new control kiosk and compound. Removal of three existing pipes within the tunnel, each at 180m in length. Installation of new electrically actuated guard and duty isolation valves, whilst working under single isolation. De-commissioning of the existing manual guard valves. Installation of the new 450mm>800mm pipework inclusive of manifold. Installation of valve house control valves/access metalwork. Security provisions. Valve chamber and tailbay - Courtesy of MMB Valve chamber and tailbay - Courtesy of MMB The historic valve house was demolished and replaced with a new buried valve chamber, and the tailbay was relined with a new reinforced concrete structure. This was due to the visual condition of the historic structures, to create a larger area for the new valve and access arrangements, and to facilitate the installation of the new pipework and valves. The first task within the tunnel was to remove the three existing pipes. During the feasibility surveys it was found that the existing pipework and fittings contained asbestos, MMB commissioned a specialist asbestos contractor to remove the pipework adopting a pipe wrapping containment and use of a wire saw cutting technique. Once the pipework was removed all existing concrete pipe supports were also removed and the existing tunnel invert made good. Once all of the existing pipework had been removed up to the existing guard valves (at the tunnel bulk head), works to remove the existing duty valves and replace with new continued under client Gold Command control due to the single isolation nature of the works. The works then progressed onto installing the new twin 450mm to 800mm diameter carbon steel pipework in tandem with installing a new level concrete tunnel floor. Due to the limited space within the tunnel and lack of lifting facility MMB used a small pick and carry crane which was able to transport the new pipework into the tunnel for installation. The tunnel was 180m in length with two 45° bends, this presented some construction challenges due to the limited flexibility in the flanged system. The new valve house arrangement was then installed and incorporated the compensation, enhanced releases, and scour valves complete with extension spindle and pedestal arrangements for operation via electrical actuation on the new raised flooring arrangement. (left) Scour pipework arrangement at the bulkhead and (right) scour pipework & thrust block - Courtesy of MMB (left) Scour pipework arrangement at the bulkhead and (right) scour pipework & thrust block - Courtesy of MMB Programme The scheme was mobilised on site in July 2020 which presented additional unprecedented safety challenges due to the global COVID-19 pandemic. The site adopted stringent social distancing working on site and use of respiratory PPE when working in close proximity within the confines of the tunnel. The works were undertaken under the supervision of the QCE, and the pipework and valve system were successfully wet commissioned in April 2022. The editor and publishers would like to thank Gregory Cornelius, Design Lead, and Jason Eddies, Contracts Manager, both with MMB, for providing the above article for publication.

Preston WwTW serves a population in excess of 250,000 and has six sub-catchments: Lytham, Fairhaven and Freckleton within the Fylde District to the west, Lea Gate and Watery Lane to the east within the Borough of Preston and Penwortham to the southwest within the South Ribble District. United Utilities (UU) has invested £20m during AMP6 at Preston WwTW and in August 2015, awarded the Preston Storm Tank Project to specialist design and build contractor Mott MacDonald Bentley (MMB). The project’s objectives were a reduction of storm water spills and improvements to both the underperforming inlet works and the primary settlement stage. The project has been handed over to United Utilities operations staff, and contract completion was 31 May 2018. Project background All of the inflows to the WwTW are pumped and the catchment generates high concentrations of screenings, particular during storms after long dry periods. Recently the existing inlet works has struggled to deal with the peak screenings load, exacerbated by the many recent UID projects undertaken within the sub-catchments. Measures to provide improved operability and resilience at the inlet works were essential. Route cause and analysis techniques were adopted to ensure the best outcome. Additional storm storage capacity was required to meet the AMP6 three spills per bathing season and ten spills per annum (shellfish) drivers; spill performance being averaged over a fifteen-year period to a 2036 design horizon, that included for climate change. Maintenance scope requirements were identified following asset surveys and a review of operational maintenance reports. Temporary propping of the PCC wall unit prior to pouring of the in situ ring beam base - Courtesy of MMB Temporary propping of the PCC wall unit prior to pouring of the in situ ring beam base - Courtesy of MMB Scope of works The scheme components include: New storm tanks with a combined capacity of 51,000m3. Storm tank fill and emptying pipework. Flow to works measurement. Concrete repairs to the primary settlement tanks (PST) numbers 1-8. Mechanical and electrical refurbishment to PSTs numbers 1-8 including replacement scrapers. Improvements to the existing under-performing elevated inlet works. All associated electrical, control and telemetry works. Landscaping. Site constraints The Preston WwTW site is located on the northern bank of the River Ribble estuary and is surrounded by areas of historic and current land fill. A desktop study also identified that areas within the WwTW have previously been used as landfill sites. The western end of the treatment works footprint, closest to the location of the proposed storm tanks, was known as Grange Farm, with the northern end being named Clifton Marsh. The site is within an area designated as being at risk of both tidal and fluvial flooding. The Ribble Estuary adjoining the treatment works site is designated as both a Ramsar and a Special Protection Area, under European and UK legislation. View down the completed storm tanks from the access platform - Courtesy of MMB View down the completed storm tanks from the access platform - Courtesy of MMB BIM and information management The Preston Project was delivered to a full PAS 1192-2 information delivery cycle. A clear defined Employers Information Requirements (EIR) was in place as part of the contract. A BIM Execution Plan (BEP) was developed to address the EIR and explain how the information modelling aspects for Preston would be carried out. Included in the BEP was a Master Information Delivery Plan detailing when project information was to be prepared, by whom and using what protocols and procedures. Data developed during the design and construction phase of a project - the Project Information Model [PIM] - was progressively developed and delivered to UU, to coincide with their decision-making processes as defined by the EIR. The asset centric PIM was prepared, compiled and delivered on UU’s BS1192 configured Common Data Environment (CDE) - Bentley ProjectWise. The Asset Information Model (AIM) including health and safety documentation, operation and maintenance data and as-constructed information including 3D models where all delivered through the CDE in a structured and defined process documented in the EIR, enabling UU to maintain the AIM through the lifecycle of the assets constructed during the Preston WwTW project. With Preston being a collaborative 3D BIM project, a federated model was compiled by amalgamating several different models from MMB, GHD and Longwood into one. The advantages included: Earlier design coordination and development. More efficient clash detection and avoidance during the design process. Efficient tool for design review, buildability and temporary works design. Enabled faster design iterations and streamlined historically time-consuming tasks. Allowed metadata to be added to existing services, confirming the accuracy of their geospatial position from inaccurate historical drawings to positions verified by trial trench data. Provided setting out data direct from the model to the site team’s survey equipment. Effective visualisation for the whole design and site teams. Autodesk’s Civil 3D was used extensively through the design stage for storm return pipework development, where large diameter pipework had to be threaded through a site heavily congested with services. The Access, Lifting and Maintenance (ALM) review for the inlet works was carried out utilising the federated model. This allowed the whole project team and client to interact with information in a 3D format. The use of a virtual reality headset was adopted, providing a new way to engage and review spatially accurate information, deliver a safe design and ensure ease of future operation and maintenance. Laying new GPR pipeline - Courtesy of MMB Laying new GPR pipeline - Courtesy of MMB Scheme optimisation Additional storm storage was required to supplement the existing 64,140m3 storm tanks to meet the reduced spill frequency requirements and also replace the structurally derelict 1938 storm tanks that have a capacity of 13,400m3. During the solution development stage, major CAPEX savings were realised in comparison with the tender design. These savings included: Storm tank volume reduced by 25% to 51,000m3. Requirement for well point dewatering eliminated. Storm tank compartments reduced from three to two. Requirement for stabilisation of excavated soil eliminated. The storm tank volume reduction was realised following extensive development and dynamic optimisation of the network model. This included amendment of the real time control functionality of the existing Preston Storage tunnel (40,790m3), matching the existing pass forward flows, whilst also ensuring no detriment to the existing network CSOs. Furthermore, the model was optimised to better reflect the efficient storm return system, modelling the variable speed pumps feeding in when flow to works drops below flow to full treatment (FtFT). Connection between new pipeline and existing elevated inlet structure - Courtesy of MMB Connection between new pipeline and existing elevated inlet structure - Courtesy of MMB Early in the design process it was recognised that due to potential contaminated soils and high ground water levels, a key objective was to reduce the depth and volume of excavation. A significant amount of additional ground investigation was carried out to better understand the ground conditions and behaviours of the water table. Adoption of a large footprint tank with reduced depth together with a better understanding of the groundwater allowing the elimination of well point dewatering. The reduction in anticipated dewatering was also welcomed by UU, as the potential discharge of additional ground water flows containing elevated ammonia levels into the treatment stream was raising concerns. The provision of precast concrete (PCC) piling to control both settlement and risk of flotation was adopted. The adoption of PCC piling also eliminated any risk of contaminated arisings which may have required disposal off-site. The flushing gate system adopted for tank cleaning has very low energy demand when compared with a traditional jet system. This was an important consideration as the site is close to its power supply limit. Contaminated land/remediation At tender stage, several significant ground risks were identified. These were associated with high water table, low strength soils and contamination. The tender design assumed that a significant amount of remediation would be required during placement of the excavated material. Prior to construction commencing, a significant amount of additional Ground Investigation was carried out to better understand the risks around contamination and high-water table. These risks were quantified in a Contaminated Land Risk Assessment, Remediation Strategy and Materials Management Plan (MMP) in accordance with the CL:AIRE Definition of Waste: Development Industry Code of Practice (DoW CoP). Material excavated from within the footprint of the proposed tanks was deposited across 2.9 hectares of land, to the west of the new tanks within the boundary of the wastewater treatment works. Combining this excavated material with that excavated from associated pipe trenches and bulking factor, approximately 24,000m3 of material was deposited. As Preston WwTW is located close to European protected sites, it was essential to ensure that the proposed works did not pose any adverse effects on the local environment, and also presented an opportunity to improve the local habitat. A combination of habitat creation and environmental landscaping was agreed with UU and Natural England. Adoption of the MMP encouraged lower project development costs through reduced works programme time, and by eliminating the need to transport and landfill material, with the associated Landfill Tax. The MMP was successfully submitted to the Environment Agency in July 2017. Civil 3D model showing inlet works modifications - Courtesy of MMB Civil 3D model showing inlet works modifications - Courtesy of MMB Storm tanks The solution called for a dual compartment storm tank with a total storm water storage of 51,000m3. The tank is 155m long by 80m wide, with a maximum depth of 6.6m. After consideration of several alternatives, MMB agreed with UU that the storm tank would feature: A single fill and draw pipeline. Precast concrete piles. An in situ concrete base sloping at 1 in 200 down to a collection channel and sump. Precast concrete walls (Sealwall units supplied by Naylor Concrete). A gated flushing system supplied by Jacopa. The detailed structural design of the storm tanks was carried out by GHD who was appointed as subcontractor to MMB. GHD designed the in situ concrete elements, including the piled base slab, internal dividing wall between two compartments, flushing reservoirs and the interface with the PCC wall units. The design ensured a Class 1 watertight interface between the precast units and the in situ base. The storm tank incorporates an innovative self-cleaning mechanism which involves holding water back in the end flushing reservoirs when draining down the storage tank. A series of gates are then released, flushing the channels of the tank. This system reduces whole life costs by significantly reducing the energy associated with traditional re-suspension pump systems. The structure is supported on 1557 (No.) precast concrete piles driven to a depth of 20m below ground level. There is a perimeter pile cap supporting the PCC walls and a 400mm thick RC concrete base slab. The two compartments are divided by a 600mm thick in situ concrete wall. Civil 3D model showing the connection between the storm return pipework and the existing structure - Courtesy of MMB Civil 3D model showing the connection between the storm return pipework and the existing structure - Courtesy of MMB A design for manufacture and assembly (DfMA) approach was adopted in