Supply Chain - Site Preparation

Scottish Water’s Bonnycraig Water Treatment Works (WTW) supplies around 9,600 customers in and around Peebles in the Scottish Borders, treating water fed by gravity from Megget Reservoir. There were operational challenges at the existing works and to secure a long-term supply of clean, safe and fresh tasting water that takes account of summer peak demands and projected growth within the area, a new £31m water treatment works using ceramic membrane technology was utilised to improve the water quality for customers. Background

The original Bonnycraig WTW was built in the 1960s and sized to 4.1 Ml/d, however this was later reduced to 2.8 Ml/d due to water quality issues. The old works utilised pressure sand filters however, due to Cryptosporidium failures, Scottish Water received a Drinking Water Quality Regulatory (DWQR) enforcement notice for both a short term and long-term solution to this problem. UV was installed within the old works in April 2017 as the short-term solution.

The long-term solution required Water into Supply (WIS) to be completed by December 2022, with the agreed solution being to build a new WTW using ceramic membrane technology. The enforcement notice provided a significant programme challenge to take the project from inception through design and construction to Water into Supply in only 3.5 years.

[caption id="attachment_13012" align="alignnone" width="1200"] Model of the new WTW - Courtesy of RSE[/caption] Bonnycraig WTW (Peebles, Scotland): Supply chain - key participants Principal contractor: Amey Principal designer: RSE Project management: Turner & Townsend Process engineering support: M2 Groundworks: APL Construction Ltd Ceramic membranes: PWNT MCC: Saftronics Ltd Telemetry integration: IDS Systems integration & chemical dosing: RSE Pumps: Grundfos Pumps Tanks: Forbes Technologies Ltd Underground tanks: SPEL Products PV solar panels: Ri Cruden Emergency generator: DTGen Kiosks: Quinshield Ltd Mixers: Statiflo International Ltd Safety showers: Aqua Safety Showers International Ltd Site security: Pointer Concrete & aggregates: Grange Quarries [caption id="attachment_13018" align="alignnone" width="1200"] (left) TTU being delivered through Peebles - Courtesy of RSE, and (right) delivery of the TTUs to site - Courtesy of Scottish Water[/caption] Project scope

The main components comprised:

A new ceramic membrane water treatment works on a greenfield site. Extensive groundworks/earthworks for new site. New external pipework facilities. New chambers, tanks and structures to facilitate the new WTW. New access and roads. Decommissioning of existing WTW.

The project was delivered by RSE for the MEICA and Amey for civil engineering, with PWNT supplying the membranes and filtration housing element for the ceramic membrane process. All working collaboratively with Scottish Water to manage, design and deliver the project in Peebles.

A summary of the construction works being undertaken including design and process considerations as well as some of the challenges encountered for these main components follows.

[caption id="attachment_13023" align="alignnone" width="1200"] Early civils earthworks at the new site - Courtesy of Scottish Water[/caption] Water treatment works

The new works will have capacity to produce up to 4 million litres of drinking water per day and will be supplied by the raw water source of Megget Reservoir, which also provides majority of the raw water to Edinburgh. Within the treatment works site, as well as the new WTW building, inclusion will be made for associated infrastructure, utilising the existing clear water tanks.

Civil engineering works

The new site is located on a greenfield site adjacent to the existing works and therefore utilises some of the existing infrastructure. There were extensive civil works to prepare the site for the WTW, these included:

Earthwork excavation/landscaping for new WTW. New external pipework facilities for the new WTW. New chambers, tanks and structures to facilitate the new WTW. New building slab. Chemical delivery area. Emergency outfall headwall at the Crookston Burn. Emergency generator, fuel tank plinth, ducting, fuel spill area and security fencing. Access roads. Site fencing. Wastewater holding lagoon. Chlorine contact pipe. Reinstatement.

All excavated materials were retained and reused on site therefore provided significant carbon and cost savings on the project. Reducing the traffic on the local roads also helped to limit the impact on the community.

The civil works began in February 2021 during the height of COVID-19 restriction across the UK, which brought with it a number of challenges to ensure the safety of all the workers while also trying to maintain the programme to comply with the Drinking Water Quality Regulatory enforcement date. It is testament to all the teams involved that the achieved this.

[caption id="attachment_13015" align="alignnone" width="1200"] Delivery of the TTUs to site - Courtesy of Scottish Water[/caption]

MEICA

The new WTW was assembled and commissioned at RSE’s specialised factory in Muir of Ord, before delivery to the site. The new WTW building was assembled as a modular construction with the design allowing the WTW to be dis-assembled, transported 200 miles to site by road and then quickly reassembled once delivered to site. The two-storey building consisted of 17 modular Transportable Treatment Units (TTU) and was RSE’s largest TTU build to date.

Utilising off-site construction allowed for significant programme efficiencies to be made of upwards of 18 months in both construction and commissioning as it allowed the existing civils works to start at the same time as the fabrication and assembly of the new building within RSE’s facility in Muir of Ord.

Furthermore, by undertaking the MEICA works in RSE’s facilities it ensured factory quality throughout. The segregated facilities with separate carbon, blasting, paint, stainless, fabrication and installation areas, coupled with all equipment and stores to hand, created a working environment that could not be matched by an on-site build.

The off-site modular approach also offered health and safety benefits by limiting the number of different trades working concurrently on site. In addition, carrying out the majority of the M&E work in the workshop made it safer for the trades as the work was carried out using standard task risk assessments in a safe predictable working environment.

[caption id="attachment_13021" align="alignnone" width="1200"] Raw water pumps and tank - Courtesy of Scottish Water[/caption]

Ceramic membranes

The heart of the main treatment process, involves passing coagulated water through PWNT’s Inline Coagulation and Adsorption vessels (ILCA®) to form a microfloc which helps to bring together the contaminants present within the water to prior to filtration provided by a series of membranes which filter out the flocculated solids and bacteriological contaminants.

Water that has passed through the membranes is then subject to further treatment processes to ensure that it meets customers’ expectations at the tap. Bonnycraig is the first site in Scotland to use this technology and only the second in the UK.

Four ILCA vessels and four C19 Ceramic Membrane Vessels supplied by PWNT are installed at Bonnycraig, and this innovative solution offers a number of benefits over conventional treatment:

Water quality: Absolute barrier - bacteriological cell reduction and Cryptosporidium removal. Lifespan of membranes: > 20 years. Water supply: Meet future demands. Resilience: Quick recovery from an outage event. Customer experience: Ability to build off-line and use of innovative technology. Small footprint: Each vessel contains 19 membranes.

The modular solution approach selected by Scottish Water along with its partner RSE has helped to achieve considerable carbon reductions by transferring the mechanical and electrical works from site to the workshop. Carbon conscious choices included opting for off-site manufacturing, saving approximately 18 months of works over traditional build methods, supported by an overall reduced project programme.

Furthermore, the roof of the water treatment works accommodates a solar array of 288 (No.) 325W solar panels that will contribute to the power supply, assisting in driving down power consumption from the grid.

[caption id="attachment_13014" align="alignnone" width="1200"] Top of ILCA® vessels - Courtesy of Scottish Water[/caption] Benefits of the modular solution

In summary, the use of the RSE modular solution provided a number of key benefits to the project:

Reduced programme: TTU construction completed in RSE factory environment, reducing the amount of site hours while also enabling fabrication and assembly to be conducted concurrently with civil construction. This was critical to achieving the DWQR enforcement date. Improved quality: Stringent quality control in RSE fabrication facilities. Reduced HSE risk: Due to the factory construction of the TTUs, a significant portion of the construction is completed in a controlled factory environment, rather than on site.

The water treatment process

The process follows the following key process stages:

10mm coarse Simplex strainer 1.0mm duty/standby raw water screening with auto backwash. Raw water break tank. Raw water transfer pumps. Raw water pH correction using sodium hydroxide and sulphuric acid to achieve the required coagulation pH set point. Coagulant dosing using PACL. Coagulation/flocculation using four PWNT in-line coagulation and adsorber (ILCA®) vessels. Filtration using the PWNT CeraMac® process (four C19 membrane streams). Facilities for backwashing and cleaning (CEBW and CIP) of the CeraMac® membranes. Permeate/backwash water tank. Interstage permeate transfer pumps. Run to waste facilities for out of spec water (both individual and common membrane permeate streams). Disinfection using sodium hypochlorite. Orthophosphoric acid dosing for plumbosolvency control. Chlorine contact pipe (1200mm diameter x 75m long). Final pH correction using sodium hydroxide dosing to control final water pH. Storage in two clear water tanks prior to gravity distribution to supply (two existing tanks being retained). Chemical waste neutralisation tanks and systems (1 x acid and 1 x alkali) including caustic and sodium metabisulphite dosing skids. Discharge of backwash waste, neutralised CEBW and CIP wastes, and instrument wastes. [caption id="attachment_13017" align="alignnone" width="1200"] The completed Bonnycraig WTW - Courtesy of Scottish Water[/caption] Conclusions

This case study has highlighted the benefits of off-site manufacture particularly achieving a very tight programme and meeting the DWQR enforcement date.

The complexity of project interfaces was also greatly enhanced due to collaborative working between Scottish Water, RSE, Amey and PWNT. The consortium has successfully managed to navigate a path through all planning, land purchase, construction and commissioning activities to achieve a project that not only benefits the Scottish Water customer with safe clean drinking water but was delivered on time and within budget. Given this was all delivered during COVID restrictions further highlights the achievements of the project.

The new WTW has been live for 18 months and while there have been some snagging/defects that Scottish Water are continuing to work through, the works has always maintained the supply of safe clean drinking water with water quality being noted as being exceptional. While a number of key lessons learned have been documented, Bonnycraig is being used as a template for future WTWs within Scottish Water.

Leamington Spa is a historic spa town with a growing population and significant development pressures. The River Leam, which flows through the town centre, is a focal point for recreation, including wild swimming, boating, and public parks. The sewerage catchment includes Leamington, Warwick, and surrounding villages, all draining to Longbridge Sewage Treatment Works (STW). Six CSOs were identified for improvement. This requirement was designed to safeguard public health and ensure compliance with the Bathing Water Directive and related water quality with the aim to reduce spill volumes and spill frequency with a variety of interventions; to give an insight into the best approach for bathing waters. Endorsed by Ofwat in 2021, the scheme is part of a broader strategy to support post-pandemic economic recovery through environmental infrastructure investment. The Leamington scheme exemplifies innovation in hydraulic modelling, and collaborative delivery within tight regulatory timeframes. Project overview

The Green Recovery Leamington Spa Sewerage Scheme is a flagship initiative under Severn Trent’s Green Recovery programme, aimed at moving a stretch of the River Leam towards bathing quality. This ambitious project addresses the performance of six critical Combined Sewer Overflows (CSOs) in Royal Leamington Spa, Warwickshire, through a suite of technically advanced designs that test a variety of complementary solutions.

Few projects manage to balance technical complexity with community benefit as seamlessly as the Leamington Spa Sewerage Scheme with live public functional spaces is technically complex but also requires attentive and agile stakeholder engagement, delivering large measurable environmental improvements.

[caption id="attachment_26765" align="alignnone" width="1200"] Surface water separation - Courtesy of Forkers Ltd[/caption]

While early guidance targeted storm overflows with direct discharges into these areas, the programme has since expanded to include overflows that pose wider environmental and public amenity impacts. This includes high amenity areas such as recreational waters and areas of interest to businesses and other organisations, even if they are not formally designated as bathing waters.

The shift reflects a more holistic approach to water quality management, prioritising interventions based on environmental sensitivity, public usage, and the potential impact of overflows. This broader targeting ensures that improvements are aligned with community expectations and environmental stewardship goals.

Hydraulic modelling & option development

The project leveraged the Longbridge Strategic Sewerage Growth model, enhanced with updated flow monitoring and surface water network refinements. Hydraulic solutions were identified early through iterative hydraulic modelling and refined through feasibility and Early Contractor Involvement (ECI) with Forkers Ltd.

By integrating advanced hydraulic modelling and real-time control, the scheme exemplifies the kind of forward-thinking infrastructure needed to meet the challenges of climate resilience and urban growth.

Preferred interventions included surface water separation, pumped and gravity storage, and network optimisation.

[caption id="attachment_26764" align="alignnone" width="1200"] Shaft storm tank precast concrete segments - Courtesy of Forkers Ltd[/caption] Leamington Spa Sewerage Scheme: Supply chain - key participants Deliver contractor: Forkers Ltd Designer: WSP Tunnelling/shafts/timber headings: Active Tunnelling Ltd Electrical/mechanical: STAL (UK) Ltd Ground support & shoring: MGF Ltd Vacuum excavation: VAC UK (Kilkern Ltd) Drainage sub-contractor: Arthur Civil Engineering Ltd Emergency temporary pumping: Selwood Precast concrete pipe & rings: Marshalls Civils & Drainage Precast concrete rings: FP McCann Ltd Plastic storage pipes: Aquaspira Ltd GEOlight® storage tank: SDS Limited Concrete & aggregates: Aggregate Industries | Cemex Plant hire: Flannery Plant Hire (Oval) Ltd Traffic management: RouteOne Traffic Management Ltd Carriageway surfacing: JMC surfacing Ltd Surface water separation (SWS)

A major surface water separation scheme was implemented between Campion Road and Milverton School, delivering significant benefits in surface water management. The project successfully disconnected impermeable areas from the combined sewer network, reducing the volume of stormwater entering the system. Additionally, it incorporated below-ground storage to help manage flood risk, enhancing the area’s resilience to heavy rainfall events and contributing to improved environmental outcomes.

[caption id="attachment_26763" align="alignnone" width="1200"] Surface water separation - Courtesy of Forkers Ltd[/caption] Pumped & gravity storage

The Lower Avenue Combined Sewer Overflow (CSO) scheme involved the installation of an 880m3 shaft tank with a return flow capacity of 30 l/s, located in the Station Approach car park. The shaft tank was designed and constructed by Active Tunnelling Ltd. At Princes Drive 19B, the scheme increased the flow into the existing storm tanks by an additional 75 l/s. Both storage systems were equipped with real-time control (RTC) logic to optimise return flows and minimise the risk of spills into the river, ensuring more efficient and environmentally responsible stormwater management.

Climate change & resilience

To ensure long-term resilience and performance under changing climate conditions, the design rainfall was uplifted by 15% to reflect projected 2050 scenarios. Spill frequency assessments were carried out using Severn Trent’s Technical Standard Rainfall Dataset, representing worst-case conditions to ensure robust system performance. All conveyance infrastructure was sized accordingly to accommodate future climate impacts, supporting sustainable and reliable operation over the asset’s lifetime.

Construction & delivery

The project was delivered under tight AMP7 deadlines, requiring early contractor involvement and agile design development. Forkers Ltd and WSP played key roles in feasibility, site investigation, and outline design.

Key construction innovations included the use of GEOlight® blocks from SDS Limited for modular storage. GEOlight® blocks offer a significant advantage in large-scale infrastructure projects due to their lightweight, corrosion-resistant design, which simplifies installation and reduces long-term maintenance costs compared to concrete or steel alternatives.

[caption id="attachment_26767" align="alignnone" width="1200"] GEOlight® modular storage tank - Courtesy of Forkers Ltd[/caption] Environmental & community benefits

Reducing the impact from CSOs has had significant social implications. Access to clean and safe recreational waters promotes public health and well-being, encouraging outdoor activities and fostering a connection with nature. This initiative does not just solve a problem, it redefines what is possible in urban water management, setting a precedent for future projects across the UK and beyond.

Spill reduction. Flood risk: No detriment demonstrated; some areas show betterment particularly through the implementation of surface water separation in the north-east, the construction of stormwater storage tanks in the south, and comprehensive improvements along the River Leam corridor aimed at enhancing water quality and resilience. Education: Engagement with Milverton School on drainage and sustainability. Broader significance & replicability

The Green Recovery Leamington Spa Sewerage Scheme stands as a testament to the power of innovative engineering and sustainable practices in addressing modern environmental challenges. This project not only resolves immediate issues related to CSOs but also sets a benchmark for future initiatives aimed at enhancing urban wastewater management.

