Supply Chain - Sewerage - Pressure Testing

Portadown is a large town in County Armagh, Northern Ireland located approximately 24 miles south-west of Belfast and nestled along the banks of the Upper River Bann. Over recent years, Portadown has transformed from a historically industrial town into a modern hub with a rapidly growing logistics sector and retail environment attracting high footfall and continued economic growth. Meadow Lane Wastewater Pumping Station (WwPS), located within the central retail area of the town, was constructed in 1966. The site forwards flow to a downstream gravity sewer system before subsequently flowing into the southern inlet of Seagoe WwPS, approximately 1.5 miles away. Need for upgrade

Meadow Lane WwPS was identified as requiring significant base maintenance interventions due to the antiquated nature and condition of existing pumps, pipework and control assets which require a high level of maintenance; thus, imposing a risk of potential significant failure. The following observations were made on site:

Existing pumps showed signs of extensive wear (supported by observed power loadings). Control motors were identified as being installed pre-1975. The existing motor control centre (MCC) did not satisfy current asset standards.

NI Water Technical Support had also advised of occurrences of flooding within the dry well as a direct result of leaking pumps which required reactive maintenance and tankering operations.

Additionally, following completion of the 2007 Portadown Drainage Area Study, Meadow Lane WwPS was identified as a required output. It was outlined to NI Water the need for the existing Meadow Lane WwPS to deliver flow to full treatment (FFT) if the upstream network spill performances are to meet the Northern Ireland Environment Agency (NIEA) requirements for the Meadow Lane catchment area.

[caption id="attachment_26864" align="alignnone" width="1200"] Secant piles with reinforced concrete capping beam - Courtesy of BSG Civil Engineering Ltd[/caption]

Model updates were completed in 2016 following flow monitoring surveys, and further inspections confirmed that the existing pumps could not deliver the required FFT. Therefore, the five CSOs identified by the NIEA as Unsatisfactory Intermittent Discharges (UIDs) could not be closed without significant intervention/upgrade at Meadow Lane WwPS. Model updates were also completed in 2020 to reflect predicted future 2040 flows.

The NIEA had identified the following five CSOs as UIDs:

Meadow Lane One CSO. Meadow Lane Two CSO. Portmore Street CSO. Clonavon Avenue CSO. Meadow Lane Health Centre CSO.

Failure to address spills would lead to potential prosecution by NIEA and associated reputational damage due to potential serious sewage flooding and pollution to the Annagh River, Upper River Bann and the surrounding area.

Early Contractor Involvement (ECI)

NI Water appointed BSG Civil Engineering Ltd as the main contractor under an NEC3 Early Contractor Involvement (ECI) Contract. As the main contractor, BSG provided multi-disciplinary design, project and supply chain management and civil engineering and MEICA works for the contract from inception to completion.

The ECI phase allowed BSG to align resources and integrate objectives with the client, NI Water, and project managers, McAdam, at an early stage to benefit overall project delivery. This allowed for enhanced collaboration, innovation, value, efficiency and reduced whole life cycle costs for the project.

[caption id="attachment_26863" align="alignnone" width="1200"] Liner wall formwork using Peri Rundflex - Courtesy of BSG Civil Engineering[/caption] Meadow Lane WwPS: Supply chain - key participants Project delivery: BSG Civil Engineering Ltd Civil, hydraulic & process designer: McAdam Temporary works design: MEA Ltd Earthworks: BSG Civil Engineering Ltd Specialist piling contractor: Quinn Piling Limited Formwork: Peri UK Reinforced concrete works: ONCCE Ltd Tunnelling contractor & TBM: B&W Tunnelling Ltd Open cut pipe installation: Phace Contracts Ltd Open cut pipe installation: O’Neill Contracts & Plant Hire Open cut pipe installation: AG Wilson Civil Engineering Groundworks: RMG Metalwork & FST designer/installer: RJ Smyth Engineering Precast roof beams: Macrete (Ireland) Ltd Precast roof slabs: Creagh Concrete Precast concrete pipes: Tracey concrete Screens: Eliquo Hydrok Ltd Submersible pumps & float switches: Xylem Water Solutions Flow meters: Siemens Control panels: Motrol Ltd Kiosks: Quinshield Ltd Primary drivers

The purpose and drivers of this project were as follows:

Ensure a reduction in spill frequency and volume through the provision of adequate storage facilities within the Meadow Lane catchment area. Closure of the five unscreened UIDs (identified by the NIEA) and subsequent provision of sewer upgrades in the upstream catchment to transfer flows from the closed UIDs and provide online storage. Resolution of three DG5 properties within the Meadow Lane area. Essential replacement of Meadow Lane WwPS with provision of a screened emergency overflow. [caption id="attachment_26865" align="alignnone" width="1200"] Pouring of 400m3 base slab - Courtesy of BSG Civil Engineering[/caption] What the upgrade involved

The upgrade of Meadow Lane WwPS and the associated network was a large-scale infrastructure project located within a complex urban environment. The project saw:

The installation of 380m of 1,500mm diameter tank sewer approximately 7m below ground level. The installation of 350m of sewers ranging in diameter from 300mm to 1500mm via open cut techniques in depths ranging from 2m to 7m below ground level. The demolition of the existing Meadow Lane WwPS. The construction of a new inlet chamber, wet well pumping station and 1,500m3 storage tank at the existing Meadow Lane WwPS site. The installation of a new MCC panel and associated glass reinforced plastic (GRP) kiosk. The installation of three 37kW foul pumps and two 9kW hydro ejectors. The installation of three screens from Eliqua Hydrok Ltd. The closure of five unscreened UIDs. 1,500mm tank sewer installation

Meadow Lane is an arterial route through Portadown town centre, providing access to several shopping facilities, restaurants and medical facilities. It was identified that significant traffic management, potentially involving lengthy diversions, would be required for an extended period to undertake the installation of the 1,500mm diameter tank sewer along Meadow Lane using open-cut methods.

[caption id="attachment_26861" align="alignnone" width="1200"] Pipejacking operation within launch pit - Courtesy of BSG Civil Engineering[/caption]

Therefore, it was determined that a trenchless pipejacking method of installation would be adopted to install the full 380m of 1,500m tank sewer. Additionally, the use of a tunnel boring machine (TBM) would allow for a reduced potential environmental impact due to the reduction in surface disruption, dust, noise and vibrations; and provide enhanced safety for construction staff due to the automated installation process.

Due to the unstable ground conditions, a closed face slurry system was used as this technique allowed the area around the TBM to be supported with a pressurised bentonite mix, preventing collapse and ensuring stability. During this process the excavated material was pumped from the face of the TBM, through the installed tunnel, to an above-ground separation system where the excavated material was removed from the bentonite mix, allowing it to be recycled and returned to the tunnel face for reuse.

The tunnelling operation was undertaken in three stages with launch and reception pits installed to facilitate each drive stage alongside ancillary tunnelling operations; drive stages varied in length between 70m to 230m. Due to the varying and difficult ground conditions present along the proposed tunnelling route, launch pits and reception chambers were installed using a combination of both segmental shafts and traditional cofferdams.

Storm retention tank, inlet chamber & wet well pumping station

The storm retention tank, inlet chamber, and wet well pumping station was designed as one structure. Due to the difficult ground conditions, high water table and proximity to existing NI Water assets, it was determined that secant piling would be implemented as a means of providing temporary support to facilitate safe excavation.

[caption id="attachment_26853" align="alignnone" width="1200"] Installation of concrete beams - Courtesy of BSG Civil Engineering Ltd[/caption]

A specialist piling contractor was utilised to install 140 (No.) 750mm diameter secant piles to a depth of 18m below ground level before the installation of a reinforced concrete capping beam to complete the excavation support system. Once installed, the secant piled wall provided a watertight structure. Localised dewatering within the secant piled structure was used to ensure excavated material remained dry and suitable for reuse on site. Approximately 3500m3 of material was removed from the 21m diameter, and 10m deep excavation.

Construction of the storm tank consisted of a 1200mm deep reinforced concrete base, a 400mm thick external liner wall, and a 500mm internal dividing wall. The liner wall formwork was designed as a single sided system using Peri Rundflex and constructed in two lifts to meet temporary works restrictions.

The roof structure was constructed using 1250mm by 900mm precast beams and 450mm thick precast hollow core slabs. Structural screed was then poured to complete the structure.

The complex roof slab arrangement consisted of a variety of construction techniques including in situ reinforced concrete elements, precast concrete primary and secondary beams, structural steel beams and hollow core precast slabs. The complete design of the roof structure was provided by five different design companies working in collaboration ensuring each element adhered to the tight tolerances required for accurate placement.

Open cut sewer installation

Six sections of open-cut sewer installation were completed in this scheme. Boxed systems were used to provide temporary works excavation support for the pipe installations. Sewers were installed to depths of up to 7m below ground level in sites with limited working room. Traffic flows were controlled by complex traffic management systems.

[caption id="attachment_26858" align="alignnone" width="1200"] Open cut sewer installation at Manhole No. 4 - Courtesy of BSG Civil Engineering Ltd[/caption] MEICA installation

The MEICA installation was completed in two stages. A new MCC was installed within the new GRP kiosk, and once all building services were installed, the NI Electricity supply was diverted to the new MCC panel which then backfed a supply to the existing MCC panel until turn of flows in April 2025.

Once civils construction had sufficiently advanced, the second phase of the mechanical fit out commenced, where the three 37Kw foul pumps and associated pipework were installed from the foul pumping station to the flow meter chamber. A 250mm Siemens MAG 5100w was then installed to measure the outgoing flow-rate. Two pump stools, 9Kw hydro ejectors and pipework were installed within the storage tank to jetwash the tank during storm events.

Three Eliquo Hydrok Ltd screens were installed into the following areas:

Inlet screen chamber: 600l/sec Mecmex™ screen. Foul pumping station overflow screen chamber: 70l/sec static Peak Screen™. Storage tank overflow screen: 264 l/sec static Peak Screen™. [caption id="attachment_26855" align="alignnone" width="1200"] Pump remote enclosures and actuators - Courtesy of BSG Civil Engineering[/caption] Additional construction challenges

The main challenges faced during the delivery of Meadow Lane WwPS were a combination of site-specific constraints, environmental constraints and equipment/asset failures during the construction period. Some of the additional challenges experienced during the construction stage have been outlined below.

Portadown has been identified within the Northern Ireland Flood Risk Management Plan as an area of significant flood risk, due to regular fluvial flooding from the Upper River Bann and its tributaries. The most recent significant flood event was recorded in 2024, which saw substantial flooding across the entire work site. This fluvial flood event led to a halt in works on site for approximately one week and caused damage to plant.

The 500mm diameter outlet pumping main from the existing Meadow Lane Pumping Station ruptured on two occasions during the construction programme. To carry out the repair on the outlet pumping main, both Meadow Lane and Annagh WwPS had to be shut down and seven tankers were mobilised to transfer effluent to other NI Water treatment facilities. BSG Civil Engineering Ltd was able to utilise the newly constructed storm tank to create temporary storage and prevent any out-of-sewer flooding during the emergency repair works. BSG received positive feedback from NI Water on how these critical network emergency repair works were managed and rectified in a safe, collaborative and timely manner.

[caption id="attachment_26857" align="alignnone" width="1200"] (left) Fluvial flooding event in 2024 within the site compound, and (right) utilising the new storm tank for temporary storage following an outlet pumping main failure - Courtesy of BSG Civil Engineering Ltd[/caption] Stakeholder communication

NI Water and the project team recognised the potential negative impacts which could arise from undertaking such a large-scale project within a busy town centre location and from an early stage embarked on a strategic communications strategy to ensure key stakeholders were informed of the works and kept updated throughout.

As part of the public relations programme the project team and NI Water Communications held early briefings with a range of stakeholders including elected representatives, town centre management, chamber of commerce, health care centre, council, roads authority, landowners and local businesses.

In addition to the numerous one-to-one meetings, letter drops were carried out in advance of each section of road works commencing and press releases issued to the local media to advise the wider public of traffic management. Variable message boards were erected on main routes and large-scale project boards helped to convey the huge investment being made by NI Water and the resulting benefits for the public.

Key project milestones were publicised along with facts and figures relating to the construction work and tunnelling exercise.

Regular project updates and lookahead bulletins were issued to stakeholders to keep them up to date on progress and advise them of future traffic management requirements. Town centre management were invited to site at key stages of the project to view progress and hear firsthand about the benefits the NI Water investment will bring to Portadown.

BSG provided a point of contact for operational queries and this, along with NI Water’s wider stakeholder communications, helped to ensure a smooth-running construction programme.

[caption id="attachment_26859" align="alignnone" width="1200"] Completed Meadow Lane WwPS (July 2025) - Courtesy of BSG Civil Engineering Ltd[/caption] Outcomes

NI Water directed significant financial investment into upgrading the existing sewer network and Meadow Lane WwPS within the Meadow Lane area of Portadown. The proposed works oversaw the closure of five CSOs within the Meadow Lane WwPS catchment area through connection into the new 1,500mm tank sewer alongside the resolution of three DG5 properties.

The collaborative effort between NI Water, BSG Civil Engineering Ltd and McAdam resulted in the smooth completion of the programme and successful testing, commissioning and handover to NI Water in July 2025. The benefits of the new infrastructure will be realised almost immediately through a reduction in spill frequency and volume within the Upper River Bann and Annagh River.

This project showcased the capabilities of NI Water, BSG Civil Engineering Ltd and McAdam to coordinate and undertake sensitive high-risk activities such as a large-scale turn of flow without issue and within a complex urban environment.