order to deliver the scheme as efficiently as possible in terms of time, cost, quality and safety. The use of PCC wall panels reduced the risks associated with fixing reinforcement, working at height, working with readymix concrete and also reduced the number of workforce required on site. The external walls are formed of a system of modular precast Sealwall panels which are bolted together and temporarily propped prior to casting them into the in situ poured perimeter ring beam. The ring beam depth varied to increase the height of the wall and achieve the required fall on the base slab. The wall panels are made water tight by a combination of surface sealant and hydrophilic strips at the bolted joint locations. Cross-site pipework A 530m long pipeline was required to transfer screened and de-gritted storm water from the inlet works to the new storm tanks during storm events. When the new storm tanks reach capacity, this pipeline provides 800m3 of additional storage, before the existing storm tanks begin to fill. Once storm flows cease, the same pipeline transfers this storm water to the existing storm return pumping station. The installed pipeline is made up of 1400mm (450m) and 1200mm (80m) diameter glass reinforced plastic (GRP) pipe. Choosing a GRP pipe solution provided a significant materials cost saving, when compared to the alternative ductile iron option. However, the adoption of the GRP solution resulted in a more technically involved installation for the site team. The increased buoyancy of GRP coupled with a high-water table made it necessary to negate flotation. The solution that was adopted utilised a geogrid geotextile as part of the backfilling detail. The geotextile is designed to mobilise additional soil loadings to counteract the flotation force. Surplus excavated material from the pipeline route remained on site, used to landscape around the new storm tanks and associated new access roads. Excavation for pilecap following installation of piles - Ccourtesy of MMB Excavation for pilecap following installation of piles - Ccourtesy of MMB A joint locking system was adopted adjacent to the pipe bends which ensured that few thrust blocks were required; this proved advantageous on a spatially constrained and service congested site. The integrity of the pipeline was proved by pressure testing to 1.5 bar once backfilling ceased. The new pipeline needed to connect to the existing reinforced concrete elevated storm channel and the existing 900mm diameter steel storm return pipeline. A steel swan neck fabrication was utilised to overcome the abrupt change in elevation necessary to connect to the existing storm channel. To form this connection, the existing concrete channel structure required a point of entry as well and an RC soffit to the existing open channel to prevent hydraulic overtopping during operation. Additionally, the channel at this point, required permanently isolating to prevent storm water from reaching the decommissioned 1930s storm tanks. The arrangement and elevation of the existing structure made this feature of the pipeline a challenging build. Careful planning ensured the extensive formwork and access falsework, was in place in good time to adhere to the programme of works. ‘Hot’ (live) tapping was adopted for the connection to the existing storm return pipeline which needed to remain live during the works. The detail at the connection included a 900mm diameter steel gate valve and a 45° bend. This connection was housed on a concrete base more than 4m below ground level. The construction of this installation was further complicated by working within a cofferdam arrangement of limited area that required regular dewatering. Preston Storm Tanks Project: Key Project Participants Project Delivery Principal Contractor: MMB Designers Principal designer: MMB Structural Design of storm tanks: GHD Geotechnical investigation: Geotechnics Ltd Sub-contractors & suppliers Precast concrete piling to storm tank: Aarsleff Ground Engineering Storm tank FRC construction: Stam Construction Inlet screen launder channels and washwater drum screen: Longwood Engineering Storm tank flushing gate system: Jacopa Primary settlement tank electrical installation: Bilfinger SE Inlet works electrical installation & storm tank flushing gate systems integration software: Boultings Ltd Inlet works mechanical and electrical installation works: Franklyn Yates Engineering Storm tank penstocks and actuators: Glenfield Invicta Primary settlement tank scraper bridge refurbishment and inlet screens washwater pipework: Integrated Water Services Supply of inlet screen washwater booster pumps: Northern Pump Supplies PST inlet penstock actuators: Rotork Primary settlement tank automation and storm tank systems integration software: Tata Consultancy Services Inlet works systems integration software: Adsyst Automation Flow to works measurement: RS Hydro Supply of precast concrete wall units: Naylor Readymix concrete supply: Cemex Supply of GRP pipework: Amiantit Supply of GRP pipework: Amiblu Norway AS Inlet works improvements To improve the performance of the inlet works the following interventions have been carried out: Replacement launder channels. Dedicated launder pumps. Automated launder stone traps. High speed actuators to the screen inlet penstocks. New inlet screen washwater system. Filtrate pumping station upgrade. Replacement laser type flow to works flow measurement. The two existing launder channels connecting the four existing escalator screens to the 4 (No.) existing washpactors in duty/standby pairs, have been replaced with four dedicated launders. This, along with ancillary instrumentation and equipment and a re-write of the PLC, HMI and SCADA control software, has simplified the control and operation of the inlet works by dedicating each washpactor to its corresponding screen. The replacement of the existing screen inlet penstock actuators with four high speed actuators, along with some additional control interlocks with the upstream terminal pumping stations, has enabled the inlet works to respond better to the large fluctuation of incoming flow rates. The existing washwater pumping set has been replaced with a new system comprising of a 3mm 2D drum screen, a 500-micron Bollfilter and a variable speed booster pump set. Due to the increase in launder flows, the existing filtrate pumping station has been upsized, including an increase of the wet well capacity, increased capacity duty/standby pumps and associated ancillary instrumentation and equipment. Replacement launder channels - Courtesy of MMB Replacement launder channels - Courtesy of MMB Conclusion Whilst delivering a challenging and complex project, MMB and their subcontractors have worked over 250,000 hours without a RIDDOR reportable incident. By driving for innovation and adoption of a highly collaborative approach, MMB and UU have realised significant CAPEX savings whilst delivering a scheme that meets the Environment Agency commitments and delivering operational improvements. The project has now been successfully handed over to United Utilities Operations staff. The editor and publishers would like to thank Chris Taylor, Technical Manager with MMB, John Littlewood, Project Engineering Manager with United Utilities, and Jonathan Edwards, Site Manager with MMB, for providing the above article for publication.

Wooler Water Treatment Works (WTW) is fed by four boreholes and supplies up to 160m3/hour of potable water to Wooler and surrounding areas, including several tourist and semi-residential holiday parks serving over 5,000 people. Seasonal fluctuation in demand can increase turbidity and increase iron and manganese concentrations in the borehole water, particularly when flows are high, interrupted or varied. The existing treatment facility was reaching the end of its asset life and did not have the treatment stages to remove the turbidity, causing flows to run to waste. Frequent power outages and varied seasonal populations led to regular manual operator intervention and a growing reliance on tankering from other sites to ensure the supply zone remained primed. Background/drivers In 2016, Northumbrian Water (NWG) awarded Mott MacDonald Bentley (MMB) an Investigate and Define contract to review potential solutions to improve treatment at Murton and Wooler WTWs. Following this, in April 2018, NWG issued MMB a NEC3 ECC Option C Design and Construction (D&C) contract to deliver the design, construction, testing and commissioning of the new treatment facilities. Design for Wooler commenced in June 2018, with construction works commencing in May 2020. The main build was completed in April 2021 and water brought into supply following testing and commissioning. The previous treatment site was set to run to waste until turbidity in the borehole water was suitable to be treated further. NWG experienced turbidity spikes on pump start-up and flowrate changes, exacerbated by frequent power outages. This resulted in time consuming, costly operator intervention, and wastage of borehole water to the environment. Disruptions in supply needed quick operator intervention to ensure no impact to the customer, often necessitating tankering to maintain supply. The rural setting of the WTW meant during winter, operators faced increased risk in accessing the site. The new WTW incorporates four large pressure filter vessels which are effective in removing turbidity, iron and manganese at higher levels. The reduction in run to waste occurrences provides a more sustainable use of water abstracted from the aquifer whilst improving water supply security to the Wooler area. Within the investigation phase MMB and NWG decided to relocate the works to a more urban setting to reduce the risk on operators and minimise risk of weather events affecting power supply and communications to the site, both of which are critical to maintaining supply to the local community. This is especially critical at Wooler, as the area benefits from a transient tourist population which puts additional strain on the water supply system. Clockwise from top left - Dechlorination plant, wastewater tanks, chlorine contact tank and treatment building - Courtesy of MMB Clockwise from top left - Dechlorination plant, wastewater tanks, chlorine contact tank and treatment building - Courtesy of MMB Design development The design phase commenced during the latter phases of construction works at the nearby sister site, enabling the design team to capture positive and negative lessons from the construction and client operations team. Over 100 lessons were collated and assigned owners to incorporate into the Wooler design. The results were evident in the programming and sequencing of the project, which halved the workforce on site when compared to Murton. Several design efficiencies were identified that further reduced the construction duration, including, designing out thrust block requirement, simplification of a complex dechlorination system and pre-washing filter media prior to delivery to reduce commissioning and significantly reducing commissioning water wastage. The MMB project team successfully challenged client asset standards which would have required an additional filter, and as such specified filtration by four sand pressure filters. The filters consist of an anthracite cap, sand, and manganese dioxide (MnO2) media. The sand and anthracite layers capture larger solids particles during periods of poorer water quality whilst the MnO2 acts as a catalytic media and further promotes manganese and iron deposition onto the filter media. By removing iron and manganese over a single stage, the project team designed out a secondary treatment stage, saving on TOTEX, carbon and minimising site footprint. The filtration method selected also provides a higher level of robustness, reliability and low operational costs compared with other technologies. The notional solution proposed maintaining use of the borehole pumps to generate sufficient pressure to drive flow through the new treatment plant to the existing service reservoir served by the site. Multiple supply chain interfaces were modelled to proactively reduce snagging - Courtesy of MMB Multiple supply chain interfaces were modelled to proactively reduce snagging - Courtesy of MMB The additional pressure required would require replacement of the borehole pumps and over 4km of mains in serviceable condition. Instead, the pressure head was broken within the site, reducing operation and maintenance risks, and improving site control and resilience through installation of high efficiency booster pumps to supply the network. Pumping of waste flows was minimised through agreeing discharges into the local sewer and surface water network, with dechlorination included for treatment of non-compliant flows. Pumping of drainage flows was also avoided through minimising site access roads, maximising green space and incorporation of SuDS trench and lagoon within the site footprint. Digital delivery was preferred from the onset, and the site location was GPR and laser scanned to produce an accurate 3D model of the current land and subterranean utility infrastructure. This model was developed further with key suppliers and multidisciplinary designers to progress to a full site-wide model of the civil, electrical, mechanical and process elements. The pressure filter, chemical dosing and metalwork suppliers uploaded models of their discrete works packages into the selected Common Data Environment (CDE) BIM360. The packages were incorporated into the overall site model, produced in Revit. This enabled the MMB design team to accurately model surrounding road structures, interconnecting pipework, services and road infrastructure in both Revit and Civil 3D. The 3D model is earmarked for use as a digital twin, to improve asset management and aid with efficiency of the everyday site operation. The site was designed such that all key instrumentation is above ground, but transfer pipework between treatment stages is below ground, giving full access to all valves and dosing points. Through development of the 3D model, operators were able to fully review the site in advance of a spade being struck, leading to changes to further mitigate operational and site hazards. Rethinking of the operating pressures has reduced operator risk within the building and the new process utilises more resilient process units than previously, incorporating a sophisticated control philosophy which minimises unintended shutdowns and enables restart at the push of a button, rather than a complex series of manual valve operations. Treatment process units being installed after off-site manufacture and testing - Courtesy of MMB Treatment process units being installed after off-site manufacture and testing - Courtesy of MMB Off-site manufacture opportunities were identified to minimise personnel operating on a relatively small site. Chemical dosing facilities were manufactured and tested within kiosks and delivered to site as plug-and-play elements of the process, improving quality control through factory testing and commissioning. Vertical pressure