Supply Chain - Site Preparation - Site Clearance & Demolition

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.

Llyn Bran is located in Denbighshire, north-east Wales and was a natural lake that was raised in 1899 by a concrete dam. The reservoir was used to supply water to the North Wales Hospital in Denbigh. The hospital closed in 1995 and Llyn Bran has not been used for drinking water since. As part of a separate discontinuance scheme at Llyn Anafon, Llyn Bran was identified as a ‘compensatory site’ for the loss of habitat at Anafon. One element of turning Bran into a compensation site was the removal of the dam, as well as other ecological enhancements. Through careful restoration work, Llyn Bran will eventually become a Special Area of Conservation. The reason for Llyn Bran discontinuance Llyn Bran Reservoir is required as a ‘compensatory site’ for the loss of habitat area that will be caused by discontinuing the dam at Llyn Anafon Reservoir, as required by the Habitats Directive. Llyn Anafon Reservoir was originally a natural lake which was raised by 1.4m in 1931 through the construction of an embankment dam. The use of this site for local water supply ended in 2002. A 2016 S10 inspection of Llyn Anafon resulted in a MITIOS (Measures in the Interests of Safety) to “develop a long-term solution to the poor and deteriorating condition of the dam”. In January 2019, it was agreed with relevant regulators that to provide a long-term solution, the reservoir would need to be decommissioned, with the dam structure removed and the lake lowered by 1.4m. [caption id="" align="alignnone" width="1200"] Llyn Bran before discontinuance - Courtesy of Welsh Water[/caption] Llyn Anafon is nationally and internationally protected for specific conservation features. This means prior to any project taking place, a full Habitats Regulation Assessment (HRA) had to be undertaken. The outcome of this assessment was that it was not possible to avoid adverse impacts to protected features and as such, the only route to proceed with the project was under the “Imperative Reasons of Overriding Public Interest (IROPI)” (Article 6.4 of the Habitats Directive) on the grounds of public safety. The Anafon Dam Discontinuance Scheme is the first IROPI case of its kind in the UK and has recently been approved by Welsh Government. To satisfy the IROPI case, Welsh Water was required to secure ‘compensatory measures’ for the loss of habitat at Anafon. Using a set of criteria agreed with National Resources Wales (NRW), Llyn Bran was identified as the most suitable site to provide the necessary compensation. A key element of the work was to ‘restore and maintain hydrological functioning’ i.e., removal of the dam to create a natural lake and restore connectivity to the downstream watercourse. Although the primary reason for discontinuing Llyn Bran was for compensation, it also had the added benefit of removing a dam which was no longer needed for operational purposes. [caption id="" align="alignnone" width="1200"] Llyn Bran dam before discontinuance - Courtesy of Welsh Water[/caption] Scope of works Create temporary construction access using bog mats. Draw down the reservoir by means of siphon pipes and pumps. Remove silt from the area immediately upstream of the dam. Demolish the entire dam and remove arisings for disposal off-site. Restore the watercourse channel downstream of the retained natural lake, incorporating silt management and retention measures. Create new water vole habitat along the shore areas of the retained natural lake using coir matting. Demolish outbuildings and associated structures with all building waste removed for disposal off-site. Remove exposed sections of pipework. Buried pipework to be sealed and filled by grouting. Install new roadside fencing along the north end of the reservoir. Install rip-rap protection around the upstream end of the B4501 culvert. [caption id="" align="alignnone" width="1200"] Ground conditions - Courtesy of Welsh Water[/caption] As with all discontinuance schemes the various surveys, permits, consents and negotiations in advance of the physical works were particularly complex, taking more than two years to complete. An overview of the consents and constraints required is below: Impoundment Licence and SSSI consent from Natural Resources Wales (NRW). Permitted Development Certificate from Denbighshire CC. Ordinary Watercourse Consent from Denbighshire CC. Protected species licence required for trapping and temporarily removing water voles (this was needed before permitted development could be granted). Annex 1 Habitats present around lake margins. Reservoir drawdown rate limited to 120 l/s. HRA level 1 & 2 required. Peat bog deposits along route of temporary access track. Bat surveys required prior to demolition of valve house & boat house. Challenges & constraints Site access With no formal access track to the dam, and the surrounding land being designated as Annex 1 Habitat due to the presence of peat, access was one of the main challenges. With 140 peat depths probes taken along the route of the proposed access track, and working closely with NRW, a methodology was developed for installing over 280m of bogmats to the dam without the need to excavate and remove the top layer of peat. This minimised the potential damage to the peat and made site reinstatement far easier. [caption id="" align="alignnone" width="1200"] (left) Bog mat access track and (right) amphibious excavator used to load barge with coir matting - Courtesy of Welsh Water[/caption] Peat The extent of peat encountered on site was far greater than expected once construction began. This resulted in an entire change in the contractors methodology for the coir matting. It was initially planned to use Bog Master excavator and tracked dumper to access the western shore of the reservoir, however it quickly became clear this was not practical. Thanks to the contractor being proactive, the methodology was quickly changed to using an amphibious excavator and barge, to transport the coir matting across the reservoir. Water voles Water voles were identified on site during the early site survey stages, meaning a licence was required to temporarily remove the voles during construction. Six water voles were captured by specialists and were transferred to a facility in Kent, where they were looked after while the work took place. A condition of the licence was that there must be 5-days with no water voles captured before it could be concluded that all voles were removed from site. Rather unluckily, there were two occasions where a vole was captured at the end of the fifth day, meaning the process took far longer than expected and the licence had to be extended. The voles are due to return home to Llyn Bran this summer. [caption id="" align="alignnone" width="1200"] Water voles were captured and transferred to a facility in Kent for the duration of the works - Courtesy of Welsh Water[/caption] Compensation flow A condition of the NRW impoundment licence was for a continuous compensation flow of at least 20 l/s for the duration of the works. This meant pumping to the watercourse, which had to be continually monitored. It was hoped to use a cloud-based telematics tool that makes it easy to monitor the pumps off-site but unfortunately, due to lack of signal, this did not work meaning William Hughes Civil Engineering needed to attend site over the weekends to check on the compensation flows. The summer of 2022 proved to be exceptionally dry, which crated a challenge in meeting compensation flows whist also not allowing the remaining lake to become too low. Flood risk The existing reservoir provided significant flood attenuation meaning the discontinuance increased the flood risk to a downstream highway culvert. Initially, there were concerns from the highways department that the culvert would need to be upsized, which would have added significant costs to the project. Following a detailed flood risk and stability assessment, Welsh Water were able to prove that the increased flood risk would not adversely affect the culvert and only minimal slope protection work around the culvert was required. [caption id="" align="alignnone" width="1200"] Amphibious excavator forming the new channel connecting to the downstream watercourse - Courtesy of Welsh Water[/caption] Llyn Bran Reservoir Discontinuance Project Construction timeline: 16 May 2022 - 4 November 2022 Project cost: £1.7m Drivers: Dam safety | Habitats Directive | Reducing costs | Ecological compensation measures Supply chain - key participants Principal Contractor: William Hughes Civil Engineering Design Partner: Stillwater Associates Environmental Consultants: Ricardo Energy & Environment Ecology/water vole licensing: Wildwood Ecology Ltd Silt management: Salix River and Wetland Services Amphibious excavator hire: Land and Water Plant Opportunities & Savings Forestry culvert At the design stages there were concerns about the condition of a nearby downstream forestry culvert and its ability to accommodate the reservoir outflows during emptying. Expertise within Welsh Water was utilised by requesting a CCTV survey of the culvert via the wastewater team. The team provided a prompt and efficient service and enabled us to confirm the capacity and condition of the culvert. [caption id="" align="alignnone" width="1200"] Cores being drilled through concrete dam to allow any extreme storm flows to pass through - Courtesy of Welsh Water[/caption] Dam safety mitigation During detailed design, the Dam Safety Team suggested coring holes though the concrete dam once the reservoir was drawn down to the required level. This would mitigate the risk of the reservoir refilling during severe weather, before the dam was fully demolished. Fortunately, on this occasion the weather was favourable and the cores were not needed. This approach will be considered for any future concrete dam discontinuances. Waste removal It was agreed with NRW that the stone from the haul road and compound could be transferred to a nearby quarry, just down the road from site. This was done under a waste transfer notice, saving costs. The arisings from the dam were removed off site. The dam was demolished far easier and quicker than expected, making the removal of concrete straightforward. [caption id="" align="alignnone" width="1200"] Dam demolition in progress - Courtesy of Welsh Water[/caption] Coir matting Due to the silt being drier than anticipated, there was spare rolls of coir matting left over. Rather than this being wasted, it was moved to nearby Alwen WTW where it is being stored before being used for silt management on the upcoming Cilcain Discontinuance Scheme which is due to start this spring. The future for Llyn Bran The discontinuance will give significant biodiversity opportunities in relation to the marginal areas around the retained natural lake and with the restored connectivity to the watercourse. The retained lake will also be used as a receptor site for aquatic plants translocated from Llyn Anafon. Long term ecological monitoring of the lake is required to ensure the compensatory criteria are met. This includes water quality and macrophyte monitoring as well as botanical surveys to check the natural regeneration of exposed shore habitats. A condition of the water vole licence is that activity is monitored until 2034. Through careful management and monitoring of the site, it is hoped that Llyn Bran will become recognised as a Special Area of Conservation.