Newthorpe Sewage Treatment Works, in the Erewash Valley in Nottinghamshire, is undergoing a major expansion. The new works will duplicate its current capacity, from 324 l/s and 41,000 population equivalent (PE) to 649 l/s and 100,000 PE, to receive the flows of the Heanor Milnhay STW catchment area. A 2.5 km dual-rising main will connect both sites. Heanor Milnhay STW, a dual-stream site in Derbyshire currently treating 258 l/s (41,000 PE), has reached its maximum capacity and its geographical location makes it impossible to cope with the projected population growth. The process will be decommissioned, and the site will be re-purposed to hold a storm storage capacity that exceeds the current storm storage capacity by more than three times. The client, Severn Trent, and Mott MacDonald Bentley, principal designer and contractor, are the main stakeholders of this project. Project objectives The main project objectives align with the current social and economic environment. With the expansion of the works, Severn Trent is aiming to: Improve the effluent quality, especially phosphorus content. The new site will reduce the phosphorus concentration in the effluent from 2 mg/l to less than 0.2 mg/l. Reduce the running costs and maintenance costs of the plant by merging two sewage treatment works and using a less-intensive chemical usage treatment process. Reduce the non-treated sewage spillage by increasing the stormwater storage capacity at Heanor from 2,200m3 to 7,000m3. Additionally, all the storm flows will be preliminary treated by physical screening and settlement. [caption id="attachment_18498" align="alignnone" width="1200"] Newthorpe STW: (left) site compound and storage, (top) existing site, and (bottom) the new expansion (August 2024) - Courtesy of MMB[/caption] Process description: Preliminary & primary treatment

Once the expansion is completed, Newthorpe flows and Heanor flows will have separate preliminary and primary treatment streams, before combining in the secondary treatment stage.

Flows from the Newthorpe catchment will arrive at the existing inlet works. This area will stay as per the current arrangement and only the mechanical equipment will be upgraded. The flows are lifted using Archimedes screw pumps to a raised inlet works structure.

This structure holds the fine screens, which are designed to capture at least 80% of all the solids above 6mm. After the screens, a detritor will settle all grit and inorganics such as sand; removing them from the process stream to avoid damage to the mechanical equipment.

The wastewater from the catchment then flows to the primary treatment area, where the first physical separation of particles using gravity to settle the fines at the bottom of the two existing primary settlement tanks is carried out.

The effluent from the primary settlement tanks, that is currently connected to a secondary treatment consisting of trickling filters and hummus tanks, will now be diverted to the new works’ expansion.

Flows from the Heanor catchment area that arrive at Heanor will be pumped 2.5km to a newly build inlet works at Newthorpe. Similar to the existing inlet works, the new inlet works will feature 2D 6mm screens provided by Longwood Engineering Company Ltd and a 4.5m detritor provided by Tuke & Bell Ltd.

[caption id="attachment_18497" align="alignnone" width="1200"] Heanor flows inlet works (August 2024) - Courtesy of MMB[/caption]

After the detritor, the flows merge, without having been settled, with the Newthorpe flows. Keeping the Heanor flows unsettled is key to provide the right load for the process to work.

Process description: Secondary treatment

The main biological treatment happens in this secondary stage, where the aim is to reduce to the consented levels certain parameters such as Phosphorus, ammonia, iron and suspended solids. The process selected for Newthorpe is an enhanced bio phosphorus removal process in a modified University of Cape Town (UCT) configuration.

The first stage in the process is the anaerobic zone, where the polyphosphate-accumulating organisms (PAOs) thrive in an environment with no oxygen nor nitrogen introduced. In this stage, the PAOs accumulate volatile fat acids which will help them being biologically competitive in the aerobic phase of the treatment.

The next stage is the anoxic zone, where recirculated active sludge (RAS) from the secondary settlement process is introduced.

[caption id="attachment_18495" align="alignnone" width="1200"] Enhanced Bio Phosphorus Removal UCT configuration - Courtesy of MMB[/caption]

This RAS recirculates the bacteria through the system as well as introduces nitrogen oxides which have been created in the aerobic section by the oxidation of ammonia (NH4). In this anoxic zone, the nitrogen oxides are transformed into nitrogen gas which escapes to the atmosphere.

The third stage of the process is the aerobic zone in which air is introduced. Under these conditions, three main processes concur:

The nitrification process, where ammonia is transformed into nitrogen oxides which then are degraded to N2 in the anoxic zone as previously mentioned. To carry out this process, the bacteria need energy which they obtain from the organics load in the sewage. The PAOs previously mentioned consume the VFAs accumulated in the anaerobic zone to accumulate phosphorus. The phosphorus accumulated at this stage is larger than the phosphorus released in the anaerobic stage, hence producing enhanced bio-phosphorus removal.

The final stage of the secondary treatment is the secondary sedimentation on the final settlement tanks, where the rich-P sludge is removed from the system and either recirculated to the anoxic zone; or thickened and wasted to produce other products such as gas and cake on sludge digestion processes.

Process description: Tertiary treatment

The final stage of the process aims to further reduce the P levels in the effluent by capturing non-organic phosphorus.

Ferric sulphate is dosed upstream of the tertiary solids removal unit to cluster the particles into larger floccules that are then removed by a physical filtration system. The system selected in Newthorpe is FilterClear (mixed media filtration), designed and manufactured by Bluewater Bio Ltd. Once commissioned it will be the largest FilterClear system in wastewater treatment.

[caption id="attachment_18502" align="alignnone" width="1200"] Installation of the tertiary solids removal units (August 2024) - Courtesy of Mott MacDonald Bentley[/caption] Delivering innovation

MMB and Severn Trent will be working together during the commissioning of the plant to understand the emissions of greenhouse gases in sewage treatment works and how to optimise the plan to reduce them. Instrumentation to measure NO and N2O will be installed on the ASP.

Nitrous oxide is produced during the biological removal of ammonia in nitrifying ASPs. Monitoring nitrous oxide emissions (along with nitrite) during commissioning at Newthorpe will not only provide STW with a baseline process emissions factor (EF) for the site but also with valuable insights into the mechanisms resulting in nitrous oxide production.

Newthorpe STW: Supply chain - key participants Client: Severn Trent Principal designer & contractor: Mott MacDonald Bentley CFD analysis, planning, mining studies: Mott MacDonald CFA piling: Van Elle ASP FRC: Bell Formwork Services Ltd Inlet works FRC: TCL Structures UK Ltd Design/build of FRC final settlement tanks: Tank Consult Ltd Rising main HDD: Johnston Trenchless Solutions (JTS) Mechanical installation: Alpha Plus Ltd Electrical installation: Main Electrical Inlet screens: Longwood Engineering Company Ltd Grit removal plant: Tuke & Bell Ltd Scraper bridges: EPS Water Glass-coated steel tanks: Goodwin Tanks MCCs: CEMA Ltd Aeration diffusers for ASP: Xylem Water Solutions Polymer dosing: Richard Alan Engineering Alkalinity dosing: Lintott Control Systems Ferric dosing: Colloide Mixers, blowers & submersible pumps: Sulzer Pumps Wastewater Ltd Progressive cavity pumps: NOV Booster pumps: Grundfos Tertiary solids removal: Bluewater Bio Ltd Gravity belt thickeners: Alfa Laval Kiosks: Morgan Marine Steel buildings: LGSF Valves: AVK UK Ltd Penstocks: Waterfront Fluid Controls Ltd Lifting equipment: T Allen Engineering Services Ltd Steelwork & storm distribution chamber: GT Fabrications Steelwork: GWH Fabrications Ltd Steelwork & GRP platforms: APT Marine Engineering Ltd FE monitoring: Servitech International Fencing: Town & Country Fencing (Midlands) Ltd [caption id="attachment_18499" align="alignnone" width="1200"] Heanor site overview (September 2024) - Courtesy of MMB[/caption] Progress: Heanor STW

At Heanor, the main structure, which is the new transfer and storm pumping station structure, is currently in its final stages.

The design of the structure was a challenging process where the proximity of nearby structures and the groundwater were the main constraints. The final structure consists of a wall of secant piles by Van Elle, which has been incorporated into the permanent structure. This secant pile provided a cut-off for groundwater that was key to delivering the pumping station installation safely. The blind tank, which is a 1,700m3 glass-coated steel tank provided by Goodwin Tanks Ltd, has been completed in September 2024. The slab and all drainage pipework are now completed. A steel storm distribution chamber fabricated by GT Fabrications is being manufactured and will be installed in October 2024. Finally, the MCC has been installed and powered in September 2024.

The site will be operational in its final configuration by December 2024 to meet the regulatory requirements.

Progress: Rising main

The 2.5km 450mm dual rising main connecting Heanor STW to Newthorpe STW is now completed by with only the pressure testing and its final connection to Newthorpe STW pending. The rising main will be ready to transfer flows in October 2024, to aid with the EBPR maturation process ahead of the regulatory commitment.

The route of the rising main crossed several historical mine sites. MMB’s geotechnical team conducted an investigation to understand the status and position of the mine entries and any other mine-related features along the route. Additionally, a watching brief was in place to quickly identify any non-natural ground features.

Thanks to this effort all the risks were mitigated, and the rising main was safely constructed by Johnston Trenchless Solutions.

[caption id="attachment_18503" align="alignnone" width="1200"] Rising main site just outside Newthorpe (August 2024) - Courtesy of MMB[/caption] Progress: Newthorpe STW

At Newthorpe, all major civil structures are completed, and on the site, a major operation of backfilling, electrical and mechanical installation is currently ongoing.

Inlet works: The new Heanor flows inlet works structure was built by TCL Structures UK Ltd, with the new 2D 6mm screens being provided by Longwood Engineering Company Ltd and a 4.5m detritor being supplied by Tuke & Bell Ltd. Final settlement tanks: The three 33m FSTs built by Tank Consult Ltd with full scraper bridges provided by EPS Water are now complete. Activated sludge plant: The four-lane ASP built by Bell Formwork & Civil Engineering Services Ltd is also complete. The aeration grid and pipework supplied by Xylem Water Solutions, the blowers and the mixers from Sulzer Pumps Wastewater Ltd, and the tank steelwork from GT Fabrications has all been installed. Chemical dosing: The four tanks of the chemical dosing area are now installed. The ferric dosing system was provided by Colloide while the alkalinity dosing system is provided by Lintott Control Systems Ltd. Site buildings: The Newthorpe site is changing rapidly and at the end of September 2024, the building that will house the Alfa Laval gravity belt thickeners and the Richard Alan Engineering polymer dosing plant, has been erected by LGSF. Tertiary treatment plant: The four Bluewater Bio Ltd FilterClear tertiary solid removal vessels are now installed on site. All ancillaries such as pipework and service tanks are currently being installed and the TSR plant will be ready to start commissioning in November 2024. Motor control centre: The MCC that will be controlling the expanded works was provided by CEMA Group and is housed in a kiosk manufactured and installed by Morgan Marine. All the electrical installation on site is being carried out by Main Electrical. [caption id="attachment_18500" align="alignnone" width="1200"] Sodium hydroxide (left) and ferric sulphate (right) dosing systems(August 2024) - Courtesy of MMB[/caption] An award-winning project

In 2024, the Newthorpe STW expansion project has been awarded two Green Apple Awards in the categories of Building & Construction and Sustainable Water Management. The project also won the first Ground Engineering Awards for MMB for the UK Project with a Geotechnical Value of between £500k and £1m.

Conclusion

Newthorpe STW and Heanor Milnhay STW have been merged in one of the major AMP7 Severn Trent projects, with Mott MacDonald Bentley as principal designer and contractor. The expansion to Newthorpe STW will be one of the largest enhanced bio-phosphorus treatment sites in the region covering a population equivalent of 100,000 and will achieve a tightened permit of 0.2 mg/l, whilst minimising the use of chemicals to remove phosphorus.

The project is currently on track to achieve the biological maturation of the EBPR by its regulatory date in December 2024.

Located next to Cricket Inn Crescent in Sheffield, the existing combined sewer overflow (CSO) is a brick-built, unscreened chamber with 375mm combined inlet, outlet, and overflow pipes discharging to a nearby surface water system flowing into the River Don. Flagged as a high-priority site under Yorkshire Water’s Sewage Spill Reduction Programme, it faced frequent and high-volume spills. The goal was to cut annual discharges from 41 to just nine, improving downstream water quality and meeting environmental targets. While the initial plan called for a storm tank with rising main return, detailed investigations and collaboration with specialist partners led to a more sustainable, cost-effective, and safer alternative, delivering the same results with added long-term operational and environmental benefits. Engineering a smarter solution for network efficiency

Site investigations uncovered critical flaws in the existing CSO system’s design and performance. Poor pipe alignment and high-velocity incoming flows caused hydraulic inefficiencies, leading to premature overflows across the benched weir wall, triggering spills before the downstream network could be fully utilised.

These findings enabled the development of an improved, gravity-based solution that eliminated the need for a pumped return shaft and its associated infrastructure. This strategic shift brought multiple benefits: simplified construction, lower operational costs, and significantly improved sustainability.

[caption id="attachment_24477" align="alignnone" width="1200"] 3D internal plan render of CSO chamber including screen from Huber Technology - Courtesy of Galliford Try[/caption]

A new WaPUG-compliant CSO chamber was proposed, designed around industry best-practice principles. Crucially, the design enabled the integration of a motorised screen from Huber Technology, addressing a key shortfall in the previous setup, which lacked any screening. The new screen removes gross solids and high-impact pollutants, dramatically improving discharge quality.

Compared to the original plan, the revised solution offered clear advantages:

Lower design, construction, and operational costs. Reduced need for temporary works and heavy machinery. Shallower excavations, improving health and safety. Lower material use and simpler site logistics.

In parallel with the redesign, Galliford Try worked closely with hydraulic modellers to validate the concept and optimise key design elements. The CSO’s inlet was upsized to a 900mm pipe laid at a shallower gradient, with a 225mm dry weather flow (DWF) channel to maintain self-cleansing conditions and improve flow control. A new weir wall and realigned twin continuation pipes (225mm and 400mm) were installed alongside a reconfigured overflow connection, eliminating the risk of early spills and boosting hydraulic efficiency.