filter units, associated pipework, and metalwork access gantry were all pre-assembled and tested prior to final offload and assembly on site. This approach was taken for the complex manifold pipework weaving between and connecting the site process plant. The 3D model was utilised by stainless steel pipework fabricators to design and detail the pipework for accurate off-site manufacture, eradicating cutting on site. Building on lessons learned from Murton, the contact tank design was changed from in-situ build to a semi pre-cast assembly, reducing the on-site build programme of the structure and reducing the trades and temporary works required. Covid19 hampered the ability to carry out informal meetings, though the digital delivery of the project meant that communication was not impacted during the critical latter stages of the design. The 3D model was utilised to facilitate key coordination meetings including ALM and HAZOP reviews, helping both MMB and NWG communicate proposals to non-technical colleagues. Enabling NWG to utilise the same model during design aided with design acceptances and operational reviews of proposed site processes. Fire and hazard reviews were carried out utilising third person perspective within the model. The integrated use of BIM360 brought more of the supply chain into the collaborative solution development allowing all stakeholders to visualise the final product in a way not possible with traditional 2D drawings. This allowed for greater clash detection prior to construction enabling designs to be tweaked at low cost in the office, reducing standing time on site. Key interfaces between each mechanical supplier were digitally inspected in advance of installation, reducing the likelihood of common avoidable defects in major treatment projects. Complex subterranean service network required careful clash detection - Courtesy of MMB Complex subterranean service network required careful clash detection - Courtesy of MMB Wooler WTW: Supply chain - key participants Design & build: MMB Hydraulic modelling: Mott MacDonald Ground investigation: Dunelm Geotechnical & Environmental Sheet piling: Van Elle Precast concrete: FLI Precast Solutions Blockwork: Gallaway Construction Structural steelwork design & build: Glendale Engineering (Milfield) Ltd Metalwork: JHT Fabrications Ltd Electrical/cabling: Dongard Mechanical & Electrical Ltd Scaffolding: Ingleford Scaffolding Ltd Shoring/temporary works: MGF Ltd Pressure vessels: ACWA Services Surge vessels: Quantum Engineering Developments Chemical dosing design & supply: Sheers Ltd Pumps: Grundfos Static mixers: Statiflo Intenational Major valves: AVK UK Ltd Steel pipework fabrication: JBF Group MCC: CEMA Ltd Systems integration: IDEC Technical Services Generator: WB Power Services Ltd Security systems: 2020 Vision Systems Ltd Roller shutter doors: Ascot Doors Ltd Security doors: Bradbury Group Construction Working within a D&C environment, constructability is considered at every stage. The Wooler construction team were identified early in the project, with regular reviews held to discuss the design, its buildability and associated temporary works requirements. These reviews, along with similar client meetings, were held to invite challenge and give the whole project team an opportunity to influence the design; reducing and controlling risk when total mitigation was not possible. Excavators with in-built GPS and intelligent machine control utilised the digital terrain model to excavate within 6mm accuracy, reducing over dig but also bringing wider programme and health and safety benefits. The programme was sequenced using the 3D model, with the order of build determined by service and structure depth. All below ground structures and pipework were set out utilising the model which, alongside excavation accuracy, ensured pipes were laid accurately with no clashes or diversions incurred despite the complex subterranean service network required. (left) Precise installation of below ground infrastructure and slab penetrations prior to main slab pour and (right) treatment building slab cast prior to superstructure installation - Courtesy of MMB (left) Precise installation of below ground infrastructure and slab penetrations prior to main slab pour and (right) treatment building slab cast prior to superstructure installation - Courtesy of MMB The accuracy minimised soil disposal resulting from over dig and designing out thrust blocks through modifications to the pipework specification further reduced excavation. Under licensed exemptions, 1000t of excavated soils were diverted to local agricultural projects and 1000t of compound stone was re-purposed for an off-site access road. Similarly, 1000t of clay arisings from a nearby project were utilised within the Wooler site. Utilising CLIP (Collaborative Lean Improvement Programming) planning and careful sequencing halved the number of people working on site, compared to the sister project at Murton WTW, minimising the number of long journeys associated with rural working. Local suppliers and local staff were embedded within the delivery team, further reducing the embodied carbon impact. Accurate modelling of the proposal in advance of construction minimised material wastage in cut to suit elements of pipework, steelwork, and reinforcement. MMB utilised the local supply chain as much as possible. Major successes were brought about through engaging with a heavy steel fabricator based within a quarter of a mile of the site and an electrical installation contractor based in Northumberland, rather than usual supply chain partners. Utilising more local suppliers meant that the level of service and quality provided was high, with benefits of carbon reductions and reduced transport of major steel elements along busy rural single carriageways. Through inviting NWG, stakeholders and supply chain to CLIP planning sessions, MMB identified programme savings for all parties through sequencing of site tasks and identifying mutually beneficial opportunities, such as sharing plant to reduce vehicles on site. For example, bringing electrical and major steel subcontractors together identified opportunities for cable containment hangers to be installed within the fabrication works at no additional cost, reducing work at height risk and task time for cable installation teams. Construction sequencing, temporary works and site aesthetic were all modified to minimise impact on the local community. Installation of the permanent access point to the site was prioritised in the programme to minimise traffic management on Berwick Road, a main artery for the village. Moving treatment processes inside the main building negated the requirement for additional security fencing and the building itself was designed to resemble agricultural buildings in the area. The permanent site footprint was minimised as much as possible but in doing so, a larger temporary compound area was necessary. The project team worked with local landowners to identify the best location for the temporary works to reduce this impact, and temporary laydown areas were returned for use as soon as sequencing allowed. Precast contact tank during construction - Courtesy of MMB Precast contact tank during construction - Courtesy of MMB Health & Safety MMB’s positive safety culture was evidenced throughout construction, where in over 75,000 hours worked, over 5,500 proactive health and safety and environmental incidents were reported, resulting in no lost-time or reportable injuries. An added complication to this project has been the Covid19 pandemic, during which the site remained operational and avoided closure. The project was sequenced to minimise the number of people working on the site at any time and method statements were developed to ensure as much work as possible could be completed whilst maintaining strict social distancing. Conclusion Wooler WTW was built as part of a two-project batch. The two sites were built sequentially, which enabled MMB to derive multiple lessons from the Murton project and deliver a new greenfield treatment works within the client’s budget and with minimal impact to the local community. MMB’s long-term collaborative relationship with NWG, combined with the use of trusted local suppliers, off-site build techniques and regular planning sessions enabled multiple sequencing and material efficiencies to be realised, further driving down the carbon impact of the project. Through digital delivery, a significant number of supplier interfaces were carefully managed, avoiding the delays and defects commonly associated with multidisciplinary projects. The editor and publishers would like to thank Jamie Boswell, Design Manager with Mott MacDonald Bentley, for providing the above article for publication. Model of multiple treatment processes within the main building - Courtesy of MMB Model of multiple treatment processes within the main building - Courtesy of MMB

The Burnley integrated catchment scheme is one of United Utilities' (UU) largest AMP7 projects with a value of £77m. The project is being delivered by UU’s construction delivery partner (CDP) framework by Advance-plus, a joint venture between MWH Treatment, J Murphy & Sons (JMS) and Stantec UK. The project commenced in 2020 and through two previous articles, UU and Advance-plus have shared the project background, the story of developing the solution and design, and commencing the build. In this year’s article, the project delivery team is pleased to provide an update on the construction progress and a look at the journey ahead as the project remains on course to achieve the December 2024 regulatory completion date. A summary of the project requirements and the integrated catchment solution scope The integrated solution scheme requirement is River Water Quality Improvement for the Water Framework Directive (WFD) driver identified in the Water Industry National Environmental Programme 3 (WINEP3) to achieve a ‘good status’ in the defined reaches of Pendle Water and the River Calder. To meet this, the treatment capability at Burnley Wastewater Treatment Works (WwTW) is to be enhanced to achieve compliance with the new enhanced, treated effluent permit standards, and management of storm discharges in the defined reaches, to achieve a compliance with the WFD 99%ile wet weather intermittent standards. The project also includes the U_MON3 spill monitoring and U_MON4 flow monitoring drivers. Through complex river water quality and network modelling, the lowest whole life cost integrated catchment solution was determined and developed. Four sites make up the integrated catchment solution which are all interdependent in delivering a total of ten regulatory outputs. ASP under construction - Courtesy of United Utilities ASP under construction - Courtesy of United Utilities Burnley WwTW Burnley WwTW serves a domestic population equivalent (PE) of 107,115 plus trade load. The site is undergoing a significant upgrade with the scope comprising design, construction, and commissioning of: New 12,000m3 detention tank with associated pumping station. New additional primary settlement tank (PST). New 1300 l/s inter-stage pumping station. New activated sludge plant (ASP) with BioMag® process. The BioMag® System enhances conventional biological wastewater treatment by using magnetite (Fe3O4) to ballast floc allowing an increase in mixed liquor suspended solids (MLSS) in the ASP and enhanced performance in the final settlement tanks (FSTs). Refurbishment of existing final settlement tanks. New surplus activated sludge (SAS) thickening process. New ferric and caustic dosing plants. Associated motor control centres (MCCs), SCADA upgrade, and power upgrade. Pipework The last year has seen great strides being made across the site and various process areas, with major civils structures constructed and taking shape. The very constrained nature of the site, existing processes and services, and the need to lay many kilometres of small and large diameter underground pipework has proven to be a major constructability challenge. Most of the pipework installation has been self-delivered by J Murphy & Sons with Saint Gobain PAM being the main supplier of the pipework and fittings. Detention tank The new detention tank, has been constructed by A-Consult Ltd using 64 precast concrete panels, standing 10.4m high. The panels were precast in their factory before being transported to site for erection and subsequent post tensioning. Utilising this construction technique, with design for manufacture and assembly (DfMA) brings benefits in terms of quality, time and safety. The tank has successfully passed its water test and is currently being drained. The feed pumping station has been constructed and the mechanical installation of pumps, mixers and pipework is now in progress. Detention tank on water test - Courtesy of United Utilities Detention tank on water test - Courtesy of United Utilities Primary settlement tank The new primary settlement tank (PST) civils construction is also complete, again undertaken by A-Consult Ltd using the precast concrete panel method of construction. It has also successfully passed its water test. Mechanical installation by EPS Water is now in progress on the ‘H’ frame steel structure which will support the scraper bridge. The design of the PST incorporates a fixed bridge arrangement with rotating scrapers beneath. This arrangement is necessary as the PST will eventually be covered with a GRP roof for odour mitigation. The odour control fans, ductwork and vent stack are scheduled to be installed in December. PST4 and ASP lane 1 on water test - Courtesy of United Utilities PST4 and ASP lane 1 on water test - Courtesy of United Utilities Interstage pumping station Due to the topography and hydraulic levels across the site, a new interstage pumping station (IPS) is required to pump the effluent leaving the four PSTs up to the new activated sludge plant (ASP) distribution chamber. Civils FRC works are being undertaken by STAM Construction Ltd and contain 94 tonnes of rebar and 900m3 of in situ poured concrete. The pumping station structure is complete and has undergone successful water testing. The internal benching is complete and the next activities planned for the coming period will be the mechanical installation of the pumps and pipework. As the pumping station is vital to keep all flows passing through the treatment process, a standby generator will also be installed. The IPS is a two compartment design to facilitate future maintenance activities preventing the need to take it completely out of service. The new pumps have been supplied by Xylem Water Solutions who have supported the designers in providing efficient selections for the large submersible pumps and optimising the layouts of the pump chambers. Activated sludge plant The ASP distribution chamber is currently being constructed with all four concrete walls having now been poured. These are curing and the structure will undergo a water test in September 2023. ASP constructed and water tested - Courtesy of United Utilities ASP constructed and water tested - Courtesy of United Utilities