Northern Ireland Water’s Cushendall Water Pumping Station (WPS) is housed on the outer perimeter of Dundonnell Water Treatment Works (WTW) situated on the outskirts of Cargan village in the middle of County Antrim. The WPS solely supplies Parkmore Service Reservoir (SR) with potable drinking water, which in turn gravity feeds three other downstream SRs (Knockans, Mullarts and Knockenny), which provide for the surrounding Glen’s of Antrim district. Parkmore SR has a capacity of 1.3 ML suppling a population equivalent of approximately 2000 with an average day demand in peak week (ADPW) of 17.6 l/s. The existing trunk main The Cushendall Water Pumping Station to Parkmore Service Reservoir Trunk Main was constructed back in the 1970s using 6” PVC pipeline across bog land on mountainous terrain outside Cargan village. This has posed operational problems over the years when locating and repairing any leakages or bursts. Repair machinery has become stuck and unable to navigate the poor ground conditions raising access issues and Health & Safety concerns for staff and operatives attending repair works. Some bursts in the off-road pipeline have caused expensive tankering operations to keep the ~2000 customers with a reliable supply of potable drinking water to the villages of Cushendall, Cushendun and Glenariff. In addition, the existing Cushendall WPS has been difficult to maintain due to the age of the surge vessel, panels and pumps. Project scope NI Water, as part of the IF105 Integrated Partnerships Framework, identified the need to relocate the Cushendall WPS and associated trunk main due to the ongoing operational problems and supply outages. The new scheme included the following scope: A new modular, prefabricated, modular, plug and play water pumping station located in the verge close to a picnic area off the Glenravel Road, approximately 0.5km south of Cargan Village, Co. Antrim. Connection to the existing 18” trunk main in the same picnic area, and approximately 400m of new suction main to deliver water to the new pumping station. Approximately 2km of new 225mm HDPE rising main to deliver water to Parkmore SR installed in the carriageway for improved access. Alternative connections to live tanks at Parkmore SR (non-siphoning), including baffle curtain works and the addition of a 200mm bypass and meter. Civil and MEICA abandonment works of existing Cushendall WPS, and re-tapping the existing chlorine residual pump. [caption id="" align="alignnone" width="1200"] Dual lay pipework inside steel sleeves - Courtesy of WSP[/caption] Detailed design and engineering challenges Following ECI works in October 2021 by the Farrans/Glanua Group Joint Venture under a NEC4 option ‘A’ contract, engineering designs were undertaken comprising of a range of elements including: Proposed trunk main route, longitudinal sections, and connection details. Scheme plans with details on bridge crossing and new water pumping station location. Reinforced concrete slab drainage and ducting detail for modular pumping station. Surge analysis report and proposals. Hydraulic assessment of the new trunk main with total head loss, average flow, and peak flow information. From these reports it was concluded that surge could occur when the pump flow increased or decreased to suit changing water demands or uncontrolled sudden pump failure. From this the WPS was designed with a 500-litre bladder type surge vessel in accordance with the selected 38Kw pumps chosen for a 35 l/s and 7 bar charge arrangement. The rising main was designed with six air valves to aid high/low pressure spikes or transients during operation. The hydraulic analysis of the new rising main from the picnic area to Parkmore SR, using the average day demand in peak week (ADPW) of 17.7l/s, calculated a total head loss average flow of 1.10m and peak flow 3.09m for the total 4.2km of the 225mm HPPE pipeline. Construction The construction contract was awarded under NEC4 Option ‘C’ Target Cost Contract to Farrans/Glanua Group JV. Construction began in December 2022 and took place over a 14-month period at a total cost of £1.3m. The scheme was situated in an Area of Outstanding Natural beauty, this brought its own unique constraints and limitations. Due to ground conditions, opencut excavations was the method of installing the 2km of 225mm HPPE pipe under a DFI Roads approved lane closure using a rolling traffic light system operated and maintained by traffic management company, McVeigh Contracts Ltd. [caption id="" align="alignnone" width="1200"] (top left) traffic management barriers, (bottom left) notice of works and lane closure for pipeline installation and (right) pipeline track excavation - Courtesy of WSP[/caption] Bridge crossing Following trail holes and liaison with DFI Roads at ECI stage, two sections of 180mm HPPE pipework were installed inside 250mm steel sleeves and C30 concrete and steel mats used for protection over the span of the 35m bridge structure. A reduced road cover level of 700mm was agreed and approved with DFI Roads to ensure the structural integrity of the underside of the bridge remained unchanged. Parkmore Service Reservoir works In tandem with the construction of the pipeline, a specialised company Waterworx Ltd carried out the alteration works to the live Parkmore SR. Each cell was shut off and drained individually to aid the installation of the inlet pipework and repositioning/installation of the new baffle curtains. All of the SR works were undertaking in close liaison with NI Water Operations who ensured stringent drain down and sampling timelines to ensure continuous water supply the local area. [caption id="" align="alignnone" width="1200"] (left) the existing baffle curtain and (right) new anti-siphon inlet pipework and baffle curtain at Parkmore Service Reservoir - Courtesy of WSP[/caption] Modular pumping station The new modular ‘plug and play’ WPS included the following elements: Pumping system and associated ancillaries. Control panels. Telemetry. Surge suppression. Building services. The kiosk and skid base of modular pumping station was supplied by Morgan Marine Ltd. The assembly of the mechanical and electrical items were completed at Profitec Solutions’ headquarters in Cookstown. Electrical switchgear was built into the kiosk to facilitate an external portable generator in the event of mains supply failure. Following a factory acceptance test, the modular WPS was delivered to site in November 2022 and craned into position on top of the 450mm reinforced concrete base slab. For the inlet supply to the WPS an under-pressure Tee was installed onto a live existing 450mm cast iron trunk main, this allowed for seamless transfer to the new section of trunk main without any disruption to current trunk main supply in the district. Parkmore Water Pumping Station & Trunk Main: Supply chain - key participants Delivery contractor:  Farrans/Glanua Group JV Design/project management: WSP Civil Design: Jacobs Design Main Contractor (Civils): Farrans Main Contractor (M&E): Glanua Group Civil team: McCormick Contracts Ltd Electrical works: Profitec Solutions Traffic Management: McVeigh Contracts Ltd Kiosk for new WPS: Morgan Marine Ltd Pumps: Grundfos Under-pressure tee connection: Waterworx Ltd Quarry products & reinstatement: Northstone Materials Ltd HDPE pipe: APP Fusion Group WPS automatic control (PLCs & HMI): Mitsubishi Mechanical, electrical and instrumentation works The Parkmore WPS consists of two Grundfos 38 KW CR125 booster pumps working on a duty/standby regime which can be controlled manually or automatically by way of variable speed drives. The duty/standby system is set to switch over after each pump stop its programmed cycle. [caption id="" align="alignnone" width="1200"] (left) The existing Cushendall WPS and (right) the new Grundfos pumps and inlet/outlet pipework - Courtesy of WSP[/caption] The two modes of control available are the primary, level-based control, and the secondary, pump fixed speed mode control. The chosen method by the client is the level-based method, remotely controlled on Telemweb with agreed low and high Parkmore Service Reservoir set-point levels (pumps on at 2.2m and off at 2.8m). The WPS automatic control is achieved using a Mitsubishi iQ-R series Programmable Logic Controller (PLC) system attached to a 12” Mitsubishi GOT Human Machine Interface (HMI). The PLC communicates status/alarms/events and exchanges set-points between the PLC and the telemetry talus unit via Modbus RS232. Critical status, alarms and controls are hardwired to/from the telemetry talus unit. The HMI provides information to the MCC for pumps 1&2 with the following list of options for NIW operatives to manually operate inside the WPS: Plant data. Plant mimics. System screen. Control system settings. I/O test pages. Trends and alarms. [caption id="" align="alignnone" width="1200"] (left) HMI screen and (right) Parkmore Dungonnell WPS - Courtesy of WSP[/caption] Project summary Commissioning of the new pumping station began in early January 2023 and the existing pumps at Cushendall Pumping Station were turned off, allowing the 28 days commissioning period to begin. Following a successful testing period and training of NI Water Operatives, the new Parkmore Pumping Station is solely suppling the strategically important Parkmore Service Reservoir regularly during the day. The redundant Cushendall WPS has been electrically isolated and associated pipework has been sealed and capped off. To date the new pumping station has supplied over 60,000m3 of clean drinking water to Parkmore SR and has proven to be a resilient and reliable trunk main asset to NI Water.

Keadby Terminal Assisted Outfall (TAO) is a strategically important asset, protecting homes, businesses and agricultural land from flooding in the Isle of Axholme. The TAO was originally constructed in 1939 and required upgrading and modernisation to ensure the continued operation of the pumping station as resilience and reliability had been lost due to age, obsolescence and general wear and tear, resulting in the need for a major investment. Keadby TAO is the outfall for the River Torne within the Isle of Axholme to the tidal River Trent. It originally comprised a gravity sluice which maintained water levels within the Isle of Axholme and discharged fluvial flow to the tidal Trent when tide levels permitted. High flows were pumped via six pumps, providing approximately 32m3/s discharge capacity when required. Finding a viable solution

Previous business cases had failed to find a viable solution and detailed design work had developed plans for the project to completely renew the existing facility. However, multi-disciplinary teams from the Environment Agency, Arcadis, WSP and Galliford Try Binnies JV (GBJV) worked collaboratively to deliver value engineering achieving savings greater than £12m by re-using existing assets.

The new solution made a switch to fish-friendly electric pumps, avoiding the long-term management of fish and eel screening, and recommended refurbishing rather than replacing the station which would deliver environmental benefits, operational savings and a 90% carbon saving.

[caption id="attachment_14188" align="alignnone" width="1200"] Outfall construction (November 2021) - Courtesy of GBJV Ltd[/caption] Project scope

The upgrade included:

A comprehensive heavy electrical system replacement. Replacement of all pipework Replacement of the entire control system. The installation of six bespoke vertical lift pumps providing 19.2m3/s discharge capacity against a hydrostatic head of 3.7m when required. A complete redesign of the outfall structure to provide three individual discharge cells which will allow safe access to the twelve (1.8m wide) gravity/pumped culverts and twelve 1.8m tidal flaps for inspection and maintenance purposes.

The project team assisted in the development of the strategic case for investment alongside an update to the Isle of Axholme Flood Risk Management Strategy, and worked closely with the strategy asset management and delivery group ensuring that stakeholder engagement was central to the delivery of the project.

Undertakings

GB JV Ltd, a joint venture between Binnies UK Ltd and Galliford Try, has been the sole engineering design and build provider for the Outline Business Case (OBC), Final Business Case (FBC), and design/construction stages. This ‘cradle to grave’ approach has provided many benefits including the complex construction sequence document (for the whole scheme) created during the FBC which considered severe site constraints and proved an invaluable guide during the design and build phase.

[caption id="attachment_14184" align="alignnone" width="1200"] Outfall construction constraints - Courtesy of GBJV Ltd[/caption] Keadby Terminal Assisted Outfall Pumping Station: Supply chain - key participants Designer & delivery contractor: GB JV Ltd Binnies UK Ltd Galliford Try Client NEC project management: Turner & Townsend Client technical advisors: KGAL Consulting Engineers Ltd Client cost consultant: Arcadis Electrical enabling works: Fairfield Control Systems Sheet piling: Keltbray Ltd Mechanical installation: Alpha Plus Ltd Outfall construction: CPC Civils Ltd Electrical installation: Centrica MCC/PLC/HMI/SCADA & systems integration: Blackburn Starling Ltd Penstocks & flap valves: Glenfield Invicta Large knife gate valves: Ebro Valves Ltd Large knife gate valves: Stafsjö Valves Pumps: Pentair Fairbanks Nijhuis Stop logs: Aquatic Engineering Ltd HV switchgear: Midland Power Networks Transformers: Wilson Power Solutions Ltd Standby generator: YorPower Ltd GRP kiosks: Industrial GRP Ltd Constructability challenges

The design involved constructability challenges as the Environment Agency operational team could only allow the release of two pumps at any one time to ensure that the operational plant was never compromised in terms of readiness for flood resilience. It also involved innovative fish pass solutions as site constraints prevented the use of traditional fish ladders and passes.

Binnies’ design team provided a solution which allowed the retention of the existing structure while completely refurbishing the installation. This was achieved by replacing the existing ‘carbon-hungry’ diesel-driven centrifugal flow pumps with electrically driven permanent magnet motors and vertically mounted axial flow pumps within the existing building envelope.

[caption id="attachment_14186" align="alignnone" width="1200"] Aerial view of final pour - Courtesy of GBJV Ltd[/caption]

Given the age of the buildings on site, the initial concept design was for the complete demolition of the existing reinforced concrete structure to make space for a new installation. A solutions-focused team looked at plans differently and included extensive early supplier engagement with pump suppliers that crucially unlocked the re-use of the existing structure; a cornerstone of the significant cost and carbon savings. A complete refurbishment rather than the replacement of the existing delivered effective resilience to future climate change.

Fish and eel friendly pumps

The existing facility presented a barrier for fish and eel migration and The England and Wales Eels Regulations (2009) required the installation to be upgraded to allow migration of elvers past the facility.

Accordingly, the fish-friendly pumps allow fish to pass downstream safely when pumping and an innovative ‘Elver Mode’ was added into the software controlling the sluicing operation allowing elver access during their migration period and subsequently safe passage into the Three Rivers Catchment and the wider Isle of Axholme, with 224km of main river available to fish and eel passage.

Pentair Fairbanks Nijhuis, the pump supplier, developed a fish-friendly impeller design that ensures fish are not struck on entering the pump, by incorporating vanes to guide them unharmed through the system. The impeller design in conjunction with the variable speed drives ensures optimal efficiency at all times. Low running speeds also improve passage for fish and reduce noise and vibration.

[caption id="attachment_14183" align="alignnone" width="1200"] Pump hall - Courtesy of GBJV Ltd[/caption] Operational access

Binnies’ design has also improved operational access to the culverts and flap valves which previously posed significant health and safety risks. Previously, some areas were accessible only by divers and other areas have never been accessed since the TAO was commissioned in 1939 as it was considered too dangerous.

The improved operational safe design has minimised ongoing maintenance difficulties.

Outcomes

Through collaboration with partners and the supply chain the team delivered the OBC and FBC stages to time and budget winning the Best Business Case of the Year at the Environment Agency’s ‘Flood and Coast Excellence Awards’ (2019). GB JV Ltd attained partial sectional completion of the flood defence asset at the end of April 2021 (four pumps operational and available for beneficial use), resulting in the Environment Agency attaining 80% of its stated outcome measures; the reduction in flood risk to 2484 of the total 3105 properties to be delivered by this project.

The remaining 621 properties were realised in November 2021 upon successful integration of the two remaining pumps. This was achieved despite COVID-19 disrupting construction work and storms in 2019 and in 2020 when the Environment Agency needed to operate the diesel pumps to reduce flood risk to the catchment, preventing construction work for approximately three months.

The former pumping station had six large and dangerously loud diesel engines (over 98 dBA when measured outside with the doors closed) and emitted large amounts of exhaust fumes. It was not safe to be inside the building with the pumps operating (even with ear defenders). The building is within 100m of residential properties so pumping activities disturbed the local community.

The new pumps are much quieter with the standby generator designed to be less than 60dBA at 1m. As the pumps can run 24 hours a day for several weeks at a time, the local community have greatly benefited from the removal of noise and air pollution.

[caption id="attachment_14187" align="alignnone" width="1200"] Outfall structure including fenders - Courtesy of GBJV Ltd[/caption]

The site is immediately adjacent to the Port of Keadby on the tidal River Trent. Close management was required with both PD Ports Ltd and ABP who had equipment within the working area, so the team worked with the port to respond to and work around vessel movements and port operations. A new river fender structure was designed and installed to reduce the risk of damage to the outfall structure from berthing vessels.

In conclusion, the carbon footprint was reduced by 90% throughout the project’s lifecycle using modern efficient fish-friendly electric pumps negating the need for a 3mm eel screen and reduced ongoing lifetime operational expenditure by the use of the existing structure.

When COVID-19 restrictions prevented foreign travel to the pump supplier in Holland, the team implemented remote attendance to witness the programme-critical Factory Acceptance Testing, allowing us to maintain programme. This also enabled a wider team to witness the testing and provided a learning opportunity for team members that would not otherwise have been able to attend. The approach continued with Design Workshops that avoided the need for the Design Team to physically attend site, without compromising the quality of work. The reduced travel also contributed to carbon reduction.

Awards

The project has won a number of awards including:

Environment Agency ‘Project Excellence Awards 2019 Winner Best Business Case of the Year at the Environment Agency’s ‘Flood and Coast Excellence Awards’. Highly Commended Asset Management Project of the Year at the Environment Agency’s ‘Flood & Coast Excellence Awards’. Institution of Civil Engineers, East Midlands Branch Large Project Award 2023. Sustainability Award 2023.