Hydraulic modelling confirmed the effectiveness of the new design. Annual spill events are projected to drop from 41 to just nine; a 75% reduction in spill volume, which is equivalent to approximately 20,000m3 of unscreened discharge avoided over 10 years. The remaining spills will now pass through a high-efficiency, Rotamat RoK2/300-1000 storm screen from Huber Technology; significantly enhancing discharge quality.

[caption id="attachment_24478" align="alignnone" width="1200"] 3D external render of CSO chamber - Courtesy of Galliford Try[/caption] Cricket Inn Crescent CSO: Supply chain - key participants Design Consultant: GHD Delivery contractor: Galliford Try Main works subcontractor: Carter Taylor Civil Engineering Pipe jack tunnelling: KIAMM Ltd Hydraulic modelling specialist: RES Environmental Temporary works/shoring: Mabey Hire Ltd Electrical contractor: Main Electrical Ltd Control panel & enclosure: Bridges Electrical Engineers Ltd Motorised screen supplier: Huber Technology HDPE CSO supplier: NOV Fiber Glass Systems HDPE pipes: Polypipe Bespoke chamber covers: Steelway Brickhouse Vegetation management: Landscape Maintenance Services Innovative off-site construction enhances efficiency & safety

With a robust design finalised, the team evaluated construction methods to identify the most efficient and low-risk approach. The solution was for off-site prefabrication of the CSO chamber by NOV Fibre Glass Systems; experts in bespoke, factory-built infrastructure.

This strategy delivered major benefits across quality, safety, and programme delivery. Manufacturing the chamber in a controlled environment ensured precision, enabled more complex design features, and significantly reduced on-site works. Constructed entirely from high-density polyethylene (HDPE), a lightweight, durable, and chemically resistant material, the chamber was delivered fully assembled, complete with benching, pipe penetrations, electrical ducts, and weir walls.

[caption id="attachment_24483" align="alignnone" width="1200"] Completed off-site manufacture of prefabricated CSO chamber - Courtesy of Galliford Try[/caption]

A key innovation was the pre-installation of the Rotamat RoK2/300-1000 screen from Huber Technology within the chamber, reducing on-site risks and complexity. The use of HDPE not only supported a durable design, but also improved on-site safety. Its lightweight properties reduced the need for heavy plant and simplified lifting operations. Integrated dry weather flow (DWF) channels within the pipework further eliminated confined space working typically required for installation.

For the 900mm pipe section, a trenchless auger bore technique was used, avoiding disruption to critical underground utilities, including high-voltage cables, a medium-pressure gas main, and a water main, significantly lowering risk to operatives in a complex urban setting.

Long-term operability was a key design focus. Through hazard studies and access, lifting and maintenance reviews, the team engaged with future maintenance crews to incorporate ergonomic and safety-focused features. This included bespoke access hatches and fall-arrest grilles, allowing routine maintenance without the need for confined space entry.

Careful planning of temporary works and sequencing reduced the need for live sewer connections and exposure to high-flow sewage environments, further improving safety.

Programme delivery was accelerated through parallel workflows, off-site fabrication progressed alongside on-site pipe installation. The prefabricated chamber required minimal integration on arrival, reducing open excavation times and speeding up construction. This approach also delivered cost and resource efficiencies through reduced site labour, shorter temporary works durations, and more streamlined logistics.

On a highly constrained urban site, limiting plant, materials, and personnel helped create a safer, cleaner, and more efficient work environment.

Delivering sustainable outcomes & lasting social value

Sustainability was at the heart of the project from the final design through to construction. A key improvement was the removal of the need for a pumped shaft tank and its associated concrete and mechanical infrastructure. This change reduced the need for extensive temporary works and heavy transportation, significantly cutting embodied carbon and simplifying site operations.

[caption id="attachment_24482" align="alignnone" width="1200"] (left) Trenchless auger bore installation of 900mm inlet pipe within large temporary works excavation and (right) prefabricated CSO chamber crane lift into temporary works excavation - Courtesy of Galliford Try[/caption]

The project team focused on optimising existing network assets, minimising the construction footprint, and enhancing performance. The CSO was upgraded to a compliant, mechanically screened system, helping protect the environment and improve water quality, both above and below the surface, in line with national and global sustainability objectives.

Using HDPE pipes from Polypipe and a prefabricated HDPE CSO chamber from NOV Fibre Glass Systems, the project reduced overall carbon emissions by around 60% compared to traditional concrete components. Additional savings came from improved transport efficiency and faster, modular installation. To streamline delivery, a standard-design motor control centre was used, allowing off-site assembly with less waste and better quality control. The revised solution also replaced two 2.5kW pumps with a single 0.63kW motor for the screen, cutting energy demand and supporting long-term operational sustainability. Engaging local contractors further reduced transport emissions and boosted the local economy.

Although four trees had to be removed for safety reasons, the project was considered ‘permitted development,’ so it wasn’t required to meet the 10% biodiversity net gain rule. Nonetheless, Galliford Try worked with Sheffield City Council (SCC) to plant eight new trees, with a two-year maintenance commitment and provisions for replanting if necessary.

Proactive communication with SCC ensured minimal community disruption. Road closures were planned, publicised, and managed effectively, and SCC supported the project by providing a nearby council-owned site for welfare facilities and a construction compound, further improving efficiency.

[caption id="attachment_24485" align="alignnone" width="1200"] Prefabricated CSO chamber in position with bespoke access covers temporarily positioned - Courtesy of Galliford Try[/caption]

Aiming to leave a lasting legacy, Galliford Try collaborated with local schools to install rainwater terrace SuDS units. These units help manage stormwater and serve as educational tools for the students. Both Arbourthorne and Hillsborough primary schools embraced the initiative, incorporating it into lessons on the urban water cycle, sustainability, and planting. At one school, captured rainwater is now used to irrigate a herb garden, supported by funding from Galliford Try. The response has been overwhelmingly positive, with schools expressing interest in expanding rainwater harvesting initiatives.

The project was also aligned with several United Nations (UN) Sustainable Development Goals (SDGs), including:

SDG 3: Good Health and Well-being. SDG 4: Quality Education. SDG 6: Clean Water and Sanitation. SDG 9: Industry, Innovation, and Infrastructure. SDG 11: Sustainable Cities and Communities. SDG 13: Climate Action. SDG 14: Life Below Water. SDG 15: Life on Land.

The project’s planning and execution reflect Galliford Try’s dedication to these global goals, aiming to deliver resilient, inclusive, and environmentally responsible infrastructure.

[caption id="attachment_24484" align="alignnone" width="1200"] The completed works - Courtesy of Galliford Try[/caption] Conclusion

This project showcases the power of integrated design, stakeholder collaboration, and sustainable construction in delivering long-term environmental and social value. Involving 31 companies and aligned with eight UN SDG’s, the project was completed with zero Health & Safety incidents from construction through to commissioning.

The upgraded CSO is predicted to reduce spill frequency and volume by 75%, equating to approximately 20,000m3 over a 10-year period. A 60% cradle-to-grave carbon saving was achieved through the use of prefabricated HDPE components and off-site manufacturing. Beyond engineering benefits, the project left a positive local legacy. Eight trees were planted to replace four removed, and 844 students were engaged in sustainable drainage education. This project exemplifies how smart infrastructure can deliver lasting, measurable benefits for both people and the environment.

The topography in and around the city of Hull makes the city extremely susceptible to flooding. Derringham is a residential suburb to the west of the city, which was heavily impacted by the 2007 floods. Significant flood alleviation works are therefore required in the area to manage stormwater to prevent an event on this scale from having such an impact when it inevitably occurs again in the future. The Derringham Aqua Greens Project has been delivered by the Living With Water Partnership, Stantec and Mott MacDonald Bentley (MMB) to provide flood alleviation in the heavily residential area. The Living With Water Partnership

The Living With Water (LWW) Partnership was formed following the 2007 floods when 16,000 properties in Hull and East Riding were flooded. It became clear that no single agency accepted any responsibility outside of their own term of reference, but that each had a part to play in maintaining the waterways in the city of Hull which contributed to the floods. The partnership brings together Yorkshire Water, Hull City Council, East Riding of Yorkshire Council, Environment Agency and University of Hull to enable them to collaboratively deliver flood alleviation schemes in the city. The first of its kind in the UK, the partnership aims to reduce flood risk in high-risk areas, while combining blue-green principles to deliver sustainable, low carbon solutions, encouraging knowledge share between all parties, building community resilience, improving local areas by providing biodiversity net gain.

[caption id="attachment_21743" align="alignnone" width="1200"] Location plan of the aqua green sites within the Derringham area - Courtesy of Mott MacDonald Bentley[/caption] The partnership has proved paramount throughout the design and construction phases as collaboration between all parties has been needed throughout. This included having the expertise of Yorkshire Water on the technical elements of drainage design, discussions with Hull City Council on how highways will be reinstated, proposed planting arrangements and gaining access to council owned green spaces and collaboration with the University of Hull to incorporate the requirements for testing & monitoring equipment within the design from the start. Project scope

The principles of the project are to allow exceedance flows from heavy rainfall, for which there is no capacity in the sewer network or nearby watercourses, to flow above ground via existing road accesses between properties, into detention basins retrofitted into existing green spaces in the area. The stormwater can be retained away from properties and returned to the sewer network once there is available capacity and the network is no longer surcharged.

The road access, or ‘10fts’, between properties are lowered to create a channel for stormwater to flow from the highway into the Aqua Green. A headwall and return sewer are installed from the low point of the Aqua Green, connecting into the existing sewer network in the main highway. Flows leave the Aqua Green under gravity, meaning that no mechanical or electrical elements are required for the operation of the solution. The lowering of the 10fts meant that property protection measures were required to the properties adjacent to the 10ft to prevent the solution resulting in them to be at greater risk of flooding. Existing boundary fences were replaced with new fence panels installed on concrete gravel boards to provide a waterproof barrier between the 10ft and the property.

Across the three Aqua Greens, over 1800m3 of storage has been proved. With a traditional grey infrastructure project, providing the same storage would have had a much higher embedded carbon measure, could not have been constructed in the small areas that were available and would have required some form of M&E installation with associated ongoing maintenance and running costs.

[caption id="attachment_21751" align="alignnone" width="1200"] Property protection on properties adjacent to the 10fts and (inset) position of manholes within narrow 10ft - Courtesy of Mott MacDonald Bentley[/caption] Derringham Aqua Greens: Supply chain - key participants Client: Yorkshire Water Principal designer & contractor: Mott Macdonald Bentley Outline design: Stantec UK Academic partner: University of Hull Local Authority: Hull City Council GCL liner & underdrainage: SIG Construction Accessories Headwall: Marshalls Water Management Hinged pole for testing & monitoring: Fabrikat (Nottingham) Pipework: John Davidson (Pipes) Ltd Flap valve: Affco Flow Control (UK) Ltd Surfacing: Calder CAD Ltd Landscaping: Craven Forestry Limited Aqua Greens design

The concept design was carried out by Stantec, who produced a full hydraulic model of the whole area to determine where the highest flood levels are seen, to identify the green spaces that would provide the most benefit if they were developed. A total of 11 green spaces in the area were investigated, with cost benefit analysis carried out to establish which of those spaces would provide the most benefit for the community. Three sites were selected to be developed in the first Work Package (WP1) with a further three sites to be developed in Work Package 2 (WP2).

[caption id="attachment_21746" align="alignnone" width="1200"] Installation of the liner and underdrainage layer - Courtesy of Mott MacDonald Bentley[/caption] One of the main aims of the detailed design phase was to produce standard details that could be implemented at all Aqua Green sites, to streamline both the design and construction phases. As the return sewers and associated chambers were to be laid in the 10ft between two properties, a standard 1200mm precast concrete manhole could not be installed as there was not space to do so. A 1200mm x 750mm standard product was therefore developed and agreed with Yorkshire Water as it was a much safer and simpler install.

The overall project programme meant that long term groundwater monitoring could not be carried out prior to the design process for WP1. For design calculations, groundwater therefore had to be assumed to be at ground level, which resulted in flotation of the liner and as a result, an additional drainage later needed to be installed below the liner to prevent flotation.

During the construction of WP1, it was observed that the Aqua Greens were retaining water before the liner was installed and that the as clay of very good quality. For WP2, permeability testing and longer-term groundwater monitoring were able to be carried out. This determined that the natural clays were of higher impermeability than the geosynthetic liner and that the groundwater was not as high as was believed during the design phase for WP1. It was therefore discussed and agreed with all relevant parties that the additional geosynthetic liner did not need to be included on site. This saved a total of two weeks on the programme for WP2, approximately 60 tonnes of carbon, material costs of approximately £60,000 and removed the risk of delays associated with the liner install in wet weather.

Construction for WP1 was from October 2023 to December 2024, with works still progressing on the WP2 sites. Sole access to the green spaces via 10ft wide access tracks introduced some difficulties to the construction. Only small plant could be used and the 5m wide liner had to be cut to 2.5m for delivery to the greens. Limited space on site also meant that excavated materials could not be stored at the greens and had to be stockpiled at the site compound, requiring a significant number of dumper loads of materials to be moved on the local road network. The nature of the project and works commencing in winter meant the Aqua Greens frequently flooded during the construction, with water regularly needing to be pumped to the drainage network before further progress could be made.

[caption id="attachment_21741" align="alignnone" width="1200"] Retention of water in Aqua Greens seen during construction prior to the installation of the liner - Courtesy of Mott MacDonald Bentley[/caption] Community engagement

Due to the location of the Aqua Greens in such close proximity to residential properties, significant community engagement was needed throughout the project, during both design and construction phases, to ensure that the community were kept up to date with what the project would deliver, how the construction works would impact them and ultimately how the SUDs solution would operate and be maintained into the future. Over 30 engagement sessions have been held with the community to date, from the start of the design development to the end of the construction phase. This has been coupled with regular letters and updates on the LWW website, providing the residents with an opportunity to raise any concerns about the works as well as to help to convey the importance of flood alleviation in the area.