In constructing the new ASP, STAM Construction Ltd have installed 650 tonnes of rebar and poured 4500m3 of concrete. The overall size of the ASP is 48m x 48m x 6.6m deep, has a capacity of 14,500m3 and comprises four lanes. Civils construction of the ASP is complete and fully water-tested with the mechanical installation of the internal pipework, aeration grids, diffusers and access platforms and walkways taking place over the next few months. Suprafilt Ltd will be supplying and installing the internal pipework, aeration grids and diffusers. Mechanical installation of the pump stations and access steelwork etc will be undertaken by Fluid Sealing & Engineering (FSE). BioMag® The Evoqua Water Technologies detail design for the new BioMag® process has been finalised and the building layout confirmed. The main equipment including four Magdrums and two shear mills, process tanks, silo and pumps, which have been manufactured and are ready for delivery to site when required. The BioMag® building is currently under construction by Gallaway Construction. The steel frame has been erected and the gantry crane and roof cladding have been installed. External wall cladding is in progress, after which attention will turn to the internal fit-out and installation of the BioMag® equipment. BioMag® building being erected - Courtesy of United Utilities BioMag® building being erected - Courtesy of United Utilities Final settlement tanks (FST) There are four existing final settlement tanks which required refurbishing to ensure adequate performance and asset life are achieved. The scope includes civils refurbishment of the tank walls which involves cutting approximately 300mm from the top of the walls before installing new reinforcement and re-casting concrete to the required coping levels. Cutting works is being undertaken by Holemasters and FRC works self-delivered by JMS. The mechanical and electrical work is being delivered by Jacopa and comprises refurbishment of the bridge, scraper assemblies, and other ancillary equipment. Three of the four FSTs have now been refurbished with the final one due to be undertaken towards the end of the year. Surplus activated sludge (SAS) thickening Civils works has been ongoing in the SAS thickening process area for the last couple of months with the storage tank, drum thickener, poly plant and kiosk bases all constructed. Underground services, ducts and pipework have also been installed and tested. The filtrate return pumping station construction is in progress with the mechanical installation due to follow on. Chemical dosing The new ferric and caustic dosing plants comprise storage tanks, dosing rigs and dosing pipelines, all of which have been designed and well progressed in manufacture. These are being supplied by NPS Engineering Group. A new chemical delivery facility will also be provided with civils construction in this area commencing towards the end of the year and installation of the new dosing plants taking place early 2024. 3D model of chemical dosing area - Courtesy of United Utilities 3D model of chemical dosing area - Courtesy of United Utilities HV works A new, uprated HV cable has been installed from the off-site substation to the wastewater treatment works, a length of approximately 900m, passing through a number of fields and 3rd party land. Motor control centres (MCCs) To control all the new assets a number of new MCCs housed within kiosks are required around the site, along with a new site-wide SCADA system. The MCCs are all in various stages of manufacture and factory testing. The electrical installation and system integration works, including dry testing, will be undertaken in phases over a period of months as the programme for each of the new process areas dictates. The MCCs are being built by Technical Control Systems Ltd, electrical installation will be by PICOW Engineering Group and system integration by Tata Consultancy Services. Looking forward to commissioning Commissioning of the new treatment process, and transitioning from the old process in a controlled staged approach, will be complex. The existing treatment stream and process compliance cannot be put at risk or compromised and months of hard work and planning for commissioning has already taken place. Wet commissioning is due to start in April 2024, gradually increasing flows into the new treatment process over several months while the new biological process builds up and matures to a point where the improved treatment standards are being met. The forecast project in use date is October 2024. Aphex construction planning software map view - Courtesy of United Utilities Aphex construction planning software map view - Courtesy of United Utilities Burnley WwTW Catchment Strategy: Supply chain - key participants Construction Delivery Partner: Advance-plus JV MWH Treatment (Advance-plus jv) J Murphy & Sons (Advance-plus jv) Stantec UK (Advance-plus jv) CFD modelling: CER Technologies Ltd GPR & topo surveys: Atlantic Geomatics (UK) Ltd Flood risk assessment: Ambiental Environmental Assessment Ltd Physical modelling: Hydrotec Consultants Ltd Dewatering design: OGI Groundwater Specialists Concrete construction: STAM Construction Concrete supply: CEMEX UK Pump station shaft: EJ Kelly Sheet piling: Sheet Piling (UK) Ltd PCC driven piling: Van Elle Concrete cutting: Holemasters Temporary works/shoring: MGF Ltd Precast post tensioned tanks: A-Consult Ltd Earthworks: D Morgan plc Blower building: Saredon Steel Buildings Ltd Access metalwork: Tushingham Steel Fabricators BioMag process: Evoqua Water Technologies BioMag building: Gallaway Construction Ltd BioMag mechanical installation: Alpha Plus Ltd Ventilation: Air Technology Systems Ltd Pumping station mechanical installation: Fluid Sealing & Engineering (FSE) HV cable installation: Smith Brothers Ltd Transformers: Winder Power Electrical installation: PICOW Engineering Group MCCs: Technical Control Systems Ltd Systems integration: Tata Consultancy Services Standby generators: DTGen SAS glass coated steel tank: Stortec Engineering Ltd PST fixed scraper bridge: EPS Water Epoxy coated carbon steel pipework & wall starters: Freeflow Pipesystems Ltd Dosing systems: NPS Engineering Group SAS drum thickeners: Huber Technology Odour control system: Air-Water Treatments Ltd PST odour covers: Corporate Engineering Ductile iron pipework: Saint Gobain PAM Ductile iron pipework: Electrosteel Castings FST scraper bridge refurbishment: Jacopa Ltd Blowers: Sulzer Water & Wastewater Aeration system: Suprafilt Ltd SAS tank air mixing system: Utile Engineering Submersible pumps: Xylem Water Solutions Valves: AVK UK Ltd Kiosks: Industrial GRP Lindred Road CSO (PEN0056) Work at this existing combined sewer overflow (CSO) site comprises the construction of an online 1,950m3 detention tank which will hold stormwater during times of heavy rainfall, reducing discharges to the watercourse. New pumps within the tank will return the effluent to the sewer for onward treatment at Burnley WwTW. The 15m diameter x 20m deep detention tank, is of segmental shaft construction and is located within the very busy and congested Lomeshaye Industrial Estate in Nelson, and was constructed by Joseph Gallagher Ltd. This was a highly challenging build within a car park of one of the local businesses and an enormous amount of planning and stakeholder management has been required. Lindred Road detention tank during construction - Courtesy of United Utilities Lindred Road detention tank during construction - Courtesy of United Utilities Work started on site in July 2022, with the first phase involving the diversion of numerous services, including gas, fibre, BT, water and power, to clear the area for the tank construction. Enabling works to provide safe access routes, segregation, and procurement of alternative car parking for the impacted business employees was also required before the main construction work could commence. Ground was broken in August 2022 with the tank construction continuing through to December 2022 when full depth was reached. Construction of the pump sumps, inlet channel and complex benching arrangement followed. The spring months of 2023 saw the mechanical works inside the tank take place with the installation of the pumps, pipework and access ladders and platforms. Once the internal works were complete, the roof beams were installed and the roof slabs placed on in May 2023. The inlet and outlet pipework for the tank has now been installed, including associated manholes and chambers. To facilitate the connection of the 1200mm inlet pipe into the existing CSO chamber, a complex timber heading arrangement needed to be constructed in order to access beneath, and protect a myriad of services crossing the vicinity. All buried pipework, chambers and ducts etc have been completed and reinstatement of the area is in progress. The civils and pipework has been undertaken by SGC Civil Engineering Ltd and the mechanical works by Fluid Sealing & Engineering (FSE). A new motor control centre and power supply is being installed for this facility. The new control kiosk was delivered and installed in July 2023 and the electrical installation is currently ongoing with the new power supply due to be energised in October. Testing and commissioning is scheduled to start in November, with the site achieving project in use in February 2024. Lindred Road Detention Tank: Supply chain - key participants Civil design detention tank: COWI UK Ltd Detention tank shaft: Joseph Gallagher Ltd Civils & pipework: SGC Civil engineering Ltd Mechanical works: Fluid Sealing & Engineering (FSE) Precast roof sections: Macrete Ireland Ltd Precast shaft segments: FP McCann MCCs: Technical Control Systems Ltd Kiosks: Industrial GRP Lindred Road: Aerial view of detention tank - Courtesy of United Utilities Lindred Road: Aerial view of detention tank - Courtesy of United Utilities Altham Outfall Fennyfold CSO (BUR0026) This existing CSO site is located in Padiham, near Burnley, and is part of the sewer network that transfers flows to Hyndburn WwTW for treatment. The solution here is to construct a new chamber over the downstream sewer, and install a new real time controlled actuated penstock valve that will regulate and optimise flows passed forward to Hyndburn, whilst reducing spills from the existing CSO. A new control kiosk and power supply are also required. This new facility is situated within an environmental and stakeholder sensitive area, adjacent to a number of allotments and the River Calder. The parcel of land required for the new kiosk and chamber has been procured and a new access track for future operation and maintenance, as well as the build, will be required and constructed. The detailed design is complete and some enabling works to set up site have been undertaken. For the main construction activity, a complex temporary works arrangement will be required, with large scale over-pumping, to carry out the works on the live sewer. Plans are currently being made to install temporary isolation rails and plates during a suitable dry weather period in preparation. This site is scheduled to be complete in spring 2024. Hyndburn WwTW To cater for the change in flows being presented at Hyndburn WwTW through the inlet sewer from the BUR26 catchment, the solution modelling has identified that by reducing the time it takes for the storm tanks to be returned into the treatment stream would ensure that the river water quality objectives could be achieved. The existing storm return pumping station is made up of fixed speed pumps operating at a duty of 100 l/s. A new variable speed storm return pumping station will be constructed which will be capable of returning flows across the range of 30 l/s to 330 l/s. This means that the contents of the storm tanks can be returned much quicker after a storm subsides. Hyndburn WwTW - 3D model of storm return pumping station - Courtesy of United Utilities Hyndburn WwTW - 3D model of storm return pumping station - Courtesy of United Utilities A new below-ground wet well type pumping station will be constructed with three high-flow pumps and two low-flow pumps which provides a more flexible and efficient system with greater turn down capability. A new single rising main will return the storm flows back to the head of the treatment works. A new kiosk and motor control centre will also be installed. Planning permissions are in place and all pre-start surveys and investigations have been completed. Detailed design is nearing completion and the site has just been established. Construction is due to start in earnest in September on the new pumping station excavation. The winter months will see the civils works progress, with mechanical and electrical works due to start in spring. The project in use is forecast for July 2024. The digital toolbox 4D digital rehearsals which link the 3D model to the programme have been used extensively by the site team to validate the constructability and sequencing of the works. Visualisation allows all parties to truly understand the construction sequence, interfaces and interdependencies which is relevant on such a congested work area with multiple subcontractors operating in close proximity. They have helped to identify high risk activities and plan mitigation measures. They also help provide programme and cost certainty and facilitate stakeholder engagement. Over the last year Aphex, a powerful construction planning software tool which enables the delivery teams to better plan and work together has been introduced. This has been used for short term, look-ahead planning, which is linked to, and aligned with the master schedule in P6. It has also enabled the construction teams to control the build, assign ownership, communicate and track plans on a daily basis. Aphex construction planning software Gantt chart - Courtesy of United Utilities Aphex construction planning software Gantt chart - Courtesy of United Utilities Challenges and collaboration A large and complex project of this type, across several sites, brings enormous and numerous challenges. These include health and safety management of large scale, complex construction in constrained working areas, on live operational sites and in 3rd party and public areas, while also working in environmentally sensitive areas and requiring engagement and interfacing with customers. Successful delivery would not happen without true collaboration. From the outset of the project we delivered a team development programme and established a co-located office which has proven to be invaluable in creating a great culture and an open and collaborative working environment over the last three years. Challenges and emerging risks and issues are dealt with almost on a daily basis as a team. The project teams continually work together to ensure that delivery stays on track, the highest standards are maintained and everyone goes home safe and well. The editor and publishers would like to thank Tony Elliott, Senior Capital Project Manager with United Utilities, and Simon Meredith, Senior Project Manager with Advance Plus, for providing the above article for publication.

