Supply Chain - Asset Maintenance & Rehabilitation - Technical Documentation

Tunstall Reservoir is located approximately 5km to the north of Wolsingham, in County Durham. It is an impounding reservoir retained by an earth filled embankment with a central clay core. The dam is approximately 25m high and 300m long. The reservoir was previously used to feed a water treatment works located at the toe of the dam; which is now decommissioned. The reservoir is now used for amenity purposes and to provide environmental compensation flows to the downstream valley. Following a Statutory Inspection under Section 10 of the Reservoirs Act, a number of measures in the interest of safety were recommended by the Inspecting Engineer in order to ensure the safety of the dam.

Section 10 of the Reservoirs Act

Following a Statutory Inspection under Section 10 of the Reservoirs Act, a number of measures in the interest of safety were recommended by the Inspecting Engineer in order to ensure the safety of the dam. These recommendations involved the following:

• Recommissioning the existing siphon that used to feed the works and was no longer in use had to be intercepted and provided with a new route in order to provide additional drawdown capacity to the reservoir.
• Repairs to the lower part of the spillway where the existing blocks were damaged.
• Filling an existing tunnel within the dam structure.

[caption id="attachment_18531" align="alignnone" width="1200"] (left) Condition of the spillway blocks prior to the works and (right) new concrete slab with stainless steel protection to the joint - Courtesy of Esh-Stantec[/caption]

Siphon re-commissioning

Various options were considered at the concept stage in order to restore the use of an existing siphon that was abandoned in the early 2000s when the treatment works were decommissioned. The preferred option involved the following:

1. A siphon discharge chamber to break the siphonic effect. This was decided given the uncertainty about the existing system and the significant difference in levels in the downstream leg. Thus, the water would flow by gravity between the chamber and the outfall. This discharge chamber also functions as a thrust block to restrain the thrust acting on the new gate valve that has been installed immediately upstream of the chamber.
2. The use of the existing settlement tanks to retain the water and aid to the settlement of suspended solids. A penstock chamber has been provided between the tank and the new discharge point to retain the water for a day before it is discharged into Waskerley Beck once the majority of the sediment has settled.
3. Routing the new pipework away from the areas of the embankment that present the most valuable Waxcap habitats. Waxcap mushrooms are rare as they are restricted to grassed areas that are not grazed, and are locally protected in Durham.

[caption id="attachment_18533" align="alignnone" width="1200"] Tunstall Reservoir dam - Courtesy of Esh-Stantec[/caption]

Spillway repairs

The original Victorian spillway structure is formed by sandstone blocks bedded in concrete. However, the Inspecting Engineer identified that the majority of the blocks in the lower part of the spillway presented signs of wear and tear and needed replacement.

The proposed solution consists of four new reinforced concrete slabs that have been placed over the existing spillway, except the most upstream slab where blocks had to be removed to tie-in with the existing structure and avoid a step. An expansion joint was necessary in the centre of the new slabs. The flexible sealant in this joint has been covered by a stainless steel plate that has been designed to protect the sealant from the predicted high velocities expected in the flows and reduce the maintenance requirements.

A number of groundwater relief drains have also been incorporated into the design in order to capture the emerging groundwater at the lower part of the spillway and both reduce the hydraulic load on the new slabs and improve the long-term reliability of both the new concrete and the remaining sandstone blocks. These discharge to a new headwall in the bank downstream of the end of the spillway.

[caption id="attachment_18535" align="alignnone" width="1200"] Tunstall Reservoir spillway - Courtesy of Esh-Stantec[/caption]

Tunnel infill works

When the dam embankment at Tunstall was completed and the filling of the reservoir began, significant leakage was observed through the eastern abutment. A concrete cut-off wall extending into the hillside was constructed in 1879 which significantly reduced the leakage rate. Nevertheless, as some leakage continued, a tunnel and shaft were constructed downstream of the cut-off wall, and an 18-inch cast iron diameter pipe was installed inside the tunnel to capture the leakage and convey it to the treatment works.

Following the Section 10 inspection of the dam in February 2021, a number of Measures in the Interest of Safety (MITIOS) were raised recommending works to address the leakage and the stability of the tunnel. One of these IOS measures recommended to fill the tunnel whilst providing some drainage, as a result of the concerns about its structural integrity and the potential risk to the integrity of the dam embankment and the spillway in the event of a collapse of the tunnel.

The project team scoped and contracted a ground investigation (GI) in Autumn 2022 to investigate the leakage paths into these tunnels.

Based on the findings of the GI and the review of the reservoir levels, it was concluded that the cut off wall is in good condition and that the main flow path goes around the concrete cut off wall. There is also a strong correlation between reservoir levels and the recorded flows, which decrease significantly when the levels are 6 m below the top water level (TWL). This was observed again during the construction works, as the water level was kept 6 m below the TWL for health and safety reasons while there was work ongoing in the tunnel and the spillway.

[caption id="attachment_18544" align="alignnone" width="1200"] (left) View in the unlined section of the tunnel (notice the beams across the soffit) and (right) view of pipe inlet and partial headwall (notice standing water on the invert) - Courtesy of Esh-Stantec and CC Informatics[/caption] Various options were considered during the Concept stage. The option of not filling the tunnel was disregarded as it would not eliminate the potential risk to the integrity of the dam embankment and spillway channel. Filling the entire extent of the tunnel was considered, however it was not preferred due to the significant constraints associated with it. These constraints include the difficult access and requirement to work in a confined space, potential land ownership issues, the presence of a SSSI immediately to the east of the abutment, and the increasing depth to the tunnel as it continues beyond the spillway. For all of these reasons, it was agreed with that filling the extent of tunnel beneath the dam and spillway would be sufficient as that would eliminate the risk to these structures.

Three possible fill materials were considered:

1. Cement grout was discounted due to concerns of potential pollution as a low viscosity mix would be likely to mix with groundwater and filter through the rock, causing a pollution incident.
2. Foamed concrete was discounted as a result of the potential constraints to place it at the furthest point inside the tunnel, and the remote location of the site and access within the site would further complicate the timely delivery of concrete.
3. Expanding geopolymer foam was selected as the preferred material as it reduced the risks associated with grout and foamed concrete; and it had successfully been used by Esh-Stantec in the delivery of other projects.

The expanding geopolymer foam was deemed to be more cost-effective than the alternatives as it offered significant savings to the installation process, because:

• It avoided the risk of pollution and therefore any mitigation works to stop grout leakage;
• Simple installation from a mobile compound, avoiding the need for complex plant and equipment;
• Geopolymer mix materials delivered to site in barrels, allowing for easy storage and transport within the site.
• Installation from the surface via boreholes every 10m along the line of the tunnel.
• Lower carbon footprint that cement based alternatives.

[caption id="attachment_18545" align="alignnone" width="1200"] (left) View of the geopolymer in the tunnel, and (right) view of the pea gravel stop end - Courtesy of Esh-Stantec and CC Informatics[/caption]

The filling was undertaken via a number of injection holes that were drilled from the surface at 10 metre intervals, and expanding geopolymer was injected via these injection points. The progress on site was as follows:

1. A pre-drilling survey took place to confirm the condition of the pipe in the tunnel ahead of the works.
2. Eleven injection holes were drilled along the dam embankment and across the spillway.
3. Prior to the injection, after the drilling had been completed, high resolution cameras were used in each injection hole and a drone survey was carried out to confirm that there was no damage caused to the pipe and that the expanding geopolymer would not enter the pipe.
4. Pea gravel was introduced through the final injection point in order to create a mound that would stop the advance of the geopolymer and prevent it from blocking the pipe. The use of the gravel mound avoided the need to carry out works inside the tunnel with the associated risks of working in the confined space.
5. Once the project team was satisfied that the drilling had not cause any damage to the pipe, the injection began, advancing at 10 metres per day on average.

[caption id="attachment_18534" align="alignnone" width="1200"] Overview of the siphon diversion route in preparation for the works - Courtesy of Esh-Stantec[/caption]

Tunstall Reservoir MITIOS: Supply chain - key participants

• Principal designer & contractor: Esh-Stantec
  • Esh Group
  • Stantec UK
• Geopolymer injection subcontractor: Geobear Ltd
• High resolution cameras & drone survey: CC Informatics
• Confined space entry specialist: MRS Training & Rescue
• Ground investigation: Ian Farmer Associates
• Topographical survey & laser scan of tunnel: Academy Geomatics Ltd
• Pipework modifications: UTS Engineering
• Steel fabrications: JHT Fabrications Ltd

Conclusion

The contract has been delivered by Esh-Stantec and the recommendations in the interest of safety made by the Inspecting Engineer have now been addressed. The siphon will provide additional drawdown capacity to the reservoir in the event of an emergency, the damaged part of the spillway has been repaired to a satisfactory standard, and the potential risk of collapse of the tunnel has been removed.

The challenge to improve environmental performance is common and topical across the industry, and Southern Water are no different; with considerable effort and headway being made to reduce said impact. A major transformational project is underway business-wide, which sees them moving from a reactive state to one that is more planned and proactive through the adoption of maintenance and reliability best practices. This case study sets out their challenges and how they have been tackled, including how they, in collaboration with consulting partners Binnies, embraced technology to provide an immersive and engaging training course to help embed the new ways of working with their field teams.

Problem statement

Southern Water historically relied on reactive responses to maintenance issues, with day-to-day operations being driven by asset failure - approximately 70% of maintenance activities were reactive. Naturally, working this way impacts an organisations resilience for dealing with asset failures, meaning the impact is greater as an urgent response is required. Uncontrolled breakdowns often result in unconsented pollution events, water quality breaches, and loss of supply events, all of which attract financial penalties, and increased pressure from regulators and their customers for improved performance.