To aid conversations with the local community about the Aqua Green developments, computerised visualisations were produced which showed how the Aqua Greens would look upon completion. While the existing greenspaces were mainly neutral grassland before works commenced, the solution was to plant wildflower seeds in the greenspaces upon completion, to increase biodiversity of the area. To provide habitat for wildlife, wildflower areas are maintained less frequently than grassland spaces and this therefore needs to be portrayed to the residents.

[caption id="attachment_21753" align="alignnone" width="1200"] (left) Visualisation image used to aid communication with the public and (right) installation of community noticeboard on site - Courtesy of Mott MacDonald Bentley[/caption]

The visualisations also helped the MMB team to discuss the proposals with the residents to see if there was anything additional, they would like to see of change as part of the design. Some residents said that they particularly liked the shrubs at the back of one of the green spaces as they provided them some security for their garden, so these were retained as part of the design. Others suggested that the proposed parking areas would not be used and that they did not want to encourage parking on the green spaces, so these were reduced in width to just passing places on the narrow roads.

Continued engagement with the community has been needed throughout the construction phase to answer any queries that the residents had about the works and rectify any problems they had been experiencing. Upon completion of the Aqua Greens, permanent notice boards have been installed at each of the sites to inform the residents of the benefits of the Aqua Green.

Continued testing & monitoring

The University of Hull have installed testing and monitoring equipment at all three of the Aqua Green sites in WP1 to understand how these Aqua Greens perform. The testing and monitoring equipment included soil moisture probes located above and below the liner; conductivity, temperature, and depth (CTD) probes in the return sewer and a weather station at a local school. The aim is that this data will be analysed and used to improve the design to enhance these assets for future installations. The weather station data is also accessible by the local school so that the data can be used for educating the students about the weather and flood risk of their local area and how we can safely live with water.

The intention is that further testing and monitoring equipment will be included on the WP2 sites so that a comparison can be made between the lined and unlined solutions to see if one of them is more effective at providing the required storage or improving the quality of the water that enters the sewer network.

[caption id="attachment_21745" align="alignnone" width="1200"] Installation of community noticeboard on site – Courtesy of Mott MacDonald Bentley[/caption] Summary

Since the installation of the first three Aqua Greens was complete, the benefits provided by the Aqua Greens has been visibly clear during periods of heavy rainfall, with quantitative data expected from the testing and monitoring installations within the next few months. These large-scale SuDS basins have provided flood protection to hundreds of properties in an area which otherwise would be at very high risk. Providing the protection via blue-green methods rather than traditional grey infrastructure has resulted in a solution with a much lower carbon impact, while also providing the areas with an improved biodiversity, making it a much more sustainable solution. The blueprint of this project, along with that of the Living With Water partnership, can be applied to other areas across the UK where properties are at high risk to deliver more types of these projects in the future.

Ballygowan is a small village situated in County Down, within the Ards & North Down Borough Council area. The towns of Comber and Saintfield are both approximately 4 miles to the north-east, and to the south respectively, with the city of Belfast 7 miles north-west. The 2021 Census indicates that the population of Ballygowan is approximately 3,138. The existing WwTW was constructed in the village in the 1950s and comprised an inlet works, a CAS basin, a storm tank and a small sludge holding tank, as well as an MCC building to control the works and was designed to treat a population equivalent (PE) of 2,700. The existing works was therefore beyond capacity to treat the present day population, and the structures had exceeded their design life. An extensive upgrade was required to provide effective and robust wastewater treatment services for the future catchment area, allowing economic growth, while improving the local environment and adhering to a much tighter discharge consent of 7mg/l BOD, 10mg/l total suspended solids, and 1.5mg/l ammonia. The new fully automated works will serve a PE of 4,513. Primary drivers for the upgrade The existing wastewater treatment works (WwTW) was undersized for the current flows coming into the works. The existing works was not complaint with the Northern Ireland Environment Agency’s discharge consent standard for Ballygowan WwTW. Future planning applications for residential properties in the Ballygowan area had been put on hold due to the existing WwTW operating beyond its intended design capacity. The existing works was not capable of fulfilling the requirements of NI Water’s long-term strategy to enhance wastewater services and ensure environmental compliance and was expensive to operate and maintain. An even tighter NIEA standard was imminent. [caption id="" align="alignnone" width="1200"] (left) Existing Ballygowan WwTW - Courtesy of NI Water and (right) demolition in progress: (top) the existing storm tank and (bottom) the existing CAS basin tank - Courtesy of  GEDA Construction[/caption] Project description & scope Designed for a 2045 population equivalent of 4,500, the new Combined Activated Sludge Plant (CASP) at Ballygowan WwTW, was to be constructed east of Dickson Park in Ballygowan, in a green field site that bordered the southern boundary of the existing site: The preliminary treatment process comprising of 6mm inlet screening and forward flow-control equivalent to Formula ‘A’. A new storm storage management facility including a CSO storage tank, and two storm tanks providing a total capacity of 224m3. The CSO storage tank and two storm tanks are equipped with a tipping bucket system for effective cleaning of the storm tank floor. Flows equivalent to Full Flow to Treatment (FFT) are pumped forward via a new interstage pumping station. FFT is then split with equal flows going to two CAS basin tanks. The selector chamber was carefully designed to assist with controlling filamentous bulking in activated sludge systems which can be a common operational challenge issue in activated sludge plants. Downsteam of the flow split chamber, there are two CAS tanks complete with final settlement tanks (FSTs) accommodated centrally, each aeration stream comprising of an anoxic zone to aid denitrification, and three individual aeration zones equipped with tapered aeration diffuser grids. The design and construction of the biological treatment process on this site was critical and to ensure compliance with an extremely stringent discharge consent of 1 mg/l ammonia alkaline was dosed at this stage in the process, detailed below. Due to the restricted footprint available for the site, the CAS tanks were selected to accommodate the final settlement stage within the biological treatment footprint. Two FSTs were constructed, with the CAS (anoxic and aeration zones) wrapped around the FSTs. [caption id="" align="alignnone" width="1200"] CAS basins  - Courtesy of NI Water[/caption] Following final settlement, the treated effluent gravitates to a tertiary treatment plant for further solids removal prior to discharge at the final effluent outfall location. A new combined RAS/SAS pumping station was constructed adjacent to the selector/flow split chamber to aid best use of available footprint. This pumping station houses two RAS pumps to replenish the bacteria within the biological treatment system and maintain the required MLSS levels for effective treatment. A further two SAS pumps are also provided to pump away sludge to the new sludge storage facilities should the MLSS levels within the treatment process exceed the desired levels. The new Ballygowan WwTW includes two sludge storage tanks, one mechanical sludge thickener and a polymer chemical dosing plant for processing sludge prior to being tankered offsite. To ensure a robust solution was provided for the client to meet the 1 mg/l ammonia consent, a supplementary alkalinity chemical dosing plant was provided for dosing into the aeration lanes. The provision of this dosing plant which utilises sodium carbonate ensures there is sufficient alkalinity available within the biological treatment process for effective and complete nitrification under all flow and load conditions. The works also comprises a new MCC room which controls all mechanical and electrical plant equipment and instrumentation, a welfare unit, a standby backup generator, and associated access and drainage. As the treatment works was built in close proximity to a neighbouring residential area, the odour model highlighted areas of the treatment process that required covers with passive odour abatement being provided. The site was also landscaped to include a site bund to reduce the visual impact on the neighbouring residential area of Dickson Park. [caption id="" align="alignnone" width="1200"] New storm tank being utilised during construction - Courtesy of GEDA Construction[/caption] Main challenges for design/construction Discharge consent The key challenge around the design and construction of the new Ballygowan WwTW, was ensuring that the new WwTW would comply with a very tight water order consent (WOC) set by NIEA. The WOC is one of the tightest consents in Northern Ireland. The discharge consent was originally advised as 7:10:1.5 mg/L (BOD/TSS/ammonia), however the design and construction was further challenged when NIEA confirmed that the ammonia consent would be restricted to 1mg/l ammonia. GEDA Construction, in conjunction with their MEICA and process subcontractor Water Solutions Ireland Ltd, reviewed the design and construction proposal to provide a solution which incorporated minimal changes, minimising costs to NI Water, but still providing effluent treatment compliance. Site location The WwTW site is bordered by agricultural land to the north and east, and has a housing development to the west. To construct the new WwTW and keep the existing plant operational, NI Water purchased an area of land (formerly a football pitch) to the south of the site belonging to the local council. The existing WwTW access road is through Dickson Park housing estate and runs directly alongside a children’s playpark. In advance of construction the project team took the proactive decision to look at creating a temporary construction access to the south of the site through agricultural land so that all construction traffic would not have to travel near Dickson Park or the children’s playpark. Extensive consultation took place with local landowners, the residents’ association and roads authority and the temporary road was successfully constructed ahead of construction start. Due to the close proximity of the new WwTW to the housing development, consideration was also given to any potential visual and odour implications to the neighbouring housing development. It was decided at an early stage to design the structures in such a way that they would have minimal visual impact. This meant designing and constructing structures as low in the ground as possible to keep them out of view of the neighbouring properties. An earth bund was also constructed to the west boundary of the site and planted with trees/bushes and shrubs in order to further hide the treatment works as well as helping to combat any odours coming from the site. [caption id="" align="alignnone" width="1200"] Ballygowan WwTW under construction (December 2021) - Courtesy of NI Water[/caption] Interface between new and old works during construction The majority of the new WwTW works was to be built on a greenfield site which allowed GEDA Construction to build most of the new structures without having to work around existing infrastructure. However, in order to construct pipelines which would eventually take the flow into the new works, and to construct the new WwTW access road, it was necessary to demolish the existing storm tank in the old works prior to the new works becoming live. GEDA Construction carried these works out by utilising the newly-constructed storm tank and incorporating a carefully developed phasing plan. A temporary 300mm gravity fed sewer was laid from the existing inlet works to the new storm tank, which in turn rendered the existing storm tank surplus to requirements, as all storm flows had been diverted away from it. GEDA Construction also had to lay a temporary 200mm pumped sewer from the new storm tank complete with temporary pumps to send the storm flows back to the existing pumping station in order for the influent to then go through the treatment process. This in turn allowed us to demolish the existing storm tank and construct the new permanent inlet sewers to the new works ahead of turning flows. This process had to be carefully managed both hydraulically and biologically to ensure the treatment process was optimised and effluent compliance was maintained at all times. [caption id="" align="alignnone" width="1200"] New permanent high-level sewer under construction - Courtesy of GEDA Construction[/caption] Turn of flows Influent flows were successfully diverted into the new works in early May 2022. In order to bring the new biological treatment process online, several tanker loads of seeded sludge were brought to site from another treatment facility and were introduced into the new CAS basin tanks to promote bacteria growth. With flows diverted, and effective treatment established through a rigorous sampling regime, approval was received from NI Water to proceed with the demolition of the remainder of the existing treatment works. Once the existing works were decommissioned and demolished, the entire new WwTW site was able to be finished and access roads completed. Demolition Post turn of flows in early May 2022, the existing treatment works was decommissioned and then demolished. Reusable mechanical and electrical assets from the old treatment process were removed for future use by NI Water, while the effluent left in the old CAS basin and pumping station was removed from the site to allow demolition to commence. Effluent was filtered through the new treatment process to minimise unnecessary removal and disposal from site. Project team As principal contractor, GEDA Construction had overall responsibility to deliver the project on time and within budget, which they succeeded in doing by working collaboratively with NI Water, project managers Tetra Tech, key suppliers and subcontractors to identify and plan for key project milestones. McAdam provided civil, structural and geotechnical design services, including the initial enabling and investigatory works carried out at the Early Contractor Involvement (ECI) stage, as well as the detailed design for construction. Water Solutions Ireland (WSI) were responsible for designing and delivering a full turnkey MEICA, process design and build solution for the new works. Ballygowan WwTW: Supply chain - key participants Civil contractor: GEDA Construction Project managers: Tetra Tech MEICA contractor: Water Solutions Ireland Civil, structural & geotechnical design: McAdam Electrical design: SBE Design Mechanical design: McWall Drawing & Design PLC software & commissioning: Ashdale Engineering Odour control: Anua Clean Air UK Storm screens: Eliquo Hydrok Ltd Grit removal plant: Jacopa 6mm inlet screening: Hydro International (M and N Electrical and Mechanical Services) Aeration blowers: Aerzen Machines MCC: Greenville IDC Pumps, mixers, fine bubble diffusers: Xylem Water Solutions Tertiary treatment plant: WPL Chemical dosing: Richard Alan Engineering Instrumentation: Park Electrical Systems Flow measurement: Siris Environmental Ltd Flow measurement: AMPM Flow & Energy Services Ltd Penstocks, valves & actuators: Flow Technology Services Storm tank cleaning tipping bucket: CSO Group Ltd GRP kiosks, FST scrapers & site-wide metalwork: Victoria Engineering 6mm bar screen, skip rails & trolleys: Graham Steelwork Engineering Potable & FE service water boosters: Dutypoint Ltd Lifting equipment: Columbus McKinnon Co Ltd Solar panels & EV charger: Solmatix Renewables Ltd [caption id="" align="alignnone" width="1200"] CAS basins in operation - Courtesy of NI Water[/caption] Solar It was recognised that a large area of land within the footprint of the existing WwTW site would be available for use following demolition of old structures. As a result, NI Water asked GEDA Construction and Water Solutions Ireland to investigate the feasibility of installing solar energy within the space available. Following a successful outcome of the feasibility study, it recommended that a 62Kw solar PV array would be installed in the free space which would provide renewable energy to run some of the WwTW operations and boost the sustainability of the site. A 22KW dual EV charger unit was also installed which is used by NI Water’s growing fleet of electric vans. Solmatix Renewables Ltd installed a ground-mounted solar PV panel system consisting of 164 solar panels within the footprint of the old works. New electrical invertors and controls housed within the new MCC kiosk were installed and cabled directly onto the new MCC. The solar system has been set up as zero export, meaning everything that is being generated on site, is used on site through the plant and other electrical equipment. The estimated payback period on NI Water’s £70k investment is 6.5 years (savings of £11,000/year on electricity costs at Ballygowan WwTW). [caption id="" align="alignnone" width="1200"] Solmatix Renewables Ltd solar farm - Courtesy of NI Water[/caption] Alkalinity A challenging issue encountered during the design and construction of the new works at Ballygowan WwTW was the high acidic nature of the incoming influent. During review of the design and aided by a sampling regime of the influent under varying flow conditions, it was determined the site required alkalinity dosing to allow the wastewater treatment process to provide adequate nitrification (in other words ammonia reduction) within the biological treatment to meet the 1mg/l ammonia discharge consent. This problem required NI Water and GEDA Construction to design, supply, install and commission a supplementary packaged chemical dosing system to increase the alkalinity levels and achieve a stable pH within the wastewater to safeguard optimum treatment. NI Water shared some past negative experiences encountered with similar alkalinity dosing plants which was invaluable to ensure that a well thought out, comprehensive solution was selected, which would deliver the requirements of supplementary dosing but reduce the ongoing operation and maintenance requirements encountered on other schemes for NI Water. The agreed solution was to provide a new proprietary sodium carbonate (powder) make up and dosing system, all housed within its own GRP kiosk and standalone control panel. Odour control Due to the proximity of nearby residential housing, the design and execution of odour containment and treatment was a major consideration for this project. Early odour models and specialist supplier engagement was imperative to ascertain the potential effects of odours. GEDA Construction provided a cost-effective, proven solution through a carbon filter plant dedicated for the inlet screening and grit removal works, and a second Mónashell Biofilter plant from Anua Clean Air UK was provided solely for the sludge treatment and storage tanks. Both systems, along with covering large areas of the works with solid top flooring, safeguard against the negative effect odours can cause. [caption id="" align="alignnone" width="1200"] Ballygowan WwTW nearing completion - Courtesy of NI Water[/caption] Collaboration and PR Collaboration was instilled throughout every aspect of the planning, design and construction phases for the new Ballygowan WwTW. NI Water and its project management team developed a proactive communication and PR strategy for project which included erection of storyboards; circulation of project brochure; issuing of regular updates to residents; briefings for elected representatives; circulation of press releases and a number of events and initiatives with the local residents’ association. A collaboration initiated with the local council also saw the creation of a small orchard by local children on an area of disused council land adjacent to the WwTW, which GEDA prepared for planting out. Outcome By working in partnership with each other, as well as myriad stakeholders, NI Water, Tetra Tech, GEDA Construction and the wider supply chain were able to successfully overcome difficult challenges to deliver a sustainable, state-of-the-art wastewater treatment solution, capable of meeting its stringent consent standard and serving the community for many years to come.