Northern Ireland Water’s Cushendall Water Pumping Station (WPS) is housed on the outer perimeter of Dundonnell Water Treatment Works (WTW) situated on the outskirts of Cargan village in the middle of County Antrim. The WPS solely supplies Parkmore Service Reservoir (SR) with potable drinking water, which in turn gravity feeds three other downstream SRs (Knockans, Mullarts and Knockenny), which provide for the surrounding Glen’s of Antrim district. Parkmore SR has a capacity of 1.3 ML suppling a population equivalent of approximately 2000 with an average day demand in peak week (ADPW) of 17.6 l/s. The existing trunk main The Cushendall Water Pumping Station to Parkmore Service Reservoir Trunk Main was constructed back in the 1970s using 6” PVC pipeline across bog land on mountainous terrain outside Cargan village. This has posed operational problems over the years when locating and repairing any leakages or bursts. Repair machinery has become stuck and unable to navigate the poor ground conditions raising access issues and Health & Safety concerns for staff and operatives attending repair works. Some bursts in the off-road pipeline have caused expensive tankering operations to keep the ~2000 customers with a reliable supply of potable drinking water to the villages of Cushendall, Cushendun and Glenariff. In addition, the existing Cushendall WPS has been difficult to maintain due to the age of the surge vessel, panels and pumps. Project scope NI Water, as part of the IF105 Integrated Partnerships Framework, identified the need to relocate the Cushendall WPS and associated trunk main due to the ongoing operational problems and supply outages. The new scheme included the following scope: A new modular, prefabricated, modular, plug and play water pumping station located in the verge close to a picnic area off the Glenravel Road, approximately 0.5km south of Cargan Village, Co. Antrim. Connection to the existing 18” trunk main in the same picnic area, and approximately 400m of new suction main to deliver water to the new pumping station. Approximately 2km of new 225mm HDPE rising main to deliver water to Parkmore SR installed in the carriageway for improved access. Alternative connections to live tanks at Parkmore SR (non-siphoning), including baffle curtain works and the addition of a 200mm bypass and meter. Civil and MEICA abandonment works of existing Cushendall WPS, and re-tapping the existing chlorine residual pump. Dual lay pipework inside steel sleeves - Courtesy of WSP Dual lay pipework inside steel sleeves - Courtesy of WSP Detailed design and engineering challenges Following ECI works in October 2021 by the Farrans/Glan Agua Joint Venture under a NEC4 option ‘A’ contract, engineering designs were undertaken comprising of a range of elements including: Proposed trunk main route, longitudinal sections, and connection details. Scheme plans with details on bridge crossing and new water pumping station location. Reinforced concrete slab drainage and ducting detail for modular pumping station. Surge analysis report and proposals. Hydraulic assessment of the new trunk main with total head loss, average flow, and peak flow information. From these reports it was concluded that surge could occur when the pump flow increased or decreased to suit changing water demands or uncontrolled sudden pump failure. From this the WPS was designed with a 500-litre bladder type surge vessel in accordance with the selected 38Kw pumps chosen for a 35 l/s and 7 bar charge arrangement. The rising main was designed with six air valves to aid high/low pressure spikes or transients during operation. The hydraulic analysis of the new rising main from the picnic area to Parkmore SR, using the average day demand in peak week (ADPW) of 17.7l/s, calculated a total head loss average flow of 1.10m and peak flow 3.09m for the total 4.2km of the 225mm HPPE pipeline. Construction The construction contract was awarded under NEC4 Option ‘C’ Target Cost Contract to Farrans/Glan Agua JV. Construction began in December 2022 and took place over a 14-month period at a total cost of £1.3m. The scheme was situated in an Area of Outstanding Natural beauty, this brought its own unique constraints and limitations. Due to ground conditions, opencut excavations was the method of installing the 2km of 225mm HPPE pipe under a DFI Roads approved lane closure using a rolling traffic light system operated and maintained by traffic management company, McVeigh Contracts Ltd. (top left) traffic management barriers, (bottom left) notice of works and lane closure for pipeline installation and (right) pipeline track excavation - Courtesy of WSP (top left) traffic management barriers, (bottom left) notice of works and lane closure for pipeline installation and (right) pipeline track excavation - Courtesy of WSP Bridge crossing Following trail holes and liaison with DFI Roads at ECI stage, two sections of 180mm HPPE pipework were installed inside 250mm steel sleeves and C30 concrete and steel mats used for protection over the span of the 35m bridge structure. A reduced road cover level of 700mm was agreed and approved with DFI Roads to ensure the structural integrity of the underside of the bridge remained unchanged. Parkmore Service Reservoir works In tandem with the construction of the pipeline, a specialised company Waterworx Ltd carried out the alteration works to the live Parkmore SR. Each cell was shut off and drained individually to aid the installation of the inlet pipework and repositioning/installation of the new baffle curtains. All of the SR works were undertaking in close liaison with NI Water Operations who ensured stringent drain down and sampling timelines to ensure continuous water supply the local area. (left) the existing baffle curtain and (right) new anti-siphon inlet pipework and baffle curtain at Parkmore Service Reservoir - Courtesy of WSP (left) the existing baffle curtain and (right) new anti-siphon inlet pipework and baffle curtain at Parkmore Service Reservoir - Courtesy of WSP Modular pumping station The new modular ‘plug and play’ WPS included the following elements: Pumping system and associated ancillaries. Control panels. Telemetry. Surge suppression. Building services. The kiosk and skid base of modular pumping station was supplied by Morgan Marine Ltd. The assembly of the mechanical and electrical items were completed at Profitec Solutions’ headquarters in Cookstown. Electrical switchgear was built into the kiosk to facilitate an external portable generator in the event of mains supply failure. Following a factory acceptance test, the modular WPS was delivered to site in November 2022 and craned into position on top of the 450mm reinforced concrete base slab. For the inlet supply to the WPS an under-pressure Tee was installed onto a live existing 450mm cast iron trunk main, this allowed for seamless transfer to the new section of trunk main without any disruption to current trunk main supply in the district. Parkmore Water Pumping Station & Trunk Main: Supply chain - key participants Delivery contractor:  Farrans/Glan Agua JV Design/project management: WSP Civil Design: Jacobs Design Main Contractor (Civils): Farrans Main Contractor (M&E): Glan Agua Civil team: McCormick Contracts Ltd Electrical works: Profitec Solutions Traffic Management: McVeigh Contracts Ltd Kiosk for new WPS: Morgan Marine Ltd Pumps: Grundfos Under-pressure tee connection: Waterworx Ltd Quarry products & reinstatement: Northstone Materials Ltd HDPE pipe: APP Fusion Group WPS automatic control (PLCs & HMI): Mitsubishi Mechanical, electrical and Instrumentation works The Parkmore WPS consists of two Grundfos 38 KW CR125 booster pumps working on a duty/standby regime which can be controlled manually or automatically by way of variable speed drives. The duty/standby system is set to switch over after each pump stop its programmed cycle. (left) The existing Cushendall WPS and (right) the new Grundfos pumps and inlet/outlet pipework - Courtesy of WSP (left) The existing Cushendall WPS and (right) the new Grundfos pumps and inlet/outlet pipework - Courtesy of WSP The two modes of control available are the primary, level-based control, and the secondary, pump fixed speed mode control. The chosen method by the client is the level-based method, remotely controlled on Telemweb with agreed low and high Parkmore Service Reservoir set-point levels (pumps on at 2.2m and off at 2.8m). The WPS automatic control is achieved using a Mitsubishi iQ-R series Programmable Logic Controller (PLC) system attached to a 12” Mitsubishi GOT Human Machine Interface (HMI). The PLC communicates status/alarms/events and exchanges set-points between the PLC and the telemetry talus unit via Modbus RS232. Critical status, alarms and controls are hardwired to/from the telemetry talus unit. The HMI provides information to the MCC for pumps 1&2 with the following list of options for NIW operatives to manually operate inside the WPS: Plant data. Plant mimics. System screen. Control system settings. I/O test pages. Trends and alarms. (Left) HMI screen and (right) Parkmore Dungonnell WPS - Courtesy of WSP (Left) HMI screen and (right) Parkmore Dungonnell WPS - Courtesy of WSP Project summary Commissioning of the new pumping station began in early January 2023 and the existing pumps at Cushendall Pumping Station were turned off, allowing the 28 days commissioning period to begin. Following a successful testing period and training of NI Water Operatives, the new Parkmore Pumping Station is solely suppling the strategically important Parkmore Service Reservoir regularly during the day. The redundant Cushendall WPS has been electrically isolated and associated pipework has been sealed and capped off. To date the new pumping station has supplied over 60,000m3 of clean drinking water to Parkmore SR and has proven to be a resilient and reliable trunk main asset to NI Water. The editor and publishers would like to thank James Gaston, Project Manager with WSP, for providing the above article for publication.