Some of the challenges which Southern Water wanted to resolve included a lack of accurate asset data, low completion rates of preventative maintenance activities, and the suitability of those  tasks, combined with an overall concern about the approach to asset health.

Project overview

The Planned Maintenance Project was developed to address maintenance challenges, focussed on improving asset health and reliability, and shifting the organisational culture. The project was designed to provide a refreshed operational maintenance strategy based on outputs from Failure Modes Effects & Criticality Analysis (FMECA), which would then be used to develop Standard Operating Procedures (SOPs) to provide a clear methodology for operators to follow. Additionally, operational staff needed to be trained on the new ways of working, so everyone impacted understood what was changing, why it was changing, and what it meant for them. Asset Management professionals will be aware of the P-F curve; the aim of the project was to get Southern Water on the journey to moving further up the curve, equipping them to easily identify asset health issues, and generate the required corrective actions to avoid a failure. The project was designed to ensure it was paced appropriately. Too many change initiatives become too big too quickly, and ultimately fail. The first step of this process wasn’t to get the teams working with predictive technology, CBM, or Machine Learning. Instead, the aim was to equip them to start utilising human senses, carrying out standardised and consistent inspections to recognise the early signs of asset deterioration and act appropriately in a planned manner.

[caption id="attachment_14634" align="alignnone" width="1200"] Image showing P-F failure curve - Courtesy of Binnies[/caption]

The original scope was focused on addressing the root cause of some of their largest financial penalties. This included 100 of the most critical wastewater pumping stations in the business, where sites had a history of pollution events or posed a significant risk to the environment or local community should there be a spill event. During the early stages of the project, Southern Water reviewed the business case and realised that expanding the scope was the right thing to do. This drove business-wide improvements and a consistent way of working, resulting in the scope being extended to cover the entirety of the Southern Water Operational estate.

Project deliverables

Asset register review: An effective maintenance programme requires an accurate asset register. Before any follow-on activities could be completed, Binnies were tasked with completing asset data capture surveys of the original 100 in-scope sites. The surveys captured all required asset attributes, plus a baseline condition report. Additionally, 3D photogrammetry was completed to create a digital twin model of the sites. The project led to 100,000 assets being surveyed, where the teams identified an additional 25% uplift in unregistered assets and corrected a 40% error margin in the data. This exercise put Southern Water in the best possible position for the next stages of the project. Companies struggle to accurately operate and maintain their equipment if they don’t know it exists, or the information held for it is incorrect.

Failure modes effects & criticality analysis: With the asset surveys complete, the next stage was to create network maps of the processes, which are used by field teams to support new starters and improve site familiarity. Within Binnies, the maps were used as part of the FMECA process as a guide to ensure all asset types within a process or site are captured within the analysis. The maps and FMECA were done on either a generic basis where common configurations had been identified, or site-specific/bespoke for higher criticality sites or those with a unique configuration.

Standard operating procedures: Completion of the FMECA exercise provided the maintenance task lists needed for each asset. The next stage was to use the tasks to populate the Standard Operating Procedures (SOPs) documents. Historically, teams would pass on their knowledge based on what they had been shown by their predecessors, or through their own understanding of a task instruction. Naturally, this brings inconsistencies with task completion, and the risk of misinterpretation. These documents provide operations with a clear set of job instructions to ensure tasks are completed consistently. Like the FMECA process, the SOPs were site-specific where needed, but used the common configurations allowing Binnies to produce templated documents in high volumes.

Through FMECA and the creation of Network Maps and SOPs, Southern Water gained over 20,000 operational documents which provided a standardised way of working and promoted asset health and reliability.

[caption id="attachment_14636" align="alignnone" width="1200"] Image showing example of Standard Operating Procedures - Courtesy of Binnies[/caption]

Dynamic risk model: To help support the internal deployment of effective, executable maintenance tasks, Binnies developed a Dynamic Risk Model for Southern Water. Understanding that risk is dynamic and not fixed, the model was developed to allow Southern Water to manage their assets based on real-time condition, understanding that time-based maintenance is not always the best solution. The model looked at fixed criticality but also took into consideration real time operating characteristics, telemetry data, and the condition data the field teams were submitting. The model was set up to enable Southern Water to schedule the right maintenance to the right assets, at the right time.

Project embedment

The final stages of the project involved training operational staff on the new tools and technology being implemented, and on-site embedment checks with the field teams to ensure the classroom learning could be applied in the operational environment. The course was designed to be interactive and immersive, reducing the passive learning time to promote engagement and interaction to ensure the operational teams were engaged throughout the sessions. The team designed a training programme which focussed around the newly created digital scans of the Southern Water sites. These scans were used to house the training content, in which the delegates were taken on a virtual tour of their sites. The course contained all key business messages along with foundational asset management knowledge to provide delegates with all of the information they need to understand what changes were being implemented, why the changes were needed, and what it meant in terms of new tools, and new ways of working. The second half of the training course was set up so the delegates could experience the practical requirements of the learning through using the 3D technology. Training scenarios were built into the models; these scenarios contained the job instructions from the SOPs, and a description of what was found when completing the inspection. The delegates discussed the consequence of the asset failing, and what the appropriate corrective action should be.

Following the classroom training, a 6-month Early Life Support (ELS) team was stood up to provide one-to-one coaching and assurance checks with the field teams to confirm they were able to put the classroom learning into action in the operational environment.

The training provided 67 face-to-face sessions, training over 500 of the Southern Water operational workforce. Additionally an eLearning course was created to be added to the Southern Water learning system. This was to be used for new starters and for anyone who needed refresher training following the ELS programme. The training received outstanding feedback from those trained. The trainers fed back to the project team that throughout the entire training deployment delegates remained highly engaged, and the use of 3D models promoted conversation in the room. Many of the delegates were familiar with the sites used to model the training which enabled them to discuss some of the issues they faced providing additional insight for the groups being trained. A temperature check was completed to gauge the delegates’ confidence in the new ways of working landing successfully, this scored 84%.

[caption id="attachment_14635" align="alignnone" width="1200"] Screen grab of 3D training model - Courtesy of Binnies[/caption]

Next steps

To further support the embedment of the new ways of working, and to overcome some of the data challenges being faced by Southern Water, the company are currently in the process of implementing a new Enterprise Asset Management System, IBM Maximo.

This platform will provide an integrated solution to data management, ensuring all key information is stored in one system, breaking down some of the barriers they had previously experienced with data management. It will enable the field teams to effectively capture and feedback asset condition data and support central teams in monitoring and trending the information in parallel with the dynamic risk model, to ensure risk management is optimised and corrective actions driven at the right time.

The deployment of the system will be carried out in a phased approach, with the first pilot deployment due to go live on the Isle of Wight in July 2024.

Southern Water and Binnies continue to work closely together, with the asset data capture surveys now being deployed across the entire water supply estate to increase the baseline asset information standard. Additionally, Southern Water are investing further in their staff by increasing their problem-solving capability through the completion of Root Cause Analysis training provided by Binnies specialist trainers.

For Southern Water, proactive maintenance is not the end state, it is very much the start of an exciting journey.

King George V Reservoir (KGV) is an operational raw water storage reservoir located in the Lea Valley at Walthamstow and is a Site of Special Scientific Interest (SSSI) with restricted access. It is controlled by Thames Water’s Lea Valley/North London Abstraction Group based at Coppermills AWTW. Seepage through the clay core at the north-east of the reservoir was identified by a Willowstick survey in 2020. MWH Treatment was awarded a contract to address the seepage issue, with the works taking place 1.4km north of the main entrance from Lea Valley Road to the north of the tidal break on the east side of the reservoir.

History of the site

The reservoir was conceived as part of an overall plan for the Lea Valley and was laid before the Royal Commission of Water supply in 1893. At this time, the responsible authority was the East London Waterworks Company. Construction took place between 1908 and 1912, and the reservoir was opened by Their Majesties, King George V and Queen Mary in March 1913. At the official opening there was a ceremonial guard of honour review, and The King signed a Grant of Arms to the Metropolitan Water Board (owners and operators at the time). [caption id="" align="alignnone" width="1200"] Google Maps - Location of King George V Reservoir[/caption]

Description of the current facility

The reservoir was formed by the construction of a continuous embankment on the floodplain of the River Lea. An earth embankment divides the reservoir into two compartments that are connected by three large diameter culverts. The external grassed embankment supports a central puddle clay core. The reservoir has a maximum capacity of 12,492 ML at its top water level (TWL) of 20.18m AOD. It is normally operated on a ‘put and take’ basis which at typical through‐flows of 60 to 100 MLD gives a theoretical retention period between 100‐150 days. The crest level is 22.50m AOD with a length of approximately 7km. The reservoir is operated in conjunction with other local reservoirs to provide a continuous supply of raw water to Coppermills AWTW and Hornsey WTW. The embankment, wave wall and clay core were raised between 1938 and 1941 to restore the 1.5m design freeboard that had been lost due to gradual consolidation settlement. The reservoir was, however, kept 1.5m below original top water level, as a wartime precaution, until February 1945. At the higher TWL leakage occurred at several points, being attributed to dryness of the very high plasticity alluvial clays within the core; consequently, the current TWL was established. A 4.5m deep grout screen was installed along an 800m length of the southwestern embankment in 1983 in an attempt to address the leakage. Access to the reservoir is located at its southeast corner from the Lea Valley Road. This access is shared with a sailing club and activities club. Sheep graze the embankments as an environmentally sustainable way of managing grass growth.

