Supply Chain - Stormwater Storage - Nature-based Solutions/SuDS

Holywell Row is a village in the Mildenhall area of Suffolk in the east of England. The Street, a key residential area within the village, is home to families and businesses who have weathered years of infrastructure challenges. Anglian Water are always committed to supporting these communities and ensuring their essential services are resilient to change. In Holywell Row, this means addressing the persistent issue of flooding caused by an outdated sewerage system.

The issue

For over past five years, residents of The Street have endured frequent flooding events. Prolonged rainfall overwhelms the receiving outdated sewerage system, leading to external flooding affecting 18 properties and a vital highway. Two properties have borne the worst of it, suffering 11 and 9 flooding incidents respectively in this period.

Contributing to the issue are occasional pump blockages and pumping station (PS) failures. At the heart of the problem is the undersized Eldon Lane Pumping Station in Holywell Row, which cannot handle the increased flow from upstream pumping stations during storms. With climate change amplifying the frequency and severity of rainfall, this incapacity poses a growing risk to residents and infrastructure.

[caption id="attachment_19981" align="alignnone" width="1200"] The cofferdam - Courtesy of Anglian Water’s @one Alliance[/caption] The solution

Anglian Water, as part of its commitment to delivering resilient and customer-focused services, tasked @one Alliance to implement a comprehensive solution to mitigate flooding risks in Holywell Row. The proposed measures were designed to address the root cause of the issue while ensuring long-term sustainability and adaptability.

The initial consideration was to install a new rising main from The Street Pumping Station directly to the terminal pumping station; bypassing three smaller pumping stations on The Street and Eldon Road. However, the solution revealed several challenges, including the need to upgrade pumps at Holywell Row No. 2 Pumping Station to manage the increased pumped total head, crossing the Exolum oil pipeline three times, and navigating permissions for work near the RAF base at Mildenhall. The route also passed through areas of high archaeological interest and posed significant disruption to a nearby business park. These risks, combined with a high project estimate, led us to revisit previously discounted options to identify a more feasible and cost-effective solution.

Therefore, the resulting solution the team implemented was an advanced off-line attenuation storage system connected to the upstream pumping station; Holywell Row No. 2 Pumping Station.

This robust design incorporates five rows of 1500mm diameter Weholite pipes, each 45 meters long from SDS Limited. Together, these pipes provide a total storage capacity of 390 cubic meters.

During storm events, the system captures excess flow that would otherwise overwhelm the existing sewerage network. Once the storm subsides and water levels return to manageable levels, the stored flow gravitates back to the pump station, ensuring a controlled and gradual return of water to the system. This storage system is connected to the pump station through a 500mm diameter concrete link pipe.

[caption id="attachment_19980" align="alignnone" width="1200"] Weholite pipe installation - Courtesy of Anglian Water’s @one Alliance[/caption]

To optimise functionality, a new level sensor has been set up at the Holywell Row No. 3 Pumping Station. The sensor inhibits pump operation during peak flows, redirecting water into the storage system. This automated process ensures the network is not overloaded while maintaining a steady and efficient return flow after storm conditions abate.

To ensure the seamless operation of these systems, significant upgrades have been made to the pump and sensor technology at The Street Pumping Station. The motor control centre (MCC) has been modified to incorporate a pump inhibit control system, enabling precise regulation of pump activity during storm events. A new level sensor has been set up at Holywell Row No. 3 Pumping Station to continuously monitor flow levels and optimise the pumping regime.

These upgrades have enhanced the responsiveness and efficiency of the system, reducing the risk of overloading while maintaining operational stability.

Finally, the design includes measures to improve system ventilation. A 160mm PVC vent pipe and a dedicated vent chamber have been incorporated to support the attenuation storage system. This ensures proper airflow and pressure regulation, maintaining the performance and longevity of the infrastructure. By addressing potential pressure issues proactively, this enhancement helps ensure the storage system operates at peak efficiency, even under challenging conditions.

Holywell Row Stormwater Storage: Supply chain - key participants Project design & delivery: @one Alliance Principal contractor: Barhale Temporary works/shoring: Groundforce Weholite stormwater storage pipes: SDS Limited Motor control centre: Paktronic Engineering Co Ltd Plant hire: Mervyn Lambert Plant Ltd [caption id="attachment_19979" align="alignnone" width="1200"] Weholite pipe installation - Courtesy of Anglian Water’s @one Alliance[/caption] The benefits of this solution

The proposed measures deliver both immediate and long-term benefits to the community and infrastructure, addressing key challenges while creating a foundation for future resilience.

One of the most significant advantages is the reduction of flood risk. The newly implemented attenuation storage system directly addresses the flooding issues affecting the 18 properties and the nearby highway. By capturing and temporarily holding excess stormwater, the system prevents water from overwhelming the sewerage network. This ensures that residents experience fewer flooding incidents and a marked reduction in the severity of such events, fostering a sense of security within the community.

The enhancements also contribute to infrastructure resilience. By resolving the capacity limitations of the Eldon Road Pumping Station and bypassing the inundated existing sewer system, the upgraded sewerage system is now better equipped to handle peak flows during extreme weather events. These improvements significantly reduce the likelihood of system failures, ensuring reliable service even under challenging conditions.

The solution also incorporates a forward-looking approach to climate adaptation. By designing the system to manage a 1-in-30-year storm event with allowances for climate change, the project ensures the infrastructure remains robust and functional as weather patterns continue to evolve. This proactive planning underscores a commitment to long-term sustainability and adaptability. In addition, the capital carbon reduction of 81% was achieved by using carbon-friendly materials and by removing the need to install a new pumping station and a 2.9km pipeline.

[caption id="attachment_19983" align="alignnone" width="1200"] Weholite pipe installation - Courtesy of Anglian Water’s @one Alliance[/caption]

The use of Weholite pipework in the attenuation system further enhances the project’s longevity and cost-efficiency. With a life expectancy exceeding 120 years, this durable infrastructure minimises the need for frequent maintenance and replacements. This long-term reliability translates into significant cost savings over time, benefiting both Anglian Water and the community it serves.

From an economic and social perspective, the project represents a substantial investment of £1m into the well-being of Holywell Row residents. The reduction in flooding incidents decreases the financial burden of repair and recovery for homeowners while minimising disruptions to daily life. These improvements enhance the overall quality of life and support the local economy by preventing costly damages.

Lastly, the project demonstrates environmental benefits by managing stormwater more effectively. By reducing the frequency and impact of flooding, the initiative helps protect local ecosystems and minimises the environmental consequences of stormwater runoff. This holistic approach ensures that the community’s needs are met while preserving the natural environment for future generations.

Working with the community

In addition to the large-scale infrastructure enhancements, Anglian Water has implemented community-focused measures to reduce the impact of rainfall at the household level. Through these, water butts have been offered to residents in the 18 affected properties. These water butts provide a simple yet effective method for homeowners to manage rainfall and reduce surface runoff. By reusing rainwater for non-potable uses such as gardening, residents can decrease the volume of water entering the sewer system. To date, 15 waterbutts have been supplied, as agreed with the customers. This initiative not only mitigates flooding risks but also fosters sustainable water management practices within the community.

[caption id="attachment_19978" align="alignnone" width="1200"] Inside the Weholite pipe- Courtesy of Anglian Water’s @one Alliance[/caption] Conclusion

Anglian Water’s mission is to deliver reliable, sustainable water management solutions that meet the needs of our customers and the environment. The flooding challenges at The Street, Holywell Row, highlight the importance of investing in infrastructure that can adapt to modern demands. This project exemplifies Anglian Water’s commitment to resolving systemic issues, empowering communities, and preparing for the future. By combining innovative engineering with community-focused initiatives, they are not just solving today’s problems, but are laying the foundation for a resilient tomorrow.

Together, with the residents of Holywell Row, Anglian Water’s @one Alliance have provided a solution that protects homes, supports livelihoods, and ensures that life flows smoothly, even in the stormiest of conditions.

Loggerheads Village, located in north-west Staffordshire, was previously served by two separate Sewage Treatment Works (STW); Loggerheads Village, now know as Sanatorium Transfer Pumping Station (TPS), and Loggerheads Sanatorium STW. The £17m AMP7 Q WFD upgrade project represents a significant investment in wastewater infrastructure by Severn Trent, which has been designed to enhance environmental compliance, improve water quality, and implement advanced treatment technologies; notably a DfMA membrane bioreactor (MBR) system. Project background

The original project comprised an outline design to improve and redevelop Sanatorium STW with flows forwarded from the ‘old’ Village STW (now called Village TPS) to Sanatorium to be treated and returned. However, this solution was not feasible due to Sanitorium STW having access limitations and general site constraints.

The project was redesigned to incorporate a third location at the site of the ‘old’ village reed beds (now called Village STW). Upgrades here were built off-line and comprise a PST distribution splitter chamber, two PSTs, an MBR system, de-sludge and sludge tanks, chemical dosing and sludge thickening. Flows from Village TPS will still be forwarded for treatment at the Sanatorium site, enabling full flow treatment from both catchments to be screened and the sent to Village STW for full treatment, from where flows will be split back to each respective site’s FE sample chamber for quality monitoring.

[caption id="attachment_25475" align="alignnone" width="1200"] (above right) Google Maps image showing locations of sites and (left) simplified schematic showing site interconnections - Courtesy of Coffey[/caption] Objectives & project scope

The goal of the project is to meet tightened discharge permits and improve operational efficiency and resilience, by upgrading and replacing outdated infrastructure and implementing a new, innovative technology for enhanced treatment.

The scope of the project is extensive and included the following:

A new inlet works package from SPIRAC Ltd. Shaft tank PS with storm retention constructed by Active Tunnelling Ltd. Two new stainless steel circular PSTs from Stortec Engineering Ltd complete with new scraper bridges. A modular containerised three-stream MBR treatment plant and MBR equalisation tank from Coftec with internal technical room chemical dosing. Sludge treatment facilities including a Huber Technology containerised S-DISC thickening plant and sludge storage. Transfer pumping stations including a new outfall pumping station returning flows to the respective outfalls via new rising mains between sites. New Fe chemical dosing plant from Colloide to meet specific dosing requirements of the new MBR. Final effluent monitoring from Servitech International Ltd. Extensive mechanical and electrical works and new control systems across the sites. [caption id="attachment_25484" align="alignnone" width="1200"] New SPIRAC Ltd inlet works package plant - Courtesy of Coffey[/caption] Inlet works

Coffey appointed SPIRAC Ltd to deliver the new inlet works package. This comprised a new stainless-steel reception tank where the forwarded flows from Village TPS would be blended with the current Sanatorium flows before passing through inlet screens. The inlet works package included:

Two FINEGUARD™ screens (duty/standby) sized for a 700mm wide x 1000mm deep channel, with each capable of screening 81 l/s. A 7m screw conveyor capable of handling <3.0m3/hr. Two SPIROWASH® screenings washing units, each capable of handling up to 2.5m3/hr volume. The units receive screenings from the screw conveyor and clean, dewater and compact the screenings, before discharging via press tubes into a skip. Support structure for the packaged inlet works installed on dedicated concrete pad. Full steel platforms and access stairs. PST tanks & splitter chamber

Stortec Engineering Ltd installed two 12m diameter primary settlement tanks constructed from ULTRASTORE® high-grade stainless-steel panels. Each tank will be installed with a reverse U-type GRP launder channel fitted with V-Notch weir plates, scum boards and associated drop box. Each PST will be fitted with rotating half bridge scrapers.