Guildford Borough Council (GBC) are progressing with the development of approximately 41 hectares of brownfield land located along the west bank of the River Wey as it runs through central Guildford and north through Slyfield Industrial Estate. Guildford Sewage Treatment Works (STW) lies within this land and requires relocation in order to enable the development to proceed. This relocation forms a critical part of the Slyfield Area Regeneration Project, and will allow the delivery of up to 1,550 new homes, partially on land occupied by the existing STW, to enable local housing needs to be met. The new sewage treatment works will be built to the north of Slyfield Industrial Estate on land that has been used for quarrying, and in turn used as a landfill site, and is currently largely unused. In addition to the construction of a new works, relocation of the works to this location will require the construction of a new transfer tunnel to divert existing incoming flows to the new site, and the construction of a new outfall to the River Wey. The existing STW must also be decommissioned to enable use by the Weyside Urban Village (WUV) Development. Design flows The new Guildford STW is designed for a population equivalent (PE) of 125,300, with room to expand the site in the future. Design criteriaDry weather flow (DWF)Average flowFlow to full treatment (FtFT)IPS peak capacity Flow rate322 l/s368 l/s746 l/s2,250 l/s Location of new works The site was formerly quarried for sand and gravel during the 1960s and 1970s, with the resultant voids filled with waste materials progressively moving from west to east (i.e., towards the River Wey), which continued until the late 1980s. There is no record relating to the exact nature of the fill materials. The site was understood to have taken household and commercial wastes, but not special or difficult wastes. Following this, the site has remained vacant and undeveloped. (left) Location of new sewage treatment works and tunnel route and (right) Slyfield Regeneration Project area - Courtesy of Adams Hendry (left) Location of new sewage treatment works and tunnel route and (right) Slyfield Regeneration Project area - Courtesy of Adams Hendry Transfer tunnel The STW transfer tunnel will consist of a 1.4km long, 1500mm internal diameter, 1780mm outer diameter tunnel, made of precast concrete pipe, which will be installed by pipejacking (microtunnelling) method. Six shafts are required to facilitate its construction and will serve as temporary launch and reception shafts. Network modelling by Arcadis verified the designed flow velocities remain self-cleansing and provide for the flow rates required. A geotechnical interpretive report has been prepared in review of the ground conditions for the scheme as whole, and to ascertain suitability for shaft sinking and tunnelling. The principal geological stratification for the site consists of Made Ground overlain principally with River Terrace Deposits, with sections of overlapping Alluvium, overlaying the solid geology of firm to very stiff clay of the London Clay Formation (LCF). The selected method of microtunnelling was chosen as it allows long pipeline sections to built, and its suitability to the ground conditions within LCF at Guildford, while limiting the exposure to personnel to underground works, against traditional methods. The microtunnelling is operated from a central control cabin at ground level, and only limited personnel access into the tunnel is required to service the microtunnel boring machine during construction. A ground movement assessment has been prepared and modelled using XDisp software by Oasys. The analysis constitutive model is based on the O’Riley & New method. The method predicts ground movements resulting from ground loss which produces strain of the soil within the influence zone, and projects the settlement in a gaussian distribution curve. Ground improvement & remediation The project team has consolidated decades of site investigation data into a unified format and 3D model. The process involves first combining data within OpenGround software and applying scripted translation to a common description - for example having all London Clay called ‘London Clay’, rather than ‘LC’ or ‘Clay’. RIC 1 and 2 pass areas - Courtesy of BAM Enpure Ltd JV RIC 1 and 2 pass areas - Courtesy of BAM Enpure Ltd JV This combined dataset is then used in Leapfrog 3D geological modelling software, which applies intelligent interpolations, and highlights anomalies that can be quickly assessed and removed. The resultant 3D model has then been used to enhance communication in the engineering AutoDesk BIM 360 federated models, and in the proprietary Arcadis SmartAtlas GIS viewer. Rapid Impact Compaction (RIC) is a method of imparting energy to the ground using a repeated but relatively short drop-weight, where a base plate (or “puck”) is in constant contact with the ground. RIC is preferred over a larger drop-weight technique due to its more progressive and less disturbing impact on the ground it is being used on. The method is also faster and uses smaller scale setups. A challenge for the RIC method was whether the energy it imparts is sufficient to densify the ground, versus other higher energy drop-weight methods. A trial was deemed necessary to demonstrate the suitability of this method. RIC is proposed to be applied over the majority of the site with an expected densification of landfill down to approximately 4.5m. Areas where assets will not be supported on driven full depth piles will undertake a second pass of the RIC method, reducing the long-term settlement of the landfill material. The predicted reduced surface will be levelled as required by the infill of depressions with imported stone or other suitable material. Improvement of the existing ground by reinforcement through installation of Vertical Rigid Inclusions (VRI) method across the site. Supporting of level sensitive and heavier elements will be on precast driven piles founded below the landfill material. The combination of methods will be designed to achieve Thames Water’s settlement performance values over 40 years, and remain within the allowable values of 50mm and 100mm. This will reduce the need for full depth driven piling which would otherwise be required. Reduction of infiltration to the landfill materials by ensuring impermeable surfaces drain to the treatment works and are released at the outfall away from the site. Gas and leachate well monitoring is provided along the perimeter of the site to monitor any impact and provide leachate removal points if required. (left) Rapid impact compaction rig and (right) pile under test - Courtesy of BAM Enpure Ltd JV (left) Rapid impact compaction rig and (right) pile under test - Courtesy of BAM Enpure Ltd JV Guildford STW Relocation Project: Supply chain - key participants Client: Thames Water Principal contractor & designer: BAM Enpure Ltd JV Client designer: Jacobs Civil designer: Arcadis Planning consultant: Adams Hendry Consulting Ltd Process & M&E: Enpure Ltd CFD analysis: The Fluid Group Physical modelling: Hydrotec Consultants Ltd Tunnel design: Joseph Gallagher Ltd Precast structures: A-Consult Ltd Precast structures: FLI Precast Solutions Rapid impact compaction: Cofra Ltd Piling: Aarsleff Ground Engineering Ltd XDisp software: Oasys Controlled modulus columns: Vibro Menard Ltd Inlet works and PST odour covers: Power Plastics Ltd Inlet pumps: Grundfos Imported sludge Strainpress: Huber Technology Escalator screens: Longwood Engineering Company Ltd Grit removal plant: Jacopa PST scrapers: Colloide Engineering FST scrapers: Purac AB Odour control plant: Odour Services International Ltd FBDA grids and blowers: Xylem Water Solutions Sludge thickening & dewatering: Kent Stainless Ltd Cake Silo: Saxlund International Cloth pile filters: Eliquo Hydrok Polymer batching & dosing: Richard Alan Engineering Ferric plant: Colloide Engineering Tank logging system (WASP): JR Pridham Services Ltd Glass lined steel tanks: Balmoral Tanks Ltd Sludge tank mixing: Landia UK Ltd Pumps, mixers & flocculators: NOV Welfare building: M-AR Limited Guildford STW - the new sewage treatment works Inlet pumping station The new STW is being designed to maintain inflow from the external catchment ranging from dry weather to 1 in 100-year storm (plus climate change allowance) with future-proofing beyond the 2041 design horizon. (left) inlet pumping station physical model and (right) inlet pump testing physical model - Courtesy of Hydrotec Consultants Ltd (left) inlet pumping station physical model and (right) inlet pump testing physical model - Courtesy of Hydrotec Consultants Ltd The pump design has been developed to fulfil the project brief load requirements (future peak IPS capacity 2585l/s) and some flexibility either side of the requirements is available due to the standard capacity equipment design offered from the supply chain. The proposed arrangement now consists of a wet well 12.5m diameter, approximately 20m deep. A common inlet will be provided to dissipate any entrained air, and two selectable pumped sections with double isolation will be provided by wall mounted penstocks on full height walls. The pumping well will be constructed in two halves, hydraulically connected in normal operational mode however each half will be able to be isolated (using motorised penstocks) in accordance with specification requirements surrounding double isolation, to allow person entry into half of the wet well at a time. Each half of the wet well will have three pumps installed giving a capability to provide full flow to treatment from two pumps with a standby permanently installed. The pumping station was first modelled by computational fluid dynamics (CFD) to demonstrate the assumed flow patterns that will occur. The pumping station was then physically modelled to comply with the specification and process design requirements particularly with respect to distribution, mixing, settlement, turbulence, dispersion, and freeboard for the full range of flows that each structure is expected to receive. Storm overflow physical models - Courtesy of Hydrotec Consultants Ltd Storm overflow physical models - Courtesy of Hydrotec Consultants Ltd Inlet works The inlet works is being designed to receive all pumped flows from the inlet pumping station (including future peak IPS capacity 2585 l/s), inlet works drainage and screening liquor return flows. Flows will enter the inlet works and then separate across the four escalator screens inclined at an angle of 45°. Each screen will be provided with a local proprietary control panel. Each panel will incorporate a differential ultrasonic level control. An emergency bypass will be provided upstream of the screens to accommodate all four screens blinding at the same time. Three 1200mm wide duty screens will be required to screen flows from low flow up to 2585 l/s, screening 6mm in two directions. The inlet works and grit treatment plant will be covered with odour covers which will be connected to the inlet works and PST odour plant. The inlet works has been classified as a Zone 2 Area under the odour covers and all equipment beneath the odour covers will be ATEX rated. Storm tanks Storm flows from the inlet work storm separation chamber will flow into two storm tanks via a 1400mm above-ground pipe. Within the 1400mm pipe between the storm separation chamber and the storm tanks there will be a partial pipe MCERTs certified flow meter to measure the total flow into the storm tanks. During normal operation the blind tank will fill first, then the spill tank will fill. In the event that both tanks are full to capacity (and still in storm flows) the spill tank will overflow via a weir and the storm tank will discharge to river. Elevated inlet works - Courtesy of BAM Enpure Ltd JV Elevated inlet works - Courtesy of BAM Enpure Ltd JV The storm tanks contents will automatically return to the inlet pumping station via 700mm gravity pipe when the flow being pumped to the inlet works drops below a predetermined set point. The return flows will be controlled to approximately 0.5 DWF via an automated valve controlled by an electromagnetic flow meter located in the gravity main, returning to the common inlet well of the inlet pumping station. Storm tank cleaning will be a pumped system with the two pumps located external to the storm tanks. Storm tank cleaning will be initiated during the latter part of the storm tanks draining back to the inlet pumping station and will not operate when the tanks are filling. The pump discharge pipe work will include connections for flushing with washwater. Ferric storage & dosing Two 45m3 ferric storage tanks will be located in a concrete bund with the dosing skid packages and control system located within an adjacent kiosk. The bund will be capable of containing 110% of the one of the storage tanks plus 10% allowance for rainwater. A drive-in bunded area for chemical deliveries will be provided and an underground chemical interceptor will contain any local spillages, complete with a Castell interlocked 3-way valve to allow the bunded drainage area either to drain into the interceptor (during a chemical delivery) or to drain into the site drainage (normal operation). Chemical dosing points will be provided upstream of the PSTs, on the common outlet channel of the ASP, and upstream of the tertiary treatment plant. The dosing points will utilise sparge systems to ensure adequate distribution of chemicals into the channels. Odour control plant The odour plant is a 2-stage system. Stage 2 filters will discharge into an 18-metre-high odour stack. The plant has been designed to achieve a minimum removal efficiency of 98% of H2S and 99% removal of odour, based upon a total system duty of 8432 m3/hr (of which 4813 m3/hr is from the inlet works and 3619 m3/hr from the primary settlement tanks). Service water A potable water main supplies a service water break tank via a ballcock (float valve). The service water break tank has a working volume of approximately 30m3 which gives a nominal retention of approximately three hours at average throughput. Service water booster pumps draw water from the tank and transfer it to the service water main network where it feeds the polymer make-up system for all thickeners