Scope of works

The key scope of works for the project was the provision of a sheet-pile cut‐off wall. The wall was designed as 15m deep; based on the pile toe being driven into the London Clay a minimum of 0.5m, and 165m long; being installed between crest chainages 1,715m and 1,880m. A low vibration technique of pile driving was promoted to minimise potential for stability issues within the embankment during construction. The scope also included provision of access to the crest and provision of temporary access road, strengthening of existing site roads and protection to existing pipework and services. [caption id="" align="alignnone" width="1200"] Google Maps - location of site compound and works area[/caption]

Technical description

A survey was carried out late 2019 to early 2020 in the area around chainage 1,750m as this had been identified as an area of interest in a previous survey. Willowstick surveying is a non-intrusive geophysical method used to map and model the subsurface water flow paths. The procedure involves energising the study area with a signature electric current between paired electrodes. The surveying equipment consists of GPS system and an instrument known as a Willowstick which measures the magnetic field response of an electric current. As the electric current flows through the survey area the preferential flow paths are identified, mapped, and modelled. The information gathered can be used in making informed, guided, and cost-effective decisions concerning how to further, monitor, intercept and mitigate seepage. The main findings from the survey were:

• A weakness zone of preferential flow identified between chainage 1,723m and chainage 1875m.
• The flow path shows the characteristics of uniform sheet flow and did not indicate a concentrated leakage path, rather a 150m zone where water was passing evenly through the core.
• The preferential flow was identified at elevation 12m AOD through the foundation underneath the embankment.
• The preferential flow path strongly correlated to the location of the original stream channel. Its characteristics indicated that seepage was concentrating in flood plain sediments deposited by the original river channel meandering through and beneath the survey area before the dam was built.

The survey report recommended remediation works in this area within a short timeframe to reduce any movement or damage to the reservoir embankment.

King George V Reservoir: Supply chain - key participants

• Principal contractor/designer: MWH Treatment
• Designer: Atkins
• Temporary works design: Noble Works Ltd
• UXO survey: 6 Alpha Associates
• Ground investigation, soil testing: Structural Soils
• GPR surveys: Technics Group
• Environmental surveys: Middlemarch Environmental
• Willowstick survey: Willowstick UK
• Noise & vibration monitors: RSK Acoustics
• Silent piling contractor: Sheet Piling (UK) Ltd
• Piling verticality survey: CMCS Ltd
• Civil works, labour/plant: Derryard Construction limited
• Electrical (site setup, gate works): SRS Electrical
• Ground maintenance: UK Landscapes
• Scaffolding/access: Clocktower Scaffolding
• General plant hire: GAP Group Ltd
• Welfare supply: Wernick Group
• Supply of Trakway Matting: Sunbelt Rentals
• Ductile iron pipework: Electrosteel Castings (UK) Ltd
• Valves: Glenfield Invicta
• CCTV, timelapse cameras: Wireless CCTV Ltd

[caption id="" align="alignnone" width="1200"] Finished temporary road before track matting - Courtesy of MWH Treatment[/caption]

Toe road and crane pad

Atkins were instructed to advise on embankment loading constraints, construction methodology and the sheet pile solution. They developed the initially suggested remedial works to achieve a detailed solution which was then agreed with Thames Water. The existing track at the toe of the embankment was the only access route to the works area. The track had a loading capacity of 12t and the crest road a 5t weight limit; both limiting machinery and plant selection. A previous project adopted an 8t excavator and 6t tracked dumpers and Atkins used this information within their assessment to complete a slope stability analysis of the embankment. This confirmed that the use of an 8t excavator was acceptable for the works on the crest road. An existing 30” pre-stressed concrete (PSC) pipe main under the road at the toe of the embankment further constrained the size of vehicles to be used during construction and required enabling works. A disused section of pipe was recovered and tested to confirm dimensions and the material characteristics to be used in the loading analysis. Atkins confirmed that the pipe had sufficient capacity to support a maximum axle load of 12t. A temporary road was installed to minimise rutting and dynamic loading on the existing track. Trackway matting was installed from the sailing club ramp to the crane pad to disperse vehicular loading and mitigate impact on the pipe and vehicle speed was restricted to 5mph for all vehicle movements. An emergency plan was put in place to ensure the Thames Water Operations team were made aware of any incident and to cover the eventuality of a pipe burst. The temporary road was designed by Noble Works Ltd and installed by Derryard Construction Ltd over a period of 8 weeks. Over 1km of track matting was hired from Sunbelt Rentals and installed over a period of 2 weeks. Along with the temporary road, a crane pad was installed to facilitate the 200t crane used to lift the piling equipment and sheet piles from the toe to the crest of the embankment. The crane pad was designed by Noble Works Ltd and constructed in MOT Type 1 granular fill by Derryard Construction Ltd. A section of the adjacent aquifer recharge pipeline was dismantled to facilitate construction of the crane pad which also included a concrete protection slab above existing underground HV and telecommunications cables. [caption id="" align="alignnone" width="1200"] Finished installation of the track matting - Courtesy of MWH Treatment[/caption]

Piling decision

Following previous successful remediation works carried out at Sir William Girling, Staines South, and Island Barn Reservoirs, MWH Treatment selected Giken silent piling. This is a vibration free press-in method that allowed the pile installation to be virtually silent. This technique enables the piling plant to ‘walk’ over the tops of the driven piles. The initial press-in to install the dummy piles was carried out utilising a reaction platform. The Giken rig then used the previously installed piles to generate reaction to enable on-going pile installation. The sheet piling works (undertaken by Sheet Piling (UK) Ltd) commenced at chainage 1,880m which is the junction of the perimeter and the reservoir dividing embankments. A wider toe area had been identified as a turning and laydown area for the storage of equipment. It was also used for the reaction platform for the installation of the dummy piles. The first 100 piles were fed to the rig by the crane at the base of the embankment. Once the radius of this crane was exceeded, the ‘non-staging’ method was adopted utilising a clamp crane and pile runner to move the piles along the crest and to feed the piles to the Giken rig. A 15m long PU32 section pile was adopted being dependant on the chosen method of installation, length of pile and expected ground conditions. The pile clutches were lined with sealant to ensure low permeability through the wall joints. Press-in driving of the piles with the Giken rig was assessed as feasible with hard/difficult driving being a low risk when reaching the London Clay layer. Subject to the approval of the reservoir Qualified Civil Engineer (QCE) water jetting was an option to achieve required toe penetration. [caption id="" align="alignnone" width="1200"] Reaction stand setup excavation - Courtesy of MWH Treatment[/caption]

Crest road works

The Giken piling method minimised the access width requirement to work on the crest, however some excavation was still required. Using an 8T excavator the crest road was excavated to expose the clay core to allow the alignment of the sheet pile wall with the centre of the core. The base width of the trench was specified at 2m to allow the Giken rig to operate. The top of the core was covered with plastic sheeting to prevent desiccation and protect the clay core from being damaged. Following the completion of the sheet piling works, the trench and crest was reinstated.

Site installation of the piles

Sheet Piling (UK) Ltd commenced work on site at the end of October 2022, with a planned 10-12 week site duration. The 200T attendant crane was stripped of all non-essential weight in order to maintain the 12T per axle load weight restriction. Once in position on the crane pad a smaller 45T service crane off loaded the initial crane ballast and commenced rigging; once part rigged the remaining ballast was self-rigged. The reaction stand was lifted into position by the 200T crane to the 6m x 6m hardstanding area finished 600mm below the top pile design level. The Giken rig was then positioned onto the reaction stand followed by counterweights. The first pile was then driven utilising the weight of the rig and counterweight as reaction. After the first pile were installed, it became a reaction pile for subsequent piles to be installed. When the rig fully sat on the dummy piles, the reaction stand and counterweights were removed. Once a pile was sufficiently driven and stable the rig releases its clamps from the reaction piles and travels forwards. This ‘self-moving’ system eliminates the need for support by a crane during the piling operation. Following installation of the first 100 piles a clamp crane was utilised as the piling works had exceeded the working radius of the 200T crane. After the clamp crane had travelled along the piles as far as possible inside the 200T crane working radius a track, formed of a temporary pile welded along the completed wall, allowed a handling train to deliver the piles to the clamp crane. Pile verticality was critical as the piles must not exit the puddle clay before penetrating the underlying London clay. During piling verticality was monitored via spirit level. Once completed Sheet Piling (UK) Ltd employed CMCS Ltd to undertake a verticality survey. This included the first five 5 piles and then 10% thereafter, resulting in a total of 32 tests. CMCS Ltd utilised the lancing tubes on the piles that were welded prior to installation. The data reported the tilt of the pile and to what extent, whether leaning towards or away from the reservoir. [caption id="" align="alignnone" width="1200"] Train moving a pile to the clamp crane - Courtesy of MWH Treatment[/caption]

Success of piling solution

After the first week of initial set up and pressing of the 3 dummy piles, Sheet Piling (UK) Ltd installed 275 piles over the next 6 weeks. The site team completed the work in advance of programme despite difficult weather conditions. The crest of the embankment was very exposed; strong cross winds resulted in several days when piling was prevented, but the team were able to boost productivity to recover lost time. The Sheet Piling (UK) Ltd team de-mobilised mid-December; this was during the weekend of a severe snowstorm with over 6 inches falling over the Sunday night. The MWH Treatment team and subcontractors mobilised additional resources to clear the site of snow, including the 1km toe road, enabling several lorries and the 200T crane to safely leave site. Site demobilisation took place earlier than planned realising 3-weeks’ efficiency on the track matting hire period. After the Christmas shut down, the trench on the crest road was reinstated and an embankment survey was carried out by Derryard Construction to confirm the final ground levels were within tolerance. A post-installation Willowstick survey was conducted which reported that the previous flow path had been cut-of. The sheet pile wall appears to be working as designed by cutting-off the preferential flow of electric current through and beneath the northern half of the sheet pile wall; interpreted as cutting off the seepage flow. The post completion survey confirmed that the remediation works had been successful.