The 4.6m x 3.1m x 2.8m cast in situ PST splitter chamber was constructed by DS Construction (UK) Ltd. This was installed with a PST bypass and penstock control. Steel access platforms and stairs were provided by Steelway.

[caption id="attachment_25481" align="alignnone" width="1200"] Stortec Engineering Ltd ULTRASTORE® PST tanks and scraper bridges - Courtesy of Coffey[/caption] Membrane bioreactor (MBR) technology

The MBR system is designed to meet stringent discharge permits and deliver high-quality effluent. Each MBR process stream includes fine screens, denitrification tanks, containerised Oxi/aeration tanks equipped with FBDA membrane diffusers and blowers, six membrane modules per stream, and a technical room fitted with pumps for membrane cleaning, chemical dosing and blowers.

The MBR system is a complex, innovative challenge to develop a containerised solution that conforms to Severn Trent’s requirements and standards. The system had to be developed to incorporate redundancy during design, which meant a shift-away from technical room mounted local control panels to an intelligent MCC for each stream. The FFT of 22.5 l/s is ditributed evenly across three streams vis a new equalisation tank. Constructed by DS Construction, the equalisation tank is 17.3m long x 12m wide with a depth ranging from 4m to 5.2m at the sump. A steel access system was constructed by Steelway along the width of the tank with each MBR stream fed via pumps with power and control from the MBR MCCs.

To accommodate the MBR system, an extensive civils programme had to be undertaken to provide all feed and permeate pipework, drainage, washwater, manholes, ducting and draw pits to each stream. Once all services were in place, a base slab was constructed for each stream.

[caption id="attachment_25489" align="alignnone" width="1200"] Installation of the containerised MBRs - Courtesy of Coffey[/caption]

The MBR system was manufactured by Coftec with membranes from Blue Foot Membranes. The system is a modular containerised arrangement comprising three parallel treatment streams, each engineered for optimal biological and membrane filtration performance. All the tanks have been coated with protective coatings from Belzona Ltd, expertly prepared and painted by Barnett Engineering.

Upon delivery to site, the MBRs were craned into position onto the pre-constructed bases prior to the end of 2024. Extensive mechanical works were undertaken by Jones Site Services & Installation (JSS&I) and electrical installation works by Elsym Installations Ltd.

Membrane bioreactor (MBR) design parameters & flow management Total flow to full treatment 22.5 l/s, distributed evenly across three streams (7.5 l/s per stream) Bioreactor MLSS 10,000 mg/l MBR peak flow handling Up to 22.5 l/s, with excess flows diverted to the storm tanks Membrane tank MLSS 13,500 mg/l Equalisation tank Balancing flow between 37.5 l/s to 22.5 l/s assuming all treatment streams operating Nominal net flux 23.6 l/m2/h Recirculation ratio 2.9 (to ensure effective biological treatment) Backwash flux 55 l/m2/h To meet the obligations of Severn Trent, one of the MBRs was partially commissioned and placed into service in March 2025. This provided valuable data and verification of performance of the MBR technology. Construction of all three MBR streams was completed by the autumn of 2025. [caption id="attachment_25479" align="alignnone" width="1200"] MBR Oxitank (left) Bluefoot membrane installation and (right) fit-out in tanks coated with Belzona protective coatings applied by Barnett Engineering - Courtesy of Coffey[/caption] Loggerheads Sanitorium STW: Supply chain - key participants Principal designer & contractor: Coffey Construction Ltd Design: Doran Consulting Survey: Murphy Geospatial H&S inspection & CDM: Hurst Setters Ground investigation: Card Geotechnics Limited Ecology & hedge removal: Three Shires Ltd Ecology & tree removal: RammSanderson Ecology MBR design & supply: Coftec Temporary works design: BSP Consulting Ltd Shaft design & construct: Active Tunnelling Main pipeline installers: A Thomas Plant Hire (ATP) Directional drillers: GMAC Utilities Ltd Mechanical installation: Jones Site Services & Installation Ltd Electrical installation: Elsym Installations Ltd Civil works: DS Construction (UK) Ltd Civils package (Sanatorium): Fortel Slide rail shoring system: National Trench Safety UK Buried service & pipe integration: Fincher Utilities Ltd Pressure testing: JMC Northern Limited Temporary pumping equipment: Pump Supplies Ltd MBR protective coatings: Belzona Ltd MBR protective coating application: Barnett Engineering Ltd MBR access metalwork: Midland Structures Ltd Ancillary metalworks: Structural Fabrications Ltd Inlet works/screens: SPIRAC Ltd Sludge thickening unit: Huber Technology PSTs: Stortec Engineering Ltd Storage & buffer tanks: Goodwin Tanks RAM desludge pumps: EMS Industries Ltd MCC package for MBRs: Te-Tech Process Solutions MCCs & telemetry: RSE Control Systems (Blackburn Starling Ltd) Lagging & trace heating: Jade Insulation Ltd Access systems: Steelway Ltd Fibre systems: PEICA Systems Ltd Pumps supply: Xylem Water Solutions Chemical dosing: Colloide GRP kiosks: NPS Engineering Group MBR instrumentation: Endress+Hauser Quality instrumentation: Servitech International Flow instrumentation: Siemens Generators: WB Power Services Site buildings: SpaceBuilder Crane hire: Dewsbury & Proud Ltd Plant hire: Flannery Plant Hire (Oval) Ltd [caption id="attachment_25490" align="alignnone" width="1200"] Temporary works: (top left) pipe and chamber installation works, (bottom left) for the Village STW main MCC and (right) for the construction of the works return PS - Courtesy of Coffey[/caption] Inter-site infrastructure & civil works

In total, over 1.7 km of pipelines were laid using various techniques including pipe ploughing, open cut works and horizontal directional drilling (HDD) under roads and watercourses.

Rising mains (pipe ploughing): Pipe ploughing was undertaken by ATP Cable Plough for nearly 1km of three rising mains, two fibre ducts and one National Grid HV supply between Sanatorium and Village STW.

This innovative method was selected by Coffey because of environmental and ground reinstatement issues; the cable plough’s efficient and low-impact method means that any complications when restoring and subsequently handing back land are dramatically reduced.

Pipe ploughing is effective on almost any terrain and because it causes minimal disruption to the ground’s geological structure, it offers a significant reduction in time, money and risk for the client and contractor. This is particularly significant when working in areas which are particularly sensitive to ecological and environmental issues. It also works very effectively on soft ground and marshland and consequently, it provides designers with an opportunity to soften the impact of schemes when route planning.

Added to this, as it cuts, installs and back-fills all in one operation, pipe ploughing eliminates any risk of trench-collapse and associated health and safety concerns, resulting in a huge increase in productivity over traditional ways of working.

Rising mains - A53 crossing: The A53 crossing required 6 (No.) 80m HDD shots at a depth of 4.0m as stipulated by the local authorities. This incurred the challenge of a significant element of open cut works to link the pipe ploughed runs to the HDD pipework, as ploughing is limited to a 2m maximum depth. Fincher Utilities Ltd was brought in to fulfil this requirement, along with all associated SRD pipework welding and setting out.

[caption id="attachment_25486" align="alignnone" width="1200"] (left) Rising main pipe ploughing and (right) pipe ploughing to HDD integration - Courtesy of Coffey[/caption]

Rising mains - Hemphill Brook crossing: Because of limited point-to-point visibility caused by forestry, newt lakes, and the brook itself, the crossing required 6 (No.) 120m gyroscopic drill shots. Additionally, this required a considerable amount of open cut work to connect the ploughed runs to the HDD pipework.

Due to the client-driven changes with the design and land access, the pipelaying work fell during the winter months, with challenging weather conditions; in particular significant rainfall and high winds bringing trees down along the main Sanatorium access route. Throughout this stage of the project, the project team operated in 24-hour shifts to achieve the completion date of December 2024 for this phase of the works.

Due to challenges found during the HDD drilling processes, accumulated air within the rising mains was found during commissioning; resulting in additional open-air vents and air release valves. During design, the intent was to mitigate this requirement due to the field being used for farming activities where significant complications of in-field structures would have been present. An innovative adaptation in the design was for a designated kiosk to be positioned in a safe location on the field boundary.

[caption id="attachment_25487" align="alignnone" width="1200"] Ongoing operations when working 24 hours/day - Courtesy of Coffey[/caption] Sanatorium transfer pumping station shaft tank

The transfer pumping station shaft tank was required to transfer crude FFT flows to the Village STW. The pumping station incorporates stormwater storage capacity of 320m3, duty/assist/standby transfer pumps, access steelwork, a UMON4 MCERTS flow meter on the pumping main to Village STW, a bypass arrangement for tank maintenance and an EDM level sensor for UMON3 compliance.

The transfer pumping station shaft tank at Sanatorium was designed and constructed by Active Tunnelling Ltd and the scope included:

A 7.5m deep, 10.5m internal diameter shaft. Reinforced concrete guide collar. Install 7 (No.)10.5m ID precast concrete segmental rings, build to one ring above collar level. 250mm deep drainage blanket including sump pipe and 100mm blinding. Reinforced concrete base slab 1.25m deep. Grouting the shaft anulus. Mass concrete benching to a maximum depth of 1.15m including forming sump. [caption id="attachment_25483" align="alignnone" width="1200"] Sanitorium TPS shaft tank - Courtesy of Coffey[/caption] Chemical dosing

Colloide provided chemical dosing plant and ferric sulphate storage with a walk-in dosing kiosk for four-point simultaneous dosing in accordance with Severn Trent’s template design. The primary dosing point is into PST distribution chamber. The secondary dosing location is into each of the three denitrification tanks and is configured to forward feed control based on the pre-MBR ortho-P monitor and the MBR stream feed pumping station flow.

Each dosing point and MBR stream has duty/standby pumps with automatic switchover to the standby; requiring eight pumps in total. Standby dosing lines are required to each duty dosing line; requiring 16 dosing lines in total.

Colloide provided 10m3 of ferric sulphate storage capacity along with chemical reception, chemical storage, and dosing kiosk bunds, and dual-contained dosing lines with capped off dual-contained standby lines. Emergency shower and eyewash stations are installed at the chemical dosing area, the poly dosing kiosk and the MBRs.

Sludge thickening

The sludge thickening solution is a containerised S-DISC thickener from Huber Technology. In addition, a glass coated sludge buffer tank and thickened-sludge holding tank were supplied by Goodwin Tanks along with duty/standby primary settlement tank desludge pumps from EMS Industries Ltd.

The S-DISC sludge thickener is a robust, efficient and reliable system using a long-life stainless steel filter cloth with minimal water, energy, and chemical usage. It offers a number of benefits including a compact design with a high sludge volume reduction of up to 90% and reduced disposal costs.