Guildford town and the surrounding residential areas are currently served by an existing sewage treatment works (STW) located adjacent to the River Wey, just north of the town centre. The land which this occupies has been identified as part of the Slyfield Area Regeneration Project (SARP), which includes the new Weyside Urban Village (WUV). This mixed-use regeneration project will include circa 1,500 new homes, new community facilities and 6,500m2 of commercial space to improve the local area. Thames Water Utilities Ltd (TWUL) is working in partnership with Guildford Borough Council (GBC) to move the STW to a new location, which is not suitable for housing.

The location chosen is on the north-east extent of the existing Slyfield Industrial Estate and is on an area previously used as a landfill site. In August 2023 Water Projects published a case study which provided insight into the extensive pre-construction design for civil and process engineering elements of the project. This article delves into the construction of the project and provides an update on the significant progress made to date on site.

Site historical use

The site for the new STW is approximately 70,000m2 and was previously used as a landfill site. It had originally been used as sand and gravel quarries and then subsequently used as landfill from the 1960s to the 1980s.

The landfill material is generally domestic and light industrial. It consists of black bag waste, timber, plastics, fabrics but contains fragments of asbestos and other materials.

The site was capped off with a granular layer in the early 1980s and has laid dormant ever since. The landfill depth varies across the site from between 2m and 6m thick. This then overlies an alluvium layer, sands and gravels and London Clay. The depth of the London Clay is approximately 10m below existing ground level.

[caption id="attachment_16131" align="alignnone" width="1200"] A screenshot of the 3D model used for design and construction - Courtesy of Bam Nuttall Ltd[/caption] Civil engineering: Basis of the design

Typically, major structures within a sewage treatment works are built below or partially below ground level to maximise gravitational energy. The new Guildford STW differs in that the strategy is to deliberately design and build above ground as far as practicable.

This is to minimise the disturbance to, and removal of the existing landfill thereby reducing the impact on the environment and the cost of disposal.

Undertakings

After a period of Early Contractor Involvement, Thames Water awarded a contract to BAM-Enpure Joint Venture (BEJV) in 2021 to design, build and commission this significant new works and once operational, to de-commission the existing works.

BEJV is a non-integrated joint venture, formed specifically to combine the excellence of experienced civil engineering contractor Bam Nuttall Ltd and the process engineering/MEICA specialism of Enpure Ltd to deliver a turnkey solution for Thames Water. The workscope split is as follows:

Bam Nuttall Ltd: Civil engineering workscope Principal contractor Civil engineering design Ground stabilisation & piling Structures Underground pipework Tunnels, shafts and connections Buildings Outfall pipeline & structure Roads, fencing & general civil engineering works [caption id="attachment_16143" align="alignnone" width="1200"] Construction of the high level inlet works structure - Courtesy of Bam Nuttall Ltd[/caption] Enpure Ltd: Process engineering/MEICA workscope Principal designer MEICA design Process design Mechanical works Electrical works Control systems Commissioning

Decommissioning of the existing STW will also be undertaken by BEJV, in addition to working collaboratively with TWUL operational and networks teams to integrate existing TWUL operational assets into the new sewage treatment works.

Site trials

BEJV undertook a series of site trials in 2021/2022. The purpose of this was to investigate the proposed ground improvement techniques further in order to validate proposals and inform detailed design. There are a combination of techniques which interface with each other in a complex manner.

The trials also gave important information about potential effects to both leachate levels and ground gas within the existing landfill to ensure there would be no impact on environment, ecology and human health.

Four trial areas were chosen, to provide a variety of conditions and in each of these areas a set of boreholes was established at increasing offsets away from the trial areas. These boreholes contained monitors for both leachate levels and ground gas volumes and were monitored 24/7. In addition, noise and vibration monitoring was also undertaken. [caption id="attachment_16140" align="alignnone" width="1200"] (left) Rapid impact compaction underway and (right) a selection of site plant in use - Courtesy of Bam Nuttall Ltd[/caption]

The three techniques tested, and subsequently used within the works were as follows.

1. Rapid impact compaction (RIC): RIC was undertaken to remove the risk of long-term settlement to the landfill. Whilst the main structures would be supported on piles, this was to remove the risk of long term ground settlement underneath and around the structures. RIC is a method of imparting energy to the ground using a repeated but relatively short drop-weight, where a base plate is in constant contact with the ground. It is undertaken on a pre-determined grid pattern. At Guildford a 9T hammer was chosen, fitted to a 35T base machine and working on a 2.5m x 2.5m grid. Each ‘pass’ of the technique used 40 blows at each point.

Within the trial areas the technique was tested with 1, 2 or 3 passes (ie, 40, 80 or 120 blows per location). Cone penetrometer tests were used to measure the extent of deep level ground compaction before and after the trials. The continuous monitoring from the boreholes demonstrated that at each ‘thump’ of the ground there was no discernible change in leachate levels or ground gas volumes, and that there was no dispersal of leachate happening throughout the landfill.

From the trials it was determined that all areas of the site that are being built on should receive either 1 or 2 passes of RIC for the permanent works.

[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] 2. Precast driven piling: The main structures and pipelines are founded on precast driven piles. These are end-bearing into the London Clay, approximately 10m below ground level. Precast driven piles were chosen as the solution as the operation does not bring any landfill to the surface. Various size piles were driven to various depths and tested with both dynamic and static tests. Borehole monitoring showed that there was no discernible change to leachate and ground gas levels and that there was no dispersal of leachate happening throughout the landfill.

3. Vertical rigid inclusions (VRI): VRIs are mass concrete piles which are used for lightly-loaded structures and areas such as roads and hardstandings. They are a displacement pile, with the surrounding soil pushed sideways by an auger. As the auger is withdrawn the resulting void is filled with concrete up to ground level. They therefore work by increasing the density of the ground. A granular layer is then installed above to remove any ‘hard spots’. Again, this technique does not bring landfill material to the surface. It was trialled in two areas and found to be suitable for use, without causing any effects to leachate levels or ground gases. It is therefore being used as part of the permanent works over the whole site wherever there are not piled structures.

The trials of all three techniques, together with the subsequent site testing proved that the design principles were correct, and gave information on how to refine the solutions further. It also demonstrated that the techniques would not cause any adverse environmental effects.

[caption id="attachment_16142" align="alignnone" width="1200"] (foreground) Ferric mixing and flocculation chambers and (background) concrete bases for sludge tanks - Courtesy of Bam Nuttall Ltd[/caption] 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 Precast concrete works: DJ Civils Ltd Precast concrete manufacturer: FLI Precast Solutions Precast concrete manufacturer: A-Consult Ltd Soil processing: Remediation Waste Management Services Concrete supplier: Heidelberg Materials Gas protection: PAGeo Contracting Ltd Crane supply: Delden Cranes Enabling works

Enabling works took place during Spring 2023 and consisted of site clearance, setting up the site offices and welfare and establishing fencing. The whole site was then covered with a 100mm thick layer of imported granular material to provide further protection against the risk of asbestos within the existing capping layer.

A series of 20 further boreholes were installed around the perimeter of the site to enable daily monitoring of both leachate and ground gas within the landfill and to ensure that none was being mobilised by our works. Mobile monitoring stations for noise, dust, vibration and asbestos were all set up, which are monitored continuously throughout the works. Over half a million data points have already been captured.

[caption id="attachment_16138" align="alignnone" width="1200"] Piles and blinding concrete for the four final settlement tanks and (left) temporary ground support for pipelaying into the centre of the tanks - Courtesy of Bam Nuttall Ltd[/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 Transformers: Wilson Power Solutions Ltd Groundworks and foundations

The permanent works started in earnest in Summer 2023 and in August, rapid impact compaction was conducted over the site, with a combination of one or two passes, as informed by the results of the previous site trials. In total the ground was hit 360,000 times! Precast piles were then driven for the major structures and pipelines. These were all 250mm square piles and varied in length from 16m to 20m. A total number of 3,422 piles have been driven using three piling rigs.

Vertical rigid inclusion installation is currently underway, with a total of 1,700 out of 9,000 already completed. The works are sequenced to avoid clashes with other work areas, on what is a congested site. Following installation, each work area is left for the piles to cure for the following seven days, thus effectively sterilising large areas of the site at a time. This therefore requires detailed collaborative planning on all work fronts to ensure that the site can remain operational.

[caption id="attachment_16136" align="alignnone" width="1200"] Activated sludge plant precast walls erected, prior to pouring base slab and concrete stitches - Courtesy of Bam Nuttall Ltd[/caption] Concrete structures

Of the 59 concrete structures, some are simple reinforced bases, however ‘the big 5’ are significant structures:

Inlet works. Primary settlement tanks (PSTs). Activated sludge plant (ASPs). Final settlement tanks (FSTs). Tertiary treatment plant (TTP).

Due to the repetitive nature of their construction, BEJV chose to construct the PST and the ASP using precast concrete techniques, which are then stitched together on site. The four FSTs and two storm tanks are also being constructed using precast panels which are then post-tensioned.

The inlet works and TTP are complex, bespoke structures with very little repetition and so are more suited to traditional in situ concrete construction. The inlet works is a particularly complex structure, and is the tallest structure on site at 13m above ground level and being formed of five separate elements.

As of August 2024, the inlet works concrete structure is half complete and the TTP structure underway. The PST precast walls are mostly in place and stitched together, with roof beams now being installed. Works have also started on the ASP walls.

Pipework to the FSTs is underway, which will then allow the construction of the bases to follow on. To date (August 2024), 4,000m3 out 14,000m3 of concrete has been poured, and 205 out of 454 precast wall elements installed.

[caption id="attachment_16141" align="alignnone" width="1200"] (foreground) PST precast walls with concrete stitches and bases and (background) ASP precast walls - Courtesy of Bam Nuttall Ltd[/caption] Transfer tunnel

The flows to the existing STW enter at the southern end of the works. A new transfer tunnel has therefore been constructed to intercept this and transport the flows to the new STW. This tunnel is 1.4km long, 1.5m internal diameter and flows by gravity. It is formed at an invert depth of 10.6m to 15.7m below existing ground level, entirely within the London Clay.

To construct the tunnel a series of six shafts were sunk. The largest of these is 12.5m diameter and forms the inlet shaft in the new STW. The raw sewage will then be pumped from this to the inlet works, from where it will then flow by gravity through the new STW. The remaining five shafts were used to launch or receive the tunnel boring machine (TBM) and pipe-jack, as well as being used for auxiliary connections to sewers in the existing network which don’t get picked up by the main connection.

The tunnel was constructed using the pipe-jacked method using a tunnel boring machine. This was named ‘Daphne’ in a competition by Bisley Church of England School. Daphne Jackson was the first female physics professor in the UK and taught and researched in Guildford. The tunnel consists of four straight sections, one curved section and one short hand-dug section to connect to the existing network.

Current progress is that all of the shafts have been sunk, the main tunnel is complete and fit out the shafts has commenced.

[caption id="attachment_16139" align="alignnone" width="1200"] Safdar Ali, Andrew Dawes and Izhar Ahmad from the BAM team at the completion of the tunnel - Courtesy of Bam Nuttall Ltd[/caption] Outlet

The outlet for the new STW consists of a 750mm diameter pipe from the TTP and a 1050mm diameter pipe which acts as a storm overflow during extreme weather events. These pipes are laid across a floodplain to the River Wey, a distance of approximately 330m before discharging via a bespoke headwall into the River Wey. This has been designed in conjunction with Environment Agency to minimise erosion in what is classified as a salmon river.

Due to Environment Agency and Local Authority permitting requirements as well as practical requirements of working on a floodplain with underlying running sand, these works are practically restricted to a short duration in the summer. This is being undertaken during Summer 2024 and the works are on target for completion within this period.

Below-ground pipework

The majority of underground assets in the new works are being constructed within the existing landfill. This brings plenty of challenges in both design and construction. Assets must be designed to withstand both differential settlement and potential degradation from existing contaminants in the land fill material.

A variety of ductile iron, carbon steel, and concrete pipes are being used with various protection methods. The work is being self- delivered by the BAM workforce and the installation of below-ground pipework is underway with a focus on where it interfaces with the new structures. This requires extensive temporary works solutions to provide a safe working environment for the workforce within the band of landfill material.

Steel sheet piles are being used to provide temporary ground support and excavated landfill material is being sorted in a material handling area on site. This is being done to reduce the amount of hazardous material being sent off site, halving the amount of excavation and disposal required using traditional open cut methods.

[caption id="attachment_16133" align="alignnone" width="1200"] Threading buried process pipework between new structures requires extensive temporary works - Courtesy of Bam Nuttall Ltd[/caption] Integration of existing assets

As well as the main connection taking flows form the existing works to the new, there are three other existing assets which are to be integrated into the new system, at various points along the length of the new tunnel. This involves extensive research and planning in an open and collaborative approach with TWUL networks teams.

Bowers Farm Main was successfully diverted in November 2023, and has been constructed such that the final connection and commissioning to the new system will be a more straightforward operation. Planning works are currently underway on both Stokes Road syphons and Abbotswood syphons in order to construct similar scenarios for future connection and commissioning.

The main connection to the existing Guildford Main at the head of the new scheme entails connecting into an existing 10m deep concrete and brick built chamber, which carries live flows 24/7. The site team have undertaken several successful drawdowns in conjunction with TWUL to ascertain the dimensions and condition of the chamber in order to plan the final breakthrough works in great detail. This design work is currently underway and the new tunnel hand drive has been stopped a few metres short of the final breakthrough and shored up, prior to the final connection to the existing network.