Biodiversity

The King George V Reservoir is a major wintering ground for wildfowl and wetland birds, including nationally important species. A total of 85 wetland species have been recorded and the reservoir also forms a moult refuge for a large population of wildfowl during the late summer months. Over the course of the project environmental consultants Middlemarch visited site monthly to monitor bird activity and to ensure site works were not affecting wildlife. The site compound took up the space of the sailing club/water sports club car park so MWH Treatment constructed a temporary car park providing sailing club patrons with continued safe parking. On project completion it was agreed with Thames Water that the car park should become a permanent overflow car park. A wildflower meadow is being planted to compensate for the biodiversity loss of the car park.

Conclusion

MWH Treatment have delivered a very successful project overcoming access, logistic, weather and environmental challenges. The sheet piling cut-off wall achieved the desired project outcome: mitigation of water seepage. The project was delivered early with an excellent safety and environmental performance. Thames Water additionally gained an upgraded toe road and improved protection for critical services. The project also fostered and maintained excellent relationships with neighbours at the sailing and activity clubs.

Leominster WwTW is a medium sized biofilter sludge works, treating a population equivalent of approximately 11,000. Welsh Water have invested £12.1m to deliver the process enhancements at the works as part of Welsh Waters’s commitment to deliver on improved water quality in the Wye River basin catchment. Other enhancement works were completed on existing sites including Eign, Rotherwas and Kingston & Madeley WwTWs. As part of the National Environmental Programme (NEP) commitments to meet the obligations of the Water Framework Directive in AMP7, new permit limits were put in place for 31 March 2025. The project exceeded this milestone by one year, achieving the tightened permit and Welsh Water’s annual commitment for river reach improvement.

Existing works

In advance of the improvement scheme, the works comprised an inlet works, primary settlement tank (PST), seven mineral media biofilters, two humus settlement tanks (HSTs), ferric dosing, two storm tanks and sludge storage.

The works treated mainly domestic sewage from the catchment of Leominster, Herefordshire.

The planned improvement works

The upgraded Leominster WwTW is designed to cater for increased treatment flows equating to a design horizon population equivalent of 16,685 (46% growth) and a tightening of the phosphorus permit from 1mg/l to 0.5mg/l. The new works design included for the integration of the following process improvements into the existing treatment works infrastructure:

• Four new tertiary nitrifying sand filters (including a tertiary lift pumping station and backwash returns system).
• New ferric sulphate dosing system for primary, secondary, and tertiary dosing points of application (including a new dosing equipment kiosk and safety shower).
• New sodium bicarbonate dosing system to supply additional alkalinity to the process for pH correction (including a chemical storage silo and dosing system).
• Inlet works refurbishment, upgrading the two existing escalator screens with two new 6mm screens, screenings trough, screenings transfer to two new compactors.
• New passive bypass screen with improved operation and maintenance access provision.
• New access platform around the screens to reduce the need for operator access into confined space areas.
• New potable water booster pumping station.
• New final effluent sampling system.
• New low voltage distribution board and inlet works MCC.
• New tertiary treatment MCC.

Scope of works

As part of Welsh Water Capital Delivery Alliance (CDA), Morgan Sindall, in partnership with designers, Arcadis, was appointed as the main contractor by Welsh Water. The scope of works for the project included the investigation, assessment, design, procurement, construction, and commissioning of existing and new treatment facilities; thus providing capacity to treat increased sewage loadings to meet discharge permit standards agreed with the Environment Agency (EA).

[caption id="attachment_15336" align="alignnone" width="1200"] (top left) Construction of tertiary treatment system December 2022, (top right) construction of tertiary treatment system May 2023, (bottom left) Construction of tertiary treatment system July 2023, and (bottom right) Construction of tertiary treatment system November 2023 - Courtesy of Morgan Sindall Infrastructure[/caption]

Innovative solution selection

Welsh Water, Arcadis and Morgan Sindall collaboratively assessed multiple options as part of the optioneering phase of the outline design, which included optioneering workshops for shortlisting, and risk and value assessments to select the most cost-effective solution based on whole life cost and risk. A schedule of innovative solutions included:

• New nitrifying sand filter to combine the need for tertiary solids removal, to achieve the tightened phosphorus permit, and increase nitrification capacity to relieve pressure on the works to meet the existing ammonia permit.  Removed need for additional secondary treatment.
• Re-use of the inlet structure for the new 6mm screens, improving access and removing need to go in confined space during routine maintenance procedures.
• Re-use of the existing ferric sulphate storage tanks.
• Assessment of innovative alternative chemical to ferric sulphate (rare earth minerals).
• Use of BIM 3D modelling to ensure integration of mechanical design and location for the alkalinity silo and tertiary plant and avoid clashes with existing underground pipework.
• Gravity fed sampling system for final effluent monitoring.
• Design for Manufacture and Assembly (DfMA) MCC kiosk (used in the development of Welsh Water standard design).
• Re-assessed the need to refurbish existing sludge holding tanks through modification of sludge imports.
• Re-use of old Dortmund style rectangular/pyramidal standby PSTs.
• Re-purposing and re-establishment of area of works with abandoned process treatment assets– reducing the need for land purchase.
• Utilise existing static mixers on secondary ferric sulphate dosing.
• Ferric sulphate dosing flexibility (primary, secondary and tertiary).

Project initiation and whole supply chain early engagement

The overall delivery programme for the treatment upgrade scheme at Leominster presented the Welsh Water CDA team a challenge to meet the NEP regulatory output dates for end of March 2025 and ODI date for 31 March 2024. To efficiently meet this milestone, the team developed a joint collaborative plan to work to with the key project stakeholders, including members from Welsh Water asset and operations teams and key supply chain members.

[caption id="attachment_15328" align="alignnone" width="1200"] Construction of tertiary treatment system February 2024 - Courtesy of Morgan Sindall Infrastructure[/caption]

The development of up-front outline design specifications and subsequent letting of Early Contractor Involvement (ECI) contracts with the supply chain allowed for all parties to truly work collaboratively in setting out and advancing the design strategy in an efficient manner. The ECI contracts enabled the supply chain and Arcadis to work together in an open and transparent manner through driving greater design efficiencies through sharing of ideas, skills, industry experiences, true value engineering opportunities, developing design and construction innovations, all resulting in a positive influence to the final scheme solution.

The successful working relationship was maintained through regular joint online progress meetings and workshops, where design efficiencies were discussed and implemented, and where any potential blockers were removed, to benefit design and construction. Other joint stakeholder meetings which assisted the advancement of the delivery programme included HAZOP’s, Access, Lifting and Maintenance (ALM) reviews, DSEAR meetings, referencing lesson learnt from previous schemes, progressing DfMA opportunities, production of outline commissioning plans early, and holding regular buildability review meetings as the design progressed. Having a common project management system, where all members of the joint delivery team shared information, was hugely beneficial, in addition to the open access to the scheme’s federated 3D BIM model.

Leominster WwTW: Supply chain - key participants

• Client: Welsh Water
• Principal contractor & civils: Morgan Sindall Infrastructure
• Designer & environmental consultants: Arcadis
• CFA piling rig: Foundation Piling Ltd
• Shaft installation: B&W Tunnelling Ltd
• Sheet piled interlocked cofferdam: Berryrange Ltd
• Mechanical installation: Industrial Pipework Services Ltd
• Electrical installation: PCS Ltd
• Earthing specialist subcontractor: BEST Services Ltd
• Tertiary nitrifying sand treatment: Brightwork BV
• Tertiary nitrifying sand treatment: Nijhuis Industries UK & Ireland
• Ferric dosing system: Colloide
• Alkalinity dosing system: Rospen Industries Ltd
• MCC & ICA controls: GPS Group
• Kiosks: Morgan Marine
• PLC network: Mitsubishi
• Below ground access chambers: Cubis Systems
• Pumps: Xylem Water Solutions
• Inlet screens and screening handling: SPIRAC Ltd
• Potable water booster system: Dutypoint Ltd
• Static mixer: Statiflo Ltd
• Temporary pump specialist: Hydrainer Pumps

[caption id="attachment_15329" align="alignnone" width="1200"] Fully constructed tertiary treatment system integrated into existing treatment works - Courtesy of Morgan Sindall Infrastructure[/caption]

Sustainable and efficient design and construction

The new tertiary treatment plant and associated pipework, utilities and control kiosks were installed in an area within the boundary of the existing treatment site, where disused sludge drying beds were previously located. Re-purposing this area led to a more sustainable solution as it avoided the associated expenditure, programme, and environmental requirements that land purchase would have involved.

Due to this area of the existing treatment site being near the final effluent pipework, it enabled the flow diversion to the new tertiary lift pumping station to be achieved via a short length of below ground gravity pipe at a shallow depth. This is also a more sustainable design as it avoided the increased excavation and carbon footprint requirements that additional manholes, longer/deeper pipe lengths and a pumped solution would have required.

Other examples included surveying existing duct runs and draw pits to review capacity and reuse, where possible, as well as refurbishing the existing ferric dosing system and containment bund, instead of installing new plant, thus providing efficiencies and cost savings to Welsh Water.

Another element of efficient design and construction was the civil bases associated with the three new MCC kiosks for the new plant and equipment being installed.

As the two larger kiosks were to be DfMA and hence delivered to site with the panels already installed within the kiosk, a support frame for the kiosk and floor was also provided. Due to the panels requiring man access below them for installation of cables, the support frame included for vertical legs and steps for access into the kiosk that was installed on a simple concrete flat slab with mesh reinforcement. This was a more sustainable solution as it minimised the excavation requirements and reduced the total volume of concrete and steel when compared with sitting the kiosk at ground level on a below ground concrete trench and base slab with more steel reinforcement. The solution led to a quicker installation and better from a Health & Safety perspective as the extent of confined space working was reduced due to the absence of a trench.