and dewatering belt presses. Primary settlement distribution chamber The distribution chamber has been CFD modelled to calculate the flow split to each downstream primary settlement tank from first principles, and assess whether the proposed design would deliver an equal flow split (+/-5%) for seven future flow scenarios. This required the inlet bellmouth to be turned down to improve flow splitting. PST distribution chamber CFD models: (left) with four PSTs in service and (right) with six PSTs in service - Courtesy of The Fluid Group PST distribution chamber CFD models: (left) with four PSTs in service and (right) with six PSTs in service - Courtesy of The Fluid Group Primary settlement Primary settlement consists of four 47.15m long by 10m wide tanks, with a depth ranging between 6.24m at the hopper end and 5.3m at the outlet length (equating to 1 in 50 floor slope). Each PST tank has three sludge hoppers at the inlet end. The outlet of the PST discharges into a common 1000mm wide outlet channel. From this outlet channel the 1000mm outlet pipe from the drop box combines with the 700mm RAS lines into an above-ground 1200mm pipe. Retractable odour covers will be provided across the PST tanks to allow for future inspection, cleaning and maintenance. The odour covers will be connected via ducting to the inlet works/primary settlement tank odour plant. All mechanical equipment installed below the covers will be constructed from 316 stainless steel or high performance plastics. The primary settlement tanks have been classified as a Zone 2 Area, and all electrical equipment beneath the odour covers will be ATEX rated. The design of the PST Tanks is based upon a maximum inflow of 3022m3/hr to all four in-service tanks, and a peak flow to each tank of 1007m3/hr with one PST out of service. In normal operation all four PST tanks will be in service. Within each PST tank a chain and flight scraper system will be provided which will utilise high-tech non-metallic materials as the main materials of construction. Scum from the primary tanks will gravitate via a rotating surface skimmer pipe to the above-ground primary settlement scum tank. The primary scum return pumps are progressive cavity pumps, operating in a duty standby configuration. The pumps are fixed speed pumps operating between a high and low level in the scum tank. The PST sludge hoppers will desludge based upon a SCADA-adjustable interval and duration. The primary desludge pumps are progressive cavity pumps, operating in a duty/standby configuration. The pumps are variable speed pumps operating to maintain a SCADA-adjustable flow set point. Once the effluent has flowed through each PST it will enter into a common 1000mm wide outlet channel. From this outlet channel flows transfer to the ASP distribution chamber via a drop box and 1000mm above-ground pipe. ASP overview - Courtesy of BAM Enpure Ltd JV ASP overview - Courtesy of BAM Enpure Ltd JV Activated sludge plant The ASP plant will have a distribution chamber using the same general arrangement as the primary settlement distribution chamber. The activated sludge treatment tank consists of four ASP lanes. Each ASP lane has a selector tank followed by an anoxic zone and then the three aerobic zones. The main aeration lane will be fitted with aeration pipework and fine bubble diffusers. The aeration vessel is 80m long and 6.1m wide with a water depth of 7.05m. The total instantaneous maximum air demand of the ASP is 10,438 m3/h. The first third of the aerated fraction of each lane will contain 50% of the aeration capacity, the middle third 30%, and the final third 20%. Each aeration lane will have three passes, arranged as channels of 6.15m width. The air for the diffuser grids will be supplied from three ASP air blowers operating on a duty/assist/standby basis. The aeration system will be controlled by an ammonia based real time control (RTC) system utilising a feed forward ammonia load input and a feedback ammonia concentration. Once the effluent has flowed through each ASP lane it enters into a common 1000mm wide outlet channel. From this outlet channel flows transfer to the FST distribution chamber via a drop box and 1200mm above-ground pipe. Anoxic and aeration zones flows - Courtesy of BAM Enpure Ltd JV Anoxic and aeration zones flows - Courtesy of BAM Enpure Ltd JV Final settlement tanks The FST plant will have a distribution chamber using the same general arrangement as the primary settlement distribution chamber. The four FSTs will consist of 32m diameter flat bottomed circular tanks with a side wall depth of 6.15m. The FST will separate solids from the flow via settlement, producing a clarified effluent which overflows a peripheral weir into a launder channel, before gravitating to the tertiary treatment distribution chamber via a 1000mm below-ground pipe. The combined clarified outlet flow from the four tanks will be monitored by a common flow meter, as well as suspended solids and phosphorus monitoring instrumentation, all provided on the common line to tertiary treatment. The design of the FSTs is based upon a maximum inflow to each tank of 1741m3/hr with one FST tank out of service. In normal operation all four FST tanks will be in service. Each tank will have a 700mm inlet pipe, which will flow into a central diffuser drum before entering the FST tank. Each tank features a 600mm outlet pipe fed via a peripheral launder channel, as well as a 400mm RAS gravity outlet pipe. Each of the four tanks features a full bridge rotating scraper system which will run continuously in normal operation. 32m final settlement tanks & sludge return (RAS pumping station) - Courtesy of BAM Enpure Ltd JV 32m final settlement tanks & sludge return (RAS pumping station) - Courtesy of BAM Enpure Ltd JV Sludge return (RAS/SAS pumping station) Sludge from each pair of FSTs will enter one of two RAS/SAS desludge chambers. The two chambers will be located side by side and will share a set of three duty/duty/standby RAS transfer pumps, which will recycle the settled sludge from both RAS/SAS desludge chambers to the activated sludge plant distribution chamber feed line. The variable speed centrifugal RAS transfer pumps will be capable of pumping 2200m3/hr at a maximum head of 8.9mhd. The pumps will operate between high and low level in the duty RAS/SAS desludging chamber, with both chambers provisioned. A pair of duty/standby SAS pumps is provided, which will facilitate wastage of surplus sludge, with each pump drawing from a single RAS/SAS desludge chamber. The fixed speed centrifugal pumps will transfer sludge to the SAS buffer tank. Control of the SAS pumps will be carried out either on a timer or based on the level in the SAS buffer tank, with the common discharge line featuring flow monitoring. Tertiary treatment Clarified effluent flow from the FSTs will pass to the tertiary ferric mixing and flocculation (post-precipitation) stage, where the option will exist to dose ferric sulphate solution into the flow in order to encourage flocculation of remaining solids. This stage will be split into two parallel streams, with flow from the FSTs initially entering via a single bellmouth inlet into a common inlet channel, before passing via twin overflow weirs into two rapid mix chambers, and subsequently overflowing into two flocculation chambers. The design of the rapid mixer chambers will ensure complete mixing (>95% CoV) of chemical in less than 4 seconds. Flow from the flocculation chambers will weir into a common outlet channel leading to a flow distribution chamber feeding the tertiary treatment stage. The distribution chamber has been CFD modelled to calculate the flow split to each downstream cloth pile filter from first principles, and assess whether the proposed design would deliver an equal flow split (+/-5%) for seven future flow scenarios. The tertiary treatment stage will comprise six cloth pile filters, which will operate with all filters in service - however the peak flow will be able to be treated with only five filters in service. The filters will be sized to accommodate a peak flow of 840 l/s, producing a final effluent of 20 mg/l TSS (95%ile) and 0.2mg/l TP (average). Bypass pipework is to be provided adjacent to the cloth pile filter structure, by which clarified effluent from the FSTs may bypass the tertiary ferric dosing/flocculation and cloth pile filter stage. Each of the six cloth pile filters will feature a central rotor drum onto which filter discs are attached. The rotor and discs will be fully submerged within the tank, with the discs supporting the physical cloth filter media. Flow entering the filters will flow from outside the discs through the cloth into the discs’ interior, with solids collecting on the external surface of the cloth pile, creating a headloss. As this headloss increases, the water level in the tank will rise and at a pre-set water level (as detected by an ultrasonic level sensor) a cleaning cycle will be initiated. Tertiary treatment flocculation chambers: Eliquo Hydrok Mecana cloth pile filters - Courtesy of BAM Enpure Ltd JV Tertiary treatment flocculation chambers: Eliquo Hydrok Mecana cloth pile filters - Courtesy of BAM Enpure Ltd JV Filtered final effluent (FFE) from the inside of the filter disc and rotor drum assembly will pass forward through the unit via a low-level aperture to an outlet chamber, from which flow will weir into the common final effluent outfall chamber. An emergency overflow weir is to be provided, allowing unfiltered effluent from the filter tank (external to the discs) to weir over into the outlet chamber. Backwash liquors from the backwash pumps will exit the filters via a common manifold, draining by gravity to the grit plant liquor PS. Eight backwash pumps will be provided per machine, giving a total of 48 pumps across all six machines. The pumps will be submersible units placed within the tank, with each pump being dedicated to three filter discs. The backwash flow rate is rated for 10 l/s (subject to the installed pipework design/headloss). Each of the six filter tanks will see some solids settlement occurring (and potential accumulation of other debris), which will create a build-up of sludge in the bottom of the tank. This sludge will be periodically removed by a set of two duty/standby sludge pumps per machine (i.e. 12 sludge pumps installed in total). The discharge from each sludge pump will be connected to the common backwash manifold, leading to the grit plant liquor pumping station. Final effluent discharge Flows leaving the cloth pile filters will pass out from the main filter chamber via a low level aperture into a small outlet chamber, from which flows will weir over into the common outfall channel. The final effluent (FE) will flow under gravity through an FE flow measurement flume, with an ultrasonic instrument for measurement of final effluent flows discharged to outfall. The FE outfall channel will feature a pipe leading to the FE washwater system, with a further line branching off this pipe servings as the suction line for FE Meteorburst Analyser. On exiting the FE outfall channel, flows will enter a dedicated FE outfall main, which will drain by gravity, discharging to the river north of the STW site. New Guildford STW: 3D model night-time overview - Courtesy of BAM Enpure Ltd JV New Guildford STW: 3D model night-time overview - Courtesy of BAM Enpure Ltd JV Guildford STW - Sludge Treatment Plant Sludge thickening equipment Primary sludge from the PSTs will be pumped via the primary sludge pumps to the primary sludge buffer tank, which will have a volume of 120m3 and will be sized to provide 4-hours of intermediate storage prior to thickening. A set of two duty/standby primary sludge thickener feed pumps will be provided to transfer sludge (at up to 7.0%DS) from the primary sludge buffer tank to the primary sludge gravity belt thickeners. Two primary sludge gravity belt thickeners (GBTs) will operate in a duty/standby configuration in normal operation, although the streams will be able to run as duty/assist if required. Each machine will be able to handle up to 51m3/h (771 kgDS/h) of primary sludge, at up to 7%DS achieving a solids capture rate of 95%. Surplus activated sludge (SAS) from the FSTs will be pumped via the SAS pumps to the surplus activated sludge (SAS) buffer tank, which will have a volume of 67m3 and has been sized to provide 4-hours of intermediate storage prior to thickening. A set of two duty/standby SAS thickener feed pumps will be provided, which will transfer sludge (at up to 2.0% DS) from the SAS buffer tank to the SAS gravity belt thickeners. Two SAS gravity belt thickeners (GBTs) will operate in a duty/standby configuration in normal operation but will be able to run as duty/assist if required. Each machine is sized to handle up to 55m3/h (332kgDS/h) of SAS, at up to 2%DS, achieving a solids capture rate of 95%. Sludge balancing/blending tanks Thickened primary sludge, surplus activated sludge, and screened sludge imports will be pumped to two thickened sludge blending tanks. The tanks will have a combined volume of 2150m3 (1075m3 each), and will be sized to provide a combined total of 4-days retention time prior to dewatering of the blended sludge. The tanks will operate in a duty/standby configuration, with either tank being available for selection as the duty unit for either filling or emptying. Thickened sludge blending tanks - Courtesy of BAM Enpure Ltd JV Thickened sludge blending tanks - Courtesy of BAM Enpure Ltd JV Each tank will feature separate inlet connections for the three types of sludge being received, with actuated valves and crossover lines allowing all sludges to be directed to either of the two tanks. The tanks will also feature outlet actuated valves, which will allow either tank to be isolated from the sludge belt press feed pumps downstream, thereby ensuring the pumps only draw from a single tank at any given time. A set of three duty/duty/standby sludge belt press feed pumps will be provided, which will transfer blended thickened and imported sludge from the thickened sludge blending tanks to the sludge belt presses. The pumps will be variable speed progressive cavity units, with a peak capacity of 30m3/h (i.e. 15m3/h per pump) at a maximum head of 48.5m, based on sludge of up to 