Located south of the village of Chilton Foliat and north-west of the town of Hungerford there is an existing sewage treatment works (STW) that serves a population of approximately 400 people. The works discharge into the River Kennet, one of England’s most important chalk streams which is home to an extensive range of rare plants and animals that are unique to the area, and as such it is designated as a Site of Special Scientific Interest (SSSI). The project objective is to divert flows from Chilton Foliat STW by extending the existing rising main from Mill House Sewage Pumping Station (SPS) in Chilton Foliat to the adjacent catchment of Hungerford and onwards to Hungerford STW, allowing for the future decommissioning of Chilton Foliat STW. Basis of design The project is part of a flow compliance scheme for Thames Water working in collaboration with the local action group, Action for the River Kennet (ARK), and the Environment Agency (EA) to improve the quality of flows discharged to the River Kennet. Mott MacDonald Bentley (MMB) developed the design to divert and extend the existing rising main pipe towards the Hungerford catchment to the south-east of Chilton Foliat. The rising main would be extended by an additional 1400m and discharge into a new 150mm diameter gravity sewer system, before connecting into the existing Hungerford sewer system approximately 310m further to the south-east. Due to the undulating topography, the rising main section contained a mix of both rising and falling gradients along its length. As a result of this alignment, hydraulic and surge assessments highlighted the need for additional air release valves and also a variation in pipe sizes between 125mm OD and 160mm OD to maintain the required flow velocities whilst preventing air locking in the pipe. [caption id="" align="alignnone" width="1200"] Aerial view of setup - Courtesy of A. Thomas Plant Hire Ltd (ATP)[/caption] Assessment of the existing pump arrangement at Mill House SPS confirmed that they would be suitable to transfer flows along the new rising main pipe alignment which had a reduced head to that of the previous arrangement. However, the existing pumps were determined to be nearing the end of their asset life and their replacement was also included. The gravity sewer section was designed to maintain self-cleansing for the expected pass forward flow of up 8 l/s with the fall gradient varying between 1 in 90 and 1 in 60. Rising main installation method selection With consideration towards health, safety, and the environment, as well as constraints within the  programme, a fast and effective pipe installation method was deemed to be crucial. Following detailed geotechnical site investigation works, various methods were explored. In consultation with A. Thomas Plant Hire Ltd (ATP), and drawing on MMB’s experience of using pipe ploughing from projects with other clients, the project team confirmed that the ground conditions were well suited to using pipe plough pipe installation equipment; with projected pipe laying rates in excess of 500m per day. Due to the SSSI status of the river and the surrounding area, and the Kennet and Lambourn Floodplain Special Area of Conservation (SAC) being home to the endangered Desmoulin’s whorl snail, MMB had to produce a Habitats Regulations Assessment (HRA) to mitigate any potential impacts of the pipe installation; a process made more onerous by a recent case law. As the largest environmental risk to the protected areas would be the contamination of groundwater or its escape overland, the use of the pipe plough would help reduce, and even eliminate, the potential for contaminated surface and groundwater from reaching the adjacent watercourses. [caption id="" align="alignnone" width="1200"] (top left) winch/anchor unit, (bottom left) bedding conveyor and (right) test pit on installed pipe - Courtesy of MMB[/caption] Pipe plough benefits The quality and safe nature of the installation, as well as the programme and carbon efficiencies made pipe ploughing a strong solution for the installation of the rising main. There are many benefits to using pipe ploughing techniques other than just improved installation time, lessened disruption and reduced visual impact. Using polyethylene (PE100) pipe jointed using electrofusion in an above-ground, controlled environment, removes the need for any persons to work within the confined space. Furthermore, the pipe plough is a pipe install method that is highly configurable and a standardised process that allows for the simultaneous installation of pipework, pipe bedding and marker tape, preventing the need for open excavations. Challenges As pipe ploughing is an emerging technology and new to Thames Water, there were some initial concerns how the design requirements would be met. However, MMB were able to offer reassurance through engagement with ATP, who provided video footage and technical data to prove that the pipeline installation would be done in accordance with the standards for sewage pipelines, sewage rising mains and civil engineering specification. Another challenge was the requirement to confirm that adequate amounts of pipe bedding would surround the pipe. This was demonstrated by the visual inspection of a 50m trial run. Where a trial hole was dug over the newly installed pipe. Happy with the information and demonstration, the project moved forward with the project. [caption id="" align="alignnone" width="1200"] The pipe plough - Courtesy of MMB[/caption] Chilton Foliat STW Flow Compliance: Supply chain - key participants Client: Thames Water Principal designer & contractor: Mott MacDonald Bentley Pipe plough pipe installation (rising main) subcontractor: A. Thomas Plant Hire Ltd (ATP) Manhole & gravity sewer installation subcontractor: Hercules Site Services Pumps: Xylem Water Solutions Progress Design Start Date: 16 May 2022 Construction Start Date: 16 January 2023 By the end of March 2023 the following works were completed: Topsoil stripped along the approximate 1800m long working easement. Above-ground electrofusion welding of PE100 pipework including a number of lengths for random destructive testing of joints. Installation of 1400m of PE100 rising main over 2 days. Reinstatement of the subsoil ready for chamber installation. Installation of 310m of clay gravity sewer by traditional open cut methods. Construction of all air valve, washout and gravity chambers. In the near future the final connection will be completed along with the final surface reinstatements. The next project in the area will be the decommissioning of Chilton Foliat STW. [caption id="" align="alignnone" width="1200"] (left) Pipe plough in progress and (right) reducer installed - Courtesy of A. Thomas Plant Hire Ltd (ATP)[/caption] Future uses of the pipe plough Due to the guidance system and the fully adjustable plough, it is also possible to lay at a set gradient, meaning the pipe plough can be used to lay gravity sewer pipeline as well. However, consideration of standards and specifications will need to be considered. ATP have also advised that given suitable design and pipe material selection together with suitable ground conditions, a ploughed pipe could be installed without pipe bedding, potentially allowing for a reduction in carbon and plant required on site; something MMB are keen to pursue. Thames Water have also been suitably impressed with the technology’s potential to reduce programme, lessen carbon, and eliminate environmental risks, and are looking to promote its use on other framework projects through their internal innovation share mechanism. A preliminary review of their asset standards  will be undertaken to see if updates could be made to encourage alternative methods of installation.

The Exmouth Offshore Project is a key element of the wider Exmouth programme of works to deliver no more than 10 significant (>50m3) spills per annum from the aggregation of Maer Road Sewage Pumping Station (SPS) Combined Sewer Overflow (CSO) and Phear Park SPS CSO. The output from the programme will reduce spill frequencies for better environmental conditions as a long-term solution with a positive impact on the bathing waters. The works were undertaken in Sandy Bay Devon Cliff Holiday Park in Exmouth and was delivered around Sandy Bay’s winter maintenance window, compressing 15,000 working hours within just 13 weeks. Overrunning the programme would have directly impacted Sandy Bay’s tourist season, with significant revenue loss (approximately £2m/day). The works were located only 4 meters from a Blue Flag beach. Introduction & background

The Exmouth Offshore Project required the installation of an 804m long, 900mm diameter, gravity long sea outfall, to achieve an increased flow rate of 991 litres per second.

The works took place in Sandy Bay Devon Cliff Holiday Park (Exmouth), one of the UK’s largest caravan sites, with over 2200 units and 10,000 visitors per week in the summer season and were only permitted during the Sandy Bay winter maintenance period.

South West Water contracted Galliford Try as principal designer and contractor for the project.

[caption id="attachment_17044" align="alignnone" width="1200"] (left) Pipe string along coastal path and (right) Pushing pipe lower car park and compound - Courtesy of South West Water[/caption] Construction

To meet this challenging programme, specialist horizontal directional drilling (HDD) contractor Peter McCormack & Sons mobilised one of the largest and most powerful drilling rigs ever used in the UK, to complete the largest forward reaming (48”) operation in the country.

The works required 18 months of planning and the programme challenge included expediting the specialist reamers, 1.2m in diameter manufactured in America and imported to precise programme requirements. The methodology and accurate planning minimised programme risk by minimising the use of marine spread.

This relied on forward reaming (pushing the pipe from land), which is an unconventional method for the length and diameter of pipe of this scale, but reduced the reliance on marine support in winter sea conditions reducing weather risk.

Early marine trenching support was mobilised to clear boulders at the exit point at seabed over two days. Survey marine vessel continued throughout the project to confirm HDD exit point.

818m of HDPE pipe was welded on land, stretching in a single length at strategically high ground to slide the pipe. This allowed to fully pressure test the pipe to give complete confidence in the weld quality. The project team considered both the safety of the public accessing the coastal footpath adjacent to the works and maintenance operations within the holiday park with accurate interface management. In addition to this, the project team worked closely with landowners to agree a route for the welded pipeline to be positioned, in readiness for the pipe push with regular communications with landowners.

[caption id="attachment_17047" align="alignnone" width="1200"] (top left) 500t drill rig compound and entry point and (bottom) pipe pushing operation at sunrise - Courtesy of South West Water[/caption]

The works naturally attracted attention, and allowed the team the opportunity to explain the work that were undertaking and the long-term benefits South West Water outfall would provide to wider Exmouth storm overflow project.

The project compressed 15,000 working hours within 13 weeks which equates to 10 months of normal working hours. This could only be achieved by running a continuous 24x7 drilling operation. Despite the intensive nature of this challenge, the team completed the HDD works ahead of programme, on budget with zero harm to the team, zero pollution incident, and minimal impact to the public. This pipe is a wider part of Exmouth stream of works including storm overflows to achieve long term goal.

Exmouth Outfall: Supply chain - key participants Client: South West Water Principal contractor: Galliford Try Design: Pell Frischmann Design of outfall route & drilling specialist/sub-contractor: Peter McCormack & Sons Ltd Topographic, GPR & boreholes: AGS Ground Solutions Unexploded ordnance survey report: 1st Line Defence 900MM PE pipe supplier: Egeplast international GmbH (Germany) HDD 500t kit & drilling tools: American Augers (USA) Pipe pusher: VanLeewen Trenchless Technology (Netherlands) Welding plant supplier: Ritmo remedy 1000FA (Italy) Concrete: Aggregate Industries Welding plant operator: Pipe Force Martin Woodcock Fiberglass systems: Pipex px Crane hire: Spence Crane Hire Ltd Plant hire: Plantforce Rentals Ltd Plant: Sunbelt Rentals Ltd Aggregate: Steve Wills Haulage [caption id="attachment_17043" align="alignnone" width="1200"] 500 T drilling rig - Courtesy of Galliford Try[/caption] Teamwork and Inclusion

Working collaboratively towards a common agenda, multiple partners were involved including the pipe supplier, drillers, pipe pushers, pipe welders, crane operators, mud pump operators, water tank suppliers, fuel suppliers etc.

A mutually inclusive team worked. Collaborative teamwork environment with no risk-taking policy with a culture of everyone working on site and delivery people have same respect with different roles and responsibilities.

Cultural Behaviour Safety videos were shared on regular basis to remind site team safety, culture, and respect aspect. Site team was well trained and fully skilled to follow safety rules religiously. No one was either bigger or lower than anyone which was demonstrated by actions through a mutually inclusive respectful culture. Shift change and intermittent toolbox talks were carried out. Several graduates and other interested people were taken to site for their learning. One of the UK’s Water Plcs were visited the site for their learning.