[caption id="attachment_25478" align="alignnone" width="1200"] (left) Huber S-DISC sludge thickener and (right) Goodwin Tanks sludge tank installation at Village STW with mechanical installations by JSS&I - Courtesy of Coffey[/caption] Electrical & control systems

The electrical infrastructure is designed to support a complex array of mechanical, process, and instrumentation systems across both the Village and Sanatorium sites. The design ensures operational resilience, safety, and seamless integration with control and telemetry systems. Intelligent MCCs are housed in dedicated kiosks at both the Sanitorium and Village sites to provide power and control for the FINEGUARD™ screens, the SPIROWASH® screenings washing units, the pumping stations and to the MBR stream.

Enhanced supply capacity was required to meet increased load demands and this included new transformers to supply both Village STW and Sanatorium STW.

Two new telemetry outstations were installed and commissioned and a fibre network provides high-speed communication between MCCs, outstations, and control rooms. A new telemetry PLC was manufactured by RSE Control Systems (Blackburn Starling) and in addition, network node boxes were installed for network reliability between Sanatorium STW & Village STW.

[caption id="attachment_25480" align="alignnone" width="1200"] LCPs from RSE Control Systems (Blackburn Starling Ltd) for the new SPIRAC Ltd inlet works - Courtesy of Coffey[/caption] Village TPS & Outfall PS

Village Transfer Pumping Station was modified to forward all flows of up to 21 l/s to Sanatorium. This required new duty/standby pumps, new iMCC & kiosk, integration of the existing works to accept all flows to Sanatorium and return flows back to the sample chamber for final effluent monitoring.

A key element of the Loggerheads scheme is to match the flow forwarded from the Village TPS to the Sanatorium STW to enable matching flow to be returned to the Village TPS outfall. The initial scope was for the Village TPS iMCC to be integral to the fibre ring for comms interface, however due to challenges and complications over resilience a new approach was adopted. The method used incorporated a new flow matching flow meter and bypass arrangement on the pumped main as it passes through Village STW to the inlet works at Sanatorium STW, where average flows over a 15-minute periods are measured and recorded.

Within the new Village STW, post-MBR treatment there is am outfall pumping station. From here, flows are separated to each respective site with an on-site redesigned solution of constant gravity flow back to Sanatorium STW outfall and a pumped arrangement back to Village TPS outfall. The pumped flow is continually matched to the measured 15-minute average of the flow matching flow meter.

It was necessary to ensure that the pumps were not starved meaning flow matching would be compromised. The original design was adjusted to a complete gravity weir arrangement, ensuring a constantly flooded wet well. This was one of several innovations that ensured the system performed without compromise and the programme pace was kept.

[caption id="attachment_25488" align="alignnone" width="1200"] Village Transfer Pumping Station final effluent monitoring equipment from Servitech International Ltd - Courtesy of Coffey[/caption] Key challenges & mitigation

Design change from a 2-site to 3-site solution: The project is complex, with the number of inter-site interfaces and many innovative assets and methods used. There was no programme extension to allow for the third location (the reed bed site) and there were land access complications. This complication led Coffey to adopt 7-day working for a number of months and during key phases, 24-hour working to ensure the expanded scope could still be delivered.

Complex logistics: The integration of multiple pumping stations, rising mains, and treatment units required precise coordination and phased commissioning.

Temporary works: The temporary works at Loggerheads were extensive. The vast range has been from trench boxes for laying pipework and rising mains, through to the installation of various large manhole ring pumping stations and, at the works return, where two 3m wide by 6m deep structures were constructed.

Environmental compliance: Meeting stringent discharge permits (0.3 mg/l Total Phosphorus at Village STW) required advanced process control and real-time monitoring. A vast array of commissioning and temporary measures were required to facilitate this operation.

Mechanical, electrical & commissioning works: This element of the project has been significant as shown by the sheer volume of electrical control assets required. The subsequent electrical installation has been met with competency and support by Elsym Installations Ltd to meet the significantly condensed programme. This same intensity has been met by Jones Site Services & Installation for the mechanical requirements on a challenging scheme.

Weather mitigation: The main construction activities took place during a harsh winter when on-site activities were impacted by heavy snow, rainfall and high winds that brought down trees and a powerline; preventing access to Sanatorium during key phases and making cranage a challenge to programme. Cold temperatures impacted concrete activities for the MBR slabs and MCC bases and wet weather provided challenges for the project team during the installation of the 100m pipeline run over the wetlands to the new outfall position at Sanatorium. [caption id="attachment_25491" align="alignnone" width="1200"] Downed trees and powerlines blocking site access during high winds - Courtesy of Coffey[/caption] Conclusion

The Loggerheads Sanatorium STW AMP7 Q WFD project serves as a prime example of contemporary wastewater infrastructure implementation. By utilising innovative design, fostering collaboration, and prioritising environmental results, the project aims to provide enduring advantages for both the community and the environment. With completion anticipated in early 2026, it is positioned as a benchmark for upcoming AMP8 initiatives.

In April 2025, the project received the ‘Triumph in face of Adversity’ Award from Severn Trent.

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

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

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

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

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

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

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

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

Previously in Water Projects

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

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

Contract

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

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

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

The project consists of the following:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Guildford STW: Civils works supply chain - key participants

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

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

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

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

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

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

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

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

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

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

Storm tanks & inlet works

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

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

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

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

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

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

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

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

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

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

Tertiary treatment plant & outfall

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

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

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

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

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

Power & control

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

Welfare building

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

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

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

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

Piling & ground improvement

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

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

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

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

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

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

The year ahead

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

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

Finham STW serves a population equivalent (PE) of approximately 500,000 in the Coventry area, treating 115 ML of wastewater per day. In 2021, as part of efforts to support economic recovery from the COVID-19 pandemic, the UK government launched the Green Recovery program - an initiative aimed at accelerating environmental improvements, creating green jobs, and fostering sustainable growth through targeted investment in infrastructure and nature-based solution. As part of Severn Trent’s Green Recovery program, the Finham Sewage Treatment Works (STW) Storm Tank project in Coventry represented a critical intervention to improve river water quality in the River Avon catchment. Project background

The Finham STW Storm Tank Project formed part of Severn Trent’s Bathing Rivers Initiative, targeting storm overflow spills reduction. The goal of the Bathing Rivers Initiative was to reduce storm overflow discharges from combined sewer overflows (CSOs) to improve river water quality for bathers and the wider environment by the 31 March 2025.

The construction of a new 4,880m3 storm tank at Finham STW, in addition to a new shaft tank at Unicorn Lane CSO, will significantly reduce spills in the catchment with flows stored at Finham before being passed for treatment once the storm event has ended.

Few projects illustrate the value of adaptability, collaboration, problem solving and technical excellence as clearly as Finham. The ability to pivot from an unfeasible initial design (due to ground conditions) to a fully operational rectangular tank within a compressed time-frame is a testament to the strength of the delivery team and the robustness of the project governance.

[caption id="attachment_25246" align="alignnone" width="1200"] Start of the piling operation – Courtesy of Keller Ltd[/caption] Technical design & construction

The initial design proposed a 15m deep shaft supported by a dewatering strategy using 32 recharge wells. However, in May 2024 a significant sub-artesian groundwater head and local aquifer saturation rendered the dewatering strategy unviable. This refers to a condition in a confined aquifer where groundwater is under pressure but does not rise to the surface.

Although not as forceful as artesian conditions, sub-artesian pressure can still cause water to seep into excavations, requiring active dewatering measures. This can lead to delays due to the need for additional pumping systems, potential soil instability, and adjustments to foundation designs. Furthermore, managing groundwater in such conditions may necessitate dewatering permits and other checks, all of which can contribute to project delays.

This led to a cease works order and a fundamental redesign of the solution, with the Finham Storm Tank project team pivoting to a rectangular tank design, developed through collaborative design sprints. The redesign addressed piling layout, inlet/outlet arrangements, cleaning and return systems, revised formation levels, and rebar schedules. This agile approach enabled the team to maintain momentum and deliver a revised solution aligned with program constraints.

To address the dewatering challenges associated with the construction of the new storm tank at Finham STW, specific design modifications were implemented to accommodate the site’s complex ground conditions. The subsurface profile, comprising 4–5m of made ground and firm clays overlying strong sandstone and mudstone, necessitated a robust foundation solution. A rotary bored piling system using 750/650mm diameter piles was adopted, capable of withstanding tension loads of up to 1000kN.

This method allowed for deep foundation installation with minimal vibration and disturbance, thereby reducing the risk of triggering groundwater ingress. By limiting the extent and depth of excavation, the design significantly reduced the need for extensive dewatering. The low-vibration, cast in-situ piling technique was particularly effective in maintaining the stability of surrounding soils and managing the sub-artesian groundwater pressure.

[caption id="attachment_25250" align="alignnone" width="1200"] Rebar in place for one of the ten concrete pours for the tank base - Courtesy of Joseph Gallagher Ltd[/caption]

Additionally, early contractor involvement facilitated proactive planning of site logistics and working platforms, ensuring groundwater risks were identified and managed from the outset. This collaborative approach enabled the team to optimise construction sequencing and minimise delays related to water management.

The design was further refined through a review of reinforcement requirements, which led to a reduction in steel usage. This not only lowered the environmental impact and construction costs but also simplified the build process, reducing the time the site was vulnerable to wet weather and other impacts of winter. Collectively, these measures enabled the storm tank to be constructed efficiently and safely, despite the presence of challenging sub-surface water conditions.

Construction delivery

Construction activities included excavation to formation level, piling, sealing of dewatering wells, diversion of existing services, and reinforced concrete works for the base slab and side walls.

Despite the significant design change, the team maintained a focused program to meet the regulatory deadline. The tank was successfully constructed and made operational before the 31 March 2025 target, demonstrating a high level of delivery discipline and adaptability.

Finham Storm Tank: Supply chain - key participants Main contractor: Kier Design consultants: Stantec UK Piling designer & contractor: Keller Ltd Dewatering: Stuart Wells Ltd FRC works: Joseph Gallagher Ltd Mechanical/pipework: Varlowe Industrial Services Tipping buckets: Jacopa MCC/panels: RSE Control Systems (Blackburn Starling Ltd) Swing jib & galvanised steel: T Allen Engineering Services Concrete & steel reinforcement: Heidelberg Materials Flow controls: AFFCO Flow Control (UK) Ltd [caption id="attachment_25248" align="alignnone" width="1200"] Slab construction and start of wall shuttering placement - Courtesy of Kier[/caption] Collaborative delivery model

The project was delivered using an Integrated Project Team (IPT) model, comprising of a multidisciplinary group of internal and external stakeholders who worked together to deliver the desired project outcomes. The IPT included Severn Trent Delivery and Commercial teams, the principal contractor, consultant designers, and subcontractors. This multi-party collaboration enabled efficient design-to-construction workflows, dynamic commercial management, real-time problem-solving, strong communication and relationship building through a spirit of trust and open discussion.

The IPT model was instrumental in managing the decision complexities of the shaft dewatering process, ensuring continuity of delivery and maintaining project progress. This collaborative framework enabled the team to align on project objectives from the outset, streamlining decision-making and ensuring that design and construction strategies were fully coordinated. The early involvement of the piling contractor, for example, allowed for the development of a detailed and practical construction methodology that was both efficient and aligned with site constraints.