The Leamington Spa Surface Water Separation Scheme, delivered as part of Severn Trent’s Green Recovery Programme, exemplifies a forward-thinking approach to sustainable water management.

Central to the project was the installation of a two megalitre GEOlight® attenuation tank from SDS Limited beneath a playing field adjacent to Milverton Primary School. The tank, connected to newly laid surface water sewers across several roads in Leamington Spa, significantly increases stormwater storage capacity within the network. This enhancement plays a critical role in protecting downstream sewage treatment infrastructure from overload and reducing the frequency of combined sewer overflows into the River Leam.

[caption id="attachment_26768" align="alignnone" width="1200"] Construction of the 2 megalitre attenuation tank - Courtesy of Forkers Ltd[/caption]

The project not only supports Severn Trent’s ‘Get River Positive’ commitments but also aligns with local and national planning policies. By integrating innovative technology with sustainable construction practices, the scheme delivers measurable environmental benefits. It demonstrates how targeted infrastructure investment can contribute to long-term river health, climate resilience, and community wellbeing; setting a precedent for future water management initiatives across the region.

Its success lies not only in the numbers (reduced spills, increased storage, improved water quality) but in the way it brings together engineering excellence, ecological sensitivity, and community engagement. The project’s legacy will be felt not just in the River Leam’s improved health, but in the model, it provides for sustainable, scalable, and socially conscious infrastructure.

Conclusion

The Green Recovery Leamington Spa Sewerage Scheme is a model of integrated water management, combining hydraulic engineering and community recreational benefit. It demonstrates how ambitious environmental goals can be achieved through technical excellence, collaboration, and innovation.

In a sector where impact is often measured in compliance, this scheme goes further; delivering outcomes that resonate with local communities, regulators, and the environment alike.

The project not only safeguards the River Leam for recreational use but also sets a precedent for inland bathing water schemes across the UK and beyond.

The Ards Peninsula is a scenic area in County Down, situated on the north-east coast of Northern Ireland. It separates Strangford Lough from the north channel of the Irish Sea and its coastal towns and villages are popular with day trippers and caravanners alike. By 2020, the wastewater treatment works serving the villages of Carrowdore and Ballywalter were operating at full capacity. NI Water investment was required to ensure that these areas could meet future EU and Northern Ireland Environment Agency (NIEA) standards. The area of Ballywhiskin only had primary settlement, which was not deemed sufficient, and the caravan parks and small settlements in the Ballywalter area were served by septic tanks, which again only offered primary settlement of wastewater before discharge to nearby watercourses. The beaches in the area represent significant tourist amenity and an extensive treatment scheme was essential to meet future bathing water quality standards in line with NIEA standards. What the scheme involved The two-year Ards North Wastewater Improvement Scheme involved the rationalisation of the Carrowdore, Ballywhiskin and Ballywalter catchments so that all wastewater flows from these areas could be transferred to a new state-of-the-art wastewater treatment works (WwTW) constructed on a greenfield site off the Ganaway Road in Ballywalter. In addition to these catchments, the new treatment works has been designed to treat wastewater flows from nearby caravan parks and small settlements, which previously had no treatment facilities. The scheme was split into two contracts; one for the design and construction of new pumping stations, pipelines and a modern wastewater treatment works, which was awarded to BSG Civil Engineering, and another for the design and installation of a new long sea outfall, which was awarded to Farrans. Project management/technical support for both contracts was provided by Tetra Tech. This article focuses on the work carried out to construct the new WwTW, pumping stations and pipelines by BSG Civil Engineering to serve the combined catchments and cope with seasonal fluctuations in population to protect the tourism potential of the area for many years to come. [caption id="" align="alignnone" width="1200"] Bulk excavation - Courtesy of BSG Civil Engineering Ltd[/caption] Early contractor involvement/design and build contract BSG Civil Engineering was appointed by NI Water as the main contractor in November 2018 under an NEC 3 Early Contractor Involvement (ECI) contract. BSG provided multi-disciplinary design, project and supply chain management and all civil engineering, process and MIECA works for the contract from start to completion. The ECI phase allowed BSG to align resources and integrate objectives with NI Water and their project management team from Tetra Tech at an early stage to benefit delivery. This proactive approach led to enhanced collaboration, innovation, value, efficiency and reduced whole life costs for the project. Primary drivers The purpose and drivers for this project were as follows: Achieve compliance with current and future EU directives on effluent discharge standards. Meet Registered Discharge Standards set by the Northern Ireland Environment Agency (NIEA). Provide a flexible design to cater for future flows and the significant summer/winter fluctuations. Minimise impacts to community and environment. Support local development, tourism and economic growth. Deliver best value for money construction making use of existing assets. [caption id="" align="alignnone" width="1200"] Ards North WwTW - Inlet works overview - Courtesy of BSG Civil Engineering Ltd[/caption] Scope of works The main elements of work included: Installation of 14km of pumping main between WwTW & new/upgraded pumping stations via directional drilling and open cut methods. 2km of gravity sewer installed between pumping stations. 6mm inlet screening and storm storage for 2 hours/3x DWF) Grit treatment and removal. 3 (No.) 131m3 primary settlement tanks with automatic desludge and scum removal. Return activated sludge (RAS)/surplus activated sludge (SAS) pumping station. Anti-septicity treatment at source at the pumping stations. 3 (No.) 12m diameter final settlement tanks with automatic desludge and scum removal. Sludge holding tank. Sludge thickening and processing. Two-stage odour control plant. 330KVA standby power generation. 52.28 kwP roof mounted solar PV array, complete with dual 22kWh EV charging points. Process flows, levels, and quality monitoring; ancillary processes to support the main process units and intelligent motor control centre (MCC) with telemetry. Programmable logic controller (PLC) and human machine interface (HMI) control system. Installation of new long sea outfall pipe (detailed in a separate article). Design criteria for the Ards North WwTW Due to the large number of caravans in the area expected to be served by the new Ards North WwTW, the plant needed to be designed to deal with significant variations in flow and load to ensure satisfactory treatment could be achieved throughout the year. This meant that the works had to cope with a summer population equivalent (PE) of 8508 and a PE of 4809 in winter months. Inlet works & flow control/balancing Flows up to Formula A from the outlying stations can arrive at WwTW simultaneously. The inlet balancing chamber balances out flows going forward to the inlet screening plant. The inlet screening plant consists of two duty/standby incline screens and a cross conveyor. Each screen has a manual inlet penstock installed to enable isolation for maintenance purposes, or for bypass through the static 6mm bar screen. [caption id="" align="alignnone" width="1200"] Inlet works side view - Courtesy of BSG Civil Engineering Ltd[/caption] Screened raw sewage continues to the grit removal plant. The grit settles in a sump underneath the grit paddle. Any grit that settles in this sump is periodically aerated using the grit blower and then removed. From here the grit is transported out of the grit plant by the grit classifier and is deposited into the grit skip. From here it is removed off site for disposal. After the wastewater has passed through the grit removal plant, flow continues to the FFT pumping station. Here influent is collected, and FFT of 48.2 l/s (summer) & 29.6 l/s (winter) is pumped to the PST flow splitting chamber. Ards North Wastewater Improvement Scheme: Supply chain - key participants Client: NI Water Project management: Tetra Tech Principal designer/contractor: BSG Civil Engineering Ltd Structural, hydraulic & process design: Doran Consulting MEICA design: BSG Civil Engineering Ltd Temporary works design: MEA Ltd Electrical installations: AW Control Systems Dewatering: Causeway Geotech Aeration equipment: Xylem Water Solutions Aeration blowers: Aerzen Machines Sludge thickeners: Huber Technology MCC: LMP Controls Inlet screening: M and N Electrical and Mechanical Services | Hydro International Grit treatment: Jacopa Storm screening: Eliquo Hydrok Ltd Actuators: Rotork Septicity dosing & booster pumps: FM Environmental Half bridge scrapers & access flooring/metalwork: Graham Steelworks & Engineering Ltd Odour control plant: John Cockerill Environment Pipes & fittings: APP Fusion Group Standby generators: PM Power Poly dosing plant: ProMinent Fluid Controls (UK) Ltd Micro-strainers: Whitewater Care Photovoltaic solar farm: Solmatix Renewables Ltd DO/MLSS & turbidity instrumentations: Hach Lange Flow meters & ultrasonics: Siemens Tipping buckets: CSO Group Ltd Precast concrete supplies: FP McCann Stormwater storage When incoming flows exceed FFT, the FFT pumping station will start to fill and eventually overflow to the blind storm tank. Once the blind storm tank has reached maximum capacity, flow will backup, allowing the level within the FFT pumping station to increase further. A higher-level overflow pipe allows flows to pass to the online storm tank. Once maximum capacity is reached here, flows will pass to the Ganaway Burn via the 6mm overflow screen and flow meter. Storm return will occur when the FFT pumping station is at a suitable low level. The storm tanks will return flow to the FFT pumping station in sequence i.e. blind tank first. Both tanks are fitted with automated penstocks which will open to return the contents of each storm tank to the FFT pumping station. Both storm tanks are fitted with tipping bucket cleaning systems from CSO Group Ltd, which help prevent build-up on the tank floor to achieve that ‘brushed floor effect’ when empty. The tipping bucket will operate when each of the storm tanks has reached the empty level. [caption id="" align="alignnone" width="1200"] (left) Ards North WwTW - Courtesy of NI Water, and (right) storm tanks tipping bucket installation - Courtesy of BSG Civil Engineering Ltd[/caption] Primary treatment The PST flow splitting chamber receives flows from the FFT pumping station and return liquors pumping station. Flow from the PST flow splitting chamber passes to three primary settlement tanks. These tanks are hopper bottomed and are desludged using automated valves to the primary sludge pumping station. Wastewater continues through to the PST collection manhole which mixes with RAS upstream of the ASP distribution chamber to feed the three ASP lanes. Sludge and scum drawn from the three PSTs arrives in the primary sludge pumping station. This station consists of two submersible pumps in duty/standby arrangement and is used to transfer sludge and scum removed from the PSTs to the thin sludge tank. Activated sludge plant The ASP lanes are identical in design and equipment. Each lane comprises an anoxic zone and an aeration zone. Each anoxic zone is equipped with a mixer. Each aeration zone is equipped with an aeration grid, air control actuator, air flow meter transmitter, two dissolved oxygen probes and an MLSS probe. Each aeration zone is fitted with mixers and aeration grids with fine bubble disc diffusers, which are attached to a central manifold which then connects to the ASP blowers. The influent entering these zones is controlled to maintain a set dissolved oxygen and MLSS level. The dissolved oxygen demand is supplied via the ASP blowers, configured in a duty/assist/standby arrangement. The blowers’ manifold is monitored by a pressure transmitter, a temperature transmitter and an air flow meter transmitter. [caption id="" align="alignnone" width="1200"] Aeration plant air manifold control valves and instrumentation - Courtesy of BSG Civil Engineering Ltd[/caption] Final treatment Flow from the ASP Lanes gravitates to the FST flow split chamber, fitted with adjustable weirs where the flow is split evenly to the three final settlement tanks. Each tank is identical and is equipped with a half bridge scraper, sludge blanket detector, ladder position switch and a proximity switch. Scum travels to the scum collection chamber and furthermore to the FST scum pumping station. The station is equipped with a duty/standby pump set which pumps its contents to the thin sludge tank. The tanks desludge is controlled via flow meters through actuated hydrostatic valves located in separate chambers that adjoin the RAS/SAS pumping station. Each tank’s settled effluent hydraulically discharges into the tank’s outlet launder channel to the final effluent/washwater pumping station. Final effluent Final effluent flows into the final effluent/washwater pumping station and on to the final effluent sample chamber. Here, the final effluent is monitored for turbidity and temperature levels and is also the dedicated location for the auto sampler. The final effluent/washwater pumping station contains two submersible fixed speed final effluent/washwater pumps in a duty/standby arrangement. These are used for supplying the washwater tank with the necessary effluent for washing the screens, sludge thickeners, etc. Final effluent is returned through a packaged plant automatic backwash strainer system located inside the control building. The automatic backwash strainer system, situated inside the sludge thickening building, is a filter that is used to remove particles from the final effluent returned from the final effluent/washwater pumping station. Final effluent flows from the sample chamber which is connected to the long sea outfall pipe. Sludge pumping, treatment & storage The RAS/SAS pumping station is equipped with two sets of pumps. RAS pumps and SAS pumps, a level ultrasonic and high-level floats are used to control both sets of pumps. The duty pump returns the desludge from all FSTs back to the PST collection manhole, continuing to the aeration distribution channel. The SAS pumps, also arranged in a duty/standby configuration, periodically pump forward sludge to the thin sludge tank. The frequency is operative set to maintain a desirable MLSS level within the ASP lanes. [caption id="" align="alignnone" width="1200"] RAS/SAS pumping station - Courtesy of BSG Civil Engineering Ltd[/caption] The thin sludge tank is equipped with an external mixer for the blending of the tank’s contents to feed the sludge thickening plant. A level ultrasonic with low and high-level floats are used in the control of the mixer. Mixed sludge from the thin sludge tank is pumped to the sludge thickening plant via the two thickeners feed pumps. These pumps are progressive cavity pumps and are arranged in duty/standby configuration. The pumps are VSD controlled to allow the flow to the thickening plant to be controlled. There are two sludge thickeners, with an individual throughput of 8.3 m3/hr @ 1.3% DS with a discharge of no more than 6%, based on a 5-hour day, 7-days per week operation at 100% of the maximum design load. The thickeners are arranged in a duty/standby configuration with two actuated isolation valves installed on the feed pipework allow this to be fully automated. If one thickener was to develop a fault, the standby thickener can resume operations without manual intervention. Polyelectrolyte is made up on site to be added to the sludge fed to the sludge thickening plant. The addition of this chemical aids flocculation and makes thickening easier. This plant is a liquid polymer set. The liquid poly is delivered within IBCs for the makeup process. The set mixes the poly from the IBC with water to a preset concentration rate and is then transferred to the poly storage tank. The duty poly dosing pump doses to the thickener’s sludge feed pipework from here. Thickened sludge from the sludge thickening plant is transferred to the thick sludge tank. Here thickened sludge is stored for removal off site. A collection tanker removes the tank’s contents off site by coupling to the tank’s Bauer Coupler connector. [caption id="" align="alignnone" width="1200"] PST No 1 & control building - Courtesy of BSG Civil Engineering Ltd[/caption] The tank is equipped with a decant valve arrangement to facilitate settlement of the tank’s contents. The tank is also equipped with a level ultrasonic, low and high-level floats for level status and control of an externally fitted mixer for tank agitation. The return liquors pumping station receives liquors from the following areas: inlet works drains, thin sludge tank decants and overflow, thick sludge tank decants and overflow, sludge thickening plant bund, FE and washwater drains and odour control plant drains. The station comprises of two fixed speed pumps, which are arranged in duty/standby arrangement. These return liquors to the activated PST splitting chamber. Washwater pumping The final effluent washwater & potable water booster sets are positioned within the sludge building. A ’dual washwater tank’ system is in place to feed both sets of pumps. The GRP dual washwater tank is designed with a lower compartment which holds 6m3 and an upper compartment which holds 1m3. The lower compartment is designed to contain the final effluent delivered via the final effluent/washwater pumping station, which in turn feeds the final effluent booster set which boosts the pressure as required for the washwater of the inlet screens, sludge thickeners, odour control, and the storm tank tipping buckets. The upper compartment is designed to contain potable water which in turn feeds the potable water booster set, which boosts the pressure as required for the nine retractable hose reels around the site for wash down, poly makeup plant water and poly carrier water. [caption id="" align="alignnone" width="1200"] Low level structures RC concrete installation - Courtesy of BSG Civil Engineering Ltd[/caption] Odour control plant The 2-stage odour control unit (bio & carbon filter) is connected to the various strategic areas. The odour control unit comprises of two odour fans, which are arranged in duty/standby arrangement. Actuated valve, flow meters, pressure transmitters and temperature transmitters are used to control the odour control system. Only odour omitted from the sludge thickening building (due to their extreme odorous compounds) will bypass the biofilter and go directly to carbon filter for treatment. Outlying pumping stations Existing treatment facilities at Ballywhiskin and Carrowdore were decommissioned and replaced with new pumping stations, while a completely new pumping facility was constructed at Sandycove Caravan Park where no NI Water asset previously existed. The last of the outlying WwPS to be upgraded was Ballywalter Fowler Terminal Pumping Station (TPS). This facility was completely refurbished with larger capacity pumps, a new MCC and additional storm storage capacity. Fowler Way TPS pumps to Sandycove WwPS which in turn pumps to the new Ards North WwTW, while the pumping stations at Ballywhiskin and Carrowdore pump directly to Ards North. [caption id="" align="alignnone" width="1200"] (left) Ballywhiskin TPS - Courtesy of NI Water, and (right) Carrowdore WwPS - Courtesy of BSG Civil Engineering Ltd[/caption] Civil construction challenges There were various challenges throughout the construction phase of the works that had to be overcome to ensure that the contract programme was achieved. As the project spanned over a 20km distance, there were varying ground conditions to deal with from very loose running sand in the gravity pipeline sections at Sandycove; soft, deep peat at Carrowdore WwPS; extremely hard rock at Ballywhisken to stiff clays with loose gravels at the WwTW site. This led to a variety of temporary works systems having to be designed and employed to deliver the works safely. Groundwater levels also varied across the scheme with various dewatering techniques used to maintain dry working spaces. Artesian water pressure and groundwater under tidal influence presented difficulties during the construction of these works. Overhead services also presented a construction issue at the WwTW site. As a result, carefully planned construction sequencing and specialised plant were employed. 13.5km of pumping main was installed along roads within this rural area. In order to keep to programme, pipe installation had to be carried out using a minimum of two separate teams at all times. Due to the limited options for suitable diversionary routes in the area, the pipe installation programme had to be carefully managed and continually communicated to the roads authority to ensure both pipe installation squads had consecutive sequencing of works throughout the pipeline installation phase of the scheme. [caption id="" align="alignnone" width="1200"] (left) Sandycove WwPS and (right) Ballywalter Fowler Way TPS - Courtesy of NI Water[/caption] Sustainability To boost the sustainability of the treatment facility, 138 solar PV panels from Solmatix Renewables Ltd were fitted to the roof of the new control building which will produce over 45,000 kWh per annum. This renewable energy could save NI Water up to £300k over 25 years. Charging points for NI Water’s growing fleet of electric vehicles have also been installed at the new treatment works. Communications & PR NI Water and its project management team developed a proactive comms and PR strategy for the Ards North Wastewater Improvement Scheme which included circulation of project brochure, issuing of regular press releases, letters to residents, briefings for elected representatives, circulation of progress updates, safety events with children, and face-to-face meetings with landowners. Myriad stakeholders were kept up to date with progress and informed in advance of pipelaying works and associated traffic management arrangements. Following completion of the project, a site tour of the new WwTW was organised to give local elected representatives the opportunity to view the modern facility first hand. Feedback from the visit was extremely positive. [caption id="" align="alignnone" width="1200"] NI Water, TetraTech, BSG Civil Engineering Ltd and Farrans along with local elected representatives to mark completion of the £18m Ards North Wastewater Improvement Scheme - Courtesy of NI Water[/caption] Conclusion A collaborative, forward-thinking approach between NI Water, BSG Civil Engineering and Tetra Tech has produced whole-life cost, programme and carbon savings in the delivery of this project. Phased flows were brought into the new Ards North WwTW between the months of November 2022 and January 2023. During this time, a process optimisation phase took place before the plant was rigorously tested and commissioned under varying flow and load scenarios. The plant was then put through a period of intensive detailed process sampling achieving highly performing results during separate 14 and 28-day sampling periods during Spring 2023. The project was successfully completed and handed over to NI Water ahead of the 2023 summer tourist season. The new Ards North WwTW is ensuring that high-quality effluent is being discharged out to sea, helping to improve the bathing water quality along this part of the Ards Peninsula in line with the project objectives.