[caption id="attachment_16164" align="alignnone" width="1200"] (left) Concrete bases for the tertiary treatment plant, (top right) cross-sectional view through the primary settlement tank, showing the piles and gas dispersal layer beneath the base, and (bottom right) precast wall panels are joined with an in situ concrete stitch - Courtesy of Bam Nuttall Ltd[/caption] Future works

Construction works of the ‘Big Build’ are continuing at pace and the BEJV Team are now focusing on ensuring a safe, effective and efficient integration of civils and MEICA elements. This will start in late 2024 and continue throughout 2025.

Following successful completion of commissioning of the new sewage treatment works in 2026, the existing works will be de-commissioned making way for the next stage of the Weyside Urban Village, providing homes and leaving a true legacy for local people and businesses.

The Little Whelnetham to Raydon Tee (LRT) Pipeline is a key part of Anglian Water’s Strategic Pipeline Alliance (SPA), designed to enhance water resilience across the East of England. The pipeline will allow between 15 and 55 million litres of water to be moved from ‘wetter’ to ‘drier’ areas of the region; helping to combat the risk of shortages, boosting resilience and securing water supplies. It will also reduce the number of homes and businesses that rely on a single water source. The project is part of Anglian Water’s Water Resource Management Plan (WRMP), which sets out how water supplies will be managed across the region to meet current and future needs over 25 years. Strategic Pipeline Alliance

The Strategic Pipeline Alliance (SPA) is one of biggest environmental projects being undertaken in Europe and is the most important in Anglian Water’s history. As the pressures of climate change and population growth demand more from existing water networks the SPA will ensure that water flows to the areas that need it most, future-proofing the region’s water infrastructure for generations to come.

The SPA comprises Farrans, MMB, Costain and Jacobs, and once complete, over 580 km of pipeline will have been laid in sections ranging from 9 km to 90 km, that will eventually join together. The Alliance has adopted number of cost saving and environmentally responsible methods to construct the pipeline, including pipe ploughing, new welding techniques, and water-less commissioning.

The entire pipeline has been designed to have the lowest carbon footprint possible, in line with Anglian Water’s pledge to reach net zero carbon by 2030.

[caption id="attachment_21982" align="alignnone" width="1200"] Site compound - Courtesy of @one Alliance/Barhale[/caption] Little Whelnetham to Raydon Pipeline

Anglian Water’s @one Alliance was tasked by Anglian Water and SPA to deliver the £70m, 36km pipeline between Little Whelnetham near Bury St Edmunds to Wherstead Reservoir in Raydon, south of Ipswich. From solving engineering challenges to preserving local heritage, and complying with regulatory environmental requirements, the LRT pipeline exemplifies what can be achieved when innovation, collaboration and resilience come together.

This case study highlights the engineering progress, environmental responsibility, and lessons learned from the LRT pipeline, showcasing the importance of collaboration and forward-thinking in delivering both infrastructure and environmental stewardship.

Project scope

The LRT pipeline is a critical infrastructure project connecting Bury St Edmunds to East Suffolk, forming an essential part of the wider Strategic Pipeline Alliance network. Spanning 36 kilometres, the pipeline includes 26 km of 630mm pipe and 10 km of 450mm pipe.

This pipeline includes major crossings, including under the A12 and the Ipswich to London railway line, further demonstrate the complexity of this project.

[caption id="attachment_21984" align="alignnone" width="1200"] (left & right) Pipelaying underway and (centre) pipe stocks - Courtesy of @one Alliance[/caption] LRT Pipeline: Supply chain - key participants Project delivery: @one Alliance Principal contractor: Barhale Designer: Jacobs Civil engineering services: Wells Services (Norfolk) Ltd Geotechnical surveys & design: AF Howland Associates Mainlaying contractor: G&V Gallagher Ltd Horizontal directional drilling contractor (HDD): OCU Utility Services Ltd Site engineering & quality control: East Anglian Site Engineering Ltd PE pipes: Aliaxis Welding: G&V Gallagher Ltd | Welding: Wells Services (Norfolk) Ltd Land drainage: Lincolnshire Drainage Company Ltd Plant hire: Flannery Plant Hire (Oval) Ltd Plant hire: Cadman Cranes Ltd Plant hire: Richardson Recycling Plant hire: GB Plant Hire Limited Plant hire: True Plant Hire Ltd Trackway: TPA (a VP plc company) Milestones

At the time of writing (May 2025) construction is well advanced and several significant milestones have been achieved:

31.7 km of pipes installed and 36.2 km welded. Five out of six drill shots have been successfully completed, keeping the project ahead of schedule. Topsoil reinstatement is progressing, with 2.1 km in Section 4 of the four sections already completed. Highways England has approved the directional drilling project for the A12 crossing, and final approval for the Ipswich to Liverpool Street (London) railway crossing is expected shortly. Archaeological discoveries & historic preservation

Prior to the team starting construction, it was necessary to complete archaeological digs which uncovered a Roman settlement from the 1st and 2nd centuries. Also, ancient structures, artifacts, and remnants of a thriving community were found alongside this too. The team worked in partnership with archaeologists to carefully document and preserve these findings, ensuring that this important history was respected throughout the construction process.

[caption id="attachment_21983" align="alignnone" width="1200"] Archeological operations - Courtesy of @one Alliance[/caption] Community & landowner engagement

Collaboration with local farmers and landowners have also been at the heart of this project, ensuring minimal disruption to their land while promoting sustainable use. Through a Soil Management Plan (SMP), developed alongside the National Farmers Union (NFU), the team has conducted daily soil sampling to monitor moisture levels and determine optimal conditions for handling. This has allowed the team to ensure transparent communication with local communities by keeping everyone informed and engaged; ensuring a successfully delivery of the project.

Weather challenges & resilience

As with any engineering project, adverse weather can play its part. However, the team’s commitment to resilience has currently ensured that any lost time has been recovered through weekend working and proactive solutions. These challenges only demonstrate the team’s adaptability and its unwavering focus on delivering the project on time and with the highest quality standards.

Biodiversity compliance: The dormice challenge

One particularly intriguing aspect of this project has been its focus on protecting dormice habitats. Dormice are a legally protected species in the UK, which means any infrastructure project that impacts their habitat must adhere to strict regulations. These requirements include minimising disruption, creating new habitat corridors, and long-term monitoring to ensure that conservation measures are effective.

[caption id="attachment_21977" align="alignnone" width="1200"] Dormouse - Courtesy of Pixabay[/caption] Conservation measures taken

In line with these regulations, the LRT project team implemented a range of innovative conservation strategies.

Existing hedgerows and woodlands were preserved to ensure safe movement for dormice. New trees and shrubs shall be planted to restore and enhance green corridors, ensuring continued habitat connectivity. Purpose-built crossings, such as dormouse bridges and tunnels, were introduced to help dormice move safely across infrastructure barriers, in order to maintain and increase connectivity.

In addition, advanced monitoring techniques, such as footprint tunnels, nesting boxes, and camera traps were deployed to track dormice activity, while regular environmental assessments ensured ongoing compliance with biodiversity regulations.

LRT Dormice Project - Specialist suppliers Rope bridges: Keystone Environmental Ltd Steel wildlife bridges: Animex International The outcome

At the time of writing the team are yet to detect any dormice on the site and as the project progresses, CCTV monitoring will continue throughout the remainder of the construction phase. As a result of findings for this project, the outcome presents an opportunity for Anglian Water to contribute to a wider discussion on evidence-based conservation policies. By sharing the results from this project, Anglian Water can help inform future environmental assessments, ensuring that investments in biodiversity are targeted, effective, and justified.

[caption id="attachment_21975" align="alignnone" width="1200"] LRT Pipeline - Dormouse Challenge - Courtesy of @one Alliance[/caption] A model of collaboration, innovation & environmental responsibility

The LRT Pipeline is a prime example of how engineering excellence, environmental stewardship, and community collaboration can coexist and thrive. The project is not only pushing the boundaries of modern pipeline engineering but also showing how forward-thinking infrastructure can respect historical and environmental legacies.

Engagement with landowners, communities and specialists has been central to the project’s success, fostering strong partnerships and ensuring that diverse interests were respected. Furthermore, the commitment to biodiversity compliance, even when the real-world necessity of certain interventions is questioned, demonstrates the project’s commitment to both environmental responsibility and regulatory adherence.

Lessons for the future

The experiences from the Little Whelnetham to Raydon Pipeline  Project offer valuable lessons for future infrastructure projects:

Evidence-based policy is key. If certain conservation measures do not yield expected results, is it time to rethink overly cautious regulations? Collaboration is vital. Bringing together engineers, archaeologists, environmental specialists, and local communities has been instrumental in overcoming challenges. Resilience and adaptability are essential. Overcoming unpredictable weather and complex regulatory processes has shown that proactive problem-solving ideologies lead to success. [caption id="attachment_21979" align="alignnone" width="1200"] Stringing out the LRT pipes - Courtesy of @one Alliance/Barhale[/caption]

This project is a powerful testament to the fact that bold, innovative engineering can deliver essential infrastructure while prioritizing environmental and regulatory responsibilities.

Ultimately, once complete the LRT Pipeline will not only enhance the resilience of the water network but also contribute to a healthier, more sustainable environment for communities, wildlife, and future generations. It is a shining example of how infrastructure can be developed with both the present and the future in mind; achieving the balance between modern engineering and environmental responsibility.

Kerse lies in open countryside approximately 3.5km from the former mining village of Patna in East Ayrshire, some 15km from the county town of Ayr. The newly constructed 3 megalitre capacity, twin cell, treated water storage (TWS) tank serves a local population of 6,500 private customers and businesses. It is situated immediately adjacent to the existing facility and is fed from the nearby Afton Water Treatment Works. Scottish Water’s Non-Infrastructure Alliance Partner, ESD JV (a joint venture comprising MWH Treatment, Binnies and Galliford Try) commenced construction in July 2022.  Water into supply was achieved on schedule on 21 May 2024. Existing facility

The existing single cell, below ground 4.5 ML clear water storage tank dates from the 1930s. It is, therefore, an ageing asset whose deterioration has recently led to some failures in water quality and general lack of resilience in the system. These drivers led to a decision by Scottish Water to commission a £6.5m replacement. Forecast modest rises in local population numbers was a secondary consideration.

Challenges

The principal challenges were:

How to build the new underground tank in a position immediately adjacent to the existing, still operating, facility. Non-interruption to the operation of the existing asset was a primary consideration. Working on the existing ageing network to fulfil the new process pipework. Undertaking testing and commissioning of the new asset whilst keeping the existing asset live and ensuring no negative impact on the network. How to stabilise the ground during excavations to ensure the continued, uninterrupted operation of the to-be-replaced tank and network pipelines. How to mitigate against poor soil conditions - mainly heavy clay - during two winter and spring seasons of heavy rain leading to severe drainage issues. The site was also located adjacent to a number of disused open-cast mines which were situated under a sludge restoration scheme, so continual coordination around access was key. Scope

The contract specified the replacement of the existing almost 90 year-old tank with a 3 ML, twin-celled treated water storage tank to be constructed on the same site, contiguous with the structure of the old tank.

The dimensions of the new asset are 29m x 21.5m x 7m to be covered by a reinforced concrete roof with waterproof membrane.

All aspects of the design of the new tank were undertaken by ESD JV’s design and engineering department. Work started on-site in July 2022. In total, approximately 850m3 of concrete was poured to construct the new structure.

[caption id="attachment_13133" align="alignnone" width="1200"] View of tank with backfill almost completed. Pedestrian crane on the left - Courtesy of ESD JV[/caption] Kerse Treated Water Storage Tank: Supply chain: key participants Client: Scottish Water Delivery contractor: ESD JV Binnies Galliford Try MWH Treatment Geotech design: Stantec UK Tower crane base design: Noble Works Ltd Mechanical design/installation: Dustacco Engineering Ltd Electrical installation: RRC Project Solutions Ltd Soil nailing: Albion Drilling Group Ltd Waterproofing: Concrete Repairs Ltd Underpressure connections: Swan Pipelines Pressure testing: Pressure Test Scotland Ltd Tank disinfection: Panton McLeod Ltd Telemetry: ID Systems UK Formwork: Peri UK Ltd FRC: AJ McAlpine Instrumentation: Processplus Ltd Control valve: CLA-VAL UK Ltd DI pipework: Saint Gobain PAM UK PE pipework: FPP Scotland Ltd Metalwork: HK Gillies Scaffolding: JD Scaffolding Ltd Tower crane: Ladybird Crane Hire Security system: Pointer Access covers: Technocover Ltd Rebar: Midland Steel Reinforcement Supplier UK Ltd Concrete & aggregates: Breedon Group Aggregates: Hillhouse Quarry Group Groundworks

In order to protect the viability of the existing tank, and as a consequence of above average rainfall in the winters and springs of 2022, 2023 and 2024, a complex bulk excavation operation was undertaken which included the extensive use of soil anchors to stabilise the ground.