[caption id="attachment_17046" align="alignnone" width="1200"] (left) Drill pipe and pilot drill bit and (right) outfall pipe, roller and guide - Courtesy of Galliford Try[/caption] Health & Safety considerations

Accurate and realistic RAMS were produced. Uninterrupted CCTV monitoring was placed. Each shift had a team of 25 highly skilled and well-trained site team with zero risk taking policy. Specific H&S steps:

Strict one-way system with separate entry and exit points for plant and construction vehicles. Separate entry and exist of South West Water Operators to make existing pumping station in safe operation. Detailed interface management plan of each operational activity including regular on site maintenance of drilling rigs. An hourly check of whole plant, Noise barriers and vibration control equipment for public safety and wellbeing with fully secured fence - large visible metal sign boards and multiple laminated signs in and around the Sandy Bay for public awareness. On duty several field marshals to navigate foot path users. Same drilling team was kept. Compressed programme 15,000 working hours within 13 weeks. Injury free 15,000 working hours into 13 weeks. No near miss. No pollution incident.

Noise barriers and vibration control equipment was installed for the safety and benefits of local community and footpath users. This was checked daily by the site team and the environmental manager to ensure there were zero environmental and H&S incidents.

Protecting the Blue Flag beach

To protect the Blue Flag beach, the entire working area was surrounded by flood barrier to prevent drilling fluids from escaping the site to avoid any risk of pollution of sea. All drilling fluids were recycled by using a recycling centrifuge system. This sustainable innovation allowed the drilling arisings to be fully dewatered, allowing transportation of the inert material without the risk of silt on the road network, causing unnecessary nuisance to the travelling public. This initiative minimised water use and mitigated 364 lorry movements through Exmouth, saving 92T eCO2.

[caption id="attachment_17042" align="alignnone" width="1200"] 900mm diameter pipe welder - Courtesy of Galliford Try[/caption] Conclusion

Despite the intensive nature of this challenge, by running a continuous horizontal directional drilling operation over a 24/7 operating pattern, the works were completed on budget and ahead of the programme. There were no time delays, no environmental impacts to the blue flag beach (just 4m from the site), and any impacts to the Holiday Park were minimal.

South West Water have showcased this project through the media and LinkedIn focusing on the engineering challenges the team faced and promoting both construction and the wider environmental benefits of this scheme.

The team have produced a presentation given by Galliford Try’s team to over 250 employees nationally to share the best practice and learnings from this project across their entire business.

South West Water are extremely pleased with progress of these works to meet their commitments with the Environment Agency.  Relationships with the Holiday Park management are extremely good, and the owners are grateful for the efforts the team and SWW have made to complete these works with minimal disruption to their business.

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.

Located in south Devon, Galmpton STW treats foul water for the hamlet of Galmpton and the surrounding catchment, including the coastal village of Hope Cove (Inner Hope Cove and Outer Hove Cove) about 1km away. As is typical with several coastal hamlets and villages in the West Country, the catchment regularly deals with significant rain events that run the risk of potentially overwhelming the outlying pumping stations; resulting in spills that may have a detrimental effect on the bathing water quality. The Hope Cove area is no different and Galliford Try was selected to support a multi-disciplined multi-contractor strategy to ensure that the local bathing waters, which are extremely important to locals and tourists alike, were protected despite increased numbers of storm events now and into the future. Location

The South Devon catchment comprises of a small inland hamlet, Galmpton, and two larger villages, Inner Hope and Outer Hope, which are joined together along the shore at Hope Cove. Hope Cove consists of two sandy bays, also named Inner and Outer Hope. As the name suggests, Inner Hope is more sheltered and is home to a small harbour tucked away behind the rocks at the northern end.

The northernmost beach is generally the more popular of the two, benefitting from a seasonal lifeguard service. Both beaches are sandy and backed by the red sandstone cliffs familiar to this part of Devon.

[caption id="attachment_10756" align="alignnone" width="1200"] Aerial shot showing Galmpton STW on the right and rising main scar through the fields on the left - Courtesy of Galliford Try[/caption] Project strategy

The intention was simply to enhance the system, enabling more combined flows to be sent to the works, protecting storage in the network for longer, and preventing spills. The strategy was to be a combination of surface water separation, which removes rainwater (collected by impervious areas such as roads, driveways and roofs) from the sewer network and delivered by infrastructure partners Glanville Environmental, enhanced upgraded pumping stations, a new rising main and additional stormwater storage at the works, allowing for treatment through the unaltered works once the storm event had subsided.

Objective

To meet the Water Industry National Environment Programme (WINEP) for Bathing Waters in North Devon driver, which was for Galmpton STW to have an average of no more than two spills per bathing season greater than 50m3 in aggregation with Outer Hope Pumping Station, Galmpton Hope Cove STW SSO and Inner Hope Pumping Station CSO/EO.

Scope of works

The Galmpton STW Bathing Waters Project was awarded to Galliford Try who undertook the following:

Significant enhancements to Outer Hope Cove Pumping Station: Following a catchment model study, it was decided that the significant enhancements to the Outer Hope Cove Pumping Station, required for the overall scheme, would gain an early benefit as the pre-construction phase was being completed for the more complex elements of the strategy. New rising main from Outer Hope Cove to Galmpton: Following the successful increase in flows to the works and away from the shoreline, Galliford Try installed a new 180mm diameter PE rising main. The 1km long pipeline from Outer Hope Cove SPS to Galmpton STW threaded through and under the historical fishing village and across farmland, outside of the tourist season. New 700m3 of below-ground stormwater storage: Galmpton STW had stormwater storage tank with pumped return which needed to be replaced. Above-ground tanks were discounted in favour of a below-ground shaft given the natural beauty and sensitive nature of the location. In parallel with the rising mains works, Galliford Try installed a below-ground shaft storage tank at the sewage treatment works fitted with tank cleaning flushing bell and storm return pumps. New mechanical screening: A new MecMex screen was installed on the inlet flow balancing tank to ensure all flow to the new tank and overflow were screened to 6mm. Inner Hope Cove Pumping Station upgrade. [caption id="attachment_10754" align="alignnone" width="1200"] Galmpton stormwater storage tank following the installation of the flushing bell and air valve release pipework - Courtesy of[/caption] Programme

Work started in September 2022 with the set up compound located in field adjacent to Galmpton STW. In October 2022 Galliford Try started on the rising main up through the Rossiter Estate. By January 2023 Galliford Try started the rising main works through Outer Hope Cove village, which was completed by mid-March 2023.

Active Tunnelling started work on the 12m diameter, 11m deep shaft on 2 February 2023, and the shaft base and pump sump with temporary return pumps were completed on 31 March. The shaft roof was installed on 20 April, and permanent pumps and MEICA completed in May. By June 2023, Inner Hope PS had been upgraded and Galmpton STW was reinstated and handed back to South West Water.

Galmpton Catchment: Supply chain - key participants Principal designer & contractor: Galliford Try Civils design: Pell Frischmann PCC shaft design & construct: Active Tunnelling Ltd Surface water separation: Glanville Environmental Site investigation/ground surveys: AGS Ground Solutions Traffic management: Amberon Ltd Installation of rising main: AT Group (SW) Ltd Rising main pipe: Burdens Precast concrete shaft segments & roof beams: FP McCann MecMex screen, flushing bell & pipework: Eliquo Hydrok Ltd Pumps: Pump supplies Ltd Storm tank return pumps: Xylem Water Solutions Tarmac reinstatement works: Walton Civil Engineering & Surfacing Contractors [caption id="attachment_10753" align="alignnone" width="1200"] Storm tank roof installation main beam lift - Courtesy of Galliford Try[/caption] Social local economic value

The project design showed this scheme would reduce stormwater spills to under two per bathing water season. All stormwater spills would also now be settled and screened, meaning that the two beaches at Inner Hope and Outer Hope should experience less spills, and a much higher quality of water, both now and into the future given the weather modelling horizon of several decades.

In the summer months these beaches are very popular with tourists and used continually through the winter by local surfers and cold-water swimmers.

Risk management

The biggest risk was being able to get all the large plant and equipment required to construct such a large below ground tank onto the very remote site. There were many tiny lanes and poor access routes roads. Galliford Try often planned the large plant movements over night while marshalling the lanes. During the rising main installation, Galliford Try had to lay the new main up an existing road which was only wide enough for one car width. With agreement from the local traffic management officer, we had to run a give and take arrangement with an escort.

[caption id="attachment_10758" align="alignnone" width="1200"] Galmpton storm tank with the precast concrete roof installed - Courtesy of Galliford Try[/caption] Stakeholder management

There were a number of local residents very interested in the project which Galliford Try’s Client Liaison Officer managed by a forum and weekly updates, our rising main works did impact a number of properties and restrict access. Galliford Try regularly informed and talked to the landowners and residents on a daily basis to ensure they were happy. The scheme did receive a number of emails from local residents concerned about the works and how they would be impacted, again Galliford Try’s project team dealt with all the issues through the forum and talking with the people involved.

Carbon savings

There were significant carbon savings on this project. With agreement from Rossiter Estate, all spoil from the shaft was used to re-profile part of the adjacent field removing undulations against the South West Water boundary. This removed all muck away (90-100 muck wagons) with the additional benefit of significantly reducing traffic through the village.

Conclusion

Galliford Try’s project team managed to get a temporary system up and running before 31 March 2023, ensuring another regulatory compliance date was achieved for the client and the main scheme was handed over to South West Water in June 2023 in line with contract programme.

The Harbour Master at Outer Hope said:

“I have noticed a huge improvement in water quality in the coves and on the beach, which was already of a high standard".

Potters Way, located in the Fengate area of Peterborough, is a recent housing development next to the A1139. The development was built on the grounds of the former Fengate Water Recycling Centre (WRC) which closed in 1988 following the construction of the Flag Fen WRC. In early December 2018, Anglian Water became aware of the collapse of a section of 1500mm diameter concrete sewer pipe in Potters Way when a small hole was found after a customer used a ride-on lawn mower over the area. Temporary repair works were undertaken by the Integrated Operational Solutions (IOS) Alliance - a partnership between Anglian Water, Kier, Barhale and Morrison Utility Services - while a permanent fix could be designed and implemented. Background By the end of December, the IOS Alliance had installed a temporary repair using a vacuum excavator to safely clear the collapsed pipe before using half-pipe and canvas to seal the collapse. The area was also fenced off to prevent pedestrian access and ensure site safety. During this period, Anglian Water received several complaints from customers over the odour created by the collapse. Following meetings with the residents, Anglian Water’s Water Recycling Networks (WRN) team further sealed the excavation and installed carbon filters to the air valves. At the same time, the team repaired holes found in the rising main pipework at the nearby tower. The site was then handed over to the Anglian Water @one Alliance to implement their repair solution with @one partner company Barhale engaged as principal contractor. [caption id="" align="alignnone" width="1200"] Installation of the overhead diversion - Courtesy of @one Alliance[/caption] Finding a solution One of the challenges presented in finding a solution for this project was the high flow rate of the pipework, with modelling of Potters Way showing flow rates of 3,700 litres per second in the event of a 1 in 30-year storm. Downstream of Potters Way, this rises to 4,000 litres per second. To make the matter even more complicated, the pipe featured several significant bends along the affected route that increased the difficulty of finding an adequate solution. An extensive survey of 2.8km of sewer identified 1.79km of concrete sewer pipework ranging in diameter from 1050mm to 1950mm had a condition grade of either 4 or 5. All these pipes were identified as having been subjected to a hydrogen sulphide (H2S) attack which had caused the significant deterioration. The @one Alliance set out to repair an area of the network by covering a key 500m of pipework which serves the majority of Peterborough. Potters Way Sewer Rehabilitation: Supply chain Project delivery: Anglian Water @one Alliance Temporary repairs: Integrated Operational Solutions (IOS) Alliance Principal contractor: Barhale Over pumping: Vanderkamp UK GRP pipe lining: Amiblu Norway AS Lining & manhole repair: OnSite Central Ltd Specialist CCTV Survey: Bright Innovations Group Foam concrete: GS Foam Concrete Diamond cutting: SCS Ltd Cover slabs: FP McCann Ltd Temporary works/shoring: Groundforce Pipe rehabilitation The @one Alliance solutions team opted for a multi-stage solution due to the complex nature of the pipework and the compact area the teams would be working in. In order to repair the sewer, it was decided that a mix of CIPP (cured in place pipe) and GRP (glass reinforced plastic) lining would be used. The majority of the rehabilitation was completed using CIPP lining which allows the lining to be inserted into the shell of the existing, damaged pipework where it is then pressurised and cured in place with ultraviolet (UV) lights. The CIPP relining was split into eight sections covering approximately 360m of the repaired pipeline. At 1375mm in diameter, this installation was the largest diameter CIPP liner that the @one Alliance had ever installed. Six of the eight lengths of CIPP were installed under the A1139. Over pumping In order to fit the CIPP liners, the team utilised an over pumping set up capable of 250 litres per second (l/s). By using bungs at split manholes on the nearby Bourges Boulevard, the team could redirect the flow and use the pumping set up to divert the rest of the flow. The over pumping solution was provided by Vanderkamp UK who had remote monitoring capabilities from the Netherlands and provided the site teams with a mobile app allowing them to see real time data giving them advanced warning of increased flows which would require the removal of the bungs. Without this passive flow management, the over pumping setup would have needed to be able to cope with an excess of 2,000 l/s. The set up was made up of two pipe bridges 350mm in diameter and 5.5m high to allow clearance for high-sided vehicles. GRP lining Alongside the CIPP lining, the team also used GRP lining on a 48m section of 1500mm diameter sewer executing the rehabilitation in live flow conditions of approximately 850 litres per second; the first time the @one Alliance had installed GRP lining in live flow conditions. [caption id="" align="alignnone" width="1200"] (left) Live flow conditions and (right) inserting a new section of Amiblu Norway AS GRP pipe - Courtesy of @one Alliance[/caption] Operating in live flow removed the necessity to install an additional over pumping solution that would have dealt with 95% of Peterborough’s sewage as it combined into one flow towards Flag Fen WRC. In order to commence the GRP lining, the crown of the pipe was removed on a bend and concrete platforms were constructed on either side ensuring a safe working area. A pipe pusher attachment was then used to insert segments upstream and downstream from the bend location. Finally, a prefabricated GRP bend section was installed and connected to straight sections. To safely cut the existing mains the team needed to excavate an area of 6m x 4.5m with a depth of 3.5m. While having to excavate in an urban area is an option the team would have liked to have avoided, the next best solution to the live flow repair would have included installing a temporary pumping station that would have taken up all of Potters Way’s parking and grass area requiring 10 pumps and a 10m x 7m x 7m temporary wet well to complete the required repair. This would have been a major inconvenience for residents and would have seen an increase in the overall cost of the project of 200%.