[caption id="attachment_15331" align="alignnone" width="1200"] Example of a Cubis Systems modular chamber and (inset) chamber being assembled at Leominster- Courtesy of Cubis Systems & Morgan Sindall[/caption] For the smaller alkalinity MCC kiosk (not DfMA), it was decided that the kiosk would sit at ground level but as it still required access under the panel for installation, a below ground trench was required. To make the construction process more efficient, the trench comprised of innovative and sustainable HDPE recycled plastic modular units from Cubis Systems, that were put together on site and built around with minimal concrete surround and base slab and backfill to support the kiosk. As well as the material of the modular solution being more sustainable, it also led to a reduced carbon footprint in delivery due to it being very light weight. This also made it a safer and quicker installation as the manual handling involved was minimal.

Cubis Systems products were also used for the draw pit construction where the rapid stack modular units were utilised to form the main structure saving man hours with additional safety benefits.

The existing layout of the inlet works presented increased risks to operations with the main components below ground level and within a confined space. The new design involved raising the working platform to ground level, around the new screens and creating a better working environment and removing the need for operations to enter the previous confined space areas.

Design efficiencies

Working together with Welsh Water and the framework MCC subcontractor (GPS Group), the team were instrumental in the development of the standardised design for manufacture and assembly (DfMA) design for MCC kiosks within the Welsh Water business. The Leominster team delivered this standard product in the form of a new low voltage distribution board kiosk and a new tertiary filter MCC kiosk at the site.

The DfMA GRP kiosks are mounted on a raised steel frame floor to support the MCC and the access covers while giving ample space beneath the structure for cable connections and testing.

This kiosk design reduced health and safety risks associated with installation and commissioning and led to considerable reduction in installation time on site, as the kiosks were delivered to site, off loaded, and fixed down, all within a few hours. [caption id="attachment_15332" align="alignnone" width="1200"] Installation of DfMA low voltage distribution board MCC kiosk - Courtesy of Morgan Sindall Infrastructure[/caption]

The early engagement, with the electrical installation subcontractor, PCS Ltd, through an agreed Early Contractor Involvement contract arrangement, ensured that cable design and routes were agreed early in the design, to the new plant and equipment.

The standard designs for lighting, junction boxes and emergency stops were used where possible. In addition, the Welsh Water Capital Delivery Alliance team worked collaboratively with PCS Ltd and BEST Services Ltd, an earthing specialist subcontractor, to fully understand the earthing requirements for the site. Regular design review meetings were held to develop a workable earthing design, considering the impact of this deliverable with numerous site constraints.

Conversion of the existing Siemens PLCs to remote I/O, allowed for integration of all existing signals into the new schemes Mitsubishi PLC network. This minimised the number of telemetry outstations on the site, bringing all control associated with these MCCs into the new PLC network.

Hydraulic integration of new process scope into existing works

The new project scope required integrated into the existing treatment works hydraulic design and included the incorporation of two new SPIRAC Ltd escalator screens and storm bypass static screen within the existing civil structure, and the installation of new flow control weirs into the existing biofilter and humus tank distribution chambers.

[caption id="attachment_15337" align="alignnone" width="1200"] New Fineguard inlet screens from SPIRAC Ltd with improved safe access for operators – Courtesy of Morgan Sindall Infrastructure[/caption]

The new weir design was needed to achieve an appropriate flow distribution across the two sets of existing biofilters and the three existing humus tanks. To ensure seamless integration and maintain safe flow throughout the facility during the implementation of these changes, a comprehensive hydraulic assessment was conducted to verify the incorporation of new process assets within the treatment stream without negatively impacting on the existing asset structures.

To maximise the reuse of the existing works pipeline infrastructure and flow hydraulics, the team positioned the new tertiary treatment filters within the site layout to optimise the existing final effluent pipework arrangement by rerouting the flows from the existing humus tanks to the new tertiary treatment lift pumping station and then reintegrated the treated effluent from the tertiary filters back, by gravity, into the existing pipework to the final effluent lift pump station.

This approach reduced costs and construction time for the delivery of the project, reduced the impact of maintaining the existing works operation during the construction period and removed the need to agree a new final effluent sampling point location with the Environment Agency.

Digital delivery

To maximise the understanding and detail of the existing site arrangement and optimise the design process, a point cloud survey was undertaken, and a 3D Revit model produced. Along with existing as built drawings, asset and topographical survey information and historical as built drawings, the 3D model was developed further and then used to produce and develop a 3D model of the design proposals.

[caption id="attachment_15334" align="alignnone" width="1200"] (top left) Federated 3D model capture of sampling kiosk with tertiary filters - Courtesy of Arcadis, (bottom left) as built sampling kiosk with tertiary filters - Courtesy of Morgan Sindall Infrastructure, (top right) Federated 3D model capture of lift pumping station with tertiary filters - Courtesy of Arcadis, and (bottom right) As built tertiary filter lift pumping station pipework with duplex filter and tertiary filters - Courtesy of Morgan Sindall Infrastructure[/caption]

The 3D model was federated to include all the different design models (including those by the design subcontractors) and then used in internal meetings to agree on design proposals, by being marked up for updating. The federated model was also used to avoid underground clashes with existing pipework and produced the 2D drawings that informed the pricing and construction of the proposals and was also instrumental in getting acceptance from the stakeholders when used in project gateway approvals, HAZOP and ALM meetings.

This digital strategy for the project led to significant efficiencies in design as the federated model that contained the developed design proposals was uploaded to a BIM Docs page for the project, where all design deliverables were also kept, reviewed, and issued to the key stakeholders via the workflows and transmittals tools. The whole project team (designers, subcontractors, suppliers, stakeholders) were able to easily access and view the pertinent design information and subsequently design reviews and project decisions could be made easily which was instrumental in fostering a collaborative approach on this project.

Engineering challenges

Groundwater: As part of the overall design, a 3m diameter and 6m deep tertiary lift pumping station, was designed to lift and transfer influent flows, intercepted and diverted from an existing 450mm diameter final effluent gravity pipe, to the four new tertiary sand nitrifying filters.

During ground investigative works, it was identified that there was a high-water table present that would make construction of the shaft difficult. To fully understand the impact, pump tests were carried out to quantitate the expected groundwater influx during excavation and allow Arcadis to prepare and submit applications for abstraction and discharge (A&D) licences from the EA.

[caption id="attachment_15344" align="alignnone" width="1200"] Lift pumping station - Courtesy of Morgan Sindall Infrastructure[/caption]

However, due to the lengthy time-frame expected to obtain EA approval for an A&D licences, the team needed to reconsider the construction methodology of the lift pumping station in order to meet the consented target date of 31 March 2024.

B&W Tunnelling Ltd, who had been appointed to undertake the original caisson installation, jointly developed a solution with Morgan Sindall that would enable the pumping station to be constructed without the need to abstract any significant amount of groundwater. The agreed method was to drive interlocked sheet piles around the perimeter of the planned structure to a depth at which it will cut off any groundwater. With the groundwater under control, the caisson could then be installed under ‘dry’ conditions.

A 4.8m x 4.8m cofferdam was installed using 12m long GU27N sheet piles to penetrate the underlying mudstone formation. During construction the piles were required to stand as cantilevers. The temporary sheet piles were used for the construction period only, and were extracted once the caisson was complete. The Berryrange Ltd cofferdam allowed for safe construction of the shaft/lift pumping station and ensured the project kept on programme.

Network Rail: The location of the new tertiary plant on the site was in close proximity to the busy railway line that runs from South Wales to North Wales and Manchester. Network Rail were consulted, and mitigation measures agreed to ensure the safest method of constructing the new asset was followed.

A basic asset protection agreement (BAPA) was approved, which enabled Network Rail to review the safety documentation of lift plans (tandem lift method), method statements and temporary works design ahead of the planned work to install the filter tanks, sodium bicarbonate storage silo and associated high level stairs and working platform structures.

An appointed Network Rail Supervisor attended site to oversee the construction operations, which included the safe operation of piling rigs, multiple cranes, concrete pumps and the safe use of excavators in the vicinity of the operational railway line. This process was undertaken for over 20 separate operations through the programme period, all of which were undertaken safely and successfully.

[caption id="attachment_15335" align="alignnone" width="1200"] Installation of tertiary sand filters adjacent to railway line under agreed BAPA procedures - Courtesy of Morgan Sindall Infrastructure[/caption]

Health & Safety

As always, during wastewater upgrades or extensions, the challenge and onus on the team is to integrate the new plant and processes, safely and efficiently, into the existing treatment works infrastructure, while ensuring that the existing process is not impacted or interrupted.

To formalise these crucial planning activities, Welsh Water required Morgan Sindall to work to their Business Continuity Plan (BCP) process. This BCP process encompasses the development and joint agreement of a detailed activity plan, initially, between Morgan Sindall and Welsh Water local operations teams, followed by presentation of the safe systems of work to Welsh Water senior managers for their final acceptance and approval.

As the integration of the new assets were built in and around the existing works, construction activities were proactively reviewed and agreed with Welsh Water to ensure minimal disruption to the operational site during the periods when these improvement works were being conducted.

Instances where the BCP process was followed included:

• When temporary over pumping was needed to construct two intercepting manholes on the existing final effluent gravity pipeline.
• During over pumping of incoming sewage from the inlet works structure and during the installation of the new screening units.
• During construction of two flow meters on the feed pipes to the two sets of existing biological filters
• During the power upgrade to site and transfer of mains control to the new LVDB MCC unit from the old.

[caption id="attachment_15333" align="alignnone" width="1200"] Leominster WwTW: Tertiary sand filters - Courtesy of Morgan Sindall Infrastructure[/caption]

In the case of the installation of the biological filter feed flow meters, a gravity solution was selected due to the hydraulic sensitivity of the biofilters and fluctuating flowrates of the incoming wastewater with the weather. The construction required several shutdowns and temporary storage of incoming flows as well as the installation of a network of above ground pipelines with flow control valves and flow meters over a 200m distance across the operational site.