This solution included some in-depth collaboration from the site team and specialist sub-contractor to design a solution to ensure no current live network pipes (which were only 6m from the top of the batter of the excavation) were damaged during the installation of the anchors. In order to achieve this, the site team undertook a survey of the existing network to establish the precise coordinates of each pipeline.

This allowed for the design to be altered to a smaller length of anchors with a revised slope angle ensuring no pipes would be damaged as part of the TW solution. All excavated material (spoil) was used as backfill for the new asset and also for the existing asset which is scheduled to be de-commissioned and removed with minimal excess being removed from site. In total, circa 10,500 tonnes of material were excavated to construct the new asset.

[caption id="attachment_13134" align="alignnone" width="1200"] (top left) Groundworks nearing completion, (bottom left) tank construction underway, and (right) view of tank interior - Courtesy of ESD JV[/caption] Innovative construction

A hydraulic assessment to decide the level of the tank resulted in the need to bury it underground. Given the damp ground conditions on-site, a water impermeable concrete was used to construct the base and walls. This maximises the lifespan of the asset and represents the best carbon solution.

The heavy clay soil resulted in the rapid build-up of water within the excavated area leading to significant drainage issues. This resulted in some pre-excavation cut off drainage ditches being constructed at the high level of the excavation along with gravel filled silt ditches and fencing installed around the site to mitigate the impact of any run-off. Due to the inclement weather encountered throughout the winter of 2022, this led to some initial delays to the programme.

However, any delays were mitigated by innovative solutions to other tasks. The team at Kerse are proud of their ‘championing’ of the use of an electric pedestrian tower crane. Operated at ground level, this led directly to accelerating the construction programme and a significant cost reduction. The selection of the pedestrian crane, which was initially proposed to be an operated crane via operator at high level, brought significant health and safety benefits by removing the need for working at height.

Also, the site team installed cameras at critical inspection points on the crane which meant all daily inspections could be carried out at ground level by the operator, again eliminating the requirement to work at height. All statutory inspections were undertaken by a third party under a safe system of work which was included as part of the sub-contracted scope.

The additional benefit from selecting this method came from a reduction in carbon output with the initial temporary works reinforced concrete pads (which were due to be in excess of 95m3) and the selection of the pedestrian ground operated crane reducing this concrete requirement to only 8m3 to fulfil the temporary works requirement.

A rechargeable electric mobile elevated working platform (MEWP) was employed, providing further benefits. The use of the pedestrian crane and MEWP significantly reduced the carbon footprint on the project in comparison to using alternative options such as mobile cranes and access scaffold which are commonly used on this type of project. The use of the tower crane to facilitate lifting operations throughout the project, along with the MEWP for high level access, proved to be a time saving, cost effective and carbon friendly solution to our buildability requirements on site.

Another innovation was the temporary works wall truss system employed.

Reinforcement for the walls of the new tank was prefabricated on-site. In itself, this produced significant cost, time and safety benefits. This solution reduced the requirement for access scaffolding to be erected, this being substituted by the MEWP system. In addition, personnel did not have to construct the reinforcement whilst working at height or manually handle the reinforcement and place it into position. Instead, this was achieved via pre-fabrication at low level, subsequently allowing full panel reinforcements to be lifted and installed into position providing further safety, time and cost benefits to the project. Another reason for employing this system was that no additional temporary support system was required to support the reinforcement.

[caption id="attachment_13132" align="alignnone" width="1200"] The almost completed structure before backfill operations - Courtesy of ESD JV[/caption] Telemetry

Throughout the project, there was regular liaison between ESD JV and Scottish Water with weekly and monthly collaboration meetings held leading to a close and productive working relationship on the project mitigating potential delays. All issues and challenges have been met in a collaborative environment.

At Kerse, Scottish Water have introduced a new telecoms telemetry system using 4G connectivity monitoring all instrumentation, including water level sensors, alarms and floats, which replaces the old PSTN line.

This option was the result of a business approach change from Scottish Water to provide either VDSL (fixed line) or LTE (4G mobile) for IP enabled communications. In order to prevent the time and cost involved in installing a VDSL line, a decision was made following a successful survey to utilise a new 4G solution for the project’s telemetry communications.

Current status

Water into supply was achieved on schedule in May 2024. This was followed by reliability testing and sampling by Scottish Water before the facility was declared fit for operation which was achieved on 30 May 2024, with the old asset now drained and ready for de-commissioning.

Currently, a new site access road is being completed and various measures of landscaping, including grass seeding, are underway. A new perimeter fence will also be installed as per SW security requirements.

Towards the end of the project, ESD JV was asked by Scottish Water to undertake the decommissioning and demolition of the now-replaced clear water tank. This was not part of the original scope of the contract. These works will be completed in the summer of 2024.

Budleigh Salterton is a seaside town on the coast in east Devon, at the start of the World Heritage Jurassic Coast, with a population of just over 5,000 people. It has been described as a picturesque town with a two-mile pebble beach for the hardy swimmers braving the seas for a dip in the beautiful clear water. South West Water’s objective was to ensure that the bathing water quality at Budleigh Salterton does not deteriorate to below ‘excellent’ within the next 20 years. This was to be achieved by providing in-line tank storage in combination with the removal of 0.31ha of surface water from the combined system, in order to ensure that no greater than two significant (>50m3) spills per bathing water season was achieved by 31 March 2022. Project background The project comprised the installation of an in-line 190m3 stormwater tank constructed from two 83m lengths of 1200mm diameter precast concrete pipes laid adjacent to the existing sewer. The inlet to the storage tank is controlled by the level within the existing sewer. So when the flow increases within the sewer, the level rises and starts filling the tanks. The outlet flow has a weir fitted with a flow control Hydro-Brake® allowing 25 l/s to pass forward. The project was constructed within a grassed field which was within a flood risk area. Temporary works piling The excavation support system (the temporary works) consisted of a 90m long x 4m wide cofferdam within the flood risk area. Galliford Try constructed an engineered haul road which doubled as the piling platform from which specialist sub-contractor, Elite Sheet Piling Ltd, installed 310 (No.) GU13, 6m long sheet piles using a 35t excavator mounted, side griping MOVAX pile driver. Once the sheet piles were installed, the ground between the sheet piles was removed and taken off site. The sheet piles were designed to cut off any groundwater entering their excavation from the adjacent river. One of the major risks to the scheme was that as soon as Galliford Try excavated the large 90m long 4m wide trench it would be inundated with groundwater, making it impossible to safely install the precast concrete pipe sections. The cofferdam worked perfectly; cutting off all incoming groundwater. Once the ground trapped within the cofferdam was removed, the excavation remained dry during the pipe installation. Drainage blanket Following the excavation of the cofferdam, a drainage blanket was installed in the bottom of the trench. This comprised a 200mm thick layer of 50mm singled sized stone which was then covered over with a 1000 guage geotextile membrane from Terram; helping to prevent the intermixing of solid particles between the layers of soil and acting as a filter layer stopping any fine material getting into the drainage blanket layer. [caption id="" align="alignnone" width="1200"] (left) Piling installation by Elite Sheet Piling Ltd, and (right) drainage blanket installation - Courtesy of Galliford Try[/caption] Pipe installation With the drainage blanket complete, Galliford Try started the installation of the 62 (No.) 1200mm diameter precast concrete pipe sections, which were laid on 20mm pipe bedding materials and aligned using a pipe laser. The pipe laser was installed by the site engineer at the correct location with the exact fall from end to end of the 90m cofferdam. A 20t excavator was used to lift the pipe sections along the haul road and down into the cofferdam where the pipe laying gang would place them in accordance with the pipe laser. Once all the pipe sections were installed, the team backfilled the pipe sections with pipe bedding then, as dug soil back up to ground level. Meadow Lane Stormwater Tank: Supply chain - key participants Delivery contractor: Galliford Try Modelling: Arcadis Piling contractor: Elite Sheet Piling Ltd Hydro-Brake®: Hydro International Geotextile membrane: Terram Cofferdam shoring: MGF Ltd Precast concrete pipe sections: FP McCann Pump hire: SLD Pumps & Power Other elements At each end of the storm tank, Galliford Try installed tee sections of pipe creating a manifold, which connected the twin pipe together to form one large tank. Galliford Try then constructed six inspection chambers to provide access and to house the Hydro-Brake® flow control. This only allows a pass forward flow of 25 l/s at maximum design head; above these flow rates it weirs over a bypass to prevent the sewer backing up. Once the storm event is over, the stormwater within the tank is slowly released back into the existing sewer during periods of dry weather flow. [caption id="" align="alignnone" width="1200"] (top left) 1200mm precast concrete pipe sections, (bottom left) backfilling the stormwater tank, and (right) Hydro-Brake® from Hydro International in flow control chamber - Courtesy of Galliford Try[/caption] Summary By providing 190m3 of offline, gravity return storm storage in the field adjacent to Halse Hill, Budleigh Salterton, the spill performance at Meadow Road CSO has been improved in line with South West Water and Environment Agency targets. As the storage is to be provided offline, normal dry weather flow is to be maintained through existing sewer. The agreed storage tank volume, flow control device and overflow weir level were derived from the Arcadis modelling report and taken as the scheme output for the storage element. The final tank volume selection/spill performance of the promoted option was operationally reviewed by the SWW operations team, commissioning engineer and asset management.

Holdenhurst Water Recycling Centre (WRC) is a Wessex Water facility situated near Bournemouth, Dorset. It is a large activated sludge works, which currently serves a total population of approximately 180,000 which significantly increases during the summer months. The WRC was identified by the Environment Agency in the Water Industry National Environment Programme (WINEP) as requiring process improvements, including the reduction of phosphorus levels in the treated wastewater prior to release to the River Stour, which then flows into Christchurch Harbour, and the provision of additional storm storage capacity. Regulatory obligations

The regulatory obligations include a phosphorus (Total P) permit of 1 mg/l during AMP7 and beyond. However, it was decided that additional investment would be made to enable the AMP7 works to meet the needs of the improved AMP8 0.8mg/l Total P stretch target. Key parameters for the treated flows are as follows.

Flow to full treatment Total phosphorus Iron: 95% ile (mg/l) Aluminium maximum 1424 l/s 0.8 mg/l 4 mg/l 3.6 mg/l

The obligations also include the requirement to provide an additional 9,000m3 of additional storm storage (increasing the total capacity to 29,800m3). Other requirements include Event Duration Monitoring (EDM).

[caption id="attachment_23584" align="alignnone" width="1200"] 3D model showing the proximity of the existing assets - Courtesy of YTL[/caption] Proposed solution

Phosphorus removal: Separate chemical dosing installations are to be provided for the two existing treatment streams within the site to achieve the phosphorus removal. The chemical dosing will utilise polyaluminimum chloride (PAC), which was selected to avoid the anticipated adverse impacts on the site's ultraviolet (UV) treatment plant which would arise from using ferric compounds.

Stormwater storage: Additional capacity is to be achieved by the construction of a new reinforced concrete below-ground, gravity fed tank (65m long x 35m wide x 6m deep) constructed on 154 (No.) 750mm diameter continuous flight auger (CFA) concrete piles. Other main elements of the project include:

Storm return pump station integral to the main tank structure and connection of all return storm flows to the existing works inlet. Pump mixers. Interconnecting pipework between the existing storm tanks and the new tank. Reinforced concrete launder channel. Storm overflow. Modification to existing storm tank weirs and addition of penstocks to control flows. Extension of washdown pipework. New MCC and automation and control systems. EDM instrumentation. [caption id="attachment_23607" align="alignnone" width="1200"] (left) Storm Tank 15: CFA piling installation and (right) Storm Tank 15 construction progress (July 2024) - Courtesy of YTL and Envolve Infrastructure[/caption]

Suspended solids resilience: In addition to the works above and to assist with suspended solids resilience, further works to install 50 (No.) Integrated Fixed-Film Activated Sludge (IFAS) modules to ensure that suspended solids performance on the existing treatment Stream 1 is sufficient. This will support compliance with the new phosphorus permit standards. The system will enable the relevant aeration lanes to operate at a mixed liquor suspended solids (MLSS) concentration of 2,400 mg/l.

The solution was to be designed for the 2040 horizon, however installation in AMP7/AMP8 will be for the 2030 horizon, but with facility to extend subject to performance and any revised horizon. It will be the largest installation of this type in the country.

Works to facilitate this installation include:

Retrofit of the existing anoxic and contact zone selector tanks to include a new IFAS MABR module support superstructure. Two scour and two process blowers. Scour and process air pipes including valves, ancillaries and pipe supports. Associated MCC, control system, kiosk, cabling and instrumentation. Permanent crane slab to enable installation, removal and maintenance of the modules.