The IPT model also enhanced communication and accountability across disciplines, which proved particularly valuable in managing health and safety on site. Daily shift briefings were led by the principal contractor, ensuring that all personnel were informed of the day’s activities, risks, and mitigation measures. This proactive approach to site management contributed to a strong safety culture and reduced the likelihood of delays due to miscommunication or procedural oversights.

Furthermore, the integrated team structure facilitated value engineering opportunities, such as the optimisation of reinforcement design. By working collaboratively, the team was able to identify areas where material use could be reduced without compromising structural integrity, leading to cost savings and a lower environmental impact. Overall, the IPT approach played a critical role in ensuring the storm tank was delivered on time, to specification, and with a high standard of quality.

[caption id="attachment_25245" align="alignnone" width="1200"] 180m3 concrete pour for slab No. 6 - Courtesy of Joseph Gallagher Ltd[/caption] Environmental & community impact

The Finham Storm Tank directly contributes to the Bathing Rivers Initiative, improving water quality in the River Avon by reducing storm overflow discharges. The project aligns with national environmental goals and supports the Water Framework Directive by enhancing ecological quality and enabling recreational use of urban rivers. This initiative does not just solve a problem, it redefines what is possible for working at pace in urban wastewater management, setting a precedent for future projects across the UK and beyond.

Successes & legacy

Although the solution required redesigning, the 4,880m3 storm tank was constructed to meet the highest standards of site safety and construction quality. It became operational by the regulatory deadline of 31 March 2025, fulfilling the objectives of both the Green Recovery Program and the Bathing Rivers Initiative.

The project’s success lies not only in the numbers - reduced spills, increased storage, improved water quality - but in the way it brings together engineering excellence, ecological improvement, and community engagement.

As part of the project’s ecological sensitivity strategy, plans are underway to enhance biodiversity and restore natural features impacted by construction. Biodiversity Net Gain (BNG) calculations have been completed to assess the ecological impact of the works and to ensure that the site delivers a measurable improvement in biodiversity value upon completion. Furthermore, the installation of bird boxes is being prepared to support local bird populations by providing safe nesting habitats. In addition, a tree replanting program is in development to replace vegetation removed during site works, with the aim of re-establishing green cover and contributing to long-term ecological resilience. These initiatives reflect a forward-thinking approach to environmental responsibility and align with Severn Trent’s broader commitment to sustainability.

[caption id="attachment_25249" align="alignnone" width="1200"] Final tank commissioning (March 2025) - Courtesy of Kier[/caption]

To support community engagement, the project team has made use of both traditional and digital communication methods to keep stakeholders informed and involved. Updates have been shared through a combination of newsletters and video content, offering insights into project progress, upcoming activities, and the long-term benefits of the works.

These efforts have helped maintain transparency, foster public interest, and ensure that the local community remains connected to the project throughout its delivery. As part of Severn Trent’s Bathing Rivers program, a dedicated virtual room was created to engage stakeholders and the public, providing updates, resources, and insights into river quality improvements and community involvement.

Flag Fen Water Recycling Centre (WRC), located in Peterborough, is a vital part of Anglian Water’s regional water management system. Named after the nearby historic Flag Fen archaeological site, the WRC’s function is to process and treat wastewater from the city and surrounding areas, ensuring the safe return of clean water to local rivers and ecosystems. Serving both a growing population and industrial sector, the facility is integral to maintaining high environmental standards and supporting the region. The facility serves as a critical hub, managing significant volumes of wastewater and stormwater while maintaining stringent compliance with environmental standards. Over time, the changing climate and urbanisation have intensified the challenges related to the WRC’s stormwater capacities, risking overwhelming existing infrastructure. The issue

As Peterborough continues to grow, Flag Fen Water Recycling Centre remains a forward-thinking facility, providing essential services to the community while protecting natural resources for future generations.

The existing infrastructure at the WRC has been increasingly insufficient for managing the demands placed upon it. Storm tank capacity had become a pressing concern, with flows during peak periods often exceeding the current capacities limits. Without sufficient storage, excess stormwater risked being discharged untreated into the local water courses, which impacts our surrounding ecosystems, plus goes against the current environmental regulations.

[caption id="attachment_21138" align="alignnone" width="1200"] 3D render of the new tanks - Courtesy of Anglian Water’s @one Alliance[/caption]

Additionally, aging systems required significant modernisation. The storm tank cleaning mechanisms and control systems were outdated, leading to inefficiencies and elevated maintenance costs. The WRC needed to integrate its operations more effectively with modern telemetry and automation technologies to enhance reliability and performance.

Compounding these issues were regulatory obligations. Under the WINEP flow driver, the WRC was mandated to increase its storm tank capacity by 7625m3 by 31 March 2025, ensuring compliance with permitted dry weather flow (DWF) levels. This requirement was further complicated by the need to manage stormwater flows under a 30-year design storm scenario while incorporating climate change projections.

The solution

To meet these challenges, Anglian Water tasked the Anglian Water’s @one Alliance to implement a £10m extensive upgrade to the stormwater storage and management systems. The solution required the installation of two new stainless steel storm tanks, each designed to provide 4,027m3 of additional storage, for a combined total of 8,055m3 as well as improvements to the storm tank cleaning systems, control mechanisms and electrical infrastructure.

Stormwater storage tanks: The new stainless steel tanks from Hayes GFS Ltd measure 37m in diameter and have a sidewall depth of 5.63m. Gravity-fed return flows are directed to the screw pump wet well by intercepting the exiting pipeline from the DWF weirs, ensuring seamless integration with existing operations. The tanks were constructed on 400mm thick, concrete base slabs, covering 1,150m2, with 120 kilograms of reinforcement per cubic meter. A 300mm gravel layer was installed around the tanks to enhance stability and facilitate drainage.

The new pipelines connecting to the tanks to the inlet works ensure efficient flow management during peak storm events.

[caption id="attachment_21137" align="alignnone" width="1200"] Bell Formwork finalising the stormwater storage tank base - Courtesy of Anglian Water’s @one Alliance[/caption]

Storm tank cleaning system: A new cleaning system was installed to the new stainless steel storm tanks; maintaining the functionality and hygiene of the tanks, and allowing Anglian Water Operations to be able to clean the storm tanks after usage.

The system featured eight new ejector nozzles in each tank, fed by four Flygt NT3202.180 dry-mounted submersible pumps from Xylem Water Solutions. Each cleaning pump provided a recirculation rate of 235 l/s, ensuring effective debris removal and minimising the need for any manual intervention.

Electrical & automation upgrades: Significant upgrades were made to support the new storm tank infrastructure and to ensure operational reliability. Firstly a dedicated storm tank cleaning motor control center (MCC) was installed in a raised kiosk to mitigate the potential flood risks. This system included ultrasonic transducers, pressure switches, and access platform lighting to enhance functionality and safety.

Alongside this, the team designed and installed a new 1,000 kVA transformer, along with modifications to the existing transformer. This in total increased the WRC’s power capacity from 2.6 MVA to 3.1 MVA.

A new fully automatic control system was added into the WRC’s existing telemetry network. This system automated storm tank emptying sequences and provided real-time monitoring for efficient operation.

[caption id="attachment_21142" align="alignnone" width="1200"] Raised MCC kiosk - Courtesy of Anglian Water’s @one Alliance[/caption] The benefits of this solution

The implementation of the upgraded stormwater management system delivered a wide range of benefits, addressing immediate challenges and positioning the WRC for long-term success.

Regulatory compliance: By increasing storm tank capacity by 8,055m³, the facility met its obligations under the WINEP FLOW driver UIMP6. Achieving compliance by the mandated deadline (31 March 2025) not only avoided regulatory penalties but also demonstrates a proactive commitment to Anglian Water’s environmental investments.

The design of the new storm tanks ensured full compliance with permitted DWF levels and storm sewage consent conditions.

Enhanced operational efficiency: The new storm tanks and cleaning systems significantly improved operational reliability by reducing the downtime and ensuring the tanks remained ready for use after each storm event.

The solution provided many benefits from an operational efficiency’s standpoint, including:

By incorporating gravity-fed and gravity-return systems, stormwater management was streamlined by reducing the energy consumption and operational complexity. The use of the advanced telemetry and control systems enhanced real-time monitoring and reduced the need for manual interventions. The increased stormwater return rate of 442 l/s represents a marked improvement, and enables faster recovery after peak flow events. [caption id="attachment_21143" align="alignnone" width="1200"] The new stormwater storage tank and raised MCC kiosk - Courtesy of Anglian Water’s @one Alliance[/caption] Environmental protection: The upgraded system will be able to prevent untreated stormwater from being discharged into the local water courses during high-flow periods. This ensures that local watercourses and ecosystems are safeguarded by providing high infrastructure that will be resilient against future environmental challenges. The risk of localised flooding in surrounding residential and industrial areas will be reduced, protecting the public health and properties of the public in Peterborough. Flag Fen WRC: Supply chain - key participants Client: Anglian Water Project delivery: @one Alliance Watching brief: Cotswold Archaeology Civil works: Bell Formwork & Civil Engineering Services Ltd Over pumping: Selwood Storm tanks: Hayes GFS Ltd Tank cleaning system pumps: Xylem Water Solutions MEICA: Kemada Project & Contract Services Ltd Epoxy pipework: Freeflow Pipesystems Ltd Epoxy pipework: Powerrun Pipe-Mech Ltd Access steelwork platforms & design: Cobra Engineering (UK) Ltd VSDs, HMI & MCCs: CEMA Group Kiosk & kiosk route survey: NPS Engineering Group Power upgrade: Power Testing Temporary generator for power upgrade: Stuart Power Scaffolding: Tubes Scaffolding Ltd Permanent Fencing: Burn Fencing Ltd [caption id="attachment_21141" align="alignnone" width="1200"] One of the new stainless steel stormwater storage tanks - Courtesy of Anglian Water’s @one Alliance[/caption] Conclusion

The £10m upgrade to the Flag Fen WRC’s stormwater management system has addressed critical infrastructure needs, while ensuring compliance with environmental and regulatory standards. The installation of two new stainless steel storm tanks, alongside the advanced cleaning and control systems, will transform the facility’s operational capabilities.

The solution had to be fully compliant with stringent environmental standards, accommodating no-detriment scenarios under a 30-year design storm with allowances for climate change. The stormwater return rate being increased from 388 l/s to 442 l/s represents a significant improvement in operational performance.

The solution minimised the visual and environmental impact of the new infrastructure by included landscaping, new access paths, and a screening bund. Additionally, the new stainless steel tanks were painted green to fit in with the surrounding landscaping features.

These measures improved the overall aesthetics of the new storm tank infrastructure.

This project highlights the importance of innovative engineering and sustainable practices in modern wastewater management. By enhancing storage capacity, improving efficiency, and protecting the environment, the WRC not only will resolve the immediate challenges but also positioned itself as a resilient and adaptable WRC in the region. Through careful planning and execution, the project delivered lasting benefits for the environment, the community, and future generations.