Enhancing communities

During summer 2023, the Leominster team approached the local country park to enquire if there was any community-based volunteering work that the team could assist with. The Park Ranger highlighted an area of which they were planning on creating a community garden.

The Morgan Sindall and Welsh Water team assisted the local country park rangers with clearing a large area of brash and vegetation at Queenswood Park to open the space up. In addition, the team assisted in providing a new stone footpath and bridge to enhance access for the public. Several bird boxes were installed to encourage and enhance local bird populations in the area.

Another example where the team have helped and supported the local community was through the provision of food parcels to the local Food Bank. Staff from Welsh Water, Morgan Sindall and the project supply chain, all donated food parcels to the local charity to distribute.

To encourage and assist with the development of future engineers, the team invited two Year 11 students to undertake work experience on the site for a week and hosted a new graduate on the site as part of the Year in Industry placement scheme.

To celebrate British Science week, the Herefordshire Women’s Institute attended site during construction. The Leominster Town Clerk and numerous local councillors were also invited to site to explain the environmental benefits of the new enhancement works to the existing treatment works.

[caption id="attachment_15338" align="alignnone" width="1200"] Fully constructed tertiary treatment system integrated into existing treatment works - Courtesy of Morgan Sindall Infrastructure[/caption]

Programme

Scheduled collaborative planning was undertaken at the design stage with all project stakeholders ensuring key deliverables were targeted and met to enable start on site. The collaborative planning sessions were also carried through to the construction phase where the main project programme was developed with all disciplines and key supply chain partners to achieve the milestones set.

Coupled with the regular planning sessions weekly site progress meetings were undertaken with all parties ensuring everyone was aware of the planned and forthcoming works with progress monitored throughout.

The main construction programme consisted of separate civil working areas ensuring the foundations and main structures were in place before mechanical and electrical supply chain partners were integrated into the programme to work alongside each safely to optimise the working time of the programme.

All parties worked together on site successfully with a standard daily safety brief to everyone ensuring all individuals were aware of the planned activities.

Anglian Water’s Toplers Hill Water Tower is situated just off the A1, south of Biggleswade, Bedfordshire, on a site which includes both the water tower and a water reservoir. The tower was constructed in June 1934 and its condition has started to deteriorate with age. Following Anglian Water’s internal inspection of the water tower, areas of concern were identified regarding the roof, internal coatings and some of the access ladders, which would require replacement or refurbishment before the tower could be returned back to service without compromising water quality to customers.

Issues

The deterioration of the water tower was clearly identifiable, with there being several leaks in the roof of the tank and any sampling of the water would be insufficient to pass due to the interior surface corrosion. Also, the instrumentation and roof interface point were not sealed, with a noticeable build-up of debris/silt/carbon and corrosion across the walls. Another issue was the broken ladder which would cause a health and safety access issue moving forward.

The option of replacing the water tower with cellular units was considered, however, due to minimal site spacing, it was discounted and the solution was to modify the existing asset.

Due to the consequence of the tank’s condition, there was a risk of low-pressure events. Toplers Hill Water Tower also provides standby storage to the adjacent Toplers Hill Reservoir, which cannot be removed from service until the water tower has been returned back to service; therefore highlighting the importance of the solution being delivered in a timely manner.

It was evident that the roof needed replacing, which required considerations for the crane’s lifting ability, the crane’s positioning, lay down areas, the weather conditions and teamwork. It was also apparent that there would be the need to reposition a number of telecommunications aerials atop the tower to ensure the site team were not at risk of radiofrequency (RF) radiation whilst working the tower.

[caption id="attachment_13576" align="alignnone" width="1200"] Toplers Hill Water Tower - Courtesy of @one Alliance[/caption]

Solution and construction

Anglian Water’s @one Alliance was tasked with developing a solution to the issues and the construction phase started in 2022.

Scaffolding: The team required safe access up the tower and around and inside the tank, so extensive scaffolding was put in place to allow this. The scaffolding works comprised the following:

• An external scaffold tower supporting an electrically-powered hoist to the top of the water tank.
• Full external access scaffolding surrounding the tank.
• Full birdcage scaffolding inside the tank with several boarded levels to the sides of the tank. The birdcage scaffold would need to be altered throughout the installation whilst repairs were taking place to enable safe access to all internal faces of the tank.

Crane pad and lay down area: Whilst the scaffold was being installed, Claret Civil Engineering designed a crane pad to facilitate the old roof removal and new roof installation. A separate levelled roof dismantling/assembly area was created nearby and covered with track matting.

Tank internals: With the scaffolding installed, the internal walls and higher levels of pipework and support brackets were prepared by OnSite Central Ltd. This included lead paint removal by high pressure water jetting, abrasive grit blasting, and re-coating the tank interior with Acothane DW; a DWI approved, solvent free polyurethane coating for potable water tank lining. The new tank coating was tested for integrity and strength as it was installed then cleaned, disinfected and sampled ready for return to service.

Roof replacement: The leaking tank roof was removed by crane by Hayes GFS Ltd and dismantled this on site. This was replaced with a new glass lined steel structure provided by Permastore and installed by Hayes. The top section of the walls had been identified as heavily corroded, so was cut away and prepared to receive the new roof arrangement. Using a crane from Cadman Cranes Ltd, the new tank roof was lifted into position onto the existing structure.

[caption id="attachment_13580" align="alignnone" width="1200"] New roof ready to be lifted - Courtesy of @one Alliance[/caption]

Water tower access: The external tank ladder with two shorter ladder runs and an integral access platform for the existing side access hatch were replaced.

Instrumentation: Whilst the existing level instruments and cabling were re-used where practicable, a new ultrasonic level transducer and associated cable runs were also installed. The old and new instruments were mounted to purpose-made apertures in the replacement roof to monitor the ultrasonic levels within the water storage tank.

Toplers Hill Water Tower: Supply chain - key participants

• Client: Anglian Water
• Design & project delivery: @one Alliance
• Refurbishment of tank internals & re-coating: OnSite Central Ltd
• Old roof removal/new roof installation: Hayes GFS Ltd
• Civils works: Claret Civil Engineering
• Glass-lined steel roof: Permastore Ltd
• Polyurethane coating: Acothane UK Ltd
• Crane hire: Cadman Cranes Ltd

Project challenges

Due to poor weather conditions, the crane lift date was delayed by several weeks. In addition, a last minute revision to the lifting plan caused delays to the lifting activities.

Having to apply the Acothane DW throughout both the winter and summer months, temperature and humidity extremes were experienced which was challenging during the preparation, application and curing of the coating.

Other challenges included nesting birds, tight site access, and several incidents of theft and on-site vandalism.

[caption id="attachment_13575" align="alignnone" width="1200"] The new roof being lifted into place - Courtesy of @one Alliance[/caption]

Health & Safety

The @one Alliance, prides itself of ‘Deliberately Delivering Differently’ and with this scheme, several H&S opportunities presented themselves as it developed. Early on it was noted that there was some concrete spalling on the external tower wall, which was a concern as small clumps of falling concrete could occur at any time. The team decided to carry out some loose concrete removal at the start of the site phase to removed this hazard.

Another anticipated H&S improvement was the use of a remote-controlled robotic paint stripper and shot blaster to prepare the internal walls for the new coating. This meant that operatives did not have to be inside the tank to manually shotblast the exiting coating, but unfortunately, the team discovered that the device could not traverse the bolt heads or tank boiler plate joints well so was ineffective.

The team also found that the internal tank birdcage scaffolding could be rationalised down to one lower level deck for tank wall access and work could be undertaken from mobile tower scaffolds. This not only reduced H&S concerns, it also saved time in having to install and strip additional scaffolding which equated to a saving of approximately £40,000.

Project status

As the date of writing (July 2024), the team are finalising the last activities of the tank refurbishment.

Once the telecommunications aerials are repositioned to their original orientation the scaffolding will be fully removed and the water tower will be handed back to Anglian Water. It will then be returned to service and the year-long warranty period will start.

Loch Katrine, a freshwater loch situated in the Trossachs area of the Scottish Highlands, is not only a natural beauty but also a critical water resource for Glasgow. The Emergency Dam Project was initiated in response to a severe storm in mid-October 2023, which caused significant damage to the dam’s spillway. The loch, approximately 8 miles long and 1 mile wide at its widest point, runs the length of Strath Gartney. The reservoir was originally formed by constructing a dam across the outlet channel at the eastern end of Loch Katrine, raising the natural loch level and significantly increasing its capacity to supply water.

History

Victorians considered the supply of clean water to be the cornerstone of a civilised society. Glasgow and other major cities in the UK suffered major outbreaks of Cholera in the middle of the 19th century, which were attributed to polluted water supplies. In 1848, a Public Health Act was passed by Parliament to promote the supply of clean water. At this time, schemes were being prepared to provide clean water supplies to all major conurbations throughout the British Isles.

The eminent engineer John Frederic Bateman selected Loch Katrine as an appropriate source of water for Glasgow, and led a team of engineers who translated the scheme into reality by raising the water height at Loch Katrine, constructing a 26-mile-long aqueduct terminating at the Mugdock (storage) reservoir.

Loch Katrine and associated aqueducts are still as efficient and environmentally friendly now as they were when built due to the fact they take water by gravity from Loch Katrine to Milngavie without the need for pumping, before it is distributed to customers.

[caption id="attachment_14708" align="alignnone" width="1200"] Aerial of the dam repair pre-concrete - Courtesy of Whitehouse Studios[/caption]

On 14 October 1859, the Loch Katrine-Mugdock Waterworks, as they were originally known, was opened by Queen Victoria in a ceremony at the Commissioners’ Cottage. A clean water supply flowed into the north of Glasgow by 1860.