The Don Regulators comprise three regulator gates on the River Rother that are owned, operated, and maintained by the Environment Agency (EA). The purpose of the regulators is to reduce the risk of flooding to settlements within the River Don catchment by attenuating flows in the River Rother. JBA-Bentley has completed the design and installation of the first regulator gate. The detailed design of the second gate is currently being undertaken, while the third regulator is being modelled as part of the optioneering phase. In addition to the installation of the first regulator gate, a bespoke full-channel fish pass has been installed directly downstream to improve migratory fish passage.

Meadowgate Regulator

The Meadowgate Regulator is located within the Rother Valley Country Park. The historic regulator consisted of a single fish belly bottom-hinged tilting gate, operated by a single electrically powered hydraulic ram.

[caption id="attachment_14798" align="alignnone" width="1200"] (left) location of the regulator gates and (right) the new Meadowgate top-down vertical control gate[/caption]

In 2023, JBA-Bentley replaced the gate with a top-down vertical control gate, improving the resilience of the structure. Alongside the regulator gate, a new control building and EA Office have been constructed. Both buildings have green roofs and EV charging. The gate was commissioned in February 2024 and is ready to operate during a flood event.

The gate is operated to ensure a maximum of 60m3/s forward flow is always maintained. When flows exceed 60m3/s the new gate is lowered and water levels in the Rother rise and begin to spill into the washlands located within the Rother Valley Country Park, which can retain approximately 1.5 million m3.

Meadowgate full channel fish pass

The removal of the bottom tilting gate provided an opportunity to improve fish passage on the River Rother through the installation of a unique full-channel width fish pass. This fish pass is designed with 4-tonne reinforced concrete ‘fish tiles’ featuring varied-height upstands supplied by Craven Concrete Ltd.

The tiles were designed with the aid of computational fluid dynamics modelling to ensure they influenced the nature of the flow to allow for varied fish species to migrate upstream while also withstanding hydrodynamic forces during extreme events. The fish species focused on are coarse fish, European eels, brown trout, large migratory salmonids, and lamprey.

The 40m long stilling basin has been removed by building up the existing concrete channel bed and grading out the levels to create a uniform slope. The ‘fish tiles’ have been laid onto the regraded channel. This is the first fish pass of its kind in the world.

[caption id="attachment_14802" align="alignnone" width="1200"] Precast concrete ‘fish tiles’ from Craven Concrete Ltd positioned in the channel - Courtesy of JBA-Bentley[/caption] Meadowgate temporary works solution: Syphon pumps & contingency planning

The fish pass installation required the full channel as a dry working area. To achieve this, an innovative syphon system, designed by Dutch water specialist Vanderkamp UK, was installed. The solution involved complex temporary works and contingency planning.

To form the upstream dam, the new regulator gate was dropped to bed level, allowing upstream water levels to build up. The gate was designed to operate this way; hence no further calculations were required. Four syphon intake pipes were installed upstream of the gate to divert up to 12m3/s of flow out of the channel for 115m, around the working area.

The syphons were primed using electric vacuum pumps which expelled all the air from the system to draw water through the pipes. By utilizing the existing gate and power supply, the syphons had a far lesser environmental impact than a typical cofferdam and over-pumping solution. The total embodied carbon associated with the syphon solution was 464 tons.

Due to the scale of the flows being diverted, the loads imposed on the riverbanks by the pipes when full were considerable. JBA-Bentley and Vanderkamp UK worked together to design a temporary support system involving ground-bearing improvements, steel and timber supports, and retaining structures. Checks were also carried out on the existing channel wall where the forces from the syphons acted upon it.

[caption id="attachment_14797" align="alignnone" width="1200"] (left) The dewatered channel and (right) ‘fish tile’ installation - Courtesy of JBA-Bentley[/caption]

In addition to work to ensure the stability of the syphons, an energy dissipation system was designed and installed at the syphon outlets to combat scour, and a bubble curtain was installed upstream to deter fish from entering the syphons. The installation of the system was done via a temporary crane pad. Due to the nature of the site and its space constraints, this was a challenging design. JBAB worked closely with the landowner, Rother Valley Country Park, to balance the desire to allow continual access into the park with ensuring the crane was safe to carry out the required lifts. To achieve this, the crane had to be placed in close proximity to the riverbank. Slope stability modelling and bearing capacity calculations were undertaken to ensure the crane could be operated safely.

Recent storm events have recorded flows higher than the syphon capacity. To manage the risk of this occurring during the programmed works, a contingency plan was developed.

The basis of the plan was developed from a bespoke JBA flow forecasting system, which forecasted the flow over a 2-day period. Using the data from the forecasting system, flow monitoring data provided by Vanderkamp UK, upstream gauge data, and the storage capacity of the washlands upstream of the gate, JBAB could make informed decisions on whether the gate needed to be raised to allow flow to pass forward.

This decision was made with the aid of hydraulic calculations and decision flow charts within the contingency plan, allowing for quick and effective decision-making, ensuring flood risk was not impacted upstream and the safety and well-being of the site team working in the channel was never put at risk.

[caption id="attachment_14801" align="alignnone" width="1200"] Syphon outlet - Courtesy of JBA-Bentley[/caption] Don Regulators: Supply chain - key participants Client: Environment Agency Project delivery: JBA-Bentley JV JBA Consulting JN Bentley Ltd Principal designer: Callsafe Services Ltd Gate design: Aquatic Control Engineering Syphon design: Vanderkamp UK Electrical installations: IMAC Ltd Building design: JP Chick & Partners Building design: Peter Wells Architects Supporting ECC Supervisor with new gate & associated equipment: KGAL Consulting Engineers Ltd Precast fish pass tiles: Craven Concrete Ltd In situ concrete works: Bells Construction Ltd Metalwork fabrications: Fabtek Green roof: ABG Geosynthetics Ltd Canklow Regulator

The Canklow Regulator is the furthest downstream of the three Regulators, approximately 3.5km upstream from the confluence of the River Rother and the River Don at Rotherham.

The existing structure consists of a single electrically powered vertical lifting sluice gate operated by an electric wire rope hoist, comprising a drive motor gearbox assembly, cross shaft with integral rope drums, and support bearings.

To improve resilience and the operation and maintenance of the asset, JBA-Bentley is completing the detailed design and build of a new vertical regulator gate and associated MEICA and civils infrastructure.

The MEICA structure consists of a 20.3-ton vertical gate, mounted on a new steel bridge and working platform, which shall also house 13.5 tons of drive equipment for operating the gate.

Two 4kW motors, working in a duty/standby configuration, will provide drive to the gate via bevel and gearboxes, which turn a single driveshaft spanning the width of the gate. On this driveshaft, one at either end of the gate, are rack and pinion gear assemblies, which convert the rotation of the driveshaft to the vertical motion of the gate. The total gear ratio from motor to driveshaft is an approximate reduction of 4410:1, allowing relatively small motors to be specified.

[caption id="attachment_14807" align="alignnone" width="1200"] (top left) the existing Canklow regulator gate (bottom left) 3D model of the new Canklow Regulator and (right) bathymetry of Woodhouse Mill Washland - Courtesy of JBA-Bentley[/caption] The power supply to the gate will be a three-phase supply routed via a new MCC, which will contain the control modules, centralised drive units, and the telemetry system for remote monitoring and operation of the gate. The operation of the gate will be from on-site or via telemetry, with some semi-automated functions. The facility for future full automation of the site has been incorporated into the design. The MCC and electrical components will all be located within a kiosk mounted on a raised steelwork platform to lift the electrical components above the 0.1% AEP flood level. Also on this raised platform will be the DNO kiosk bringing power onto the site from the national grid, and a standby generator to provide resilience in case of power failure.

To support the new gate structure over the next 50 years, a new anchor restraint system has been designed. A buried sheet-piled ‘dead-man’ wall will be installed with ten 36mm anchor rods, evenly spaced, connecting to a waling beam on the wet side of the existing channel wall. This will be mirrored on both riverbanks.

The new infrastructure replicates the existing system, which has been determined to be past its design life and insufficient in supporting the new gate.

The existing superstructure of the control houses will be demolished, the foundations will be retained and extended where required to support the new gate structure using cast-in bolt sets.

A new permanent crane pad will be constructed on the south bank for the construction, maintenance, and decommissioning of the gate. This will double as parking spaces for EA operatives when not being used by a crane.

The JBA-Bentley team worked collaborative to optimise the delivery. This meant that site constraints were identified, and the design was completed with buildability and safety as the focus. A key constraint on the scheme is the proximity of the Northern Power sub-station and overhead power lines. The design of the dead-man walls, crane pad, and steelwork platform was completed to ensure that the plant and temporary works required for construction and installation were outside of the powerline exclusion zones.

[caption id="attachment_14796" align="alignnone" width="1200"] Overhead power exclusion zones within model - Courtesy of JBA-Bentley[/caption] Woodhouse Mill

The Woodhouse Mill Regulator is situated between Canklow and Meadowgate. It uses a single electrically powered vertical lifting gate to retain water. This gate is operated by an electric wire rope hoist, which includes a central drive motor and gearbox assembly, half shafts, spur and pinion driven rope drums, and support bearings, all counterweight assisted.

JBA-Bentley is currently carrying out hydraulic modelling on behalf of the EA as part of the optioneering phase. The options include passive solutions, such as a baffle or orifice plate spanning the width of the channel to continue to utilize the upstream storage. Due to the size of the Don catchment, the modelling required three individual models to be run together:

The Rother. Don/Dearne. Lower Don.

Multiple return periods are being considered, resulting in hundreds of models runs. The modelling also uses a continuous simulation approach, which adds to the complexity of the model runs.

Summary

The upgrading of infrastructure of the Don Regulators will ensure continued flood risk benefits into the future for the Don Catchment and surrounding area with improved resilience and reliability of the new assets. Alongside the reduction in flood risk, the environment and biodiversity will improve in the River Rother as a result of the Meadowgate Fish Pass.

Gouthwaite Dam impounds the River Nidd on its route from the head of Nidderdale, North Yorkshire, and is the last in a cascade of three reservoirs within the valley; those upstream being Angram and Scar House. The Category “A” Dam was constructed between 1893 and 1901. The project undertaken by Mott MacDonald Bentley (MMB) on behalf of Yorkshire Water was for the construction of a new reservoir drawdown siphon pipe with a hydraulic capacity of 13,500 l/s to allow the water level in Yorkshire Water’s second largest reservoir to be lowered by 5m in 5 days in the event of an emergency, following best practice and guidance from the appointed Qualified Civil Engineer (QCE). Background to the project

In 2017 (AMP 6), MMB was contracted to produce an acceptable design and construction of the downstream leg of the siphon. In 2021 (AMP 7), MMB resumed works, assessing opportunities in a period of detailed design, with construction of the upstream and crest elements of the siphon commencing in November 2022.

Design

The additional outflow capacity required to achieve a 5m drawdown after five days with a Q10 inflow was confirmed during the 2017 concept design phase to be achievable by installing a siphon. The hydraulic design of the siphon was acceptable to the QCE. The design of the siphon inlet was required to prevent the development of air-core vortices forming at the inlet end of the siphon at levels approaching 5m below Top Water Level (TWL). This was achieved by ensuring the inlet of the siphon was suitably submerged, with a 3m x 3m bar cage proposed, with a solid roof situated on suitable rock armour.

The design constraints within the reservoir related to the ground profile, which is normally below water. To map the profile, a bathymetric survey was undertaken by APEM Ltd to ascertain the surface profile, with a sub-bottom profiling survey (silt survey) also undertaken by APEM to understand the potential levels of soft, silty material on the reservoir bed.

[caption id="attachment_12577" align="alignnone" width="1200"] Pontoon excavator - Courtesy of Mott MacDonald Bentley[/caption] The design of the upstream leg of the siphon included a 70m length of 2000mm Ø flanged steel pipework leading from the inlet to the crest, with excavation of the reservoir bed to install at the designed depth necessary to attain the required submergence depth of the inlet end of the siphon. Excavated material could then be utilised as backfill and provide sufficient resistance to thrust forces about bends near the crest. Prior to passing through the crest, the siphon tapers from 2000mm Ø to 1600mm Ø.