Campbeltown has experienced flooding over many years, which has affected residential properties, businesses, roads, and community life in general. In June 2022, construction started on a 24-month, £16m scheme, (co-funded 80% by the Scottish Government and 20% by Argyll and Bute Council) under the Flood Risk Management (Scotland) Act 2009 where the council is responsible for developing sustainable flood management solutions. DAWSON-WAM Ltd was appointed as principal contractor, with AECOM employed by the council to provide design and project management support throughout the contract. Flooding sources

The existing sewer network system in the Burnside and Meadows areas could not cope with increasing amounts of surface water. The sewer network combined surface water with sewage water from households. When the system was overwhelmed during periods of heavy rain, fouled water backed up out of the system and flooded streets and premises.

On the outskirts of the town is the Millknowe Burn which, due to several steep catchments, is the most dominant flood source in Campbeltown. Flows from the Balgreggan Burn also caused overtopping during extreme events at the Dalaruan culvert intake and resulted in overland flows and flooding in the town.

[caption id="attachment_18234" align="alignnone" width="1200"] Google Earth image showing Campbeltown FPS site locations[/caption] Scope of works

The scope of the scheme was to reduce the risk of flooding from the Millknowe and Balgreggan Burns and from localised surface water in Campbeltown. The project was rolled out over four working areas:

Millknowe flood storage reservoir. Dalaruan culvert. The Meadown SuDS. Burnside Square. Millknowe Flood Storage Reservoir

Millknowe Field is located beside the watercourse channel, which acts as a catchment area for rainwater. It floods onto nearby roads and streets; particularly the main A83 trunk road which provides the primary access into the town. There are two block of flats beside the field, built essentially on the same floodplain that is prone to flooding during heavy rainfall when the watercourse and culvert cannot cope with the flow of water.

Snipefield Industrial Estate is located on the northern side of the watercourse channel, which is home to many local businesses. This was also prone to flooding from the field during heavy rainfall events.

The scope of works at Millknowe included:

Construction of a flood storage reservoir in Millknowe field to provide temporary flood water storage within the watercourse channel during high rainfall events. Realignment of the watercourse channel along a new sheet piled wall. Installation of over 500m of new back of wall drainage ranging in diameter from 225mm to 600mm and new outfalls with flap valves through the new flood wall. [caption id="attachment_18237" align="alignnone" width="1200"] Installation of AZ sheet piled wall with TM22 piling rig to form reservoir - Courtesy of DAWSON-WAM Ltd[/caption]

Flood storage reservoir

The reservoir was constructed in line with the Reservoir (Scotland) Act 2011 and comprised a 125m long AZ19-700 sheet piled wall encased in a 2.6m (average height) earth embankment dam and concrete spillway. A 325m AZ20-700 sheet piled flood wall formed the enclosed dam structure and provided flood protection to Snipefield Industrial Estate. The sheet piles were driven into cohesive soils and ranged between 6m to 9.5m in length. A new concrete culvert passing through the dam with headwall and orifice plate was constructed to throttle the flows. The exposed piles were capped off with a precast concrete coping.

To facilitate the installation of the 450m of steel sheet pile wall, a 6m wide x 600mm deep stone temporary piling platform was installed to support the 90T ABI TM22 piling rig.

Where space allowed, the piling platform was constructed in Snipefield Industrial Estate to the north of the watercourse. This minimised the length of the watercourse that was required to be culverted and reduced the impact on agricultural soils and the watercourse, and reduced the amount of imported stone required.

DAWSON WAM’s in-house heavy-duty steel mats were utilised which further reduced the amount of imported material for the piling platform. Three temporary bridge culvert crossings were constructed using the mats which allowed full access along the length of the wall during construction.

[caption id="attachment_18243" align="alignnone" width="1200"] Temporary bridge crossing watercourse using DAWSON-WAM Ltd’s heavy duty steel mats - Courtesy of DAWSON-WAM Ltd[/caption]

The sheet piles were purchased from Arcelor Mittal in Luxembourg, and were stored in DAWSON-WAM Ltd’s yard in Bedfordshire. The piles clutches were sealed using Biguma SV and were delivered to site in a just-in-time basis throughout the project.

DAWSON-WAM Ltd used an ABI TM22 piling rig to complete the piling installation works. This rig with its powerful 36VV vibro hammer  is the most powerful leader rig mounted vibro in the UK and Europe. Interchangeable attachments were mobilised, including the preaugering with advanced cased CFA and the HydroPress system, which allowed increased production and mitigated risks where unforeseen ground conditions were encountered.

Service crossings

The new sheet piled wall installation required to perpendicularly cross a 225mm asbestos cement Scottish watermain and a high voltage (HV) Scottish Power cable. These two services were critical to the town infrastructure and any disruption or shutdowns would have caused a extensive disruption to the town’s residents.

Traditionally these services would have to be diverted through the wall in a phased approach, resulting in inefficiencies and several shutdowns on the services. Through DAWSON-WAM Ltd’s in-house expertise and utilising its specialist vibrationless HydroPress piling equipment, installation of the piles adjacent to the utilities was successfully achieved without diverting the services. This involved early liaison and working closely with the designer and utility providers, undertaking trial pits to ascertain the ground conditions, installation of vibration monitors on the services to highlight vibration levels during install and agreeing a short shut down of the services during pile install.

Earth embankment

The earth embankment at Millknowe consisted of an up to 4m high 125m long embankment with a 21m in situ reinforced concrete spillway. The embankment footprint was excavated removing 3000t of topsoil, 6000T of peat and associated soft soils to form the earth embankment foundation on alluvial or raised beach deposits with a Cu value greater than 40Kpa.

To consolidate the formation level prior to construction, trial pits were excavated along the footprint of the structure and with the aid of a shear vein test, the employer-appointed Reservoir Construction Engineer witnessed and approved the formation levels on site.

2,600t of locally sourced Class 6C compacted in accordance with CESWI 7th Edition in a 500mm deep layer formed the foundation of the embankment. The main body of the embankment was constructed using 5,800t of compacted Class 1A granular fill, with the maximum embankment height of 4m with sloped of 1V:3H. Class 6N granular material was used to segregate the Class 6C and Class 1A material around the piles.

The embankment was capped with a 300mm layer of site won screened topsoil and reinforced with coir matting and seeded. Associate embankment toe drainage and a hardstand access road was provided for future maintenance access.

[caption id="attachment_18233" align="alignnone" width="1200"] Realigned burn along sheet piled wall reinforced with coir matting - Courtesy of DAWSON-WAM Ltd[/caption] Dalaruan culvert

270m of the existing Dalaruan storm water culvert required upgrading from the Millknowe flood storage reservoir intake to downstream of Dalaruan Street intake. This online upgrade would convey flows and provide additional inline storage from the Millknowe reservoir and prevent overtopping flows from the Balgreggan Burn during extreme rain events.

The exemplary design proposed the install of concrete culverts however as Dalaruan Street is straddled by terraced houses with listed boundary walls and with a congested mix of utilities of various eras, it was decided from an early stage in the contract a detailed survey be undertaken including trial digs to ascertain existing utility positions. This work proved prudent as a design change was requested to provide a more buildable solution while managing live flows and to avoid extensive service diversions.

The contractor and designer worked collaboratively, and through engaging with the supply chain and by re-modelling validation, the section of culvert was changed to a twin line using AquaSpira pipes.  This solution provided a bespoke steel reinforced twin piped culvert which had both health and safety and constructability benefits and prevented extensive costly service diversions.

In total, 110m of twin 900mm and 45m of twin 675mm pipes were installed including 115m of single 675mm pipe to form the new culvert. AquaSpira’s prefabricated manhole units were used, which proved to be considerably easier to install compared to the traditional concrete manhole rings, and benefited the management of the existing live storm flows, as well as a faster build time.

During the 6-month construction phase of the Dalaruan culverts, as the majority of the works required the closure of the Dalaruan Road, an extensive public relations exercise was undertaken prior to works commencing. Following the extensive liaison, a phased programme of work plan was developed which merged the phasing of the works and the concerns raised from the public events.

This plan was then shared prior to construction commencing and was supplemented with a full-time public liaison officer, this resulted in the successful installation of the replacement culvert in time to take the first storm flows.

[caption id="attachment_18240" align="alignnone" width="1200"] (left) Installation of twin 675mm diameter AquaSpira pipes and (right) installation of prefabricated manholes - Courtesy of DAWSON-WAM Ltd[/caption] The Meadown SuDS

The Meadows catchment area consisted of an existing, out of date, undersized combined sewer network system that during periods of heavy rainfall events caused out of sewer flooding to occur. This, combined with the existing culverts in the Witchburn and Meadows areas that could not convey sufficient volume of stormwater,  resulted in regular localised flooding events.

The solution was to provide 6500m2 of storm separation on the existing road network by installing over 1.2km of new storm pipe ranging in diameter from 150mm to 375mm and connecting over 65 existing storm gullies to the new infrastructure. This new pipe network conveyed storm flows to three new detention basins with a total capacity of 1500m3 to temporarily attenuate surface water runoff before releasing it back into the existing Witchburn Culvert system. The shallow detention basins were constructed in existing green spaces with 1:4 slopes with a 3D cellular confinement system installed on the basin slopes to improve soil stabilisation and control erosion.

Flows from the basins are retained by flow control manholes fitted with Storm Brake valves, which limit storm flows to between 4.5 l/s and 7.7 l/s into the culverts in a more forgiving manner.

Biodiversity within the detentions basins was enhanced by planting a wet meadows mix plant and a combination of birch and willow trees surrounding them. Due to the poor quality of the existing road surfacing, new full width reinstatement was undertaken to all roads that acquired new storm drainage significantly enhancing the whole road network.

[caption id="attachment_18244" align="alignnone" width="1200"] Reinstated detention basis at Meadows - Courtesy of DAWSON-WAM Ltd[/caption] Burnside Square

A new underground geocellular attenuation tank in Burnside Square was constructed to temporarily store and attenuate 540m3 of surface water runoff from 1.6km newly constructed storm separation pipework in the Witchburn and Burnside areas during high rainfall events before releasing it back into the existing culvert network.

As Burnside Square was at the heart of the town, it posed several construction risks none less than excavating near three-storey properties that dated back to the 1700s with stone foundations, while having to maintain safe access to the business and residential premises contained within.

Due to the level of disruption anticipated in this area, the contract had restricted these works to be completed during the winter months and required it to be re-opened for public use by June 2023 in time for the peak tourist season.

Following the completion of a detailed ground investigation, it identified that there was largely granular materials withing the dig area for the new attenuation structure, with a water strike just at dig level. Due to the above mentioned buildability concerns, a battered excavation solution posed many risks, therefore a secant piled box cofferdam solution was opted for which would act as both permanent and temporary works for the tank.

DAWSON-WAM Ltd utilised its in-house cased CFA piling rig to install the 300 (No.) 450mm diameter secant piled cofferdam, with its vibrationless installation method eliminating the risk of vibration on the surrounding properties, with this solution the space around the perimeter of the site was able to be maximized, resulting in sufficient space for pedestrians to access the premises safely during the construction period.