Additional sludge storage: Surplus sludge is pumped from Holdenhurst WRC to Berry Hill Sludge Treatment Centre (STC). As a consequence of dosing with PAC, increased sludge production is anticipated, and therefore 740m3 of additional sludge reception and holding capacity was constructed at the Berry Hill STC. The main elements of works for this include:

Refurbishment of currently disused tank to provide additional raw sludge reception, including new stainless-steel panels, GRP roof, high-level access platform, mixer system and pipework. Refurbishment of existing SAS/raw mixing tank including new stainless-steel panels, GRP roof, high-level access platform, mixer system and pipework. New 740m3 stainless steel SAS reception tank, GRP roof, new piled foundation and base slab, mixer system and pipework. Two raw sludge transfer pumps, two SAS transfer pumps and replacement of existing SAS GBT feed pumps. Modifications to rising mains. Associated MCCs, control system, kiosk, cabling and instrumentation. [caption id="attachment_20816" align="alignnone" width="1200"] Berry Hill STC sludge thickening tank - Courtesy of Galliford Try[/caption] Project delivery

Project Delivery was managed by YTL Construction (Wessex Water) under its external workstream comprising:

Design consultants: Mott MacDonald Principal & civils contractor: Envolve Infrastructure MEICA contractor: Trant Engineering Automation & Commissioning: YTL Construction Berry Hill sludge capacity civils & MEICA: Galliford Try

The collaborative approach by all delivery partners and industry specialists enabled this £30m capital investment programme of works to be effectively developed from optioneering, through detailed design, construction and commissioning to achieve successful delivery of this complex and challenging project in little over 24 months.

Holdenhurst WRC: Supply chain - key participants CFD Modelling: Invent AG Dewatering design & CAT3 check: Richter Associates Dewatering subcontractor: Dewatering Services Ltd Piling subcontractor: Balfour Beatty Ground Engineering Cofferdam & temporary works designer: JIG Consulting Engineers Temporary works/shoring: MGF Ltd Temporary works/piling: SPI Piling Coring & demolition: Southern Counties Drilling Solutions Reinforced concrete subcontractor: Carney Construction Reinforcement: ROM Reinforcements Specialist sub-designer/IFAS membranes: DuPont Water Solutions | OxyMem Ltd Steelwork subcontractor: Woodhams Group MCC, panel & kiosk: GPS Group Valves: AVK UK Ltd Actuated penstocks: Glenfield Invicta Storm return pumps: Xylem Water Solutions Storm mixer pumps: KSB Pumps Lifting gantry: Able Lifting Chemical storage tanks: Forbes Group Pipework: Saint Gobain PAM UK Pipework: Frazer Civils Infrastructure Concrete: Avon Material Supplies Ltd Berry Hill STC: Supply chain - key participants Civils sub-contractor: Bartlett Contractors Ltd Piling design & installation: Suttle Projects Ltd Electrical installation: Spectrum Electrical Group Stainless steel tanks: Hayes GFS Ltd Tank mixer pump supplier: Hidrostal Pumps: Nov Process & Flow Technologies UK Ltd MCC, panel & kiosk: GPS Group Stainless steel pipe fabrications: ABC Stainless Ltd Access platform fabrications: Atom Fabs Ltd Trace heating & lagging: Jade Insulation [caption id="attachment_23590" align="alignnone" width="1200"] Storm Tank 15 (July 2024) - Courtesy of Envolve Infrastructure[/caption] Design & ECI

Through early contractor involvement (ECI) during the design phase, Envolve Infrastructure and Trant Engineering were able to use their specialist sector knowledge to guide the project team through key constructability decisions.

Assessments were made with regards to safety, quality, time and cost aligning with all partners underlying business ethos.

At the outset, Envolve Infrastructure worked closely with all stakeholders to develop a construction methodology for the storm tank. Numerous options were considered for providing the circa 9,000m3 of additional storage including caisson shafts, secant piling, precast concrete tanks and variables of an in situ RC tank, and a detailed comparison report was undertaken for all methods. The concluding findings were that a 65m x 35m x 6m rectangular in situ RC tank would provide the optimum solution due to the challenging ground conditions, time constraints, ongoing operability and whole-life cost.

In addition, further crucial decisions were considered in relation to the storm return pumping station; initially options were presented for a standalone construction, however Envolve Infrastructure worked with the stakeholders to develop a solution of an integrated pump station which generated both programme and costs efficiencies.

[caption id="attachment_23596" align="alignnone" width="1200"] Storm Tank 15: Frame removal - Courtesy of YTL[/caption] Challenges & mitigation

Stormwater tank construction - existing ground conditions: Ground conditions at Holdenhurst WRC are inherently poor, consisting of a high-water table and the presence of running sands.

The large-scale cofferdam required for the stormwater holding tanks posed significant geotechnical challenges and demanded a specialised design to ensure safe and effective excavation.

Envolve Infrastructure undertook additional ground investigation including a reduced size trial cofferdam. The ECI provided by Envolve throughout the design development stages of the project identified the significant advantage of using a cantilevered sheet pile arrangement rather than a traditional top frame support of the cofferdam.

The proposal allowed for the cofferdam sheet piles to be propped at tank base slab level by filling the 2.5m gap between the sheet piles and base slab with mass concrete, therefore allowing the removal of the top frame, and construction of the tank walls in a single lift rather than two, providing an enhanced solution in terms of safety, quality, time and cost.

[caption id="attachment_23588" align="alignnone" width="1200"] Storm Tank 15 (March 2025) - Courtesy of YTL[/caption]

Groundwater: Due to a high-water table and high permeability of the ground, Richter Associates were consulted to advise on dewatering requirements to enable the construction of the storm tank.

Pump tests were undertaken to inform the dewatering design and for inclusion in the EA Abstraction License application. The final design catered for an abstraction rate of 60-100 l/s, targeting a drawdown level of approximately 8m below ground level. It comprised of 20 wells around the internal perimeter of the cofferdam, together with three internal passive wells to depressurize the Poole Formation.

Groundwater was delivered to a booster pump station by 20 down hole pumps, which then pumped the groundwater to the discharge location. The pumping arrangement had to be robust, with duty/standby pumps as well as back-up power supplies.

Strict EA permit conditions required the discharged water to meet set levels for turbidity, pH and flow rate. The dewatering discharge was via the storm overflow pipework to the River Stour and, while the trials indicated that the discharge should not present a pollution issue, real-time water quality and CCTV monitoring linked to remote alarms and automatic shutdown was provided at the point of discharge to the storm overflow pipework to mitigate the risk of pollution events occurring.

The dewatering system was in place for 9 months with 20 pumps discharging 100 l/s, 24 hours/day and worked flawlessly over the duration of construction, providing ideal conditions for the construction of the new stormwater storage tank.

[caption id="attachment_23593" align="alignnone" width="1200"] Storm Tank 13/14 overflow & connections - Courtesy of Envolve Infrastructure[/caption]

Existing assets: Adjacent to the new stormwater storage tank are three 42” spun iron feed syphon pipes, located approximately 3m away from the main cofferdam at an invert level of 3.5m below ground level. These are critical assets for Wessex Water and any compromise could lead to loss of incoming flows and a major pollution event.

A detailed asset protection plan was drawn up and maintained throughout construction, covering installation and removal of the cofferdam sheet piles, CFA piling works, plant/construction loadings, deflection of the cofferdam during excavation and settlement due to dewatering activities.

The pipes were assessed by CCTV and non-destructive testing to determine their condition, and industry specialists employed to establish permissible movement and changes in stress/strain.

The pipes were monitored throughout construction using the following techniques:

Position/movement Stress/strain gauges Down hole extensometers Vibration Down hole inclinometers Groundwater level

Throughout the excavation process, a series of monitoring methods were deployed including inclinometers and survey monitoring to measure movement of the cofferdam due to dewatering and the cofferdam construction sequence.

Alarm levels were set at approximately 70% of the assessed maximum, and with any exceedance causing construction to pause and assess impact on the syphons.

Due to the rigorous monitoring plan and tight control during construction, the stormwater storage tank was completed without incident and no exceedances recorded.

IFAS MABR module steelwork superstructure: To suspend the IFAS MABR modules within the existing anoxic and contact zone selector tanks, YTL Construction commissioned Mott MacDonald to develop a steel superstructure. This design was required to take into account of and manage the complex interactions between the existing tank structure, capacity, the module loading and placement, ancillary elements and the superstructure itself. [caption id="attachment_23583" align="alignnone" width="1200"] IFAS steelwork 3D model - Courtesy of YTL[/caption]

Significant consideration was given to the module and walkway placement and layout. This limits potential damage to the modules during installation and removal for maintenance by ensuring sufficient clearances and ensure safe access for operatives to undertake maintenance.

This was undertaken collaboratively with input from the module designers (OxyMem Ltd) and contractor (Trant Engineering), and an iterative design approach was utilised where required between parties.

Interface with existing assets: There have been several challenges associated with the interface with live operational assets including:

Adjustment of existing storm tank weirs whilst tanks remain live in case of storm event. Construction of IFAS MABR steel superstructure within the existing anoxic and contact zone selector tanks requiring temporary over-pumping whilst the treatment stream remains live.

Planning and management of these activities have required liaison between designers, contractors and Client Operations, and also consideration of timing in relation to weather patterns, to ensure the works were completed safely with no impact on the treatment process.

[caption id="attachment_23595" align="alignnone" width="1200"] IFAS steelwork installation - Courtesy of Trant Engineering[/caption] Efficiencies & sustainability

A collaborative approach was adopted throughout the design stages to improve buildability, involving YTL Construction, the design consultants and technical specialists together with early contractor engagement.

YTL Construction's off-site build (OSB) in-house team provided the design, manufacture and supply of pre-assembled standardised equipment. Benefits of this approach are numerous and include improved efficiency and consistency, shorter construction programmes and improved health and safety for workers. The approach can also result in reduced carbon expenditure due to efficiency savings, reduced vehicle movements and reduced site construction time. For this project, the team provided equipment for both of the existing treatment streams such as chemical dosing kiosks, point of application boxes, emergency showers and lighting columns. These were installed on site along with heated chemical storage tanks with working capacity of 65m3 and 40m3, protection bunds and supporting services to provide the new completed chemical dosing facilities.

The image below shows an example of the new facilities as shown in the BIM 3D model developed for the project. This utilised items from a ‘Standard Products Library’ developed by the OSB team, reducing modelling time and improving model standardisation.

[caption id="attachment_23605" align="alignnone" width="1200"] 3D model of chemical dosing arrangement (courtesy of YTL Construction) and the as-built chemical dosing (Stream 2) delivery & storage bund - Courtesy of Envolve Infrastructure[/caption] The innovative IFAS MABR technology from OxyMem Ltd is also associated with significant efficiencies for the wastewater treatment process. These include energy savings resulting from smaller blowers and preventing wastage of unused oxygen, reduced sludge production due to a less turbulent fluid flow and a reduced footprint due to the ability to suspend the modules into existing tanks. Environmental/carbon reduction

The importance of reducing the carbon and energy impact of our services on the climate is an important and valuable objective for the strategic partnership between the stakeholders. Civil engineering can also be obstructive to local environments; therefore, the delivery team formulated a strategy to ensure the project left a positive lasting legacy for the local environment and community:

Inclusion of the Environment Agency into the stakeholder management strategy to plan works through classified Watercourses in line with most appropriate and complimentary methods and planned dates. Utilising HVO fuel for all plant and equipment. Replanting of hedgerows and trees with native species. Preservation and protection of local habitats. Establishing tree protection zones and safety of trees subject to protection orders. Re-use of excavated material on site, reducing both landfill and vehicle movements. Off-site manufacturing. [caption id="attachment_23586" align="alignnone" width="1200"] IFAS steelwork installation - Courtesy of Trant Engineering[/caption] Project completion & summary

To ensure that the regulatory output was achieved and to mitigate against the resultant challenging timescales, the project delivery strategy included advanced procurement and critical enabling works for the major construction elements.

Works started on site in September 2023, and all regulatory outputs were achieved on 30 March 2025. This impressive achievement was due to the collaborative approach to project management, construction, and commissioning by all partners.

At the time of writing (July 2025) the works at Holdenhurst WRC are nearing completion. This complex but ultimately successful project ensures that future development growth can continue in the Bournemouth area with a significant improvement to the treatment process and quality of final effluent.

The project has been delivered to the highest quality and Health & Safety standards and is testimony an aligned project delivery team and wider supply chain.

Foyle Street and Water Street are situated in the heart of Derry~Londonderry’s city centre, within the Culmore Wastewater Treatment Works Drainage Area catchment. Foyle Street is located in a busy shopping and tourist area, with Derry City’s Historic East Wall and Foyleside Shopping centre adjacent. The existing sewerage infrastructure on Foyle Street consisted of one combined 1350mm by 900mm egg shaped sewer, collecting both storm and foul flows. The existing sewerage infrastructure serves over 30+ small businesses, a major shopping centre, a bus station, a multi-storey car park and several government offices. Odour problems, and the aging state of the sewer network, became a growing concern for local stakeholders and had received media attention in recent years. Project background & scope

The existing system bifurcated into two pathways; one leading to a trunk sewer along the Foyle Embankment, which flows north along the embankment to a pumping station and another discharging directly into the River Foyle via a surface water outfall. The sewer was therefore at risk of discharging wastewater directly to the River Foyle at various locations, potentially resulting in pollution incidents. The River Foyle is tidal, which resulted in the existing sewers being heavily silted, which had led to known grease and odour issues in the area.

The Foyle Street Network Upgrades Project was a critical investment by NI Water to extensively upgrade the existing sewer and storm network, reducing pollution and malodours while ensuring compliance with environment standards. The scheme also increases capacity to support future urban development.