The constraints through the crest of the dam were with respect to minimising the impact to the earth embankment dam and the overflow channel downstream of the gravity dam. The level of the siphon through the crest were dictated by the hydraulics of the siphon, with the horizontal alignment of the pipe such that it was sat on the concrete core, some of which required removal, of the earth embankment dam. The vacuum pump priming system, air release pipework and 1600mm Ø isolation valve was positioned within the crest, with the siphon proceeding downstream towards an actuated gate valve installed just prior to the discharge location into the spilling basin, with the route taking consideration into its proximity to, and level of, the existing right-hand overflow collection channel.

Enabling works

With the dam sited along the River Nidd, one of the major challenges of the scheme was the extent to which the reservoir could be drawn down, given the compensation flow requirements required to provide a constant feed to a downstream fish farm throughout the year. There is little to no control of inflow into the reservoir, with the compensation pipework being the only means of draining it down.

[caption id="attachment_12582" align="alignnone" width="1200"] Offloading pipes - Courtesy of Mott MacDonald Bentley[/caption]

Any drawdown required a variety of factors to be assessed; the catchment is very ‘flashy’ with levels directly associated to rainfall in the large catchment. Any drawdown needed to be low enough to provide protection to the crest works within the cofferdam and beach area for pipe construction, but not too low that pontoons may ground out. With works programmed over a 16-month construction period, designs had to consider periods of very dry and very wet weather, whereby a drop in reservoir levels would see the crane unable to service the pontoon, and an increase in them leading to the in-reservoir works area being flooded out. A 2.7m drawdown was calculated and agreed with the client and other stakeholders, prior to being implemented in March 2023.

The drawdown provides 1-in-5-year storm protection without the reservoir overflowing, whilst retaining 50% of the reservoir’s water stock to be used at compensation flows, which feed the downstream fish farm.

A temporary pumping arrangement was also installed, the primary use of which being to draw off clean water from the top of the reservoir to maintain compensation flows should siltation be an issue when installing the siphon within the reservoir basin. The pumps and bagging were situated on a purpose-build pontoon cited 200m behind the dam, with flows discharged into the existing spillway channel. The pumps could also be utilised to assist in the drawdown of the reservoir as required.

Given the water level fluctuation, a means of isolation from the reservoir to the works within the crest was required to facilitate construction and protect the embankment during site works. A cofferdam was designed to protect the crest from up to a 1-in-1000-year storm event, allowing the site team to carry out works even when the reservoir is at top water level. The design had to be flexible, given that the concrete base and chamber were to be installed within it, alongside the large 1600mm Ø pipework and gate valve.

[caption id="attachment_12578" align="alignnone" width="1200"] Cofferdam installation around the concrete core - Courtesy of Mott MacDonald Bentley[/caption] Working closely with Groundforce, MMB assessed different phases of the work and how the cofferdam could be optimised to suit construction requirements. The existing concrete core was utilised in the design to resist frame loadings throughout, alongside whilst the bottom frame was designed to be removed following the casting of the slab to facilitate further construction of the siphon.

Alongside frequent reviews with Groundforce, MMB undertook internal reviews for the cofferdam, highlighting possible failure mode, such as frame rotation, slope stability and the strength of the concrete core, implementing additional design checks and site to ensure a safe and effective design that could be constructed and maintained on site.

The project has aimed to minimise the impact of the enabling works by incorporating them into the permanent works where possible. It was proposed to install an area on the beach of the reservoir once it had drawn down to facilitate the forming of the upstream pipework and to position a crane, which could be utilised to lift pipes and equipment onto the pontoon. A ramp from the crest to the beach was installed using reclaimed stone from another scheme, which shall be retained for future maintenance purposes, reducing 1500T of muckaway from the site and reducing the number of vehicle movements.

The placement of a crane within the reservoir as opposed to on the crest reduced loadings on the embankment, as well as mitigating potential access issues to the remainder of the site. Embodied carbon within the scheme has also been reduced by utilising surplus stone from the site compound to construct the permanent vehicular access to the downstream valve, further reducing imported materials, alongside ensuring careful removal of wave wall masonry and stone pitchings, to ensure that they can be reinstated, maintaining the heritage of the structure.

[caption id="attachment_12574" align="alignnone" width="1200"] Installation of the large diameter siphon pipes - Courtesy of Mott MacDonald Bentley[/caption]

Surveys and previous workings within the reservoir had encountered peaty soils, which would require excavation prior to the installation of the upstream leg of the siphon. A silt mitigation plan was compiled by MMB with input from Yorkshire Water, the Environment Agency and Jifmar Group; the specialist marine subcontractor undertaking the in-reservoir works. Physical measures taken to contain silt included the installation dual silt curtains anchored to the bed of the reservoir, with an additional curtain installed around this.

Monitoring points installed in three locations by Meteor Communications Ltd provided real-time readings of pH, turbidity and dissolved oxygen, enabling out of hours remote monitoring/alarms and reducing the need for people and water interface. Text alerts were sent to the project team when readings exceeded those denoted in the silt mitigation plan, with MMB and Yorkshire Water operatives undertaking agreed actions and tests dependent upon the works being undertaken at the time (enabling works, low-risk and high-risk).

[caption id="attachment_12572" align="alignnone" width="1200"] Installation of the large diameter siphon pipes - Courtesy of Mott MacDonald Bentley[/caption] Gouthwaite Reservoir: Supply chain - key participants Design & build: Mott MacDonald Bentley Bathymetric survey & silt survey: APEM Ltd Silt monitoring: Meteor Communications Ltd Upstream pipework installation methodology: Jifmar Group Cofferdam: Groundforce Piling: Sheet Piling (UK) Ltd Siphon pipework: Powerrun Pipe-Mech Ltd Siphon pipework: Freeflow Pipesystems Divers/pipework installation: Jifmar Group Valves: AVK (Supplied by Glenfield Invicta) Actuators: AUMA Actuators Ltd Air release pipework: Dax Air Ltd Site electrics & power: Total Automation & Power Kiosk: Morgan Marine Construction

MMB mobilised to site in November 2022, with the crest and downstream siphon leg constructed by JN Bentley, and the in-reservoir works subcontracted to Jifmar Group. At this stage, collaborative planning sessions and Synchro software were utilised to enable teams to visualise the scale of the project and highlight potential programme clashes, driving efficiencies within the scheme from the offset.

[caption id="attachment_12571" align="alignnone" width="1200"] Screenshot of Synchro software showing workings around the crest - Courtesy of Mott MacDonald Bentley[/caption]

Having drawn down the reservoir, the silt curtains were installed, and the beach area utilised to accommodate the lifting pad for the crane and pipework storage. A pontoon was lifted in, with a 35T long-reach excavator positioned on it to commence excavations within the reservoir. As this was undertaken, the 2000mm Ø pipe assembly was joined together on the beach, complete with buoyancy aids to ensure the pipe would not sink should reservoir levels rise. Once both elements were completed, the pipe was floated out into position and floats cut to ease the pipework into the excavated trench.

Meanwhile, MMB commenced the construction of the downstream leg of the siphon, connecting onto the length previously installed in 2017 as well as installing the cofferdam. To facilitate the length of siphon through the crest, a section of the concrete core required removal. The use of wire cutting reduced HAV’s to zero and provided a perfect surface for reinstatement; with 82 tonnes of concrete removed.

Once the siphon pipework was installed within the aperture, the core was sealed by dowelling into the existing core and pouring a new fibre-reinforced concrete surround, saving time constructing reinforcement and providing carbon savings.

Hydrotite was applied around the pipe-concrete interface, with imported puddle clay compacted on top to Peak Flood Level.

[caption id="attachment_12576" align="alignnone" width="1200"] Concrete core: (top left) before and (bottom left) after wire cutting with 82t of concrete removed, and (right) Reinstated concrete core following installation of 1600mm pipe prior to connection with the upstream leg - Courtesy of Mott MacDonald Bentley[/caption] Project status

As of May 2024, the scheme had in excess of 300 ‘Perfect Days’, with zero service strikes or lost time incidents. Multiple work experience students have visited and spent time on site, to witness the scheme and sample construction work life. Significant elements including siphon pipework and priming apparatus have been installed, with final installations and site reinstatement ongoing prior to full commissioning taking place in June 2024. The Gouthwaite Reservoir Project has prioritised being sympathetic to the local environment, bringing a 19th century structure up to 21st century safety standards and ultimately providing safeguards to the downstream community.

Bourn Reservoir is an above-ground reservoir complex located approximately five miles outside Cambridge, England. Only one tank was still operational after the other two were removed from service due to natural degradation. A new tank was required to meet demand from large-scale developments in the supply area. A review was conducted to ascertain the total water volume required, revealing the need for an additional 8 ML of storage on top of the capacity of the remaining tank by the summer of 2022. Stonbury was contracted to demolish the disused circular prestressed tank in 2020, whilst the other remained in service, and in 2021, Stonbury commenced the construction of a new concrete tank next to the operational reservoir. Scope of works A summary of the works undertaken is as follows: Disconnection and demolition of the old Reservoir No 2. Ground investigation works and tree removal. Groundworks. Design of new concrete tank. Construction of new tank, drainage and connecting pipework. Installation of MEICA elements. Site description The Bourn Reservoir site is a small, spatially-constrained compound that originally contained Reservoirs 2 and 3. Land owned by the farmer adjacent to the site was utilised for the site compound which housed welfare units, a storage area, and turning space for vehicles and machinery. The land was returned after the programme was complete. [caption id="" align="alignnone" width="1200"] View of tank under construction with newly painted exterior walls - Courtesy of Stonbury[/caption] Project team The project was delivered for the client, Cambridge Water Company, by direct-delivery water sector specialist contractor, Stonbury, as principal contractor and principal designer, and Mason Clark Associates as their designer. Bourn Reservoir: Supply chain - key participants Client: Cambridge Water Company Principal contractor: Stonbury Designer: Mason Clark Associates Subcontractor: GM UK Ltd MEICA installation: IWS Mechanical & Electrical Ecological appraisal: Middlemarch Environmental Ltd Concrete delivery: Hanson UK Concrete pump hire: Camfaud Concrete Pumps Ltd Crane hire: Emerson Cranes Handrail & staircase supplier: L&G Engineering Ltd Internal steps & ladders supplier: Chemglass Access doors & hatches: Technocover Ltd Project challenges The build possessed several unique challenges due to constraints on time and space. The planning application review period was extended for further environmental assessment as part of the Tree Retention Scheme, which introduced significant time constraints to the programme. Proactive action was taken to minimise delay, and a revised foundation plan was submitted accounting for the proximity of tree roots and including provision of a perimeter root barrier trench for additional protection. Planning permission was granted in October 2021, leaving under a year to complete the project by summer 2022. Innovative pre-construction planning was required to overcome the issues posed by the constrained size of the operational area. As the site footprint dictated a tank shape that was non-optimal for water flows, a computational fluid dynamics (CFD) analysis was completed to identify a ‘best practice’ design to reduce dead spots and protect water quality. As the new tank footprint was partially on virgin ground and partially on ground where the previous structure had stood, there was a risk of differential settlement. To mitigate this risk, a tailored ground investigation was conducted to obtain data for a predictive settlement analysis to inform the engineered fill design and ensure a robust outcome. [caption id="" align="alignnone" width="1200"] Tank under construction, showing precast concrete slabs being maneuvered into place by a crane - Courtesy of Stonbury[/caption] Design Mason Clark Associates was responsible for the civil and structural design of: The reinforced concrete twin-compartment reservoir, excluding the detailed design of precast roof slab panels. The reinforced concrete valve house. The surface, underdrainage, and foul water drainage systems. The external steel roof access staircase. The client stipulated that each cell would require the following features: Opposed high-level inlet and a low-level outlet, connected to the existing network. Automated control valves. Combined metered washout/overflow pipe. Overflows with sufficient capacity to take design inflow whilst maintaining sufficient freeboard to the soffit of the roof. Washouts, sized suitably to enable the drain down of each cell over a 24 to 48 hour period without causing flooding to surrounding watercourses. Sufficient ventilation to ensure that each cell is not over-pressurised during filling or a vacuum created during drawdown. Access doors and hatches to meet LCPB 4 rating and SEMD requirements. All necessary ductwork for telemetry and security cabling. Mains alterations to accommodate the new reservoir. Arrangements for taking compliance samples. The proposed tank was to have an approximate footprint of 850m2 and operate with a top water level of 79.2mAOD (ground level is approximately 71.4mAOD). The inlet was to be connected to the pumping main, whilst the outlet connected to the same main as Bourn Reservoir 3 so that they would operate hydraulically together. The placement of inlet and outlet valves, baffle walls and weir boxes were designed in accordance with results from the CFD analysis. [caption id="" align="alignnone" width="1200"] Demolition of the disused circular tank prior to construction - Courtesy of Stonbury[/caption] Addressing the drive to build assets with lower embodied carbon and to reduce the length of the programme, the design incorporated the use of precast concrete roof slabs in addition to conventional in-situ pour concrete. This was preferred to a fully precast solution due to the risk of perennial ingress issues at precast joints. This would help to reduce embodied carbon by approximately 10% compared with a traditional build and make the 48-week programme possible. The structural elements of the reservoir and pipework were to have a minimum design life of 50+ years, and 20+ years for all other elements. All structural and geotechnical design was in accordance with the relevant section of the Eurocodes, and all concrete elements were designed with a water-tightness classification of 1. All work was designed to be carried out in accordance with the latest CESWI, WIMES and Cambridge Water Company general engineering specifications and to meet DWI requirements for potable water storage units and the current SEMD guidance. Environmental management A Project Site Environmental Assessment sought to register and mitigate site-specific environmental impacts such as noise, land and watercourse pollution, waste materials and damage to local ecology. Identified environmental risks were controlled through measures detailed in Risk Assessments and Method Statements. A preliminary ecological appraisal was undertaken during the pre-construction phase to determine the presence of dedicated nature conservation sites and protected species in proximity to the site. The site was not within or near an SSSI. No notable plant species were identified but some notable animal species were. Recommendations were provided based on the ecological mitigation hierarchy to avoid, mitigate, and compensate during and after the programme. [caption id="" align="alignnone" width="1200"] Construction workers building reinforcement cage for walls - Courtesy of Stonbury[/caption] Health & Safety A detailed H&S file was prepared for the client. During construction, special site-specific health and safety considerations were planned, managed and monitored using a variety of means, including: Site-suitable PPE. Approved RAMS. Vibration, noise and CoSHH assessments. Daily Point of Work Risk Assessments (PoWRAs). Suitable barriers and safety signage. Obstructions or trip hazards protocol. Agreed working hours and strict adherence to quiet periods. Asbestos protocol. Demolition In 2020, existing services into Reservoir 2 were disconnected and removed in preparation for tank demolition. Due to the spatial constraints of the site, demolition was carefully planned with an appropriate methodology to mitigate risk to the live operational tank. An excavator was employed to demolish the roof, with an attached claw to cut the concrete walls into small vertical sections. All broken material was pushed into the middle of the tank during demolition to protect the adjacent asset. Once demolished, material was removed from site. [caption id="" align="alignnone" width="1200"] The site for the new reservoir after demolition of the previous tank - Courtesy of Stonbury[/caption] Site preparation A site compound was constructed for offices and welfare facilities. This area also had space for limited parking, temporary materials storage and a turning area for construction vehicles. Heras fencing was erected on the boundary of the compound area and construction warning notices were posted at the site entrance gates. To prepare the area for the reservoir, the locations of services were pre-determined using a combination of existing service drawings, site knowledge and CAT scanning using a signal generator followed by hand-excavated trial holes. Base construction The site for the new tank was excavated, removing spoil and saving a small stockpile for backfilling. Old balancing pipework was removed, and the existing pipes were capped so that they could be reconnected upon project completion. Underdrains were installed. Fill-to-base was completed in accordance with the design informed by the predictive settlement analysis. The area was levelled, filled with type 1 material to the specified formation level and rolled. A 50mm concrete blinding base was poured from a dumper and levelled by hand. Concrete square bars were laid by hand to support the reinforcement steel placed directly on the blinding slab and tied, ensuring correct laps in accordance with the design. Timber formwork was levelled using a laser level placed on each end. Once this was braced, the floor was completed in four separate concrete pours. The sump was poured at the same time using a concrete pump and vibrated constantly as the concrete entered the reinforcement. [caption id="" align="alignnone" width="1200"] Formwork panels - (left) outside view during construction of the upper wall, and (right) inside view during construction of walls and columns – Courtesy of Stonbury[/caption] Wall construction A panel system with film-faced plywood was built for the wall and column formwork according to drawings. Completed shutters were lifted into place using an excavator for the 3m high lower walls and a tower crane for the 7.8m high upper walls. Reinforcement cages were fabricated on the ground and lifted into position with a tower crane to minimise working at height. Inner shutters were held in place with push-pull props drilled and fixed to the base slab. Outer shutters were fixed using Dywidag bolts and tie bars on the outer edge. Timber stop ends were fixed to the ends of the shutters. The concrete was poured in sections and vibrated as filling proceeded, employing both external formwork vibrators and 10m long internal vibrators to achieve the required concrete finish. Shutters were lifted, cleaned and re-positioned for each 5m wide pour section. Once all sections were full, laser levels were used to check levels and tops were floated off. Pipework At this stage, trenches were excavated for overflow and outlet pipework. Outlet pipework was installed first and connected to the existing valves. A flow meter was installed in line and a chamber was built around it. Pipes were capped prior to installation, chlorinated and bagged off to prevent contamination. Once installed, pipes were pressure-tested and the trenches were filled with stone and backfilled in layers. The flow meter chamber was excavated using a 5-tonne excavator and concreted with formwork and vibration. A Technocover lid was drilled and fixed to the cover slab and a galvanised ladder was affixed to gain access to the flow meter. Ducting was installed for the control panels and mains power. Once the main walls were complete, internal access and pipework were installed. [caption id="" align="alignnone" width="1200"] Construction workers guiding precast concrete roof slabs into place - Courtesy of Stonbury[/caption] Roof construction To construct the roof, 30 steel beams were lifted onto the reinforcement cage using a tower crane with two operatives in scissor lifts to guide them. The tower crane was then used to manoeuver 86 precast concrete panels (150mm) to create the roof slab. The panels were attached to the crane with a four-legged chain and lifted into position, guided by operatives in scissor lifts. Once all the panels had been placed on the roof, the joints were in-filled with concrete ready to take a 150mm structural concrete screed and Lytag levelling screed, laid with a fall of 1:80 front to back to allow water to run off from the roof. The outer walls were washed, spray-primed and painted with anti-carbonation green camouflage paint to protect the concrete from weathering and reduce visual impact from the road. A waterproof liquid seamless coating system was applied to the tank roof with anti-slip walkways. Finally, a permanent exterior access staircase and perimeter handrailing were installed. Leak tests The reservoir was filled with water and underwent a seven-day drop test to ensure there were no leaks. Once successfully passed, the tank was drained for a final inspection, clean and chlorination. Outside, attenuation drainage was installed and security fencing was erected. MEICA elements were installed by specialist contractor IWS Mechanical & Electrical. Their scope included a full ICA upgrade of the site, reservoir level monitoring, electronic security and electrical distribution for the site. [caption id="" align="alignnone" width="1200"] (left) Construction worker using the newly installed exterior staircase, and (right) the completed tank undergoing an integrity inspection - Courtesy of Stonbury[/caption] Post-construction Earlier CFD modelling and ground investigations had indicated the requirement to fill both cells immediately upon commissioning and keep them simultaneously in use for the first six months of operation to ensure ground was consolidated following the build. As a consequence, the inspection of the internal dividing wall could not be completed during the asset handover. To provide assurance to the client, Stonbury arranged to undertake a further inspection after six months, which confirmed integrity. Conclusion The project was completed according to programme without delays or health and safety incidents. The new tank was connected to the network in October 2022 and will increase water security within Cambridgeshire for decades to come.