Amiblu relining pipes to protect sewer networks from H2S attacks - Courtesy of Amiblu Norway AS

Manhole rehabilitation As part of the pre-work checks, it was identified that eleven manholes along the section of pipework required rehabilitation of various levels with the most severely affected requiring structural repair as a result of H2S attacks. Core samples were taken from one manhole which identified that in some places, more than 150mm of concrete had been lost to H2S attacks with no rebar remaining in any of the samples. To repair the manhole, the team used a concrete spray to bring the walls back to their original 250mm thickness, once this had cured a primary and finishing layer were added to ensure full protection against H2S attacks in the future. A new cover slab was also installed after the original was removed to provide access to the manhole, made of precast concrete the slab was also treated for H2S protection. [caption id="" align="alignnone" width="1200"] (left) H2S attack on a manhole and (right) inside a relined section of pipe - Courtesy of @one Alliance[/caption] Challenges Weather provided a significant challenge for the implementation of the solution as the site experienced an unusually heavy rainfall. Flow rate analysis for Flag Fen WRC shows that in the previous five years the average rainfall for the area fell between 35mm and 60mm. August 2020 saw average rainfall of 137mm. Because of the heavy rainfall several weather warnings were issued placing all CIPP lining activities on hold. The impact of the weather was so severe the flow of water increased from its usual 850l/s to 4,000 l/s in just 10 minutes. In order to reduce the risk of flooding outside the Magistrates Court the bungs were deflated, and the flow reverted. Due to the innovative combination of flow diversion and overpumping used in the CIPP lining the impact of the delay was significantly reduced compared to if the team had used the temporary pumping station solution. Rising mains issues During the repair of the sewer the @one Alliance became aware of complaints from the residents regarding the twin rising mains on Potters Way which used to feed into the old Peterborough STW and was diverted into the new gravity sewer discharging into Flag Fen WRC. The primary complaint from customers was the odour produced by the rising mains. The old Peterborough STW was sold for development and the rising mains tower was marked for removal. In early 2022 the @one Alliance returned to Potters Way removing the rising mains and installing a pumping station kiosk removing the odour and significantly reducing the visible profile in the area. Result Anglian Water invested £2.8m into the Potters Way project which will now allow customers across Peterborough to continue to use their taps and flush their toilets without second thought. The relining of the sewer network has ensured the network in the Potters Way area is now protected from H2S attacks for the next 50 years. Colin Handley, Construction Manager said:

“There was fantastic team collaboration between our Tier 2 Supply Chain Partners, the Principal Contractor (Barhale) and the @one Alliance, making it one team delivering the programme. The teams worked tirelessly to monitor the smells and reduce odours, whilst working in open excavations. They purchased additional fans and diverted rising mains to lower H2S and to allow the teams to work safely.”

Ravenhill Avenue is located in south Belfast, close to the city centre. It is a densely populated residential area which has seen recent development of historically industrial sites. In recent years, customers have experienced flooding of their properties during heavy rainfall when the combined sewers fill with stormwater. From concept, it was expected that this project would present many challenges. Existing infrastructure dates back to early 20th century, and with the area being so densely populated, construction would have major customer impact. Project success would be measured against time, cost and quality, so it was important to have the right delivery partners, procured through the most effective form of contract. Background

As part of Belfast’s strategic ‘Living with Water Programme’, NI Water has invested £7m on the Ravenhill Avenue Flood Alleviation Project to upgrade the existing infrastructure in order to:

PROTECT against Flooding: Removing 11 properties from the DG5 (internal flooding) Register. ENHANCE the Environment: Storm separation of 9 hectares of impermeable ground and return to River Lagan. GROW the Economy: Providing first time services (storm sewers) for 572 properties.

NI Water used existing framework partners to develop and deliver the solution:

AtkinsRéalis was appointed through an NEC3 PSC Option E contract to provide modelling support. AECOM was appointed through an NEC3 PSC Option A contract to develop a reference design, and professional services including project management, cost management and site supervision. AECOM acted as NEC Project Manager. GEDA Construction was appointed as the Contractor through an NEC4 ECC Option C contract. [caption id="attachment_12368" align="alignnone" width="1200"] Laying storm sewer on Ravenhill Road - Courtesy of GEDA Construction[/caption] Choosing an Option C Contract

An NEC Option C contract is a cost reimbursable contract with a target price and pain/gain share mechanism. This means that if the costs of the project exceed the Target Cost the excess, or ‘pain’, is allocated between the Client and the Contractor, and if the project comes in under Target Cost then the ‘gain’ is allocated.

The philosophy behind this type of contract is to actively encourage all parties to work together to manage the costs of the works.

As the Client, NI Water wanted to achieve best value. This type of contract incentivised the Contractor to develop value engineering solutions that would generate cost savings to benefit both parties. Payment was through an open-book accounting approach; meaning the Client had full transparency of costs. This also provided good data for the Client’s cost database.

It was recognised that the challenges and complexities of the project should be addressed and risk mitigated through a spirit of collaboration. In an NEC Option C contract, the Client and Contractor share the financial risk, which incentivises collaboration. Through Early Contractor Involvement the project team adopted an open and collaborative relationship.

Then through successful collaboration, risk was effectively managed. On a project of this scale changes are inevitable, but this approach encouraged shared problem solving and fostered a non-adversarial approach.

Managing an Option C Contract

When an NEC Option C Contract is suggested, people often worry about mounds of paperwork. AECOM were appointed as Project Manager for the NEC ECC Option C Contract which included providing cost management services. As with any NEC contract there were monthly valuation assessments and change control to be managed through compensation events. Importantly, with an Option C Contract, interim audits were completed at regular intervals during the project to keep on top of the paperwork and also help verify contractor forecasts.

The Contractor was open and accommodating with the auditing process, understanding the importance of regular checks and the cost elements that make up the Schedule of Cost Components plus what would be a Disallowed Cost or included in the Fee. It was important for the Contractor and the project manager to remember that it was not a ‘Cost-Plus’ type form of contract and that project controls were imperative to ensure a commercially acceptable outcome.

While regular checks of invoices and payments would be expected in an NEC4 ECC Option C contract, the Contractor effectively managed and utilised the Cl.50.9 mechanism to gather records for part of the works at these regular intervals, invite the Project Manager to inspect them, and demonstrate that they have been correctly assessed. Such notification puts a time limit on the Project Manager to review and make a decision on these records, ensuring that assessments are accurate throughout the project, rather than a time-consuming substantial audit at the end.

While a Contractor would normally carry out regular internal updates to their forecasts on other forms of contracts, it was encouraging to see under NEC4 ECC Option C that the Contractor makes this information readily available to the Project Manager and to the Client to aide their various monthly reports and understanding of how the project is progressing. While forecasts can understandably change, the Contractor was required under the Contract to explain any changes made from the previous forecast had been submitted. Inevitably this stimulated further collaboration between the Project Manager and the Contractor to discuss and mitigate risks where possible through the early warning and value engineering processes if appropriate.

[caption id="attachment_12369" align="alignnone" width="1200"] Manhole construction – Courtesy of NI Water[/caption] Risk mitigation on an Option C Contract

As already noted, Option C contracts share the risk and reward between Client and Contractor with everyone focused on balancing cost, time and scope. Typically once a contract has been awarded the Client will not move on scope, as they see scope and quality being interlinked. On Ravenhill both the Contractor and Client understood that value engineering, requiring a change to scope, could benefit both parties.

Value engineering was only possible due to the buy-in from NI Water’s Operation & Maintenance team. Non-man entry manholes to the 1800mm combined sewer were proposed by the Contractor to save on time and cost, whilst also reducing health & safety risks during construction. It was also agreed with NI Water that non-man entry would act as a deterrent for anyone attempting to access the manhole without the required equipment.

Another example of value engineering originated when a clash was predicted between the new storm sewer and an existing alleyway sewer. Again the Contractor and designer worked with NI Water’s operations to develop a solution which not only resolved the clash by sleeving the combined sewer within a ductile iron pipe but also reduced the number of new manholes that were required. Thus again a change of scope saved on time and cost.

[caption id="attachment_12364" align="alignnone" width="1200"] Reference design cross section sketch - Courtesy of AECOM[/caption] Construction

The initial tunnelling stage of the project was detailed in a previous article published by WaterProjectsOnline in 2022. After the tunnel was completed, the next phase was to replace the brick egg sewer which was identified to be in very poor condition, and the 1050mm combined sewer, which included a concrete surround associated with timber heading construction. These two sewers were to be replaced by an 1800mm combined sewer which would create space to lay the 900mm storm sewer required to achieve the proposed storm separation. There were many challenges with this proposal including laying a 1800mm combined sewer up to 6m deep in a narrow residential street. Also, and most notably, major flow control was needed which effectively meant building a mini temporary pumping station.

In order to minimise the risks associated with the proposed works, an early warning workshop was held between all parties. A list of alternative solutions were proposed, relevant assessment criteria selected and then each option was evaluated. From the workshop an alternative more sustainable solution was proposed which retained the existing 1050mm concrete sewer, negating the need for flow control and instead involved laying a new 1050mm concrete sewer at a shallower depth above the existing to provide the required capacity. It is estimated that the revised design saved the project £850k and at least six months on the construction programme. Again all relevant stakeholders including NI Water operations were included in the value engineering process.

[caption id="attachment_12365" align="alignnone" width="1200"] Revised design cross section sketch - Courtesy of AECOM[/caption] Ravenhill Avenue Flood Alleviation Project: Supply chain Main contractor: GEDA Construction Project & cost management: AECOM Civil design: McAdam Modelling support: AtkinsRéalis Geotechnical designer: Cassidy Geotechnical (Belfast) Civil engineering: Campbell Contracts Tunnelling: Active Tunnelling Ltd Tunnel design: BSP Consulting Temporary works: Groundforce Temporary works designer: Byrne Looby Precast concrete: Tracey Concrete Pipeline supplier: APP Fusion Group Metalwork: LA Steel Fabrication Traffic management: Graham Reinstatement: Breedon Landscaping: Annett Landscaping Tree surgery: JC Tree Surgery Fencing: Kane Fencing Construction materials: McNaughton & Blair [caption id="attachment_12370" align="alignnone" width="1200"] Storm separation at Millar Street - Courtesy of GEDA Construction[/caption] Delivering an Option C Contract

So what was an Option C Contract like to deliver from a contractor’s point of view? GEDA Construction, the Contractor had successfully delivered many NEC Option A and B contracts and other bespoke contracts but had limited experience of NEC Option C.

There were many learnings regarding the particulars of delivering an NEC Option C Contract including:

Collaboration across the client and contractor team is essential for the project to work. There is full visibility of costs whether it be valuations, compensation events or value engineering proposals. Usually with an Option A the Contractor will draw down against a sum of money for various tasks completed on site. Instead in this form of contract, the Contractor had to get all costs from their accounting department, present these costs in the correct template for an Option C Contract and carry out a projection for the next four weeks work in each valuation. AECOM would then assess, query and certify each valuation. The Contractor also had to present back up for the various costs in each valuation for regular audits. In the case of Ravenhill, five interim audits were undertaken at regular intervals throughout the project. Everything was checked by AECOM, from subcontractor costs, to materials, to people and plant rates. Overall, the Contractor noted the use of an Option C Contract was the correct contract type to deliver this project. Compensation events were agreed in a reasonable time frame. Also, the risk is shared between the Client and Contractor creating more of a team environment. There is always the incentive of achieving gain not pain to keep everyone’s mind focused. [caption id="attachment_12372" align="alignnone" width="1200"] (left) Preparing for reinstatement at Bakers Court and (right) Permanent reinstatement on Ravenhill Avenue - Courtesy of GEDA Construction[/caption] Conclusion

Through good project management, successful utilisation of the NEC4 Option C Contract and collaborative working, the project team delivered a solution that met the project drivers.

PROTECT against Flooding: Removing 11 properties from the DG5 (internal flooding) Register. ENHANCE the Environment: Storm separation of nine hectares of impermeable ground and return to River Lagan. GROW the Economy: Providing first time services (storm sewers) for 572 properties.