To safely and efficiently execute the works, a full road closure was implemented on Foyle Street between Shipquay Street and Water Street. Prior enabling works included the relocation of city centre bus services that operated on Foyle Street to a temporary bus facility which was constructed within the existing Foyle Street car park. Pipelaying on Foyle Street commenced only once this temporary bus facility was fully operational and the road closure granted.

[caption id="attachment_26418" align="alignnone" width="1200"] (left) Construction of the temporary bus station and (right) temporary bus station in operation - Courtesy of BSG Civil Engineering Ltd[/caption] Primary objectives The key aims of the Foyle Street Project were as follows: Reduce pollution incidents to the River Foyle. Increase sewer network capacity and provide storm separation in the area. Ensure that suitable measures are put in place to help eliminate the grease and odour issues in the area. Achieve Northern Ireland Environment Agency (NIEA) compliance and reduce risks of fines. Improve customer experience and reduce the number of complaints. Reduce NI Water operational input and associated risks. Foyle Street Network Upgrades: Supply chain - key participants

As principal contractor, BSG Civil Engineering Ltd held overall responsibility for delivering the project on time and within budget, a goal successfully achieved through close collaboration with the wider project team.

Arup’s role encompassed both NEC Project Management & Supervision duties, as well as responsibility for the detailed design. This involved design input from several disciplines, including drainage, geotechnical, highways and pavement engineering teams.

Client: Northern Ireland Water NEC project management: Arup Principal designer/contractor: BSG Civil Engineering Ltd Designer: Arup Civil contractor: Phace Contracts Ltd Surfacing contractor: Breedon Traffic management contractor: Highway Barrier Solutions Ltd (HBS)

The success of this project was largely attributed to the outstanding collaboration among all the project team. From the beginning, everyone was dedicated to maintaining clear and open lines of communication. Regular check-ins and collaborative tools kept everyone on the same page, enabling the team to address issues promptly and adapt to changes when required. As a result, the project was completed on time, within budget, and to a high standard of quality, demonstrating the power of effective teamwork.

[caption id="attachment_26417" align="alignnone" width="1200"] (left) Existing Victorian egg shaped sewer and (right) new foul and storm pipes - Courtesy of BSG Civil Engineering Ltd[/caption] Key risks

There were a number of key risks including:

Ground conditions & utilities: Ahead of construction on Foyle Street, a series of slit trenches and trial holes were excavated to assess existing ground conditions and identify underground services in proximity to the proposed sewer alignment. These investigations also provided valuable insights into the road’s construction and material composition. Soil and material samples were collected for analysis to accurately determine ground characteristics. The findings were critical in informing appropriate methods for spoil classification and disposal, ensuring compliance with environmental and waste management regulations. Traffic management: To minimise disruption to local businesses and the general public, the work was delivered in a phased, sectional manner as per the construction phasing plan below. This approach enabled more effective control of traffic flow, site access, and safety throughout the construction period. Tidal ingress/egress management: Given the tidal influence of the River Foyle, construction activities were carefully scheduled around tidal cycles to maintain safe working conditions. Temporary bungs and other tidal control measures were installed as necessary to manage water ingress and egress during key phases of the works. Early contractor involvement (ECI) & design development

An early contractor involvement (ECI) phase was undertaken as a key part of the project’s planning and risk mitigation strategy. This collaborative approach between NI Water, Arup, and BSG enabled informed decision making during the pre-construction stage and brought significant value to the delivery of the Foyle Street Network Upgrades.

During the Early Contractor Involvement (ECI) phase, Arup’s design development identified an opportunity to replace the initially proposed pumped solution with a gravity sewer. This optimisation, informed by detailed analysis and site investigations, removed the need for a pumping station, reducing programme duration, capital and operational costs, while still meeting all project objectives.

[caption id="attachment_26413" align="alignnone" width="1200"] Google Maps image of Foyle Street. The highlighted areas show the construction phases – Courtesy of BSG Civil Engineering Ltd[/caption]

Another critical outcome of the ECI phase was the decision to adopt an online construction strategy, installing the new sewers along the alignment of the existing combined sewer rather than pursuing an offline route. This approach was selected based on several technical, logistical, and practical considerations:

Single trench working: Online construction allowed both foul and storm sewers to be installed within a single trench. This simplified temporary works, improved sequencing, and reduced the overall construction footprint. Greater confidence in lateral connections: Installing the new sewers along the same line as the existing system provided more certainty about the levels of incoming lateral connections, helping to avoid design and construction complications. Reduced utility clashes: The corridor of the existing sewer had fewer intersecting utilities, as many services had historically been routed away from it. Favourable ground conditions: The existing combined sewer had been in place for over 100 years, meaning the underlying ground had settled and consolidated over time. This provided a more stable foundation for the new infrastructure and reduced the risk of post-installation settlement.

The ECI stage also enabled a series of early investigations, including slit trenches and trial holes, to confirm ground conditions and identify buried services. In addition, the existing system was CCTV surveyed, jet-cleaned, and dye tested to check for blockages and confirm any misconnections, allowing for design adjustments before construction began.

Importantly, the ECI phase also created an opportunity to coordinate the replacement and upgrade of the existing watermain that ran along Foyle Street. Rather than delaying this work and potentially requiring future excavations and disruptive road closures, the project team opted to complete the watermain upgrade in parallel with the sewer works.

This forward-thinking decision reduced the likelihood of future inconvenience to the public and eliminated the need for another road closure in this busy city centre location.

Additionally, early stakeholder engagement formed a central part of the ECI process. Due to the project’s location and associated road closures, early and ongoing communication with local businesses, public bodies and other key city centre stakeholders helped inform phasing, traffic management, and access arrangements. This engagement proved vital in building local support, managing expectations, and ensuring that construction impacts were minimised throughout the duration of the works.

[caption id="attachment_26420" align="alignnone" width="1200"] Foyle Street construction – Courtesy of NI Water[/caption] Main construction

Works commenced within the Foyle Street car park as part of the enabling phase, allowing for a phased approach to construction on the street while ensuring uninterrupted services for Translink. The existing car park was converted into a six-bay bus loading zone, along with three waiting bays.

To facilitate bus movements, a new ingress point was created from the Foyle Embankment into the car park area, with vehicle egress via the existing exit location. Automated entrance and exit barriers were installed to manage height restrictions and bus shelters were provided for passenger convenience.

As part of this reconfiguration, Arup’s designers liaised closely with the Department for Infrastructure (DfI) and undertook a road safety audit to ensure the temporary arrangement met all safety requirements. With these modifications in place, a phased plan for bus operations and passenger access was implemented, enabling the main network upgrades to commence at the Water Street junction.

Phase 1 of the upgrade involved works at the first access chamber, an existing manhole containing a 300mm pipe connected to an existing outfall pipe leading to the River Foyle. Within this chamber, a Tideflex valve was installed prior to commencing pipelaying activities. Approximately 15m of pipe were then laid to reach the first newly constructed storm manhole and a new foul manhole which provided the connection into the existing foul line. These two manholes, positioned side by side, formed the starting point of the new foul and storm lines along Foyle Street, linking into various other manholes installed in accordance with the detailed design specifications.

[caption id="attachment_26420" align="alignnone" width="1200"] Foyle Street construction – Courtesy of NI Water[/caption]

To ensure the safety of the workforce, public, pedestrians, and local stakeholders, secure hoarding was installed around active work areas, marking the start of Phase 2A/B. As part of the stakeholder-focused approach, a local artist decorated the hoarding with designs promoting the local community and creating a more visually appealing area during construction. The works were carefully phased to minimise disruption and maintain access for essential services like deliveries and taxis, helping local businesses and residents maintain a sense of normality. A manned barrier was also positioned to manage access effectively and promptly address stakeholder needs throughout the project.

Various temporary works were used to manage existing services and laterals. Over-pumping was initially required to control tidal ingress, a challenge that eased as construction moved further along the street. A vacuum excavator was employed to safely expose critical services, reducing the risk of strikes in the complex and densely serviced city centre environment.

Phase 2A/B progressed ahead of schedule, allowing the decision to be made to remove all hoarding and fully reopen the road for one month over the 2024 festive period. This provided improved access during a time of heightened activity for local businesses. Following the festive break, works resumed in January 2025 with the commencement of Phase 3A/B. Adjustments were made to the layout of the open side of the street to maintain delivery and taxi access, while also enhancing accessibility for blue badge motorists. Hoarding was reinstated and pedestrian ramps were introduced to ensure safe passage through the area.

Upon completion of the twin sewer installation, the existing 10” cast iron watermain, was replaced with a new 225mm PE pipe along with updated valve arrangements. Given the poor condition of the existing infrastructure, it was deemed prudent to undertake this work concurrently with the sewer works. This proactive approach minimised future disruption to the public and city centre stakeholders.

[caption id="attachment_26416" align="alignnone" width="1200"] Foyle Street reopened - Courtesy of BSG Civil Engineering Ltd[/caption]

During the construction of the water main, one of the key challenges was locating the unknown positions of tees and valves on the existing asset. To overcome this, a non-intrusive under-pressure CCTV technique was procured by BSG Civil Engineering Ltd, successfully identifying these features. Without this approach, extensive excavation works would have been required, leading to additional disruption, cost and time.

Phase 4 involved constructing a new manhole at the junction of Foyle Street and Water Street. Works in this area required intercepting an existing storm lateral that previously discharged into the culvert. This lateral was redirected into the existing storm chamber at Orchard House, which contains a Tideflex valve as mentioned in Phase 1.

A Manhole was installed at the head of the existing culvert line within the junction, providing a dedicated jetting point to facilitate future maintenance and de-sludging.

Following completion of works in the Foyle Street area, a full kerb-to-kerb road overlay was carried out, including a section of the Water Street junction, in agreement with DfI. This allowed normal traffic and Translink buses to return to Foyle Street, enabling the temporary bus facility to be decommissioned and reinstated as a car park on a like-for-like basis.

Project timeline DATE PROJECT MILESTONE January 2023 Early Contractor Involvement phase start April 2024 Early Contractor Involvement phase finish May - August 2024 Construction of temporary bus facility for Translink August 2024 Phase 1 construction August - September 2024 Phase 2A construction September - December 2024 Phase 2B construction January - February 2025 Phase 3A construction February - May 2025 Phase 3B construction June 2025 Phase 4 construction June  - August 2025 Demobilisation of temporary bus facility and reinstatement of car park September 2025 Project completion and handover Stakeholder engagement

NI Water and the project team were acutely aware of the potential negative impacts arising from such a large-scale pipeline project and from an early stage embarked on a strategic communications strategy to ensure key stakeholders were informed of the works and kept updated throughout.

As part of the public relations strategy the project team held early briefings with a range of stakeholders including elected representatives; Derry City & Strabane District Council; Department for Communities; Department for Infrastructure (DfI); Translink; City Centre Initiative; Londonderry Chamber of Commerce; Visit Derry; Millennium Forum; Foyleside Shopping Centre; taxi companies, coach operators and local businesses.

Dedicated briefings were held for businesses on Foyle Street and questionnaires circulated to capture the operational needs of all the shops in the area. The information gathered was fundamental in shaping the different phases of the project and helped keep disruption to a minimum.

[caption id="attachment_26414" align="alignnone" width="1200"] Foyle Street project team with City Centre Initiatives and street artist at painted hoardings - Courtesy of NI Water[/caption]

Letter drops and project updates were circulated to stakeholders in advance of each new phase of work commencing and press releases issued to the local media to keep the wider public informed. Signage and variable message boards were erected on the main routes to Foyle Street and large-scale project boards helped to convey the huge investment being made by NI Water and the resulting benefits for the city.

Street art and children’s paintings adorned the construction hoarding to improve the visual appearance of the works area and boards, highlighting the historical importance of the area, which created further interest and information for passers-by.

NI Water and the project team are indebted to the myriad stakeholders for their help during the year-long project. Completing the work on Foyle Street ahead of schedule is a testament to the scale of support received and the close working relationships developed.

Conclusion

The Foyle Street Network Upgrades Project was completed ahead of schedule and under budget, successfully achieving its primary objectives of enhancing sewer capacity, reducing pollution and odour issues, and ensuring compliance with environmental regulations. Stakeholder engagement was central to the project’s delivery, contributing to its smooth execution and overall success.