As assets age, they start to work less efficiently than they did at their installation. Anglian Water proactively CCTV surveyed the sewers and found evidence of hydrogen sulphide attack, which corrodes concrete sewers resulting in weakening of the pipework and eventual collapse. In September 2023, the @one Alliance Sewer Rehabilitation Team completed a project in Grays, Essex, off the A1012 Treacle Mind Roundabout near the A13, where they rehabilitated over 840 meters of 900mm concrete sewer pipe along Lodge Lane - a crucial lifeline for a highly populated residential area. Planning

From the outset, it was clear that this undertaking would require an innovative approach beyond conventional sewer lining and over pumping techniques. Two main challenges were faced by the project team.

The first challenge was to determine how to rehabilitate a 324m manhole-to-manhole stretch at this massive diameter at such a busy location and under tight highways restrictions. The team realised that they needed to trace the line and identify an optimal location for a new access point - a crucial step to break down the sewer into more manageable sections. Considering that the sewer crosses Lodge Lane halfway through, added with the need to avoid existing services and our bypass pipework, it became apparent that this was not a viable option.

[caption id="attachment_13360" align="alignnone" width="1200"] Overpumping pipework - Courtesy of @one Alliance[/caption]

The second challenge the team faced was the need for the sewer to be empty while the rehabilitation works took place. The team decided that in order to resolve this challenge, they needed to install a temporary above-ground pipe to divert the sewage flows.

This job was a significant undertaking, and one that required close collaboration with Vanderkamp UK. Working together, the @one Alliance/Vanderkamp UK team considered sustainable solutions to mitigate flows and ensure the continued integrity of Anglian Water’s infrastructure.

To manage flows and ensure uninterrupted service to customers, temporary connections were established on the existing 600mm and 375mm dia. rising mains within the Treacle Mine Roundabout. These mains, originating from the Stifford Corran Way and Stifford Clays Pumping Stations, require pumping of up to 350 l/s.

The aim was to maintain seamless flow and mitigate any potential flood risks, so the bypass was routed through in-line duty/standby booster pumps strategically positioned within the roundabout. This innovative approach eliminated the need for suction pits or wet wells. Through extensive modelling, the team identified the need to incorporate booster pumps, as the existing pumping stations could not pump the additional 1km of 500mm bypass pipework, which included 16 pipe bridges and hoppers.

Vanderkamp UK undertook continuous and meticulous remote monitoring which ensured the successful execution of this complex and critical project.

[caption id="attachment_13366" align="alignnone" width="1200"] Vanderkamp UK’s temporary overpuming pipework while OnSite Cental undertake the CIPP lining works - Courtesy of @one Alliance[/caption] Grays Sewer Rehabilitation: Supply chain - key participants Client: Anglian Water Project delivery: @one Alliance Bypass pipework (1km of 500mm pipe): Vanderkamp UK Cured in place relining: OnSite Central Ltd CIPP liner supply: IMPREG GmBH Traffic management: TBF Traffic The 324m manhole to manhole stretch

Addressing the first challenge of rehabilitating the large manhole to manhole stretch, the team collaborated closely with Tier 2 Supply Chain partner OnSite Central Ltd, to prove a cured in place pipe (CIPP) relining solution. The @one Alliance challenged OnSite to develop a game-changing method that would enable a one-shot installation of the 324m length.

After exploring various options, including a single-cure installation that posed complications due to power cables, a 50/50 cure approach was selected, partially curing the liner in both directions.

To ensure the liner’s integrity throughout this process, OnSite Central Ltd ingeniously employed special sluice bags to keep the liner inflated while moving the light train to the other manhole; effectively preventing any shear damage to the liner during the transition between cured and uncured sections.

[caption id="attachment_13362" align="alignnone" width="1200"] OnSite Central’s CIPP lining operation - Courtesy of @one Alliance[/caption]

The deployment of specialised equipment, including a large 20-ton winch, a larger roller bed, crane pads, and sluice bags, incurred additional costs, however, savings totalling approximately £35k included avoiding the need for an additional liner installation, a week of over-pumping, and substantial running costs. Additional significant savings were gained by removing the requirement for a new 6m deep access point and extended road closures.

In terms of sheer length, this installation now holds the record as the longest the Anglian Water @one Alliance Sewer Rehabilitation Team has ever undertaken. OnSite also suspect that it might even be a record-breaker for UV installations in the UK, if not globally! Typically, cable length restrictions cap such installations at around 300 meters, making this 324m achievement truly exceptional!

Challenges

As with any project, challenges arise. Added to the previous challenges mentioned, the team had plenty more to overcome.

Ensuring resources: Learning from concurrent @one Alliance projects, from the outset, the team knew that they needed to ensure resources were available for the project to commence, therefore early resourcing was required to overcome issues on programme later down the line.

Avoiding planning issues: Once the project started, the tight highways restrictions throughout and multiple live permits in the area could have caused planning issues if the team had not realised these early and planned for them at the start of the project, so they worked with Highways early to identify a suitable working window.

[caption id="attachment_13363" align="alignnone" width="1200"] Traffic management during the works - Courtesy of @one Alliance[/caption]

Emergency road closure: Another issue was having to emergency-close Lodge Lane due to two leaks across the pipe bridges. The team identified these by using treated final effluent to ensure no pollution events would occur. To resolve this issue, an emergency road closure was put in place on Lodge Lane for 2 hours from 8-10 PM in order to safely access the pipework at the leaks and tighten the bolts. After collaborations with Highways the closure in place safely put in place.

Additional cleaning: Once flows had been diverted and a detailed CCTV survey was undertaken, it was apparent that more cleaning of the sewer pipe was required, taking longer than was originally anticipated. In order to claw this time back and ensure the project completed on time, the team installed two liners in a week. To do so, the final liner installation needed to be extended into the weekend. This required an adjustment to the road closures on Windsor Avenue which was agreed with Highways and communicated to the local residents.

Avoiding potential issues: Challenges do not only affect the project team; they also affect customers. The team was made aware of visibility issues due to the temporary pipework obstructing the view from a junction, creating a potential blind spot. Responding promptly to feedback from the public, the team worked with the Highways Inspector to install temporary mirrors and mitigate the issue.

Customer engagement

The @one Alliance has a clear purpose to bring environmental and social prosperity to the Anglian Water region, and this is dones by ‘Making Today Great – every day, in every interaction’.

[caption id="attachment_13365" align="alignnone" width="1200"] Customer information boards - Courtesy of @one Alliance[/caption]

The @one Alliance was aware that the work at Grays would impact customers throughout the project lifecycle, so processes were put in place to effectively communicate with customers across the area in a variety of ways.

Open day: On April 26th, 2023 an open day was hosted at Stifford Parish Hall to give the community the opportunity to meet the team and ask any questions or share any insights before the project began to ensure they had a clear idea of the plan for the project. Communications: Customers were notified about the works via letters, emails, SMS campaigns and a dedicated scheme board. In total, over 1,444 letters and 970 emails were sent to residents on top of 13 SMS campaigns which resulted in 2,755 customers receiving text messages to let them know of specific road closures and project updates. Social media: Projects updates were regularly updated on Anglian Water’s “In Your Area” website for customers to view and on its Facebook page. The Facebook page reached 63,387 customers in total throughout the project. CSAT score: A record number of 9+ scores were received for a scheme with a resulting in a 9.18 CSAT score.

Meticulous planning ensured customers were aware, questions were answered, and feedback was received. Overall, customers have praised the work that has been undertaken; emphasising the minimal disruptions and their appreciation for the use of temporary traffic lights.

Outcome

The works started in June 2023 and completed in September 2023 with the removal of the temporary pipe bridges and traffic lights. Over 840 meters of 900mm sewer pipe have been successfully rehabilitated along Lodge Lane. The project was delivered on time, and gained positive customer feedback, positive relationships with the local council and Highways authorities and a great working relationships with our Tier 2 suppliers Vanderkamp UK and Onsite.

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 criteria Flow rate Dry weather flow (DWF) 322 l/s Average flow 368 l/s Flow to full treatment (FtFT) 746 l/s IPS peak capacity 2,250 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. [caption id="" align="alignnone" width="1200"] (left) Location of new sewage treatment works and tunnel route and (right) Slyfield Regeneration Project area - Courtesy of Adams Hendry[/caption] 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’. [caption id="" align="alignnone" width="1200"] RIC 1 and 2 pass areas - Courtesy of BAM Enpure Ltd JV[/caption] 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. [caption id="" align="alignnone" width="1200"] (left) Rapid impact compaction rig and (right) pile under test - Courtesy of BAM Enpure Ltd JV[/caption] 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 Temporary works/shoring: MGF 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 Ltd 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. [caption id="" align="alignnone" width="1200"] (left) inlet pumping station physical model and (right) inlet pump testing physical model - Courtesy of Hydrotec Consultants Ltd[/caption] 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. [caption id="" align="alignnone" width="1200"] Storm overflow physical models - Courtesy of Hydrotec Consultants Ltd[/caption] 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. [caption id="" align="alignnone" width="1200"] Elevated inlet works - Courtesy of BAM Enpure Ltd JV[/caption] 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. [caption id="" align="alignnone" width="1200"] PST distribution chamber CFD models: (left) with four PSTs in service and (right) with six PSTs in service - Courtesy of The Fluid Group[/caption] 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. [caption id="" align="alignnone" width="1200"] ASP overview - Courtesy of BAM Enpure Ltd JV[/caption] 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. [caption id="" align="alignnone" width="1200"] Anoxic and aeration zones flows - Courtesy of BAM Enpure Ltd JV[/caption] 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. [caption id="" align="alignnone" width="1200"] 32m final settlement tanks & sludge return (RAS pumping station) - Courtesy of BAM Enpure Ltd JV[/caption] 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. [caption id="" align="alignnone" width="1200"] Tertiary treatment flocculation chambers: Eliquo Hydrok Mecana cloth pile filters - Courtesy of BAM Enpure Ltd JV[/caption] 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. [caption id="" align="alignnone" width="1200"] New Guildford STW: 3D model night-time overview - Courtesy of BAM Enpure Ltd JV[/caption] 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. [caption id="" align="alignnone" width="1200"] Thickened sludge blending tanks - Courtesy of BAM Enpure Ltd JV[/caption] 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. [caption id="" align="alignnone" width="1200"] (left) Outfall route plan - Courtesy of Bam Enpure Ltd JV, and (right) outfall low flow scenario CFD model - Courtesy of Arcadis[/caption] 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.

Guildford, the county town of Surrey, sits a commutable 30 miles south west of London and 70 miles from the south coast. Boasting a castle, a cathedral, a picturesque town centre and a university, it is surrounded by Green Belt countryside. The River Wey flows through the town centre and then northwards through water meadows where it provides the outfall for the STW. The Wey eventually discharges into the Thames. The current STW serves a population equivalent (PE) of around 107,000, but the town has a growing population which is expected to grow to circa 125,000 PE by 2041. Background

The town and immediate area are currently served by a sewage treatment works established at the turn of the last century and upgraded over the years. It is located beside the River Wey, to the north of the A3 trunk road and north of Guildford town centre. It lies just south of Slyfield Industrial Estate. The current STW has a capacity to cater for a population equivalent of around 120,000.

Guildford Borough Council’s Local Plan adopted in 2019 allocates a site to the west of the River Wey wrapping around the eastern side of Slyfield Industrial Estate for mixed use development. Part of the 40 Ha allocated site is currently occupied by the existing sewage treatment works.

Weyside Urban Village is a mixed-use regeneration project which will provide some 1,500 new homes, new community facilities, Gypsy and traveller pitches and 6,500m2 of additional light industrial and trade space. 11Ha of the site are allocated for waste management purposes. The plans include a new council depot, a public recycling centre and a new, relocated sewage treatment works.

In order to bring the development site forward, within the plan period to 2034, Guildford Borough Council (GBC) have entered into partnership with Thames Water Utilities Ltd (TWUL) to build the new STW as the first phase of the redevelopment. The new location is slightly further north on the eastern edge of the Industrial site and is a brownfield site, formerly a gravel quarry and subsequently a landfill tip.