However, this approach delivered other benefits that set a platform upon which to build a collaborative relationship to deliver future projects:

Health & Safety: More than 700 days accident-free. Stakeholder engagement: Considerate Constructors Scheme: ‘Excellent’. Social value/legacy: Successfully achieved through education and community involvement. United Nations Sustainable Development Goals: The project contributed to at least 6 goals: Quality education. Clean water & sanitation. Decent work and economic growth. Industry, innovation & infrastructure Sustainable cities & communities. Climate action.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Challenges

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

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

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

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

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

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

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

Customer engagement

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

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

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

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

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

Outcome

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

A municipal wastewater treatment plant in Poland was struggling with a persistent issue; hydrocarbon contamination in the wastewater coming into the plant. The plant had not been designed to deal with high levels of hydrocarbon contamination, such as that coming from untreated industrial wastewater, which meant that every time there was a contamination event in the sewerage system, the WwTP performance was affected and, in the worst case, contamination was also released into the environment and regulations were broken. Moreover, the activated sludge performance was affected and, if the levels were high enough, this could lead to the process needing to be stopped altogether. The solution In the spring of 2022, Multisensor Systems Ltd’s Polish distributor (GREMES) was contacted to review options and following preliminary discussions, engineers at GREMES proposed an MS1800 VOC gas analyser to be installed directly above the sewage line. The MS1800 is designed to monitor VOC concentration in the headspace above the wastewater and from this, calculate the hydrocarbon contamination within the wastewater. [caption id="" align="alignnone" width="1200"] Installation diagram - Courtesy of Multisensor Systems Ltd[/caption] The instrument was installed in a temperature controlled cabinet, ensuring that the analyser’s technical specifications were met in the open air. The system was linked to a remote control system to provide a live data feed and allow the user to generate reports and alarms. The site selected for the installation is a wastewater pumping station, the last before the intake of the WwTP. This has made the installation more straightforward and, with a constant flow of wastewater, reduced the risk of H2S build-up that could be detrimental to the longevity of the system. The data The instrument was installed in July 2022 and, aside from a brief pause, has (at the time of writing - April 2023) been working non-stop ever since. The data below shows how the instrument has clearly identified several peaks over the course of several months. These peaks have been positively associated with contamination events and corroborated by analysis carried out by the WwTP. After several months of testing the client is extremely satisfied with the results and is in active discussions with GREMES to develop the next phase of the project that will consist in deploying a network of analysers across strategic points in the sewerage network. [caption id="" align="alignnone" width="1200"] Graph showing hydrocarbon readings from September 1, 2022-March 1, 2023 (graph produced by independent software) - Courtesy of Multisensor Systems Ltd[/caption] Uses The MS1800 in this installation will be mainly used to identify contamination events and locate the source of pollution but also to protect the WwTP by diverting industrial wastewater for separate treatment. Strengths This system allows the accurate on-line monitoring of hydrocarbon contamination in the sewage system, without touching the water, designing out of the equation words such as 'cleaning', 'maintenance' and 'filtering'. Conclusion As can be seen from the data above, the MS1800 is an excellent solution for the monitoring of hydrocarbon contamination in any sewerage network. If your operations are suffering from unexpected hydrocarbon contamination at the raw wastewater intake of your WwTP, you can get in touch and discuss your case with our consultants. This article was prepared by Multisensor Systems Ltd Alexandra Court | Carrs Road | Cheadle | SK8 2JY P: +44 (0)161 491 5600 | E: [email protected] | www.multisensor.co.uk  

East Budleigh is a small village in East Devon, UK located about 2 miles (3.2km) north of Budleigh Salterton. The village features a bypass culvert, constructed in the 1970s. The culvert is approximately 280 metres in length, of Armco construction, oval shaped and constructed from corrugated metal sheeting (with a concrete floor laid over it during the last 10 years). The existing culvert was in a poor condition, with joints failing and large voids appearing in the material outside the culvert structure. These failures led to a small localised collapse in the road above during flooding in 2012 and there were concerns that in the future that a larger collapse could occur, causing a failure in the highway surface. It was decided that this culvert required structural strengthening due to minimal cover to the busy road above, and to maintain flows through the culvert in storm conditions. [caption id="" align="alignnone" width="1200"] (left) Host pipe inspection and (right) site preparation - Courtesy of MDA Ltd[/caption] Project scope The Environment Agency employed Atkins to design the culvert rehabilitation, with Kier appointed as main contractor who in turn appointed specialist contractor Matt Durbin Associates to consult on rehabilitation options and carry out the work. Given that the location was a highly trafficked residential area with minimum cover to the road, it was decided that lining with a structural GRP segment lining system offered the best solution and Amiblu‘s NC Line, non-circular GRP Structural Relining system was selected for the project. In total some 300 metres of Amiblu NC Line Arch Shape liner, 2360mm wide x 1350mm high was manufactured to the required WRC Type II standard and ISO 16611. Amiblu’s application engineers worked in partnership with Matt Durbin Associates to understand specific performance criteria required in order to create the optimal shaped pipe to fit the needs of the project and production started in January 2022 at Amiblu’s Gdansk factory in readiness to commence February deliveries. The culvert meandered with the local water course, and on inspection for the design of the linings was found to include long radius bends which were designed for pre-manufacture so that they would install without issue on site. Despite the apparent loss of cross-section in the culvert the design and smooth internal finish of the linings ensured that the flow capacity requirements for the culvert would be met. Given the small village size and the traffic management requirements for the installation works, coordination with local residents and parish councils regarding the large deliveries to site was essential and worked extremely well. [caption id="" align="alignnone" width="1200"] Amiblu NC Line 2360 x1350mm ready for installation[/caption] Work commenced on site on 14 February with site preparation works. Installation into the culvert commenced in March. In total, all installation and annulus grouting operations were completed in just 8 weeks. Amiblu’s NC Line provides structural rehabilitation to existing non- circular culverts and host pipes that have reached a point in their service life where the asset owner must decide to renovate or replace. GRP pipe systems made by Amiblu maintain excellent long-term stiffness, corrosion and abrasion resistance and are engineered for 150 years‘ service life. Project parameters Country: UK City: East Budleigh Year: 2022 Application: Culvert reline Installation: Trenchless Technology: Amiblu NC Line Total length of pipe: 300m Nominal Diameter DN (mm): 2360 x 1350mm Nominal Pressure PN (bar): PN1 Nominal Stiffness SN (N/mm2): As per design criteria Supply chain Client: Environment Agency Contractor: Matt Durbin Associates Ltd Consulting engineer: Atkins Structural GRP pipe liner: Amiblu [caption id="" align="alignnone" width="1200"] Completed installation - Courtesy of MDA Ltd[/caption] What they said Daniel Gay, Project Manager for the Environment Agency:

“From a client perspective, the GRP liner solution has provided a cost and time-effective approach to prolonging the asset life. We were hopeful to avoid any requirement for open cut solutions to minimise the impact to the local community and meet delivery deadlines. We also needed to ensure that the flood risk standard of protection was not altered to upstream or downstream receptors. The structural GRP liner allowed for a bespoke unit to be installed which optimised the culvert capacity to retain the flow performance and extended the life. The outcome of improvements to the culvert have reduced flood risk to 27 residential properties, significantly reduced future maintenance costs and health and safety risks to the public.” 

Adrian Parker, Senior Project Manager, Kier:

“This project is a great example of how accelerated delivery can be achieved under the Environment Agency’s Collaborative Delivery Framework. From identification of the scheme for fast tracking in June 2021, the scheme was on the ground in February 22 and complete by June 22. MDA have done a great job and thanks also to Amiblu.” 

  For more information: Amiblu UK | +44 (0)7786 013574 | www.amiblu.com    

Gipsy Patch Lane, Bristol is a main road forming part of a new Cribbs Patchway Metrobus route in South Gloucestershire. As part of an asset assesment programme a few years ago, a CCTV survey showed many defects throughout the length of the surface water culvert at Gipsy Patch Lane. The defective sections ran under the busy carriageway so, as an interim maintenance measure the local authority excavated a section of the road and installed a concrete slab over the pipe to protect it from further deterioration or collapse. During heavy rainfall over the summer of 2020, the same pipe was found to have suffered structural defects and root ingress through open joints and connecting laterals resulting in localised blockages of up to 90%. A new man-entry survey showed the pipe beneath the concrete slab to be deformed. Major works were already under way in the area to replace a railway bridge on Gipsy Patch Lane, so South Gloucestershire Council took the opportunity to make improvements to the sewer in conjunction with the Network Rail works to minimise disruption, which was further aided by lighter traffic due to the regulations set in place for Covid-19 pandemic. Under the Council’s Climate Resilient Scheme, the task was to find and deliver a suitable solution before opening the road up to traffic and risking a pipe collapse; two options were considered; open-cut to replace the section of pipe or trenchless technology to reline the affected pipe with little disruption to the area. [caption id="" align="alignnone" width="1200"] First post-Brexit delivery of Amiblu pipes (January 2021)[/caption] Doug MacKay, Project manager, South Gloucestershire Council consulted with Julian Britton, Critical Sewers Manager, Wessex Water and Matt Durbin Associates; specialist confined space and GRP structural relining installer to determine the most efficient and economic technique. As with many suburban roads, Gipsy Patch Lane is laden with many services within the carriageway, so rehabiliatation of the existing pipeline through trenchless installation of 210m x DN800 structural GRP jacking pipe supplied by Amiblu was decided upon. As the contract was classed as emergency works, subject to time constraints and speed of execution the use of Amiblu’s GRP pipes meant that MDA were able to remove the need for costly over-pumping and install the pipes in live flows, whilst minimising their work area to a single lane closure for uninterupted access to local businesses. During the installation of the initial contracted 210m, a further 70m section of the pipe downstream required attention, so MDA undertook the additional works saving additional costs and disruption at a later date. Amiblu jacking pipes are often utilised in pipe rehabilitation projects such as this as they offer a high compressive strength and, compared with conventional materials, an improved hydraulic coefficient. The hydraulic analysis carried out for Gipsy Patch Lane showed no reduction in hydraulic performance and as the pipes are designed to offer a service life in excess of 150 years with minimal maintenance, the life expectancy of this asset is greatly improved. [caption id="" align="alignnone" width="1200"] (left) GRP pipe installation and (right) the completed relining - Courtesy of MDA Ltd[/caption] Doug MacKay, Project Manager with South Gloucestershire Council, commented:

"For this project, the Council had concerns about the risk of potential pipe collapse under traffic loading. The fact that road was already under a full closure due to an adjacent project to replace an old railway bridge meant that timing was critical for this project. It was essential that the work had to be completed before the proposed re-opening of the carriageway. Additionally, there was a limit to the funds available through the Climate Resilience budget to complete the scheme. We worked very closely with MDA and our designers to review the site constraints, risks to programme delivery and budget constraints to determine the most appropriate remedial solution. I was grateful for the time, input and patience spent by MDA during this period to explain the construction process and provide answers to all our questions and concerns in advance of making the final decision on the preferred option.

Once the decision was made to proceed with the pipe-jacking option the process was relatively straight-forward and stress-free from the Council side of things. In the main this was down to the excellent communication, planning and execution of the works by MDA. Both projects were completed on-time, within budget and with minimal disruption to the public and businesses that rely on using Gipsy Patch Lane.”

[caption id="" align="alignnone" width="1200"] Amiblu pipes require minimal site storage - Courtesy of MDA Ltd[/caption] Project details Country / city: UK, Bristol Year of construction: 2021 Installation time: 4 weeks Application: Sewer rehabilitation Installation: Trenchless technology Technology: Hobas Total length of pipe: 280m Nominal diameter DN (mm): DN800 Nominal pressure PN (bar): PN1 Nominal stiffness SN (N/mm²): 32,000 Supply chain Client: South Gloucester Council Contractor: Matt Durbin Associates Ltd Consulting engineer: South Gloucester Council Structural GRP jacking pipe: Amiblu Amiblu Structural Relining Pipes Amiblu pipes have a smooth, resin rich internal surface with high abrasion resistance which consistently prevents fouling and build up, leading to low maintenance costs and high flow rates even at low gradients. Both Jacking and relining pipes are supplied with in-line flush joints which prevent the intrusion of roots and further ensure the integrity of the asset. Available in diameters from DN300 to DN3600, in varying strengths and lengths. Amiblu’s systems are cost effect, durable alternatives to traditional pipe systems.   For more information: Amiblu UK | +44 (0)7786 013574 | www.amiblu.com    

The waterproofing challenge Thames Tideway is London’s new “super sewer” which will run from Acton to Beckton and prevent millions of tonnes of pollution reaching the River Thames. The West Section is being It is constructed by the joint venture between BAM, Morgan Sindall and Balfour Beatty. During the design phase, technical discussions were held between SMR Projects and the JV designers Morgan Sindall Underground Professional Services to explore how Xypex’s crystalline technology could assist in reducing the permeability of the concrete. This was especially important across the construction joints. Trials were undertaken in conjunction with a ready mix company to establish how the crystalline technology behaved within the very specific mix design. In addition this was to prove its water tightness over standard tunnel construction methods. A number of trials were set up with and without Xypex products for a clear comparison. Successful trials The trial results proved that the addition of Xypex C-Series Admix to the concrete gave the greatest protection against permeability. The growth of the crystals across the joint gave a seal in excess of what was thought possible. When tested across the 45 degree “day” joint, cores were taken through the joint in 3 axis to test for water permeability and the results were more than enough to confirm that this technology was superior. [caption id="" align="alignnone" width="1200"] Courtesy of SMR Projects Ltd - Xypex UK Distributors[/caption] Change of design The western section was originally planned to be constructed using a sprayed concrete primary liner and a cast in situ secondary liner with a waterproof membrane placed in between the two layers. The addition of Xypex C-Series Admix meant that, following the trials, the stakeholders were satisfied enough to remove the membrane in the Hammersmith connection tunnel. The proven benefits of using Xypex C-Series Admix lead to its use throughout the whole of the Western Section. Added benefits of Xypex The Xypex C-Series Admix waterproofed the concrete and the joints during the hydration period of the concrete. It also provided additional benefits over and above non-active pore blocking admixtures by having the ability of self-heal cracks up to 0.4mm. Furthermore, microbial induced corrosion is common to sewage collection and wastewater treatment structures. It’s a challenge well known to engineers as they address the ever-increasing requirement for structures that will meet the growing demands of industry, the environment, economics, and the need for improved water supply and sanitation. Xypex is proven in new sewage and wastewater treatment structures. It is excellent at handling chemical attack in severe biochemical conditions. [caption id="" align="alignnone" width="1200"] The Xypex solution; Xypex C-Series Admix - Courtesy of SMR Projects Ltd - Xypex UK Distributors[/caption] The final specification SMR Projects supplied 100,000 kilograms of Xypex C-Series Admix. This was used on the primary liner incorporated within the sprayed concrete, awaiting the secondary liner to be cast directly against it.   For more information: SMR Projects Ltd - XYPEX UK Distributors: +44 (0)1295 279747 | www.smrxypex.co.uk