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 Excavation works began in 2017 at the Dancing Hill Reservoir site as part of a £6 million project to upgrade the Water Supply GRID for Bridgwater and the surrounding areas. Major upgrades are required due to large-scale developments in the area. Issues & solutions The design was particularly challenging due to the complicated nature of the ground surrounding the reservoir tank. A sizeable berm was built on the ground profile around Cofferdam 4 to ensure a safe and stable excavation. This exaction also had to accept other loadings from Cofferdams 1, 2 and 3. Multiple 203UC tank brace frames were used due to the strict lift plan limit of 1 tonne. Larger or heavier brace systems could risk the collapse of existing foundations. Vibration pile driving was not permitted due to the detrimental effect it could have on the high-pressure water mains that supplies customers. There was also a HV cable running through the site that had to be avoided. The exact location of other services created additional challenges and ongoing surveys had to be monitored throughout the duration of works. As of 2017 there are four connected cofferdams in place allowing safe working space to combine new pipeworks to the main reservoir tank. Multiple back-to-back 203UC tank braces with special alignment of bracing has been key in the design, combined with KKD 600 sheets to secure the trench. Several Lightweight DavitSafe systems allow safe access into the 10m deep cofferdams. Sector: Water & Utilities Client: Wessex Water Location: Bridgewater, Somerset Scheme: Water Supply GRID Upgrade MGF depot: Bristol Products hired: Multiple 203UC brace, KKD 600 sheets, lightweight davit [caption id="" align="alignnone" width="1200"] Dancing Hill - Courtesy of MGF Ltd[/caption] For more information: MGF Ltd | +44 (0)1942 402700 | www.mgf.co.uk    

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

   

Scope of works National Grid, working with North Lincolnshire Council and East Riding of Yorkshire Council, developed a plan to construct a tunnel under the River Humber to replace the existing pipeline. The three-year project will provide National Grid with a 5km long, 3.65m diameter tunnel bored 30m under the river bed. A single 1200mm concrete-weight coated steel pipe will be inserted into the tunnel in a single string, making it the longest gas pipeline insertion of this kind in the world. Issues and solutions The River Humber pipeline is an important pipeline - connecting an import location for gas at Easington, on the East Yorkshire coast, to the national network – delivering gas supplies to millions of households throughout the UK. The original pipeline, Feeder 9, is buried in a cut-and-cover trench under the river bed where tidal patterns have eroded the river bed uncovering the pipeline. Remedial work was undertaken to provide a short-term solution while a long-term solution was developed. Working with the joint venture consisting of Skanska, PORR Bau GmbH and A.Hak, MGF’s in-house design engineers developed and manufactured a bespoke temporary works propping solution for the tunnel boring machine (TBM) launch pit excavation. The contractor required the design to allow for the following key factors: Use of a load monitoring system. Design of bespoke connection details to sheet piles or capping beams where steel walers were not used. Design of bespoke 'headwall' beam to eliminate knee bracing at the end of the tunnel portal to increase working space. Design of prop connections to withstand 10 tonne accidental load. The excavation was 209m long by 8m at its widest point, ramping from ground level to 11m depth. The deepest section, including the portal wall, was constructed with secant piles with PU32 sheet piles forming the remaining walls. The propping solution consisted of 406UC hydraulic braces with 2500kN 400 series struts. To accommodate the TBM installation the longer, high-level props were twinned with spans of up to 11m between pairs of props. The headwall beam was primarily required for ease of excavation as knee braces are notoriously hard to navigate around with an excavator. This ensured that the temporary works was sufficiently robust whilst maintaining an accessible working space; a technical aspect which separated us from the competition and was completed to Eurocodes. Additionally, there were concerns that accidental impact of the struts by plant could cause failure of the system, particularly during the TBM lift, as there was only 200mm space between the paired props. To mitigate this risk MGF designed bespoke connections to the capping beam, wailing beams and sheet piles to withstand an impact of 10-tonnes. MGF used its in-house load monitoring system which actively measured the load and temperature of each individual prop, waler axial loads and bending and axil load in the headwall beam. The data collected during the monitoring regime will have a significant impact on creating efficiencies in the design of hydraulic strutting and support of narrow closed trenches going forward. Stephen Barker, Major Projects Engineer said:

"This project was particularly challenging due to the multiple levels of framing, high loads and strict robustness criteria. As the design was required to survive the loss or damage of a prop and withstand a 10-tonne impact load more props were required, however we had to balance this with ensuring that the contractor had sufficient space to excavate efficiently. The design of the headwall beam contributed significantly to this as it removed the requirement of having knee bracing at the end of the excavation, opening space and making bulk excavation easier."

The project will take approximately two years to complete and top level of the temporary works will stay in place during this time. In an adjoining field, the pipework is being welded in top strings in readiness for insertion. The tunnelling is currently underway with a slurry TBM.   For more information: MGF Ltd | +44 (0)1942 402700 | www.mgf.co.uk    

In the Norfolk seaside town of Great Yarmouth stands Grist Mill. Dating back to the late Victorian era, the building is of local historical significance and stands directly alongside the western bank of the River Yare in the Cobholm Island area of Great Yarmouth. The existing quay wall and apron had deteriorated to a quality where it provided little, if any protection to the foundations of the timber framed Grist Mill, so the services of Ivor King were engaged to install a new sheet pile flood defence around the building. The works were part of wider £42.5 million Environment Agency Tidal Defence Initiative in the area to protect against the threat of East Coast flooding in the Norfolk seaside town. We carried out a virtually silent and vibration-free installation into hard ground to form a three-sided cofferdam waterside to the building, ensuring its future longevity. The Challenge The mill, located directly next to the River Yare, three miles up from where it flows into the North Sea, is set in a residential area, with neighbouring properties in close proximity. In addition, 23.5 metre ‘Z’ section steel sheet piles would need to be delivered into site and passed over the three-storey building in pairs for installation into hard ground conditions. The Solution Giving consideration to the impact of works on the local neighbourhood, along with the fragile nature of mill’s foundations and its environmentally sensitive riverside setting, our Giken Supercrush solution was selected as the only truly viable way of meeting all challenges. Supercrush is an extension of the Giken silent and vibration-free installation method, whereby sheet piles can be pressed into the ground without causing noise or vibration, whilst also overcoming hard ground conditions by simultaneously augering the ground during the installation process. Equipped to deliver Delivering the 23.5m long (more than twice the length of a London bus) sheet piles into site in pairs was facilitated by Ivor King’s in-house transport team. The route in (the last part being particularly challenging – narrow and twisty) was meticulously planned and deliveries were carried out using our special extendable rear-steer trailer, specifically designed for transporting long loads into sites with limited access. Two 300 tonne Liebherr Crawler Cranes were used for the lifting operations. One to manoeuvre the collosal sheet piles over the three-storey building in pairs and into the chuck of the Silent Piler. Another to steady the Supercrush auger (necessary due to the hard ground conditions), itself standing some 30 metres tall and weighing circa 30 tonnes, during the piling process. Using reaction force, each pair of ArcelorMittal AZ40-700 sheet piles, up to 23.5m in length, were installed by one of Ivor King’s mighty Giken ‘Double-Crush’ Silent Pilers, which clamps onto previously installed sheet piles and is capable of ‘walking’ along the piles to travel forward.

Vibration-free installation of cofferdam - Courtesy of Ivor King - The Piling People

Respecting the environment Further to our environmentally friendly installation technique, compressed air was used to create a bubble curtain, (sometimes known as a pneumatic barrier) to obstruct silt caused by augering from escaping into the flow of the river. Following sheet pile installation, wailing and capping beams, plus anchor ties were added to increase the integrity of the structure, ready to accept a concrete slab to complete the upgrade to the mill’s foundations. Client: JN Bentley on behalf of Environment Agency Project cost: c. £1.7m Completion date: October 2022  Project period: 19 weeks Plant utilised: Giken SCZ675 'Double Crush' Silent Piler 300T Liebherr LR1300 Lattice Boom Crawler Cranes Broshuis Rear Power-Steer Triple Extender Trailer The specialist silent and vibration-free piling technique provided by Ivor King and their Giken Supercrush helped us deliver our objective of better protecting the people and property of Great Yarmouth from flood risk whilst overcoming the challenges of working in a very residential area, within meters of a locally significant building and on the edge of the environmentally sensitive site of Breydon Water. Thanks to Ivor King for their support of JBA Bentley in delivering this project. Tom Stanley, Environment Agency Project Manager

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

J Murphy Group awarded Aarsleff the contract to install a temporary sheet piled cofferdam on the River Severn, as part of the £300 million Birmingham Resilience Project. The scheme is one of Severn Trent’s largest ever infrastructure projects, specifically to develop an alternative water supply for Birmingham to complement the Elan Valley Aqueduct (EVA). The Birmingham Resilience Project will create a new abstraction point and pumping station on the River Severn, at Lickhill Quarry near Stourport, to which water will then be pumped along a new 25km pipeline, through pipes with a 1.0m diameter, to the water treatment works in Birmingham. Aarsleff’s sheet piling works allowed a dry working area for J Murphy to construct the secant piling to the intake structure. Sheet piles will then be subsequently removed and the entire structure submerged. Water is to be taken from the River Severn which will provide a new source for the aqueduct, while maintenance takes place on the original EVA. When the resilience plan is in operation, the city of Birmingham will be drawing water from at least four sources, rather than just one. Early contractor engagement between J Murphy and Aarsleff identified significant technical deficiencies in the early engineering proposals for the temporary works cofferdam. Aarsleff’s proposed design was safer, quicker and cheaper with significantly less risk to the environment, their clients program and operatives. Aarsleff installed the bespoke temporary sheet piled cofferdam which comprised 154 (No.) AZ26-700 steel sheet piles, with an integral enhanced toe support system comprising of 53 (No.) H-Section piles. These were required due to the very shallow underlying bedrock, which only allowed for a limited sheet pile penetration. Access was provided by a temporary access works platform allowing safe working over water. Aarsleff employed a high frequency vibratory hammer and an impact hammer to drive its piles (using panel driving techniques) and employed a 110-tonne capacity mobile crane operating at a maximum 25m radius to unload and handle piles and hammers. [caption id="" align="alignnone" width="1200"] Courtesy of Aarsleff Ground Engineering Ltd[/caption] Senior technical estimator Ashley Carter said:

“This was a technically challenging scheme to be involved with requiring a lateral thinking approach to resolving the challenging problems. The prestigious project demonstrates the high level of experience and expertise Aarsleff’s sheet piling department can offer to its clients”.

Aside from delivering the project on time and within budget, Aarsleff were also able to reduce risk and environmental damage. Risk reduction through application of practical construction methodology, and Reduction in Environmental impact, (as the original scheme involved drilling underwater and spoil flushed directly into the watercourse). Steel sheet piles will also be recovered for re-use making this element of the scheme carbon neutral. Aarsleff took the technical challenge and applied sense and reason to develop a practical, constructible and engineered solution, which benefitted all parties for the aforementioned Environmental, Commercial and Safety aspects. Meeting a tight construction programme at the front end of a long complex scheme gives Aarsleff great satisfaction. Scope of works 154 (No.) AZ26 steel sheet piles (section modulus 2600cm3/m of max length 8.0m) Integral enhanced toe support system comprising of 53 (No.) 254/254/132 S355 JO H-Section piles Prefabricated box section connection detailing at 1.26m centre to centre Construction period 21st July 2017 - 13th Sep 2017   For more information: Aarsleff Ground Engineering: +44 (0)1636 611140 | www.aarsleff.co.uk

   

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    

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

NTS UK were first contacted by KPM Contracting in February 2023 with regards to providing a ground support system for a 13m x 3m foul pump tank to be installed at 5.5m below ground level. NTS UK provided a ground support system utilizing their Double Slide Rail tie-back system to provide a clear internal opening of 14.2m x 4.2m. Since the successful installation of the first foul pump tank NTS UK have gone on to provide the ground support solutions for an additional nine tank installations undertaken by KPM across the site. These excavations ranged from double tank installations at 20m x 15m plan dimensions to manhole installations 3.5m x 3.5m in plan with incoming services on three sides accommodated by the NTS UK pile chamber solution. The ground support systems utilized at the site incurred a number of challenges including high and variable groundwater, varying ground conditions, tight programme, unknown existing infrastructure and the neighbouring River Derwent. NTS UK were able to provide a design solution using their Slide Rail System. Many of the tank excavations were designed to allow for the re-use of components between different excavations, cutting down on transport, therefore reducing the carbon footprint attributed to each excavation. Fewer components than traditional shoring systems are used with the NTS UK Slide Rail system, this ensures fewer lifting operations and a much quicker and safer installation method. The system was installed using the dig & push method of installation which allows for no eccentric vibration and a no-toe solution, ensuring the risk of impacting any unknown services was mitigated. [caption id="attachment_1914" align="alignnone" width="1200"] (left) First tank being lifted into the open excavation and (right) twin tank Slide Rail excavation 20m x 15m x 4.5m - Courtesy of NTS UK Ltd[/caption] One of the larger 20m x 5m x 4.5m excavations at the site was close enough to the River Derwent for a sheet and  frame solution to be considered. NTS UK’s temporary works designers deemed that an excavation this size at the site required 85 (No.) 7m Long Larssen Piles with two levels of the NTS UK System 80 frame. In contrast the NTS UK Slide Rail System utilized for the construction of the ground support system consisted of fewer than 50 components. The absence of any frames has also resulted in concrete/material, and therefore environmental and cost, savings for KPM Contracting. The components from this excavation were then utilized on two other excavations at the site. KPM Contracting were able to excavate, install & backfill the 20m x 5m x 4.5m excavation in seven working days – far quicker than would have been possible when using traditional methods, highlighting the environmental & commercial benefits of the system. NTS UK’s Slide Rail is becoming ever popular in temporary works circles as the preferred method for fast, safe, cost-effective temporary excavation solutions. Martin Munnelly, director of KPM Contracting.

“The system is so easy to use, far quicker, much safer and reduces our material costs significantly. It will definitely be explored for all future excavations,”

Geoff Bates, Area Sales Manager NTS UK.

“The guys on site have been brilliant, and have all fully embraced the system.” 

    For more information contact National Trench Safety: 03332 076 007 | https://www.ntsafety.co.uk/