At the ceremony, Queen Victoria said:

“It is with much gratification that I avail myself of this opportunity of inaugurating a work which, both in its conception and its execution, reflects so much credit on its promoters, and is so calculated to improve the health and comfort of your vast population, which is rapidly increasing round the great centre of manufacturing industry in Scotland.

“Such work is worthy of the enterprise and philanthropy of Glasgow, and I trust it will be blessed with complete success. I desire that you convey to the great community which you represent my warmest wishes for their continued prosperity and happiness.”

Later that century, chief engineer James Gale deemed that the storage capacity of Loch Katrine should be increased and that a second line of aqueducts and another storage reservoir should be constructed at Craigmaddie above Milngavie.

The reservoirs represent an outstanding example of Victorian municipal engineering and, as with many feats of engineering from this time, the adventurism, innovation, and quality of workmanship, are outstanding. The engineering design and construction skills employed to supply Glasgow with clean water from Loch Katrine are truly awe-inspiring.

Project drivers

Water that flows through the aqueducts from Loch Katrine goes on to supply 1.3 million people across much of Greater Glasgow and as far east as West Lothian and to areas like Grangemouth and the Ineos refinery; which is crucially important to Scotland and the UK.

The project was driven by the urgent need to repair the spillway to prevent a potential dam failure. The detachment of concrete apron slabs during the October 2023 storm event posed a significant risk, prompting the formation of an emergency recovery team within Scottish Water.

[caption id="attachment_14713" align="alignnone" width="1200"] Detached concrete apron slabs - Courtesy of George Leslie Ltd[/caption]

Loch Katrine Dam Repairs: Supply chain - key participants

• Principal contractor/designer: George Leslie Ltd
• Designer/technical advisor: Mott MacDonald
• Drilling works for anchor rods: Albion Drilling
• Coring of pressure relief holes: Beattie Demolition
• Joiners for formwork: Beatties FRC
• Tree clearance: Caledonian Tree Services
• Concrete pumping: Camfaud Concrete Pumps
• Reinforcement: Central Rebar
• Anchor plates: HK Gillies
• Interlocking blocks: Mellex Group Ltd
• Scaffolding/access: Peoples Safety Scaffolding
• Grout for anchor rods: Resapol
• Pumps: Selwood
• Welfare buildings: Wernick Hire
• Project photography/drone footage: Whitehouse Studios

Optioneering & design

The design and construction approach focused on ensuring the safety of both workers and the public while addressing the immediate risks. George Leslie Ltd, with the assistance of Mott MacDonald, was engaged to repair the damaged areas.

The main tasks involved installation of Legato blocks, as part of the temporary works design, reservoir drawdown, silt mitigation, drilling and fixing L-Bars, installing mesh and formwork, pouring concrete, and installing pressure relief pipes, all while ensuring safety for workers and the public.

[caption id="attachment_14709" align="alignnone" width="1200"] Installation of fabric mesh and environmental protection - Courtesy of Whitehouse Studios[/caption]

Before full mobilisation, preparations for the crane pad were deliberated and built on-site in anticipation of positioning the 60-tonne mobile crane. Concurrently, during these initial phases, nearby residents received briefings about the projected plan and what they could anticipate in the ensuing weeks. This practice of keeping the local community informed was maintained consistently during the project’s duration.

Regular meetings involving all parties (Scottish Water, George Leslie Ltd and Mott MacDonald) took place every day to review what was needed for the investigation, which would then inform the design stage. Excavation work was carried out to reveal specific areas of the spillway construction. These findings were relayed to Mott MacDonald, contributing to the progression of the design, ensuring a smooth flow from investigation to design, then to planning and execution.

The project’s schedule of work was frequently revised, often in response to planning made during Teams calls. It necessitated regular updates and rebriefing for the onsite team.

Managing environmental pollution was particularly demanding while the reservoir continued to spill over.

On-site logistics posed difficulties with spatial constraints and the necessity to maintain operations at the Loch Katrine steamship workshop throughout the construction period. Careful scheduling of deliveries and the selection of specific transport machinery to accommodate the dimensions and configuration of the access route were vital for ensuring safety and preventing any obstruction in the vicinity of the access path and work zone.

The George Leslie Ltd supply chain team demonstrated exceptional flexibility with the project, expediting delivery schedules, facilitating deliveries outside of normal business hours, and reorganising their work to be on-site for the urgent repairs. Such dedication was instrumental in ensuring the emergency work was completed smoothly.

The project required consultation, inspection, and design to carry out repairs to safeguard the listed structure at the reservoir. This included daily meetings set up by the client for reporting.

[caption id="attachment_14712" align="alignnone" width="1200"] Repairs to concrete apron underway - Courtesy of George Leslie Ltd[/caption]

Implementation and Health & Safety

Due to access challenges with a single track road to the site, the size of equipment utilised was limited. The main tasks included the innovative use and the installation of Legato Blocks, to potentially reduce flows over the weir and divert away from the construction area. Reservoir drawdown, silt mitigation, drilling and fixing L-Bars, installing mesh and formwork, pouring concrete, and installing pressure relief pipes was also required.

Health and safety was paramount, with rigorous risk assessments, emergency procedures, safety training, incident reporting, and monitoring compliance forming the backbone of the project’s safety culture.

Impact & benefits

Scottish Water is a public sector body answerable to the Scottish Parliament through Scottish Ministers and our principal activities are the supply of water and waste water services to around 5.4 million customers in homes and businesses across Scotland covering an area of 30,810 square miles.

Our vision is to be trusted to care for the water on which Scotland depends. Reflecting that, our customers expect us to provide excellent customer service by delivering high levels of water quality and environmental performance, all for an affordable price.  Using Scotland’s natural resources and the skills of our people, Scottish Water is committed to improving our services for customers and communities while protecting and enhancing the environment of Scotland.

This project not only restored the dam’s functionality but also reinforced its structure against future threats, ensuring the continued safety and security of water supplies to Milngavie WTW and Balmore WTW. It also addresses the major business risk associated with loss of supply to these strategic assets, which output potable water to a population of approximately 1.3 million people in central Scotland and provides vital water for commercial and industrial use.

This project is important to Scottish Water as it continues to build the trust and confidence of customers and communities across Scotland by maintaining and investing in the company’s assets.

[caption id="attachment_14710" align="alignnone" width="1200"] Katrine Dam: (left) looking north prior to concrete pour and (right) looking west- Courtesy of Whitehouse Studios[/caption]

Conclusion

The Loch Katrine Emergency Dam Project stands as a shining example of engineering excellence, showcasing the ability to swiftly and safely respond to emergency situations while maintaining a strong focus on health and safety. The next phase of the work is already underway, promising to further solidify the dam’s role in safeguarding the region’s water supply.

Ise Valley, Wellingborough, is home to the £1bn Stanton Cross housing development just off the B571 in the east of England. In late 2022, parts of the development were struck with leaks in the underground rising mains, causing disruption to many new homeowners during the Christmas period. In November 2022, Anglian Water was made aware of several leaks on each of the 700mm ductile iron rising mains from Ise Valley Terminal Pumping Station (TPS), which pumps flows of up to 1500 l/s. Both rising mains are required for normal operation of the pumping station and to convey the maximum flow, however, surveys showed that both mains had reached the end of their asset life due to both internal and external corrosion, and further leaks would occur if no action was taken.

Background

Once the team attended site, it became apparent that both the north and the south mains had leakage issues. Non-destructive testing confirmed external pitting and internal abrasion wearing in the upstream sections and an internal hydrogen sulphide (H2S) attack on the downstream section, which was determined to be the primary issue.

With two leaks occurring in close proximity, and previous leaks occurring over the last 10 years, there was a substantial risk of more. The @one Alliance was engaged on 1 December 2022 with the immediate priority being to design, install and commission an temporary above-ground bypass to mitigate the impact of any further potential leaks while the permanent solution was identified.

The Stanton Cross housing development was recently constructed over the area along the route of the rising mains, with houses as close to the asset as 4m in places and leaving no clear route to bypass the flows. As an added complication, some residents located close to the rising mains reported feeling vibrations from the mains;  the cause of which needed to be investigated.

[caption id="attachment_13372" align="alignnone" width="1200"] Temporary pipeline ready for assembly - Courtesy of @one Alliance[/caption]

Temporary solution

It was identified that the rising main leaving the building from the north could be isolated and cut into, to provide a temporary overland pipeline fed by the existing pumps, which would avoid the need for temporary pumping equipment over what would have been the Christmas period. Although the five pumps had recently been mechanically overhauled, the team found several electrical issues that required repairs. As such it was arranged for three temporary variable speed drives to be installed as a matter of urgency, to better manage pump performance and to help prevent further bursts before flows could be diverted.

Utilising contacts across the @one Alliance’s supply chain, specialist overpumping contractor Vanderkamp UK was contracted to provide a temporary bypass in short order. The teams decided on a 1m diameter pipe to give the equivalent flow of the existing twin 700mm diameter pipes to avoid reducing pump capacity.

Working around the clock to find a suitable solution, Vanderkamp UK, the @one Alliance and Anglian Water’s Water Recycling Networks (WRN), allowed for a quick design and installation of the bypass. The whole team aided the process from construction design management documentation to hydraulic design, temporary works, customer and PR, supply chain and enabling.

Ise Valley Sewer Rehabilitation: Supply chain - key participants

• Project delivery: @one Alliance
• Bypass pipework: Vanderkamp UK
• Cured in place relining: OnSite Central Ltd
• CIPP liner supply: IMPREG GmBH

[caption id="attachment_13369" align="alignnone" width="1200"] Road closures were necessary while installing the pipe bridges - Courtesy of @one Alliance[/caption]

Overpumping bypass pipeline installation

In order to build the overpumping solution as quickly as possible, the @one Alliance team collaborated with the Integrated Operational Solutions (IOS) Alliance that provided provisional enabling works such as electrical isolation of services, excavation of the point of connection and temporary ground drainage/pollution avoidance provisions. With the initial works complete, the @one Alliance took full control of the site and initiated the installation of the pipeline.