[caption id="attachment_18238" align="alignnone" width="1200"] (left) Secant pile installation using cased CFA at Burnside Square, and (right) Geocell attenuation tank at Burnside Square prior to backfilling - Courtesy of DAWSON-WAM Ltd[/caption]

Upon the excavation of the 2700T of granular material, the area was bedded with single-sized rounded stone which provided the base for Polypipe’s lightweight Polystorm-R crates. The crates were delivered in articulated lorries and were built in situ and wrapped in a welded impermeable liner and geotextile protection fleece.

Inspection chambers and a manifold pipe arrangement was formed to enable the filling, emptying, and maintenance of the tank. To prevent overloading of the tank in the temporary condition, the tank was backfilled with imported aggregate in a sequence using small plant, a 100mm layer of Bitmac then formed the foundation for the 900m2 of new block paving.

As the existing square was predominately used for car parking, the council grasped the opportunity to reinstate the area into a multi-functional space that could be utilised for community events as well as serving as daily parking.As part of the final reinstatement, over 52 new bollards and an array of new street furniture and planters were installed.

Supply chain: key participants Main contractor: DAWSON-WAM Ltd Project management & client design: AECOM Materials testing: MATtest Limited Culvert pipes/chambers & twin pipe culvert (Dalaruan Street): Aquaspira Ltd Sheet piles: Arcelor Mittal Attenuation tank installation: Hydro Water Management Solutions Ltd Precast concrete: FP McCann Civil contractors: McFadyen’s Contracts Campbeltown Landscaping: MW Groundworks Attenuation tank drainage crates: Polypipe Civils & Green Urbanisation Drainage & ducting materials: Huws Gray | Jewson Transformers: Wilson Power Solutions Ltd [caption id="attachment_18241" align="alignnone" width="1200"] Storm separation pipework installation at Witchburn - Courtesy of DAWSON-WAM Ltd[/caption] Community benefits

It was obvious from inception that, engineering challenges aside, one of the key challenges for the project team would be constructing the works within this rural town in Scotland which would not have previously witnessed a construction project on this scale.

Effective consultation with stakeholders, which included road users, local businesses, residents, the general public and affected landowners, would be key to the minimising disruption and to the project’s successful delivery.

Several pre-construction pop-up events were held locally with the residents, businesses and stakeholders. Consultations were carried out through Argyll and Bute Council’s internal communications team and monthly newsletters were issued through the portal giving updates on construction progress and programme of works and queries were managed through the site-specific e-mail and emergency contact number. Public drop-in meetings and letter drops were undertaken in advance of entering a new area of works.

A project of this size and complexity will always have a significant local impact and it was important that the project team endeavoured to engage with and, for the duration of the project, be part of the community.

[caption id="attachment_18235" align="alignnone" width="1200"] Realigned burn along sheet piled wall reinforced with coir matting - Courtesy of DAWSON-WAM Ltd[/caption]

Initiatives to promote community engagement included:

Visits from the construction engineering team to Dalintober and Drumlemble primary school, educating the children on the dangers of construction sites. Donations of PPE waterproofs to the school to help support their learning and exploration group. Donation of a ‘LEGO education spike prime Set’ to help engage STEM learning and problem-solving skills. Donation of Ukuleles to the local kids’ music group. Local charity donations including a donation to the Kintyre Sea Sports charity to purchase new equipment to aid in the training and development of the local disadvantaged children in water activities. Donation of 6T of topsoil to Campbeltown Climate Action for use in their community garden. Voluntary repairs to the Campbeltown youth football team goal posts and changing facilities access paving prior to a kid’s football tournament. Supply and installation of a bicycle rack in Burnside Square.

The most significant community benefit was the employment of a local sub-contractor to undertake much of the construction works. This provided and supported employment to the residents of Campbeltown and supported the local businesses as the money stayed in the community.

[caption id="attachment_18236" align="alignnone" width="1200"] Reinstated Burnside Square - Courtesy of DAWSON-WAM Ltd[/caption] Conclusion

In Autumn 2023 during two periods of heavy rainfall, the Millknowe Reservoir, the Meadows detention basins and the Burnside attenuation tank protected the town from flooding and reduced the load onto the wastewater network.

The successful delivery of the Campbeltown Flood Scheme was a brilliant example of collaboration between the contractor, client, designers, and the local community; ultimately resulting in the success of the project as well as providing an asset that will efficiently protect the town and its residents for years to come.

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

Marchmont is a residential area of Scotland’s capital city, Edinburgh. The area is characterised by four and five storey sandstone tenements blocks built in the Scots Baronial style. Most of the area was developed in the 1870s and 1880s and there has been little change to its structure since then. It is a mile from Edinburgh’s Old Town and is located right by the popular Meadows and Bruntsfield Links. The area remains popular with older residents, young professionals and students due to the short distance to the University, the city centre and the abundance of parks on their doorstep. For several years, persistent flooding has been impacting businesses and residents in the area of Edinburgh due to a lack of capacity in the existing sewer network and an increase in frequency and intensity of heavy rainfall events. Introduction

Scottish Water is investing £8.9m to increase the sewer network capacity and storage within the Marchmont catchment which will reduce the risk of flooding to businesses and residents who have been affected by flooding.

Starting on site in August 2022, Marchmont Road Flood Alleviation Project is being delivered by Scottish Water’s alliance partner Caledonia Water Alliance, with completion scheduled for December 2024.

[caption id="attachment_14698" align="alignnone" width="1200"] Google Maps image showing location of the site[/caption]

The solution involves the installation of 700m of new and upsized sewer along Marchmont Crescent off Marchmont Road, which connects back to the existing network at Meadow Place. Storm flows will then spill via a new bifurcation chamber on Marchmont Road into a new 20m diameter, 3,000m3 volume offline storm storage tank located within Bruntsfield Links.

Sewer levels will be monitored in the downstream network and following a heavy rainfall event, storm flows will be pumped back into the network.

Project scope Construct a 20m internal diameter, 17m deep attenuation tank using underpinning methods to provide 3000m3 of storage and housing a internal tank cleaning system Vacflush™ column from CSO Group Ltd. Install two pumps (duty/standby) with two DN250 DI rising mains with pumped return to the existing combined sewer network. Install approximately 700m of new, upsized sewer ranging from DN250-DN900, with a range of materials: ductile iron, concrete, polyethylene and GRP. Install 24 PCC manhole to a depth of 4.5m. Retain the existing mature trees around Bruntsfield Links and Marchmont Crescent, by using two trenchless construction methods: Guided auger bore on Marchmont Crescent with a steel sleeve 762mm OD with a GRP slip lines within 672mm internal diameter. The works had to be undertaken below mature tree roots. Timber Heading in two directions within Marchmont Road into Meadows Park and out into Meadows Place to avoid RPAs and to maintain traffic flow on a major bus and emergency services route. Install a bespoke PCC bifurcation chamber/break discharge chamber. Install two kiosks: (i) MCC kiosk for pump operation, and (ii Vacflush™ kiosk for tank cleaning system. [caption id="attachment_14702" align="alignnone" width="1200"] Storm tank under construction - Courtesy of Paul Milligan & CWA[/caption] Marchmont Road FAS: Supply chain - key participants Project delivery: Caledonia Water Alliance (CWA) Designers: AECOM/CWA Shaft & timber heading trenchless work: Fineturret Ltd MEICA installation & commissioning: Ferrier Pumps Ltd Pipe drive/pipe jack: Pipeline Drillers Ltd VacFlush™: CSO Group Ltd Composite steel reinforced pipe: Aquaspira Ltd Storm tank pumps: Xylem Water Solutions Access covers: EJ Group Precast supplier: Macrete (Ireland) Ltd Temporary ground support: Groundforce Over pumping: Selwood Construction issues and carbon, cost & programme savings

Excavation within rock: Bedrock was encountered throughout the site approximately 1m below ground level. This resulted in slow digging periods for pipelaying within Marchmont Road and lengthy road closures.

Deep excavations in public space: The installation of the below-ground attenuation tank required excavations down to 17m within public green space. This has required extensive excavation support.

Trenchless construction: At both areas of trenchless construction, CWA deployed methods which preserved the mature trees in the area as required by City of Edinburgh Council ensuring compliance with the approved planning conditions and avoiding reputational damage to CWA and Scottish Water.

[caption id="attachment_14700" align="alignnone" width="1200"] Marchmont FAS project site - Courtesy of Paul Milligan & CWA[/caption]

Changes to the pipe specification within the augerbore: For the trenchless construction elements, for both safety of personnel and carbon reductions, the design was changed for DN900 ductile iron pipework to DN900 Aquaspira; a composite steel reinforced pipe. The Aquaspira pipework installed was over 7.5 times lighter per metre than the equivalent ductiile iron pipework. This allowed for the pipework to be pulled by hand along the track.

GPR pipeline installation within augerbore: There were significant carbon savings with the installation of GPR pipe, which is 10% of the weight of the equivalent diameter concrete pipework.

Removal of valve chamber: As agreed with Scottish Water during the detailed design stage, CWA designed a 5.5m wide x 5m long x 5.1m deep PCC valve chamber. The reason for this removal was that the relevant fittings and valves could be accommodated within the attenuation tank and downstream flow meter chamber. This was met with the acceptance and praise from Scottish Water as it reduced the excavation within Meadows Park, meaning a greater chance of planning approval, and a result, in carbon savings. The removal of the valve chamber for flood alleviation schemes with large diameter storage tank installation, is being promoted as a new standard for future designs.

Storm tank construction

The new storm tank will hold up to 3.5 million tonnes of stormwater, which will be directed to the tank via the new pipework. The tank fills up during a storm, and the water is pumped back into the sewer network once the storm subsides. This allows further capacity for future storm events.

The new storm tank was constructed under the Bruntsfield Links to reduce the risk of internal and external sewer flooding in the Marchmont area. CWA hit a huge milestone in March 2024, when the roof of the storm tank was lowered into place. The roof is made up from reinforced concrete beams and slabs, and weighs over 400 tonnes, covering the 15 metre wide by 20 metre deep tank.

[caption id="attachment_14701" align="alignnone" width="1200"] Storm tank roof installation - Courtesy of Paul Milligan & Caledonia Water Alliance[/caption] Interface with the public & other utilities

Due to the location of works being adjacent to property and business owners, Caledonia Water Alliance was required to maintain access to these properties at all times. This dictated the construction programme and traffic management set-up. As a result, it has also driven the construction methods of sections of the works; such as the timber heading trenchless construction.

The urban environment of the works resulted in the excavation works being in close vicinity/below other public utility providers’ assets. This has required close liaison with providers, watching briefs, vibration monitoring and change to construction methods.

Local residents have been kept informed throughout all phases of the project as well as regular one on ones with local businesses. A public information event was held in Meadows Park before the work commenced, allowing customers to discuss the upcoming project with professionals from both CWA and Scottish Water.

The dense rock breaking in close proximity to residential tenements proved challenging and expected noise levels were published on the customer notice board on a weekly basis. Extensive pre/post condition surveys were offered to all residents. Site hoarding was specially designed to include information about the project and the local history of Marchmont.  Scottish Water campaigns such as ‘Bin the wipes’ were also promoted.

Together with Scottish Water, CWA helped launch a new water ‘top-up-tap’ in Meadows Park to leave a legacy for the park users and reduce the amount of single use plastic bottles. On completion of the project, the area around the tank will be seeded with a wild meadow mix chosen by the Marchmont community.