[caption id="attachment_26867" align="alignnone" width="1200"] Figure 2: Site overview: BIM model of new Guildford STW - Courtesy of BAM Enpure JV[/caption]

The new sewage treatment works allows for an increase in capacity to serve a population of 125,000 allowing for predicted population growth in the town and surrounding area as well as more stringent effluent discharge standards.

The new site also includes areas within the new works for future expansion and increased treatment capacity as need arises.

Previously in Water Projects

The scheme to build a new sewage treatment works (STW) in Guildford is now mid-way through construction. This article provides an update to the project following on from previous articles published in Water Projects. In 2023, Enpure Ltd’s Project Delivery Director Shaun Christopher described in detail the process and assets being provided in the new works and in 2024, Dan Russell, BAM’s Operational Lead, gave an update on the progress of the project one year into the construction.

This article also covers some of the planning considerations and requirements for the scheme.

Contract

In 2021 TWUL awarded a contract to a BAM-Enpure Joint Venture to design, build and commission a new STW for Guildford, and once operational, to de-commission the existing works. BAM-Enpure Joint Venture (JV) is a non-integrated Joint Venture, formed specifically to combine experienced civil engineering contractor BAM with the process engineering MEICA specialism of Enpure, to deliver a turnkey solution for TWUL.

Construction began in the spring/summer of 2023 with BAM undertaking design and construction of the civils works and Enpure providing process and MEICA design and installation. BAM have employed Arcadis as their main civils designer and the JV has let a number of specialist sub-contractor design packages alongside.

[caption id="attachment_26869" align="alignnone" width="1200"] Figure 3: 3D design using a model hosted by Arcadis, image from Autodesk’s Navisworks viewer - BAM Enpure JV & Arcadis[/caption] The project

The project consists of the following:

A transfer tunnel. An inlet pumping station. Inlet works screening. Primary settlement. Activated sludge treatment. Final settlement. Tertiary treatment of final effluent. Chemical dosing facilities. Storm storage tanks. Import cess and sludge facilities. A new control centre. New welfare building. Outfall into the River Wey.

A detailed description of the process and assets being installed is set out in the previous Water Projects article published in 2023.

Timeline Phase 1: Ground improvement: Started summer 2023 and completed February 2025 Phase 2: Civil engineering: Started summer 2023 with completion due in late 2025. Phase 3: Mechanical & electrical engineering: Started autumn 2024 and is due to complete summer 2026. Phase 4: Commissioning: Starts winter 2025 and is due to complete in spring 2027. [caption id="attachment_26883" align="alignnone" width="1200"] Figure 4: 3D model of the sludge processing area - Courtesy of BAM Enpure JV & Arcadis[/caption] Developing the site

The new site comes with additional challenges in that it is brownfield site formerly used for gravel extraction and then landfilled through the 1960s, 70s and 80s, with mainly domestic and some commercial waste. The site is classified as a waste development such that the local planning authority is Surrey County Council (SCC).

The planning permission granted was subject to a number of conditions and commitments, not only relating to the siting and development of the STW itself such as visual impact, odour, noise and traffic generation, but also to the remediation and reuse of the landfill site. Plans and construction methods needed to ensure that there was no temporary or permanent environmental damage to the surrounding area as a result of the impact on or disturbance of the buried waste material and that operatives working on the new STW were protected from any ill effects of the landfill during operation of the site. The landfill also poses particular constraints and hazards during the construction phase.

The strategy for the site was to leave as much of the landfill waste in situ and build above and through the waste. A detailed remediation strategy formed part of the planning requirements. The plan set out how the construction and operation phases of the project would manage issues of ground water and ground gas, potential ground water contamination and leachates, contaminated solid material including asbestos, and short- and longer-term settlement of the landfill.

Dan Russell’s case study in Water Projects 2023 provided a detailed description of the use of a combination of ground improvement and foundation techniques, which consisted of:

Rapid Impact Compaction (RIC) to improve ground strength and reduce long-term settlement of the landfill. Vertical Rigid Inclusions (VRI), a displacement concrete pile technique which provided support for roads, lighter structures pipes and ducts. Driven concrete piles bedded in the London Clay below the land fill to support large structures, tanks and pipelines.

Figures 5 (below) show the historic gravel extraction map and depth of landfill determined by ground investigation - both images were extracted from the project’s Detailed Remediation Strategy.

[caption id="attachment_26880" align="alignnone" width="1200"] Figures 5: (left) Spatial variation in landfill thickness 2023 and (right) historic site layout (1976) with present day boreholes overlaid - Courtesy of Arcadis[/caption]

However, the impact of the waste material goes beyond its bearing capacity. The site was already being subject to long term monitoring for ground gas and groundwater quality by Thames Water to provide a baseline for the project. Additional boreholes were sunk and a Groundwater & Ground Gas Monitoring Plan was approved by the local authority. Daily and continuous automatic remote monitoring was undertaken during the ground improvement and excavation phases with trigger levels set and exceedances reported back to SCC and a requirement for quarterly summary reporting. Monitoring will continue during commissioning of the site at less frequent intervals.

Asbestos: Asbestos had been discovered in a third of samples taken during the ground investigation and so a monitoring regime was established. Air sampling around the perimeter of the site ensured any airborne particles were detected and works could be stopped if necessary. Proximity asbestos monitoring and identification of asbestos material in excavation has also been used extensively during excavation across the site. The project used Socotec to undertake asbestos monitoring and testing.

Ground gas: A ground gas protection design has been necessary to reduce risk of ground gas entering occupied buildings, kiosks, tanks and chambers where operational or maintenance access is undertaken. A ground gas design protection strategy was set out by Arcadis with PAGeo Contracting Ltd providing expert advice and a detailed ground gas design, PAGeo then supplied gas dispersal matting, venting components and gas membranes. Both the strategy and the detailed design for ground gas protection have been submitted to and approved by SCC.

Independent verification of the gas protection installation has been provided by MTS Ltd as verification of the installation and subsequent reporting to SCC is a planning condition.

[caption id="attachment_26872" align="alignnone" width="1200"] Figure 6: Gas protection void former being laid on stone blanket prior to tank base blinding, Connections to vents at tank perimeter - Courtesy of BAM[/caption]

Surface drainage: On-site surface drainage has been carefully designed such that new impermeable areas are positively drained to the site drainage system to remove the risk of a spill causing environmental pollution. This surface water is then fed into the inlet pumping station for processing through the works. As the permeable area of the site has been greatly reduced this also significantly reduces leachate mobilisation.

Biodiversity: Another planning condition is the provision of Biodiversity Net Gain (BNG). In conjunction with GBC, the project provides 10% net biodiversity gain by use of on-site planting and off-site enhancement of the land directly to the north of the new STW. A Site of Natural Green Space, biodiversity enhancements to an area of farmland, and a marshy meadow along the River Wey are being provided.

The Environment Agency have also constructed a new fish pass in this area allowing fish to migrate around Old Bucks Weir.

Guildford STW: Civils works supply chain - key participants

Main contractor: Bam Nuttall Ltd Planning consultant: Adams Hendry Consulting Ltd Civil engineering design: Arcadis Group Ltd Boreholes & testing: Geo-Environmental Services Ltd Asbestos monitoring: Socotec Ltd Rapid impact compaction: Cofra Ltd (Boskalis Group) Vertical rigid inclusions: Foundation Piling Ltd Concrete piling: Aarsleff Ground Engineering Ltd Temporary works specialist: Mabey Hire Ltd Temporary works specialist: MGF Ltd Tunnels & shafts: Joseph Gallagher Ltd In situ concrete works: Kelly Formwork Ltd In situ concrete works: DJ Civils Ltd Precast concrete manufacturer: FLI Precast Solutions Precast concrete manufacturer: A-Consult Ltd Pipe supplier: Electrosteel Castings (UK) Ltd Pipe supplier: Saint Gobain PAM UK Soil processing: Remediation Waste Management Services Concrete supplier: Heidelberg Materials Gas protection: PAGeo Contracting Ltd Gas protection system installation verification: MTS Ltd [caption id="attachment_26876" align="alignnone" width="1200"] Figure 7: Sludge processing area: MCC kiosk (grey in foreground), sludge blending tanks (top left), poly dosing kiosks (top right) - Courtesy of BAM[/caption] Overview of project progress

As of summer 2025, civils works are nearing completion and MEICA fit out has started.

The installation of piled supports has been undertaken, and all major structures are complete. Installation of the below-ground pipework and buried ducting is in progress and the welfare building is watertight and available for equipment installation. Moving towards installation of MEICA equipment, the water testing of structures started in the February of 2025.

Steel staircases and high-level walkways are mostly complete. The inlet screens and grit removal system are in place. GRP tanks for sludge processing are being installed and many control kiosks are in place. Electrical supply buildings are near completion.

MEICA work commenced in February 2025, overlapping with completion of civils to maximise programme efficiencies. Designed alongside the civils elements of the site, the MEICA installation has taken place apace with the first bridges on the final settlement tanks attached, the larger glass coated steel tanks for the sludge area in place, and generators and some kiosks have been installed.

BAM has started the installation of the above-ground pipework and cable pulling in buried ducts, and the fit out of control rooms will commence shortly. Construction of MCC basements has been completed and two of the three MCC kiosk, and power supply and distribution works are nearing completion.

[caption id="attachment_26878" align="alignnone" width="1200"] Figure 8: Sludge processing area: (left) the bases for elevated cake silos, (middle), sludge belt presses, and (right) the poly prep & dosing kiosks - Courtesy of BAM[/caption] Guildford STW: MEICA works supply chain - key participants Main designer/contractor: Enpure Ltd CFD analysis: The Fluid Group Cake silo: Saxlund International PST scrapers & ferric dosing plant: Colloide Inlet works & PST odour covers: Power Plastics Ltd Grit remover plant: Jacopa Escalator screens: Longwood Engineering Imported sludge Strainpress: Huber Technology Sludge thickening & dewatering: Kent Stainless Ltd Odour control plant: Odour Services International Ltd FBDA grids & blowers: Xylem Water Solutions Cloth pile filters: Eliquo Hydrok Ltd Storm tank cleaning system: Sulzer Pumps Wastewater Ltd Tank logging system (WASP): JR Pridham Services Ltd Glass lined steel tanks: Balmoral Tanks Ltd Sludge tank mixing: Landia UK Ltd Tunnel

A 1.5m diameter gravity tunnel, 1.5km long, transfers flows from the existing works and intercepts minor sewers en route. There are six shafts along the tunnel route, some of which act as junctions between the new tunnel and the existing sewers. Shafts were sunk by Joseph Gallagher using the caisson method and the tunnel was driven between them using a full-face tunnel boring machine, (named Daphne by a local school). The tunnel and shafts were completed in 2024 and the final work remaining are the completion of the large inlet pumping station (IPS), shaft (E2) at the new works and connection of Guildford’s main sewer to the head of the tunnel, which will allow all flows to be diverted to the new tunnel.

[caption id="attachment_26873" align="alignnone" width="1200"] Figure 9: (top left) 3D model of the Inlet Pumping Station (IPS) - Courtesy of Arcadis, (bottom left): steel fixing to IPS internal walls - Courtesy of BAM Enpure JV, and (right): IPS shaft construction - Courtesy of BAM[/caption] Inlet pumping station

The new inlet pumping station (IPS) is a 12.5m diameter shaft with a depth of 17m, which houses six pumps with the capacity to lift flows of around 2,500 l/s from the tunnel entry, at the base of the shaft, to the inlet works where all flows are screened. The shaft is complete except for the internal walls and installation of penstocks which allow isolation of half the well at any time for maintenance of the pumps. This will be completed in the autumn of this year.

Storm tanks & inlet works

Two storm tanks provide a combined capacity of approximately 8 million litres to which flow can be diverted to temporarily hold sewage arriving at the new works should flows exceed the capacity of the works. Constructed onto in situ bases, the walls of the storm tanks were prefabricated, placed and post-tensioned by A Consult Ltd.

The inlet works and larger chambers were entirely cast in situ due to lack of repeatable sections and logistics. In situ concrete work for these was undertaken by Kelly Formwork. The inlet screens have been installed and walkways are in place.

[caption id="attachment_26874" align="alignnone" width="1200"] Figure 10: Circular precast storm tanks and Inlet works (August 2025) - Courtesy of BAM[/caption] Primary settlement, activated sludge plant & final settlement tanks

Screened flows from the inlet works will then pass through primary and secondary treatment tanks comprising rectangular primary settlement tanks (PSTs) and activated sludge plant (ASP) tanks. The walls for these tanks were designed and supplied by FLI Precast Solutions Ltd and installed by BAM and DJ Civils Ltd on in situ bases prepared by Kelly Formwork Ltd. These tanks are complete with pipework being fitted and the ASP has commenced water testing.

To ensure watertightness of the larger rectangular tanks, Heidelberg Materials and Sika’s concrete technology were used.

Concrete containing Sika WT-200 P was utilised for the PSTs and the ASP. Sika WT-200 P is a combined water-resisting and crystalline waterproofing admixture used to reduce the permeability of concrete, making it suitable for water retaining structures.

Gas protection has been laid under all large tanks. Materials were supplied by PAGeotechnial Ltd and verified by MSL Ltd. Void former mating laid on a bed of single grade 40mm stone provides a preferential escape path for ground gases and is connected to vents at the tanks periphery allowing ground gases to vent to atmosphere.

These tanks are not habitable spaces and only require a dispersal system to discourage any build-up of gas below the large tank bases.

[caption id="attachment_26875" align="alignnone" width="1200"] Figure 11: From top: Activated sludge plant, primary settlement tank, and two of the four final settlement tanks - Courtesy of BAM[/caption] Final settlement tanks

The four final settlement tanks were also precast, supplied, installed and post-tensioned by A-Consult Ltd onto in situ bases prepared by Kelly Formwork Ltd. The FSTs are complete with bridges and scrapers installed and are currently being water tested.

Tertiary treatment plant & outfall

Following final settlement, flows will pass through final filtration in the tertiary treatment plant before being discharged to the River Wey via new, twin outfall pipes. Civil construction is complete and MEICA installation of cloth pile filters and drums from Eliquo Hydrok Ltd is underway.

The outfall pipework has been fully installed across the water meadow and the headwall has been constructed at the discharge point into the River Wey.

[caption id="attachment_26877" align="alignnone" width="1200"] Figure 12: Tertiary treatment plant construction (August 2025) - Courtesy of BAM[/caption] Sludge processing

The project also provides a dewatering facility for imported sludge from other small treatment works. This area is nearing completion with the larger coated glass sludge blending tanks in place and the smaller buffer tanks being installed. Gas vent pipes have been installed below the extensive concrete slabs to allow venting of ground gases to the atmosphere.

The sludge belt presses from Kent Stainless Ltd for sludge dewatering and thickening have been installed adjacent to the bases for the elevated sludge cake silos. The silos from Saxlund International have been sized to provide storage of seven days’ worth of processed sludge, which can be discharged to trucks for export from site.

Power & control

Power supply and distribution infrastructure is now in place. The three MCCs have been constructed in sequence and the first two are being fitted out.

Welfare building

A new welfare building houses the automated systems for running the new plant and controlling effluent quality as well as office and mess space for Thames Water staff and operatives. The building is watertight with cladding being installed and the fit out of building fixtures and plant control equipment is in progress.

[caption id="attachment_26871" align="alignnone" width="1200"] Figure 13: Welfare building housing plant control systems - Courtesy of BAM[/caption] 3D modelling

Design has utilised a 3D model hosted by Arcadis with each designer adding in modelling information as their design capabilities have allowed. This has enabled precise integration of designers individual input and interrogation of the integrated design

The model is used extensively by engineers on site. 3D modelling has, for example, allowed duct chambers to be precast with precision positioning of cable openings, saving on in situ working and substantially reducing programme on these installations.

Piling & ground improvement

To enable the STW to be constructed on the site without the waste being removed a combination of ground improvement techniques have been employed including driven concrete piles, Rapid Impact Compaction, and Vertical Rigid Inclusions.