7.0%DS. Dewatered cake leaving each belt press will enter a discharge cake hopper leading to the suction end of a sludge cake pump. Three pumps will be provided, with a single pump dedicated to a single machine; each pump will operate in conjunction with the associated belt press upstream. The pumps will be variable speed progressive cavity units, with a peak capacity of 7.4m3/h of sludge (up to 30%DS). The pumps will transfer the cake via individual discharge lines to the sludge cake silos, with manual discharge crossover facilities allowing sludge from the pumps to be directed to either of the two silos as required. Cake silo storage & discharge Dewatered sludge cake will be pumped to two truck-loading cake silos, with a combined storage capacity of 600m3, sized to provide 7-days of storage at average cake production. Each silo will feature a discharge screw conveyor (with a sliding frame ‘anti-bridging’ device) which will discharge the cake through a hydraulically operated slide gate valve. Odour control plant The odour plant will be a 2-stage system. Stage 2 filters will discharge into an 18-metre-high odour stack. The plant has been designed to achieve a minimum removal efficiency of 98% of H2S and 99% removal of odour, based upon a total system duty of 6629m3/hr, extracted from the various tanks and thickening/dewatering machines in the sludge plant area. New STW outfall Outfall route The outfall route from the new works site location was assessed thoroughly in the ITN 2 stage of the project’s life and from exiting towards the middle of the works site, proceeds north towards the River Wey. The route deviates initially to minimise any impact on significant trees that exist within the floodplain, and any impact on the band of vegetation around the perimeter of the site. Final effluent & stormwater pipeline The final effluent pipeline will be a 750mm diameter pipe. This will be situated above ground from the final effluent channel to the edge of the site, and will be supported by piles when within the treatment works site. The pipeline then proceeds below ground through the embankment (to be reinstated using clay stanks) and under the adjacent ditch via an inverted siphon arrangement. A jetting/access point will be provided just before the pipeline dives below ground, giving the facility to clean this arrangement and flush from a more direct point than the pipes exit from the final effluent channel. Air relief may also be provided at this point, subject to detailed design. The storm overflow pipeline will be a 1050mm diameter pipe. This will be situated below ground from the storm tanks to a sampling manhole at the edge of the site; supported by piles when within the treatment works site. The pipeline will then proceed from the manhole through the embankment (to be reinstated using clay stanks) and under the adjacent ditch via an inverted siphon arrangement. The sampling manhole will provide an ability to clean this arrangement. (left) Outfall route plan - Courtesy of Bam Enpure Ltd JV, and (right) outfall low flow scenario CFD model - Courtesy of Arcadis (left) Outfall route plan - Courtesy of Bam Enpure Ltd JV, and (right) outfall low flow scenario CFD model - Courtesy of Arcadis Outfall structure The outfall structure will consist of a reinforced concrete headwall, set back from the river channel, to be founded in the river terrace deposits and flared to direct flows downstream and minimise the impact of upstream debris from collecting. The headwall will have duckbill valves on the discharging pipes, and erosion control products utilised in the surrounding area to tie the headwall into the natural riverbank and bed. The erosion mattress employed following the headwall structure will provide a secondary point at which turbulent flows can dissipate energy without eroding the natural bed of the river. Where the headwall ties into the natural riverbank, the hard/soft interaction between headwall and natural soil will be reduced by the installation of Rock Rolls erosion control and willow stakes at the base, and the installation of a natural hydro-seeded CocoBN blanket or equivalent (to be seeded with local seed varieties) which will retain the slope shape until vegetation establishes and provides an effective natural erosion control. This will also provide a gradual slope to access down to the river. Programme The project obtained planning permission in October 2022, with construction works starting on site in July 2023. Detailed design of the civil, mechanical and electrical works are due for completion by December 2023. Construction of the works will be complete by August 2025, with commissioning due to commence in from April 2025 through to December 2025. Flows from the existing works will be diverted to the new works from December 2025 (10% flow) in a 7-stage commissioning process with 100% flows diverted to the new STW by March 2026. Following 100% flow diversion the existing STW will be de-commissioned ready for handover to Guildford Borough Council. The editor and publishers would like to thank Shaun Christopher, Project Delivery Leader with Enpure Ltd, for providing the above article for publication.

Water utilities face challenges dewatering clean water sludges as they possess different key properties when compared to wastewater sludges. Clean water sludges exhibit lower fiber and organic content, thus lowering its compressibility. The challenge to dewater clean water sludges is common to all dewatering technologies; to achieve adequate separation of water from dry solids with low energy and polymer consumption. However, one benefit of dewatering clean water sludges is that pathogenic regulations are not applicable as compared to wastewater sludges. Therefore, the processed dry cake can be used directly by local farmers, ensuring zero waste and ultimately helping the water utilities move towards their net zero carbon pledge. Volute Dewatering System Evergreen Water Solutions have implemented the innovative technology of the Volute to ensure the water industry can face the challenges of the future. These challenges include: Reducing the lifetime energy consumption of dewatering equipment towards the Net Zero carbon pledge. Reducing consumption of polymers. Reducing operating and maintenance costs. During Volute operation, pre-dosed polymer mixed sludge is pumped into the flocculation tank. Within the flocculation tank, an agitator assists in the floc formation and polymer mixing. The flocs weir over into the Volute’s dewatering screw chamber where they are pushed along the central shaft by a V-screw encased by a series of fixed and moving rings. As the sludge moves up the central shaft, the distance between the rings decreases, further increasing the pressure along the screw which causes the sludge to be further compressed. The sludge is thickened and dewatered due to this increasing compression along the screw, causing more and more carrier water to be removed as filtrate. With the filtrate water removed from the feed, a dry cake is produced at the end of the Volute screw chamber as a result of this process. Sectional view of the Volute Dewatering Press - Courtesy of Evergreen Water Solutions Sectional view of the Volute Dewatering Press - Courtesy of Evergreen Water Solutions Process benefits of Volute technology Dry sludge cake: up to 35% dry solids. > 84% energy reduction compared to typical centrifuge technologies. High filtrate quality: < 50mg/l suspended solids. Low polymer consumption: < 4kg/tonne of dry solids (TDS). High total solids capture: up to 99.9%. Dewaters a wide range of sludges. Integrated flocculation tank with upstream static mixer. Auto-self cleaning shaft which significantly reduces maintenance, water consumption and odour. Low operational maintenance & downtime. Screw service interval < 30,000 hours. Ring service interval < 10,000 hours. Capable of 24 hour unsupervised, automatic operation. Low power usage (<4kW per/TDS for municipal sludge) Energy consumption (kW/hr of usage) for the Volute is extremely low when compared to all other dewatering systems, which is a fundamental driver in process selection. This puts the Volute technology at the forefront when considering equipment to move toward the net zero carbon pledge across the industry as a whole. The figure below highlights the comparative energy values for a Volute against other dewatering technologies. It clearly demonstrates a significant reduction in power consumption. With energy prices sharply rising, the long-term power consumption is a key consideration when analysing the Volute’s whole life cost. Comparison of power consumption among sludge dewatering equipment (throughput 45 kg-DS/h) - Figures based on research by AMCON Comparison of power consumption among sludge dewatering equipment (throughput 45 kg-DS/h) - Figures based on research by AMCON Quiet operation Another key design feature of the Volute Dewatering Press in comparison to other dewatering technologies is its low noise and vibration. The Volute operates at 63 decibels and is therefore under the permissible levels requiring ear protection. The motor speed of the Volute typically runs at a speed of 2-6 RPM. This significantly helps to mitigate against harmful decibel levels and noise pollution to both operators and the local environmental community. This quiet operation also reduces the need for additional sound deadening. Case study: Williamsgate Water Treatment Works Williamsgate Water Treatment Works (WTW) is a newly built drinking water facility designed to meet the growing demand for water consumption in the north-west of England. The site is designed to process untreated water from a regional reservoir, utilising a combination of modern process selection and dewatering technology to efficiently dewater sludge. Incoming untreated water from the reservoir leaves Williamsgate WTW as either treated clean water, or as dewatered sludge cake. The processed cake can then be deposited directly into trailers for re-use. This avoids conventional process methods, which further increase flows to the wastewater network and may risk exceeding flow discharge permits of local sewage works. Williamsgate WTW is the home of the UK’s first permanent Volute dewatering installation on a clean water site. Evergreen Water Solutions were employed by Advance JV on behalf of United Utilities to provide an innovative sludge dewatering and cake conveyor system based on the following performance criteria: Polymer consumption: < 6kg/TDS Filtrate: < 500mg/l Dry cake solids: >18%DS. The dewatering plant consists of two Volute FS351 systems installed in a parallel configuration, which are paired to operate in a duty/assist arrangement. The Volute dewatering plant at Williamsgate WTW has been selected and sized to process clean water sludge as a result of incoming site flows of up to 80 mega litres per day (MLD). (left) 3D model of installed Volutes and (right) 3D render of Volute and cake trailer design - Courtesy of Evergreen WS (left) 3D model of installed Volutes and (right) 3D render of Volute and cake trailer design - Courtesy of Evergreen WS The sludge fed to the Volutes arrives from upstream lamella clarifier tanks where the solids are accumulated and pumped periodically into two 60m3 sludge holding tanks. The Volutes are capable of dewatering a wide range of sludge thicknesses. At a recent pilot trial, Evergreen Water Solutions proved the Volute’s capability by successfully dewatering a 0.1-3% DS sludge into a dry cake of > 18% DS. The Volute’s ability to adapt to a wide and varying range of incoming sludge properties is due to its integrated software. The control philosophy of the Volute dewatering system at Williamsgate WTW allows the Volute to automatically adapt to varying throughput characteristics whilst achieving a consistent %DS dry cake production. The system’s automatic control is sufficiently sensitive that operational parameters are adjusted accurately, and with a minimal requirement for operator intervention or supervision. The two Volutes at Williamsgate WTW, direct their cake filtrate into lamella clarifiers. This ensures protection from a high concentration of suspended solids being returned to the head of the process. The filtrate performance of the two Volutes support this process intent by outputting an average filtrate suspended solids concentration of 25mg/l. This in-turn allows the lamella clarifiers to achieve a further reduction, resulting in a supernatant output suspended solids concentration of <5mg/l. To improve filtrate quality, the Volute’s split filtrate pan design allows the filtrate to be separated into two sections; the ‘Thickening’ and ‘Dewatering’ zones. The Volute filtrate highest in volume and lowest in suspended solids concentration is collected below the Thickening Zone; this is the Volute filtrate directed to the lamella clarifiers. Conversely, the Volute’s filtrate collected below the Dewatering Zone is lower in volume and elevated in suspended solids concentration relative to the Thickening Zone. This filtrate is returned to the sludge holding tanks for the Volutes to reprocess, thus screening the filtrate quality to the lamella clarifiers. The Volutes’ filtrate divergence ensures a high quality filtrate output with a high total dry solids capture. The Volutes at Williamsgate WTW have achieved an overall total dry solids capture of 99.9%. Volute operation - Courtesy of Evergreen Water Solutions Volute operation - Courtesy of Evergreen Water Solutions Williamsgate current data and process overview Processed cake at an average of 19% dry solids. Filtrate at < 50mg/l suspended solids concentration. Average sludge flow rate of 5m3/hr per Volute. Polymer consumption of 5.5kg/TDS. Each Volute screw motor is running at just 1kW during operation. Solenis LT22S was the selected polymer, based on jar tests and site trials. Feed sludge is in a range of 0.5-0.8 % DS. At the time of writing (September 2022) the commissioning process is ongoing with performance testing and handover due to take place by the end of 2022. Volute Dewatering Presses are sold under license in the UK and Ireland by Evergreen Water Solutions Ltd. The editor and publishers would like to thank Evergreen Water Solutions for providing the above article for publication.