[caption id="attachment_14697" align="alignnone" width="1200"] Customer information event - Courtesy of Scottish Water[/caption] Conclusion/summary

The next phase (five) of the project commenced on 7 July 2024 to upsize the sewers work on Marchmont Crescent. Phase 5 involves excavating within the road to install larger sewer pipes, and to install new manholes.

Due to the extensive works being carried out, traffic management will be in place to ensure the safety of customers and residents. Throughout the road closures, CWA have ensured that local business will remain open. To further minimise the impact to residents and business, all work is being conducted in short phases.

At the end of the project, CWA will fully reinstate Meadows Park and are planning to team up with the local community to plant wild meadow seeds in the area.

The project is due to be completed by December 2024.

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

Hawkchurch is a small village on the Devon/Dorset border, 3 miles north-east of Axminster and 4 miles north of the fishing town of Lyme Regis. The existing sewage treatment works was constructed in the 1980s and serves a population of around 500. It was typical of the era, with an old style Dortmund tank with percolating filter and humus tank off the back end. Final effluent is pumped from the site to an outfall into the Blackwater River. The project driver was to reduce the number of unconsented spills to the environment by providing a capacity of 45m3 storm storage and inlet works screening to remove solids and enhance the operation of the works. Project scope

At the scoping stage, Galliford Try worked closely with South West Water to establish the most cost-efficient solution when considering both operational expenditure (OPEX) and capital expenditure (CAPEX) to ensure South West Water achieved the best whole life costs. From this exercise it was established that the scope outlined below was to be included for construction on site:

A new above-ground concrete storm tank with capacity of 45m3 (exceeding the EA’s required storage volume of 40m3). New access platform to span the storm tank for washing down of the storm tank. New LCP for the control of duty/standby pump for return of effluent within the storm tank. One Jacopa wave screen to be installed on the overflow from the storm tank. One new HAIGH 590 series, 6mm 2D mechanically cleaned screen and 10mm 1D hand raked bypass screen from Haigh Engineering to be installed within existing inlet channel. The site

Access to site was challenging, as the site was only accessible via one narrow road with infrequent passing places for the larger vehicles required to get construction equipment and materials to site. Additionally, the footprint of the site was only 880m2 of which only 180m2 was usable for the construction activities.

[caption id="attachment_12435" align="alignnone" width="1200"] (left) Piling rig set up, (middle) piling reinforcement, and (right) piles cropped - Courtesy of Galliford Try[/caption] The stormwater storage tank

Prior to construction it was identified that there was contaminated water within the ground. After the initial sampling, Galliford Try requested further sampling to take place to identify if this was a one-off fuel spill or not. After the second survey, it was identified that contaminated water was still present and was an issue that required managing.

Galliford Try’s environmental team looked into the best practice options to manage this, and then engaged AGS Ground Solutions Ltd to undertake a Tier 2 survey of the site, as it was considered possible that a new fissure could be created during the piling stage which could expose the contaminated water to the environment.

Through further studies and multiple discussions around this topic, to mitigate the risk, Galliford Try utililised contaminated water handling plant and pumps from Siltbuster Ltd to manage flows. Along with this, Reconomy was engaged for the removal of any contaminated arisings.

The new storm tank was built upon twelve piles due to the strata within this area a mixture of Charmouth mudstone formed some 190 million years ago and poorly stratified angular rock with clayey hillwash. To undertake the piling, a piling mat and temporary works were required, which allowed Aarsleff Ground Engineeing to mobilise to site and install the twelve CFA piles at 450mm nominal diameter.

Throughout the piling exercise, contaminated water was managed through the Siltbuster Ltd plant, and the piling activity was successfully completed with zero impact to the local water courses.

With the piling compete, steel for the base was installed and tied into the piling reinforcement, shuttered and poured in two sections due to the need for a sump to install the return pumps. Wall steelwork was then installed up to 3m above ground and shutter pans used for the concrete pour.

Overflows from the new tank will spill into an existing chamber on the site and to screen these flows further, Jacopa Ltd fitted a new 2D wave screen to screen all flows to 6mm within the storm tank.

[caption id="attachment_12436" align="alignnone" width="1200"] (left) Base shuttered and wall starters, and (right) steelwork for base slab - Courtesy of Galliford Try[/caption] Inlet works screening

One of South West Water’s aims is for everyone to feel confident about the water at their favourite beach, river, or lake. Galliford Try have installed a number of inlet works enhancement screens on multiple sites throughout Devon as part of SWW’s WaterFit Programme, and through this have gained useful experience in installing screens whilst managing flows through to the works.

Following discussions on how to manage flows at Hawkchurch STW, a new 590 Series screen from Haigh Engineering Ltd was installed into the inlet channel. Flows are screened to 6mm, with bypass flows screened to 10mm.

Hawkchurch Storm Tank: Supply chain - key participants Project delivery, civils & MEICA: Galliford Try Ground surveys: AGS Ground Solutions Ltd Civil design: Eastwood & Partners Contaminated water handling: Siltbuster Ltd Removal of contaminated arisings: Reconomy Piling: Aarsleff Ground Engineering Tank construction: D Wall Construction Services Steelwork: GT Fabrications Wave screen: Jacopa Inlet screens: Haigh Engineering Ltd Pumps: Xylem Water Solutions Pipework: Saint Gobain PAM UK Flow meter: Siemens Instrumentation: Pulsar Measurement Kiosk: GR PRO Precision Manufacturing [caption id="attachment_12431" align="alignnone" width="1200"] (left) Jacopa wave screen in the storm tank, (top right) Inlet screen installation in the channel, and (bottom right) inlet screen in action - Courtesy of Galliford Try[/caption] Carbon savings & in-house capability

Local resources and materials were used where possible including subcontractors, which as a result provided the local economy with a financial boost during the construction phase. Where local suppliers were not available, Galliford Try strived to use off-site build solutions where possible to minimise commuting.

In-house resources that were utilised included project management, electrical design, LCP design/build, process control, and commissioning. The in-house workforce undertook  the site establishment, civil engineering, landscaping, MEICA works, and finally the demobilising the site.

Stakeholder management

At pre-construction phase, all third-party stakeholders were identified and entered onto a management plan. Galliford Try’s Customer Liaison Officer contacted all stakeholders prior to commencement to provide them with the appropriate project contacts should they have questions, queries, or complaints and to establish their requirements and desires throughout the construction phase of the works. As part of the management plan all communications where complaints or agreements are made are formally recorded, resolved, and closed out.

Conclusion

Initial progress on site was good with setting up site and setting the project up for an efficient delivery until delays were encompassed by switching the piling rig out due to the environmental considerations. Once this was managed and piling underway, the remainder of the project ran through a smooth transition and was delivered by the regulation date of 31 March 2024.

In recent years, the village of Boherbue in north-west Cork has undergone considerable expansion, resulting in increased demand for housing. This growth has presented challenges, particularly for the existing wastewater treatment facility, which has struggled to cope with the surge in population. Additionally, the plant has fallen short of the Environmental Protection Agency’s treatment standards, underscoring the pressing need for an upgrade. Of particular concern is the discharge of treated wastewater into the River Brogeen, a protected conservation area that serves as the habitat for the freshwater pearl mussel. In collaboration with Uisce Éireann (Irish Water) and Cork County Council, a comprehensive project has been undertaken to modernise and enhance the capacity of the treatment plant. This initiative not only addresses the immediate needs of Boherbue’s growing community but also ensures compliance with environmental regulations. Early Contractor Involvement

The project, delivered under the innovative Early Contractor Involvement (ECI) framework, aimed to address the overloaded and outdated infrastructure while ensuring compliance with regulatory standards and meeting the evolving needs of the community. The innovation in this project lies in its multifaceted approach to efficiently treat wastewater, reduce carbon emissions, and protect natural ecosystems.

Leveraging the ECI framework allowed for the integration of innovative solutions such as solar energy, natural sludge drying reed beds, and the preservation of existing constructed wetlands for stormwater overflow. This innovative approach not only sets a new standard for sustainable wastewater treatment but also ensures long-term environmental benefits for Boherbue and its natural surroundings.

[caption id="attachment_16527" align="alignnone" width="1200"] Google Earth image of Boherbue[/caption]

The scope of works for the upgraded facility included:

A new inlet works. A stormwater storage tank. Biological treatment processes. Tertiary solids removal cloth filtration system. Sludge drying reed beds.

A description of these key features follows.

New inlet works

An inlet works with fine screening to 6mm in 2D and a manual bypass screen to 19mm with a stone trap upstream of the screens were installed. The screens were designed to cater for the Phase 2 Formula A flows of 23.2 l/s screens are to be designed to cope with a minimum of 150% of the design capacity for works under 2,500 PE, i.e. a design capacity of 35 l/s based on the Design Formula A. The hydraulic design of the inlet works was also based on the fine screen(s) being blinded by a minimum factor of 70%. The screen selected by the ECI team was the Definitive Ecology SF/T3 in-tank screw screen, with SDACA (specially designed anti-clog auger) system to ensure compliance with the screening handling requirements.

[caption id="attachment_16526" align="alignnone" width="1200"] Inlet works preliminary treatment - Courtesy of Glanua[/caption] Stormwater tank

Flows exceeding the plant’s peak design flow, overflow by gravity (weir discharging via overflow screen) to the stormwater holding tank, which has been designed to provide a retention time of two hours for the difference between the Design Formula A and FFT flows plus 40 l/PE for SWO compliance as only 1:7.1 dilutions will be available for the WwTP effluent in the Brogeen River (based on DWF and 95th percentile river flow).

The stormwater holding tank is provided with a Eliquo Hydrok CWF flushing bell in order to automatically clean the tank once the storm flows have abated and the tank has been emptied; which is an innovative approach to this, requiring no energy input.

The CWF Storm Flush system is a highly effective non-powered cleaning system for all stormwater retention tanks, utilising the sewage stormwater for the flushing process thus requiring no additional fresh water. Storm return pumps located in a sump within the storm tank, which will reduce retention of larger volumes of waste and reduce the risk of odour.

Biological treatment processes

The secondary treatment stage for Boherbue includes the following:

Two anaerobic selector tanks with three separate selector cell volumes. Two 624m3 aeration tanks with 109m3 of anoxic volume each for denitrification. Settlement provided by two 5m diameter/3.5m side wall depth secondary settlement tanks. [caption id="attachment_16524" align="alignnone" width="1200"] Secondary aeration treatment - Courtesy of Glanua[/caption]

Each aeration tank is 15.6m length x 5m width x 4m working depth. Aeration is provided to the tanks using a fine bubble diffused aeration system designed to achieve an overall peak standard oxygen transfer rate of 66.15 kgO2/h (i.e. 33kg O2/h per cell).

The aeration system comprised three screw blowers from Kaeser Kompressoren operating on a duty/duty/standby basis, with automatic changeover of the standby blower on a time-basis; ensuring equal use of the equipment. Air from the blowers is forwarded to each aeration cell by an air header, which feeds individual branches into the aerobic cells. The diffusers are disc membrane units from Xylem Water Solutions.