The Rapid Impact Compaction work undertaken by Cofra was completed in late summer of 2023. From July 2023 to the spring of 2024, to support the larger structures, tanks and main process critical pipelines, 3500 concrete piles were driven through the landfill into the clay. The design and installation of this piling operation was undertaken by Aarsleff Ground Engineering.

[caption id="attachment_16135" align="alignnone" width="1200"] (left) Driving precast concrete piles and (right)Vertical Rigid Inclusion installation - Courtesy of Bam Nuttall Ltd[/caption]

In areas where settlement criteria were less critical, but needed controlling (for example roadways and minor pipework), a Vertical Ridged Inclusion (VRI) piling technique was used. The system involves displacement drilling a column in the landfill and filling the void with concrete. This works by consolidating the soil around the pile, transferring load to lower layers, thus increasing bearing capacity and reducing settlement over time.

Since 2024 the installation of VRIs by Foundation Piling has been completed with 7500 inclusions installed across the site. During detailed design, the project was able to remove the need for a load transfer platform above the VRIs across much of the site. This was done by detailed analysis of the 3D model to target differing requirements for support and by reducing inclusion spacings, thereby reducing the expected landfill removal by 37,500m3.

The load transfer platform remains below roads, but pipework sits within the grid of VRIs.

The year ahead

Completion of the mechanical works is expected in the first part of 2026 with installation of electrical and control systems expected to complete in the second part of 2026. Dry and wet commissioning will be undertaken sequentially across the site throughout the coming year, ensuring the new works is ready to commence process commissioning.

The final, and arguably most challenging activity, will be to connect the existing sewer network to the new tunnel, diverting flows from the existing STW to the new STW. A series of interventions will be required to intercept the various sewers, along the route of the tunnel, all the whilst ensuring the new STW is performing within strict limits and the existing STW is able to maintain its performance during the ramp down of flows.

Dawlish is a traditional seaside town on the south coast of Devon, approximately 12 miles south of Exeter and is a popular holiday and day trip destination. South West Water (SWW) and Galliford Try’s objective was to ensure that the bathing water quality did not deteriorate within the next 20 years by ensuring that there are no more than two significant (>50m3) spills from the Brook Street CSO per bathing season by 31 March 2022. The proposed solution was to be achieved by providing 30m3 of offline, pumped return stormwater storage in the Manor House council office car park on Brook Street to improve spill performance at Meadow Road CSO in line with SWW/Environment Agency targets, in combination with the removal of surface water from the combined system; being delivered as a separate element of the overall project by another delivery partner. Description As part of the overall SWW objective to achieve less than two significant spills from Brook Street CSO per bathing water season, this project supplemented the scope from the infra delivery partner. Provision of 30m3 of unscreened, stormwater storage upstream of the Brook Street CSO, by the installation of a 4m diameter x 3m deep tank with duty pump return. Provide a flow control device (Hydro-Brake®) to limit PFF to 10 l/s with an unrestricted bypass arrangement within an overflow chamber. Once the tank is full, additional flow will bypass the Hydro-Brake® via a high-level weir. The agreed storage tank volume, flow control device and overflow weir levels have been derived from the Stantec UK modelling report and taken as the scheme output for the storage element. The final tank volume selection/spill performance of the promoted option has been selected at SWW IPC and has been operationally reviewed by SWW operations team, commissioning engineer and asset management. [caption id="" align="alignnone" width="1200"] (left) Flow control chamber showing overflow weir and Hydro-Brake® and (right) looking down into the 30m3 stormwater tank showing the float controls, pump, pump guides and sump - Courtesy of Galliford Try[/caption] Project scope Site mobilisation and temporary works, to include road closure of Brook Street and suitable traffic management/diversion. Construct 4m diameter x 3m deep (internal) PCC shaft in Brook House car park. Construct 30m of connecting pipework and associated manholes to connect new tank to existing sewerage network. Construct PCC overflow chamber to include Hydro-Brake®, spill weir and bypass weir. Install new single 5 l/s return pump and associated control cabinet, cabling, ducting, instrumentation and return rising main. Site reinstatement. In-house capability Galliford Try self-delivered this project, designing all civils and MEICA elements, as well as being the principal contractor and lead designer on the scheme. Galliford Try managed the site, direct labour, installation and commissioning, all within an incredibly tight programme (made tighter by severe storms). Brook Street CSO: Supply chain - key participants Design & construction: Galliford Try Modelling: Stantec UK Shoring/temporary works: MGF Ltd Hydro-Brake®: Hydro International Ltd Pumps: Xylem Water Solutions Access covers: Technocover Ltd Traffic Management: Amberon Ltd Fabrications: Thorne Fabrication Limited Electrical items: Edmundson Electrical Ltd Diamond drilling works: 24-7 Diamond Drilling & Sawing Services Ltd Civils items: Keyline Civils Specialist Plant hire: Gap Group Ltd Aggregates: Hanson Aggregates Construction Products: Jewson Plant hire: Plantforce Rentals Ltd Crane hire: Spence Crane Hire Ltd Tarmac surfacing: Devon Tarmasters Planning & collaboration The site footprint consisted of a small section of The Manor House carpark (which belongs to the Dawlish Council offices), a 20m x 20m area in which Galliford Try managed to contain their welfare facilities and site office, working area and laydown of plant, equipment and materials, a 5.5m diameter, 5m deep shaft and two flow controlling combined sewer inspection chambers with a pumped return, MCC cabinet, two weirs and a Hydro-Brake®. Galliford Try also had to construct two inlet and outlet inspection chambers within a very tight street with multiple existing services. They accomplished this using road closure notices and daily communication with the residents of the local area. During the works, Galliford Try had to excavate the shaft using a 14t wheeled excavator, an MGF TWD of sheets and frames, 5m away from a listed building. SWW estates team carried out a structural survey on the building before they started, and no evidence of any movement was detected associated with the works. Galliford Try mucked away 225t of spoil from the shaft while working closely with another SWW contractor during the construction phase to reduce their footprint further, they arranged joint use of their muck away process meaning reduced footprint of their working area and around half the amount of muck wagons going through Dawlish town centre. Galliford Try also required a 40t mobile crane to lift in the large pre-cast concrete shaft section which required an intricate lift plan and careful logistics. To connect the stormwater storage tank and flow control inspection chambers into the existing network Galliford Try had to accurately survey the existing sewer and optimise the inlet point inspection chamber missing two water mains, a gas main and a surface water drain. To return the flows to the existing sewer they had to precisely know at which point their tank would spill to contain the required volume of storage. The existing sewers in Brook Street were incredibly old and fragile, they had to delicately expose the existing sewer and break in without cracking the upstream and downstream section of pipework. Galliford Try managed to install the chambers using the minimum amount of new pipework. [caption id="" align="alignnone" width="1200"] (left) All weather kiosk constructed off-site, containing the alarms, telemetry, pump return and mains in-comer and (right) access cover within the Manor House Car Park into the 30m3 stormwater tank all completed day before handover - Courtesy of Galliford Try[/caption] Off-site build All four new inspection chambers were concreted from PCC sections and all sections of the shaft were also PCC, reducing installation time and costs. The kiosk was constructed off-site by Galliford Try and installed by their panel shop and then commissioned three days before the commissioning, date reducing storage and on-site presence. Challenges & risks Galliford Try used a vacuum excavator (the fastest and most economical method of excavation) to dig around existing services. Benefits include: reducing reinstatement costs, eliminating the hazard of utility strikes, and reducing the amount of manpower/equipment required. The construction challenges: Small footprint/working area. Existing services in road. Managing access for stakeholders. Temporary works - excavating deep shaft adjacent to existing buildings. Completion & carbon savings Galliford Try completed this work following on from a previous project to remove the surface water run-off from the local catchment; greatly reducing the combined sewer flow rate and reduced the time the storm tank would fill, further reducing the risk of a spill during the bathing water season. The overall scheme (including the surface water separation) would at some point become carbon negative, due to reducing the combined sewer flow to the local STW and not paying the energy bill to treat the additional storm flow now going straight into the Brook. This reduces the amount of flow being stored and pumped back into the combined sewer on time. [caption id="" align="alignnone" width="1200"] Completed car park area day before handback - Courtesy of Galliford Try[/caption] Community Whilst road closures were in place, Galliford Try helped residents by assisting with taking their bins out to the new temporary location, as well as helping the older residents bring their shopping in.

Along the tidal estuary of the River Crouch in Essex, a 40 metre length of embankment had slumped at Hullbridge, requiring repairs to damage caused by the tide. Ivor King installed over 100 permanent steel sheet piles to form an ‘anti-slip circle’, which also provided a safe working environment for repairs to take place in the form of a cofferdam. Overcoming limited access and tidal flow Landward access to the site was not possible due to the close vicinity of neighbouring properties. Owing to their close proximity, the solution had to be silent and vibration-free to limit disturbance, whilst also overcoming challenging ground conditions. In addition, the work area was subject to tidal flow, which necessitated a jack-up barge to be deployed for piling operations to be carried out. A jack-up barge is a floating platform with movable legs which can be lowered into the sea bed. The legs anchor the barge so that the platform can then be ‘jacked up’ to clear the waterline, counteracting any movement caused by tides and passing vessels. The only viable installation method that satisfied all criteria was Giken Supercrush – a vibration-free piling technique used for hard ground conditions, whereby augering takes place at the same times as piles are being pressed-in. The Giken Silent Piler uses reaction force to install piles. However, working from a jack-up barge meant the initial reaction piles could only be installed by welding the Giken reaction stand to the platform of the barge. Once the starter piles were in-situ, the silent piler could carry out installation in the usual manner, clamped on top of previously installed piles.

Sheet piles installed vibration-free from a jack-up barge, on a river subject to tidal flow - Courtesy of Ivor King - The Piling People

Grouting the voids The sheet piles, up to 15 metres in length, were also grouted to seal any voids – the grout was pumped from a nearby on-shore mixing plant during periods of low tide. Once installed, remedial work could take place in safety, protected by the sheet pile cofferdam. Following the completion of works to fit new revetment blocks to the embankment, the sheet piles were cut down to form the anti-slip circle that guards against future slippage. Location: Brandy Hole, Hullbridge Client: Jackson Civil Engineering Project cost: c. £900k Completion date: November 2021 Project period: 9 weeks lant utilised: Giken F301 Silent Piler operating in Supercrush mode

Aarsleff has completed the CFA and Sheet piling works for a major new scheme that will protect homes in Newark from sewer flooding and provide a reliable water supply for decades to come. In 2016, Nick Wallace from Severn Trent explained that £60 million would be spent to replace more than 12 miles of old pipes with new, larger ones. Aarsleff worked on Queens Road to facilitate the replacement of a tunnel with a 1.5 metre diameter one. We employed an ABI TM13 /16SL with a Hydropress to pre-auger,and further installed 28 (No.) PU22- 12m long sheet piles. Due to being in a residential and restricted area, Aarsleff employed a Silent Hydropress to drive in the sheet piles to reduce the vibration. Scope of works CFA -  28 (No.) sheets Equipment ABI TM13/16SL with Hydropress Construction period 10th May 2017 - 25th May 2017   For more information: Aarsleff Ground Engineering: +44 (0)1636 611140 | www.aarsleff.co.uk

   

The Stephenson Street Flood Defence Project on the eastern riverbank of the River Usk in Newport, South Wales is a National Resources Wales and Welsh Government led scheme to protect homes and businesses in the area vulnerable to flooding, as a result of heavy rainfall and high tides. The River Usk at Newport is both a Special Area of Conservation and a Site of Special Scientific Interest (SSSI), with only a narrow corridor from which to work and not enough room for a standard crane to operate. For this reason, Ivor King’s Giken Full GRB (or Giken Reaction Base) system was selected as the only viable method of installing sheet piles. Ivor King's GRB system is the way forward for a vibration-free, compact installation Not only is the GRB System eco-friendly, hydraulically pressing-in sheet piles noise and vibration-free, but it also works on the principle of a footprint-free installation. Compact and streamline in nature, all procedures, from pile transportation, to pile pitching, to the pile installation itself are carried out from on top of previously installed piles – ideal for sites with restricted access. How it works The GRB System consists of a Silent Piler and Power Pack (on a unit runner to transport the power source) at the front, followed by a Clamp Crane to pitch piles and a Pile Runner to transport piles from the storage area.

Ivor King’s GRB System the way forward for a vibration-free, compact installation - Courtesy of Ivor King - The Piling People

First, the pile runner, effectively a flatbed trailer which moves along on rollers, is loaded-up with sheet piles at the storage location. Once loaded, the pile runner, driven by remote control, travels back along the pile line, locking into position immediately behind the clamp crane. The clamp crane, which as its name suggests, is a specialist crane that clamps onto previously installed piles, lifts sheet piles individually from the pile runner, slews 180º and pitches them into the chuck of the silent piler. Finally, the silent piler presses-in the sheet pile using reaction force from previously installed piles. After pile installation, the silent piler and clamp crane raise their main bodies and ‘walk’ to their next position, whilst the power pack and pile runner move along using their runners and roller assembles ready to repeat the installation process. The GRB system eliminates the need for temporary platforms and workspaces for cranes, and is particularly effective on sites with limited access and tight, narrow working conditions, especially over water or on sloping ground. This project saw us install 1000 sheet piles in total to form a new flood barrier, spanning a distance of some 600 metres, alongside the foreshore of the River Usk. Steel capping beams manufactured by Ivor King complete the project Sheet piles were topped off using a steel capping beam, manufactured in Ivor King’s workshops to design specification and welded into position. The capping beam will protect the people from any sharp edges once the footpath which will run adjacent to the sheet piles opened to the public. For added sustainability, EcoSheetPiles were used on this scheme – manufactured with 100% recycled material and 100% renewable electricity. Location: Stephenson Street, Newport Client: Griffiths Project cost: c. £1.8m Completion date: October 2023 Project period: 6 months Plant utilised: Giken F201 Silent Piler Giken Power Pack & UR3 Unit Runner Giken CB3-4 Clamp Crane Giken PR4 Pile Runner (Transporter)

Severn Trent is investing £60 million to upgrade Newark’s sewerage and water system to help protect homes from sewer flooding. The scheme will provide a reliable water source for decades to come. In 2016, Nick Wallace from Severn Trent explained that more than 12 miles of old piles will be replaced with new, larger ones. In May 2017, Aarsleff worked on Queens Road in Newark, to facilitate the replacement of a tunnel with one at 1.5m diameter. Here, 28 (No.) sheet piles were installed. As part of the same scheme, and for the same client, Aarsleff was awarded the contract to construct a sheet piled cofferdam on Harcourt Street. Aarsleff installed 46 (No.) sacrificial steel sheet piles, with pile width 600mm and 12.0m in length. There was a retained height of 10.2m, forming the overall cofferdam. Again, Aarsleff’s work will facilitate the replacement of an old water course. [caption id="" align="alignnone" width="1200"] Courtesy of Aarsleff Ground Engineering Ltd[/caption] As Aarsleff was piling in the middle of a residential street, it drove the sheet piles using an ABI leader rig with pre-augering taking place in advance of main works where it utilised a Silent Hydro pile press to reduce the noise and vibration. A 50-tonne capacity crawler crane was employed, operating at a maximum 6m radius to unload and handle piles and hammer. Aarsleff’s Senior Technical Estimator Ashley Carter said:

“It is a great endorsement of Aarsleff’s work that we have been awarded our second contract for the same scheme in Newark, just 7 months later. There are around 400 homes in Newark that are currently at risk of flooding, demonstrating just how important sheet piling projects like this are in future-proofing our infrastructure and communities."

[caption id="" align="alignnone" width="1200"] Courtesy of Aarsleff Ground Engineering Ltd[/caption] Scope of works 46 (No.) steel sheet piles Pre-auger Equipment ABI rig Silent hydro pile press Contractor BNM Alliance (an nmcn PLC and Barhale joint venture) Construction period 11th December 2017 - 20th February 2018   For more information: Aarsleff Ground Engineering: +44 (0)1636 611140 | www.aarsleff.co.uk    

The Strelley to Redhill Pipeline Project involved constructing and installing a large steel pipeline to connect the Strelley and Redhill Reservoirs. This pipeline will significantly boost the flow rate between the reservoirs, allowing up to 35 million litres of water to be delivered each day. This strategic upgrade would ensure a robust and reliable water supply for Nottinghamshire and surrounding areas; particularly in anticipation of future AMP8 developments. The route for the new pipeline, located 6km northwest of Nottingham City Centre, traversed a diverse landscape that included agricultural fields, residential areas, railways, highways, car parks, business parks and existing Severn Trent land and infrastructure. Avove was contracted by Severn Trent to construct the 16km major infrastructure project. To facilitate the pipeline’s construction, Avove’s Vegetation Management teams worked closely with operational and construction teams to clear hedgerows, vegetation and woodlands along the designated route. Throughout the process, environmental sustainability was at the forefront of operations, safeguarding local ecosystems and fostering positive relationships within the community. This collaborative, ecologically responsible approach resulted in successful outcomes for all stakeholders, including Severn Trent, Avove, local wildlife, local residents and the broader community. [caption id="attachment_18185" align="alignnone" width="1200"] The Strelley to Redhill site compound showing the TBM being lowered into the shaft and the pipes ready to be laid - Courtesy of Avove[/caption] The challenge The Strelley to Redhill pipeline project presented several significant challenges, which required the Avove Vegetation Management team to conduct land surveys to identify potential issues with the proposed route. The following specific challenges were identified at this phase: Complex route intersection: The proposed pipeline route needed to intersect major UK infrastructure, including a Network Rail line and the A610. Navigating these intersections required careful, comprehensive planning and coordination to avoid disruption in the local area and to ensure the safety of both the team and residents. Design adaptations & approvals: Land surveys revealed potential risks associated with the original design, necessitating the quick development of alternative design solutions and diversions. These solutions required thorough testing for feasibility and swift approval to avoid delays. Community engagement & representation: Ensuring that local residents were adequately represented and consulted during the vegetation management works was crucial. The team needed to address community concerns and ensure that the project proceeded with minimal disruption to the daily activities of local residents. Environmental & ecological risks: The clearance of vegetation across agricultural sites introduced ecological risks, such as the presence of invasive Japanese knotweed that presented a significant health and safety risk due to its ability to cause damage to infrastructure; including sewers, drains and water mains. In addition, the work needed to be completed before the onset of nesting season, to prevent disruption to local wildlife. The team had to develop a delivery strategy that mitigated these risks, whilst maintaining the project’s timeline. Preservation of heritage sites & vegetation: The project needed to include the preservation of local heritage sites, such as Bestwood Country Park and the protection of mature wildlife, including a 150-year-old oak tree. The team faced the challenge of balancing the project’s infrastructure goals with the preservation of these valuable natural and cultural assets. [caption id="attachment_18762" align="alignnone" width="1200"] Courtesy of Avove[/caption] To overcome these challenges, the Vegetation Management team worked alongside other Avove teams involved with the project to develop solutions that reflected best practices. Being able to leverage the existing expertise of colleagues ensured that bespoke solutions could be developed, representing simplicity, innovation and cost efficiency for Severn Trent. The approach The Avove Vegetation Management team, working in collaboration with in-house design and ecological functions, successfully delivered the work according to Severn Trent’s requirements, providing cost-effective design amendments that rectified the challenging planned route. Design diversions & alternative solutions: Avove quickly identified operational risks and suggested route diversions to avoid potential hazards. For example, they a small diversion was designed to avoid uprooting Japanese knotweed, an invasive species that grows rapidly and requires costly chemical treatment to successfully eradicate it. This solution not only mitigated the risk this plant caused to the project, but also provided a cost efficiency of approximately £250,000 for Severn Trent. Protection of vegetation: The team took special care to protect local heritage sites and mature trees. For instance, they implemented excavation techniques that preserved the root systems of protected lime trees near a local church. Excavation was undertaken using vacuum techniques to avoid damaging the root plate. The team also designed a route diversion to protect a 150-year-old oak tree near Bestwood Country Park. In areas where excavation was necessary to the project, such as outside of Bestwood Country Park, near to a local housing estate, the team engaged with the community to develop replanting initiatives that ensured the greenspace would be restored to its former state. Community engagement: Avove prioritised community engagement throughout the project. The team held replanting forums and consultations to ensure that the local community needs were met and that their concerns were addressed. This approach helped to build positive relationships with residents and reinforced both our and Severn Trent’s commitment to social responsibility. The Solution Avove successfully delivered this vegetation management project in line with Severn Trent’s requirements, maintaining a significant portion of the original design whilst ensuring that all vegetation clearance was completed within an 8-week period. This rapid execution was crucial for facilitating the construction of the pipeline and ensuring that the pipeline project, as a whole, remained on schedule. In addition to the efficient delivery of this project, we collaborated with Severn Trent to ensure that that the execution of the original design didn’t present unexpected commercial complications by suggesting alternative routes, leveraging the expertise of our in-house functions to provide a one-stop shop solution to risks that would have otherwise been complicated to manage. [caption id="attachment_18761" align="alignnone" width="1200"] Courtesy of Avove[/caption] Benefits The successful execution of this stage of the Strelley-Redhill Pipeline Project, delivered numerous benefits for Severn Trent, the local community and the environment. These included: Cost savings & efficiency: The design amendments, such as the diversion around Japanese Knotweed, resulted in substantial cost savings for Severn Trent and ensured the project would be completed within the designated timeframe. Proactive community engagement: The team built trust and fostered positive relationships within the community, which alleviated concerns and ensured comprehensive communication. Environmental responsibility: The commitment to environmental responsibility ensured that the project had minimal impact on local ecosystems, safeguarded mature trees and involved replanting initiatives, which preserved the area’s natural heritage. Enhanced water supply infrastructure: The new pipeline significantly increases the flow rate between the Strelley and Redhill reservoir, ensuring a reliable water supply. Innovations Efficient route diversions: By leveraging the expertise of their integrated functions, we developed and implemented route diversions that minimised the environmental impact and avoided costly complications. Multi-disciplinary approach: The synergy between the Avove Vegetation Management, Design, Ecological and Customer Service teams offered a holistic approach to project management, which ensured that potential risks were managed effectively and the project’s design and execution were optimised for simplicity, innovation and cost-efficiency. The Results The Strelley to Redhill Pipeline Project stands as a successful example of Avove's ability to deliver complex infrastructure projects, whilst balancing environmental, community and client needs. The project was completed on time, within budget and to the highest standards of quality and safety. The results of this project also demonstrated the value of a multi-disciplinary approach to project management, which integrated Avove's expertise across vegetation management, design and environmental sustainability. In conclusion, the project’s success highlights commitment to innovation, environmental responsibility and community engagement and reinforces Avove's reputation as a leader in delivering large-scale infrastructure solutions that provide lasting benefits for clients, communities and the environment.

Scope of works The purpose of the job was to design and supply temporary and permanent support for a hydro power house and turbine chamber (plus associated inlet channel and tailrace) constructed at the side of an existing weir on the banks of the River Derwent in the centre of Derby. Issues & solutions The design incorporated a single level of modular 406UC Hydraulic Brace system in conjunction with Larssen piles up to 10m in length, toed in mudstone, covering a perimeter of over 150m. MGF's design allowed early removal of the brace by using a permanent concrete base slab as a low propped cantilever. The design had to take into consideration the complicated construction sequence; and the location of a large crane during installation and removal of the river piles. During the project Balfour Beatty and MGF collaborated to develop the Stairsafe system (the UK's first temporary steel stair system designed specifically for excavations). The system proved a great success in providing rapid and safe access into excavations leading to greater site productivity. The system is now being used throughout the UK on excavations up to 6.5m in depth. [caption id="" align="alignnone" width="1200"] Courtesy of MGF Ltd[/caption] Project details Sector: Energy & Waste Client: Derby County Council Contractor: Balfour Beatty Consulting engineer: Atkins MGF Depot: Midlands - Rugeley Product hired: 406UC Hydraulic Brace, 10M Larssen Piles The verdict From early in the tender process MGF have been heavily involved with Balfour Beatty to develop an innovative, cost effective and highly complicated cofferdam design; which helped make Balfour Beatty's tender attractive to the client, Derby City Council. Michael Rummens, Balfour Beatty Site Agent, commented:

"MGF were brought in at tender stage to assist in the value engineering of the cofferdam and support frames. Upon contract award, MGF's technical team were extremely proactive in producing a workable design in line with the projects requirements. The professional, amenable and expedient attitude continued throughout the process from design, technical support, plant hire and delivery and site assistance."

    For more information: MGF Ltd | +44 (0)1942 402700 | www.mgf.co.uk    

Curdworth Lagoon is located within Minworth Sewage Treatment Works next to the River Tame. Ivor King - The Piling People was asked to design a solution to retain and stabilise the lagoon embankment, whilst protecting against erosion from the adjacent river. Due to the risk of landslip coupled with adverse ground conditions, we deployed Giken Supercrush technology using one of our ECO700S Silent Pilers. This ensured we could overcome hard ground conditions whilst using a silent and vibrationless, environmentally sensitive method of installation. The operation was supported by AGD Equipment’s Giken clamp crane, due to a narrow corridor of working which prevented the use of piling mats. Ivor King are the only owners of Giken Supercrush Silent Piling Technology in the UK and the largest in Europe.

Curdworth Lagoon Embankment Stabilisation - Courtesy of Ivor King - The Piling People

The resultant pile line spans almost half a kilometre, comprising 750Nr PU28-1 steel sheet piles ranging from 7 to 11 metres in length, complete with weep holes at regular intervals to overcome ground water pressure over the retained height. The method of installation proved to be so efficient, we delivered the project four weeks ahead of schedule, giving considerable savings on programme time to the client. Sheet piles were mobilised to site using a tractor and bespoke trailer due to weight restrictions which precluded Heavy Goods Vehicles. Location: Minworth, Sutton Coldfield Client: Costain Project cost: c. £1.4m Completion date: October 2018 Project period: 16 weeks Plant utilised: Giken ECO700S Supercrush Silent Piler IHI 70 tonne Lattice Boom Crawler Crane Giken CB2-5 Clamp Crane Tractor and bespoke trailer by Ivor King

The project required the contractor to excavate within 25m of Beaumaris Castle – a UNESCO World Heritage site and one of the best examples of 13th and 14th century architecture in Europe attracting over 100,000 visitors last year. Faced with the challenge of installing 600m of 1.5m diameter polypipe in 6m sections between existing manholes, John Kelly Construction spent time researching the products available on the market, before finding that MGF’s High Clearance Trench Boxes were ideal for the job. [caption id="" align="alignnone" width="1200"] Courtesy of MGF Ltd[/caption] The 7m x 2.9m wide High Clearance Trench Boxes coupled with Top Boxes saved time and money to the contractor when compared to sheets and frames. The strength of the box allows suitability and capability of going to 5m depth and having high clearance struts on both ends of the box allows access at both sides – ideal for installing larger diameter pipes. [caption id="" align="alignnone" width="1200"] Courtesy of MGF Ltd[/caption] Paul Cowen, Technical Sales for MGF commented:

“Beaumaris’ most recent floods in 2017 was the catalyst that something needed to be done regarding the surface water drainage system. MGF became involved to supply the excavation support equipment to alleviate the threat of flooding to protect the natural beauty and tourism trade in the area”.

MGF’s stock logistics team confirmed availability of the kit at our Dartford depot and coordinated transfer to the Astley depot before delivery to site with three 40ft articulated vehicles and two 15t wagons to ensure the order was met. [caption id="" align="alignnone" width="1200"] Courtesy of MGF Ltd[/caption] John Kelly, Managing Director of John Kelly Construction, stated:

"I was very impressed with MGF as a company as they were very quick to respond to our queries, provided designs and all equipment ordered arrived on site with no delays."

Sector: Water & Utilities Client: Isle of Anglesey County Council Contractor: John Kelly Construction MGF depot: North West - Astley Products hired: High clearance trench box, top boxes & titan manhole box   For more information: MGF Ltd | +44 (0)1942 402700 | www.mgf.co.uk    

The Lincoln Defences Project is a £6 million investment led by the Environment Agency to improve the city’s flood defences for around 4,000 homes and businesses. As part of the scheme, we installed a total of 340 linear metres of steel sheet piles up to 9.5m in length on a stretch of the Sincil Dyke in Lincoln for bankside stabilisation works. Challenges & solutions The close proximity of residential properties meant the Giken silent and vibration-free method of installation was required. In fact, sheet pile installation happened mere metres away from the houses and gardens of neighbouring properties, which were directly in front of and parallel to the watercourse where works took place. For extra efficiency, two Siken Silent Pilers were set up to work in tandem, installing piles synchronously either side of the dyke. Heavily restricted access at this site required supporting ancillary equipment and power packs to be accommodated directly behind the Silent Pilers on modular steel platforms, sitting atop previously installed sheet piles. As the Gikens ‘walked’ along the pile line to their next positions, so the crane mats and equipment were moved along in a direct line with them.

A vibration-free installation into hard ground close proximity to residential properties - Courtesy of Ivor King - The Piling People

It was also necessary to access the far end of the site through an existing warehouse building. To overcome low headroom, a tractor and trailer assisted with the movement of plant and equipment through the building, including a 90T crane needed to pitch piles, which also had to be broken down into modular form. The crane was then rebuilt once through the warehouse building, ready to support piling works. Due to hard ground conditions the two Gikens operated in Supercrush mode, where the ground is pre-augered as piles are simultaneously pressed-in. Because Giken technology is virtually silent and vibration-free, disturbance and disruption to the daily lives of local residents during works was able to be kept to an absolute minimum – a key requirement on this project. Location: Minworth, Sutton Coldfield Client: JN Bentley on behalf of Environment Agency Project cost: c. £1.1m Completion date: December 2021 Project period: 16 weeks Plant utilised: 2 x Giken ECO700S Silent Pilers in Supercrush mode 2 x 90T Lattice Boom Crawler Cranes 35T Excavator Tractor & Trailer

When you’re installing sheet piles at the end of a residential cul-de-sac, next to an adjacent river, your installation method needs to be silent, vibration-free and environmentally friendly. Add hard ground conditions into the mix and you’re going to need our Giken Supercrush solution. Lady’s Walk is a picturesque footpath on the bank of the River Wansbeck in Northumberland, connecting Morpeth town centre with the nearby village of Mitford. During the rainy Easter weekend 2018, 35m of river retaining wall and footpath subsided and fell into the river.Northumberland County Council engaged the services of Ivor King to install a sheet piled retaining wall in to order to stabilise the land, enabling necessary repairs to be carried out and ultimately for the public footpath to be reinstated. Challenges & Solutions Hard ground conditions, environmental issues and extremely restricted access made this project particularly complex; site access was via a 3.2m wide residential cul-de-sac, with neighbouring properties within close proximity and an environmentally sensitive riverside location. Using Giken Supercrush technology, we were able to overcome hard ground conditions, whilst pressing-in piles using silent vibration-free methodology. This ensured minimal impact to residents in neighbouring properties as well as protecting local flora and fauna in and around the adjacent river. (Note: in the video below, pay special attention to the group of ducklings swimming past undisturbed, oblivious to the installation, proving our Giken solution really is silent and vibration-free!)

Riverbank sheet piling to enable reinstatement of public footpath - Courtesy of Ivor King - The Piling People

Furthermore, the expertise of our in-house transport team was called upon, with all deliveries were meticulously planned and executed by Ivor King Transport into a site where access was extremely tight and barely wide enough to accommodate an articulated lorry. Once our sheet pile retaining wall installation was complete, repairs could take place to the the riverside path with eventual reinstatement and reopening of this popular walking route in Northumbria. Location: Lady's Walk, Morpeth Client: Northumbrian County Council Project cost: c. £269k Completion date: November 2018 Project period: 8 weeks Plant utilised: Giken Supercrush Silent Piler JCB JS360 Excavator with Side Grip Movax Attachment Marchetti Crawler Crane