Tertiary solids removal systems

Following settlement, secondary treated effluent is passed onto a tertiary solids removal treatment stage for final effluent polishing prior to discharge to the Brogeen River. The TSR process was required in order to ensure compliance with the WwDL ELVs, and in particular with the phosphorus ELV of 0.25mg/l, through coagulation/flocculation and filtration treatment.

[caption id="attachment_16528" align="alignnone" width="1200"] Cloth filter tertiary treatment - Courtesy of Glanua[/caption]

During the design stage and evaluation of the ECI team, the supplier Eliquo Hydrok was found to have the most reliable, energy and cost-efficient equipment that includes both flocculation and filtering stage. The package unit includes a flocculation stage comprised of one stream with two chambers that split into the cloth filters.

Sludge drying reed beds

The implementation of sludge drying reed beds (SDRB), which significantly increases sludge concentration to up to 40% dry solids (DS) after 10 years of operation is a key innovation. This revolutionary approach reduces sludge export volumes by more than tenfold compared to conventional methods, thereby minimising transportation and dewatering costs while substantially reducing the carbon footprint of the Boherbue WwTP. SDRB sludge can also be directly land spread without the need for additional chemical conditioning, further enhancing its environmental benefits.

There are numerous benefits in the inclusion of the sludge drying reed beds vs traditional sludge management practices. These include but are not limited to the following:

Reduction of carbon footprint of the plant by approximately 45 T over a 10-year period. Carbon capture via natural plant growth. Up to 25% organic matter removal due to mineralisation. Dewatering process completed with zero energy consumption. At full design loads, the SDRBs will remove over 49 (No.) 20,000 litre tankers from the road per annum. [caption id="attachment_16533" align="alignnone" width="1200"] Sludge drying reed beds to process wastewater sludge naturally - Courtesy of Glanua[/caption]

The construction of the sludge drying reed beds (SDRBs) commenced in early February 2023, incorporating earth embankments and precast concrete wall sections for formation. Each cell was meticulously lined to ensure water-tightness, with feed and drainage pipework installed for optimal functionality. Reeds were planted in late April to establish and grow during the summer months, aided by the importation of sludge to promote growth. This comprehensive approach ensures the effectiveness and sustainability of the SDRBs in treating wastewater and reducing the carbon footprint of the Boherbue WwTP.

Solar technology

The use of solar technology underscores the project’s commitment to renewable energy sources, contributing to further reductions in carbon emissions. By leveraging these innovative technologies and practices, the initiative sets a new standard for sustainable wastewater treatment, offering a replicable model for other treatment plants to follow. This holistic approach not only improves operational efficiency but also promotes environmental stewardship, paving the way for a cleaner and more sustainable future in the wastewater sector.

50Kw solar panels from The Low Carbon Energy Company Ltd have been installed which will produce 42,500Kwh of electricity per year. This alone will introduce a carbon saving of 13.7T/CO2 per year which shows significant savings versus a traditionally built wastewater treatment plant of this kind.

[caption id="attachment_16532" align="alignnone" width="1200"] Solar panels for clean, renewable energy - Courtesy of Glanua[/caption] Reuse of constructed wetlands

The integration of the existing constructed wetlands into the wastewater treatment facility which was core to the design development brought a multitude of benefits, ranging from low operational costs, support for diverse ecosystems as well as sustainable water management. The wetlands improve water quality of streams and rivers in surrounding area creating conditions for aquatic life to thrive, and also create a scenic area in the village, promoting biodiversity and providing a habitat for small animals.

Boherbue WwTP: Supply chain - key participants Precast concrete: Glanua Group Designers: Jennings O’Donovan & Partners Designers: Construct Engineering Precast concrete: Shay Murtagh Precast Precast concrete: Carlow Tanks Precast concrete: FLI Precast Solutions Precast concrete: Tracey Concrete PLCs & automation: UMAC Systems Inlet screens: Definitive Ecology Tertiary solids removal cloth filters: Eliquo Hydrok Ltd Aeration blowers: Kaeser Kompressoren Aeration diffusers: Xylem Water Solutions Solar panels: The Low Carbon Energy Company Ltd CWF Storm Flush system: Eliquo Hydrok Ltd Steel modular buildings: Shanette [caption id="attachment_16530" align="alignnone" width="1200"] (left) Precast concrete aeration tanks reduced construction time and safety risks and (right) view of final clarifiers and cloth filters - Courtesy of Glanua[/caption] Innovative construction methods

Throughout the entire design process, Glanua Group and Uisce Éireann’s PMO team evaluated several project aspects such as energy efficiency (BEP), TOTEX costs, and environmental impact.

Energy efficiency of all motors and equipment (BEP). Process and equipment selected on TOTEX costs (including CAPEX, OPEX and capital replacement at end of life). The impact to the local environment was carefully assessed for all design options considered during the planning phase. Modular and off-site construction

Modular/off-site construction was used to reduce the carbon footprint and on-site safety risks, with precast panels and BCAR-compliant steel modular buildings used to promote efficient delivery and enhance safety.

Precast panels were instrumental in constructing the main aeration tank, reducing construction time and mitigating safety risks compared to traditional in situ methods. Precast wall sections were used to separate the sludge drying reed beds sections to reduce the footprint size and again to reduce construction time and safety risks. Throughout the project, precast process tanks were used extensively contributing to streamlined construction processes and improved safety measures.

A BCAR-compliant steel modular building from Shanette was used for the control room, laboratory, and caretaker’s office facilities. This has a significantly lower carbon footprint than that of a conventional block-built structure and in turn reduced health and safety risks significantly during construction due to fabrication being completed before assembly on site.

[caption id="attachment_16529" align="alignnone" width="1200"] Off-site fabrication of steel building, fully assembled as works have been completed (April 2024) - Courtesy of Glanua[/caption] Sustainability

The construction of the Boherbue Wastewater Treatment Plant is an example of Uisce Éireann and Glanua Group’s commitment to sustainability across various dimensions, including environmental, social, and economic considerations.

The inclusion of sludge drying reed beds demonstrates dedication to environmental sustainability. These beds offer an innovative solution for sludge management, reducing the environmental impact of waste disposal while also providing opportunities for ecological conservation.

By using nature-based solutions to treat and manage sludge, the carbon footprint associated with traditional disposal methods is minimised; thereby mitigating environmental harm. The SDRBs also significantly reduces operational costs, providing a long-term cost-effective solution.

The integration of solar technology underscores the commitment to renewable energy and carbon reduction. By harnessing solar power to supplement the energy needs of the wastewater treatment plant, reliance on fossil fuels is reduced, contributing to the transition towards a more sustainable energy future. This not only reduces operational costs but also mitigates greenhouse gas emissions, thereby supporting climate action efforts and environmental preservation.

Socially, the decision to reuse the existing wetlands demonstrates dedication to maintaining and sustaining biodiversity in the Boherbue community. By incorporating natural elements into the design, not only is disruption to local ecosystems minimised, but also to the overall health and vitality of the local environment.

Darran O’Leary, Programme Manager at Uisce Éireann said:

“We are delighted to have delivered this important project for the community of Boherbue. The modernisation and improvement of the wastewater infrastructure will accommodate further growth in the area and ensure that cleaner and safer treated wastewater is being discharged into the Brogeen River.

“It also adds biodiversity value to the area and remains sensitive to the surrounding landscape. This, coupled with the use of solar energy, demonstrates our commitment to putting sustainability at the heart of everything we do”.

Boherbue WwTP upgrade works is a flagship project for sustainable and carbon saving treatment processes and will serve as a reference project for future similar projects within the industry.

By demonstrating the feasibility and benefits of integrating renewable energy, advanced treatment technologies, and ecological conservation practices, this project sets a precedent for industry-wide innovation and best practices.

It complies with stringent Environmental Protection Agency (EPA) discharge consent standards, while minimising impact on the existing landscape, demonstrates a commitment to environmental sustainability, operational efficiency, and community well-being, making it a catalyst for positive change within the wastewater treatment sector and beyond.

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

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

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

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

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

SDS Ltd has completed the installation of its latest smart rainwater management systems at homes in Forton, Lancashire, and Deal, Kent, as part of Water Companies’ ongoing efforts to reduce sewage spills into rivers and the sea. The company’s Intellistorm®-equipped rainwater harvesting tanks use smart technology to retain and release their contents automatically, thereby increasing, by several times over a standard water butt, their capacity to protect the sewers from being overwhelmed by excess surface water from heavy rainfall. More than sixty systems have already been installed by agreement with homeowners by SDS in January and February 2023 for United Utilities and Southern Water. The two Water Companies have committed to deploying several hundred tanks over the next few weeks, including at properties served by United Utilities at Wrea Green in Lancashire, and by Southern Water at homes in its “Pathfinder” locations in Kent and the Isle of Wight. Intellistorm® works by releasing water from the tank prior to rainfall. By analysing weather forecast data the system calculates how much water to release based on the roof size and the size and location of the tank. This ensures that there is always water available for homeowners to use, for example in their gardens, but also sufficient spare capacity in the tank to accommodate the next rainstorm. A typical water butt fills once in the winter and then remains full and overflows until water is taken out by the homeowner, often only when summer has arrived. Consequently, a standard butt contributes little to holding back water from sewer networks during the wettest months of the year. SDS has carried out an assessment of the performance data supplied by the initial 25 tanks at Forton after their first month of operation. Extrapolated across 12 months, and using average rainfall statistics, it has been established that the tanks could hold back up to 75 times their nominal volume, equivalent to each tank holding back 30,000 litres of water a year from the combined sewer at times of peak flows, which is when sewers typically overflow. In Forton alone this equates to a surface water attenuation volume of up to three quarters of a million litres of water per year*. That water is then released once the rain event has passed and the sewers can cope. [*based on average rainfall accumulations – these figures will vary if the weather is drier or wetter than the average]. Johnny Phillips, Surface Water Strategy Development Manager for United Utilities, said:

“We’re delighted to be launching this initiative in Forton. Having looked at a number of areas, we think the smart water tanks will make a real difference in the village and help to increase capacity in our sewer network and deliver local environmental improvements, and the early findings are backing this up.”

Dr Neil Sewell, Director of New Technology Services at SDS, said:

“We’ve made exciting enhancements to the Intellistorm® technology since our early projects with South West Water, Anglian Water and Severn Trent Water and we’re pleased to show how the latest version of the tanks begins to deliver some really strong performance in Forton and Deal.”

These projects show that Intellistorm®-equipped smart tanks have the potential to be a really valuable tool for Water Companies in the battle against sewer overflows and flooding, particularly when they are coupled with other sustainable drainage systems and sewer network improvements. They have the added advantage of providing a supply of non-potable water for homeowners, thus reducing the demand for mains-supplied, drinking-quality water for purposes for which its high level of treatment is not required, whether that’s for watering the garden and washing the car or even flushing the toilet and supplying the household washing machine. It is also a great way for local people to get involved with helping to solve flooding and pollution, thereby improving water quality in our rivers and bathing waters, as well as protecting the country’s declining natural water resources from over-abstraction, in order to feed a growing and increasingly water-dependent population. Thanks to their multiple benefits SDS is seeing significant interest from Water Companies in its Intellistorm® systems.     For more information: SDS Ltd | +44 (0)1934 751303 | www.sdslimited.com