Work of this scale required a coordinated customer strategy which was designed and implemented by the @one Alliance Customer Team who notified all affected customers of the planned works and continued to provide updates throughout the various stages of work making sure customers were informed and suffered the least impact possible over a busy Christmas period.

To make the connection to the bypass pipework, all flows were diverted to the south main and twin 600mm tee pieces were installed in the north main within the terminal pumping station compound. This arrangement allowed the south main to remain in service if required over Christmas. The connection was completed on 9 December with installation of the 1m diameter pipework commencing the following day.

Due to the new housing development, it was not possible to follow the route of the existing mains and care had to be taken to ensure the bypass pipework would not interfere with a permanent solution or the ongoing operation of the pumping station. A route along Driver Way and Irthlingborough Road was selected which included several pipe bridges in order to allow unrestricted customer access. Emergency road closures were agreed with both the local property developer and North Northamptonshire Highways to safely install the pipework.

[caption id="attachment_13373" align="alignnone" width="1200"] Installing the temporary overpumping solution - Courtesy of @one Alliance[/caption]

The pipework installation was completed in just 10 days during an extreme cold snap which saw the @one Alliance and Vanderkamp UK operatives installing the overpumping pipeline in temperatures of -6°C. Nevertheless, the team worked two consecutive weekends to ensure the bypass was live and operational before Christmas. On 20 December 2022, the bypass was commissioned on time and to ensure there were no customer issues, inspections were carried out every day over the Christmas period.

Permanent solution

Testing and inspection of the mains showed that in the base of the pipe there were a series of what could be best described as wave patterns. The waves - the result of erosion of the pipe material - has been caused over many years by grit within the flow of sewerage. As the pipes rise steeply uphill the grit had settled at the base. Coupled with external and internal corrosion, susceptible areas of the ductile iron pipes have locally pin-holed, which had allowed leakage, and confirmed zero life span remaining in places.

Following the inspection and testing of the pipework, an accelerated Risk, Opportunity & Value sprint was held with all stakeholders to confirm the most suitable permanent solution. The team decided against the removal and replacement of the existing main due to the amount of time it would have taken to execute, additional disruption to customers and local traffic, and the small working space available to the team. It was then determined that the most effective solution was to use a structural liner.

The location of the trial holes, which had been used for examination and non-destructive testing of the mains, had been carefully selected as potential relining pits in the event this solution was to be used. This allowed for an accelerated programme to prepare for the relining works and a reduction in carbon and costs.

[caption id="attachment_13371" align="alignnone" width="1200"] Re-lining rig - Courtesy of @one Alliance[/caption] Rehabilitation of the existing mains using specialist pressure-rated cured in place pipe (CIPP) liners was selected. Framework supplier OnSite Central Ltd installed the liners using a combination of ultraviolet and water cure techniques to suit the challenging pipe conditions. Aware of the time constraints, OnSite Central Ltd worked with the project team to ensure the liners were delivered promptly from IMPREG GmBH in Germany, and that installation gangs were available to work extended shifts to ensure the challenging programme was delivered.

Once the relining was complete Vanderkamp UK  began dismantling the overpumping, all of which was removed by the end of May 2023. Pressure and vibration monitoring of the temporary bypass pipework identified a correlation between pressure spikes and vibrations. This resulted in a change to the pumping station regime and, along with the new variable speed drives and the liner acting as a barrier, resulted in a large reduction of vibrations felt along the route once flows had been returned to the rising mains. Post works vibration monitoring at a number of previously affected properties confirmed the vibration issues had been resolved.

Challenges

The team had to take into consideration a plethora of potential risks during the entire project lifecycle. From contaminated ground, congested buried services, extreme weather conditions, an construction challenges such as relining through 45° bends. The team had to sufficiently ensure a timely plan was in place, following many detailed impact plans created to overcome these issues to ensure efficiency in completion of the project, and reduce the disruption to customers over the festive period.

[caption id="attachment_13367" align="alignnone" width="1200"] Overpumping termination point - Courtesy of @one Alliance[/caption]

Customer liaison

One of the big challenges for this scheme was the disruption to the customers during the festive period, with the scheme attracting significant nationwide media attention over the duration of the works from national and local newspapers, BBC television (“Look East”), BBC radio (Jeremy Vine), and news and social media websites.

While this work went on, the @one Alliance Customer Team kept residents up to date with the team’s progress while helping manage expectations as to how long the work would take, and how long the temporary structure would be in place. Communications to the local residents were consistent throughout the project lifecycle (from 2/12/2022 to 24/4/2023), ensuring constant updates, programme times, and responses to queries were included at all stages.

Outcome

Anglian Water’s £2.8m spend and proactive response to this issue enabled the successful relining of the existing pipe. The relining solution, which will give the pipe an expected 100 years of extra service, has been in service for over a year with no issues.

The Saltcoats Rising Main project involved upgrading just over a kilometre of existing pipe on the most burst-prone section of the rising main, which stretches between the towns of Saltcoats and Stevenston in North Ayrshire. The rising main was originally installed in 1992, and it runs approximately 3km from Saltcoats WwPS towards Stevenston WwTW. The existing main is a 700mm diameter ductile iron (DI) pipe, ranging from two to five metres in depth, conveying a flow of around 500 l/s.

Background

The driver for this fast-tracked project was that the main had burst on various occasions, with four bursts before Caledonia Water Alliance’s (CWA) involvement and a further burst during the design phase.

The failure on the pipe became evident along the invert, with noticeable ‘channelling’ discovered after taking cut-outs during the repair works. There is a bathing water nearby and bursts were causing the pumping station to spill and have a direct impact on the water, prompting Scottish Water to seek permanent solutions to improve the pressure main’s functionality instead of continually responding to leaks.

[caption id="attachment_13076" align="alignnone" width="1200"] (left) Aerial view of the project and (right) rising main failure - Courtesy of Caledonia Water Alliance[/caption]

Project scope

• Lining of the first 1km of existing 700mm diameter DI rising main from Saltcoats WwPS.
• Installation of cured in place pipe (CIPP) lining by hot curing.
• Installation of one air valve and one scour valve. The scour valve to be relocated off carriageway for future ease of access and maintenance.
• Excavation of five lining pits to enable lining in both directions.
• Two  bypass installations to enable over pumping of all flows during lining works.
• Planned shutdown to install valve arrangement for bypass.
• Installation of approximately 1km in length of overland 700mm steel pipes.

Site investigation

Given the environmental impact of bursts to the nearby bathing waters, the project started moving quickly and CWA were engaged to review potential solutions. While reviewing the requirements for a potential offline replacement, it became apparent that this would take some time and require multiple third-party approvals before any work could take place.

It would also involve finding a suitable location for a new pipe, which would involve executing the works through an existing golf course and through the only access road in and out of a busy caravan park. To limit the impact of the works and reach the site quicker, Scottish Water agreed to use a trenchless solution and re-line the existing rising main. Scottish Water instructed Caledonia Water Alliance to focus on the first 1km of the main, as this would cover the section of previous bursts to date.

This would make the scope more achievable in lieu of the bathing season approaching, given the location of the remainder of the pipe.

[caption id="attachment_13074" align="alignnone" width="1200"] Pipe delivery - Courtesy of Caledonia Water Alliance[/caption]

Project summary

• Project name: Saltcoats Rising Main
• Project cost: £4m
• Start date - design: 1 November 2022
• Start date - construction: 31 March 2023
• Completion date: 27 October 2023

Planning

With the agreed solution of lining the pipe now in place, the focus turned to getting on site as quickly as possible. This meant fast-tracking numerous stages, such as ground investigation and detailed design, and instead progressing with a high-level detail of the proposal, with various assumptions in place. The main issue which arose was how to manage the flows.

Caledonia Water Alliance proposed different options to SEPA, ultimately suggesting that they could turn the pumps off and tanker/spill the flows while working on lining the pipe. This would have been the quickest solution but would involve the rising main being offline for several months, which SEPA, as a regulator, could not accept.

SEPA did however appreciate why Caledonia Water Alliance were asking the question. Caledonia Water Alliance had anticipated this being the case with the only other option to bypass the flows with an overland pipe while working on the existing main. However, this posed issues - mainly around laying 1km of 700mm diameter pipe over a golf course and how they could cross a busy road. Given the services within the road and the time constraints, Caledonia Water Alliance could not bury it, even partially.

[caption id="attachment_13070" align="alignnone" width="1200"] Assembly of overhead pipe bridge - Courtesy of Caledonia Water Alliance[/caption]

This led to the proposal of an up-and-over bridge crossing. Caledonia Water Alliance was initially reluctant, given the visual impact this would have but, realistically, had no other choice. In the end, this worked out well, through extensive communications with the local residents, businesses, and caravan park, all agreeing the work was necessary to rehabilitate the rising main. The next challenge was to get the 1km bypass installed and operational before the bathing season beginning on the 31 May 2023.

From receiving the project at the end of October 2022 and starting on site in March 2023, Caledonia Water Alliance was able to collaborate with Environmental Techniques Ltd to design a cured-in-place liner with pit locations; working alongside their specialist subcontractor Selwood, to develop the overland bypass pipe.

As above, Caledonia Water Alliance went to site with some assumptions of the rising main location and depth, so they knew there would be changes as the project developed on site.

Saltcoats Rising Main: Supply chain - key participants

• Project delivery: Caledonia Water Alliance
• Trenchless rehabilitation & liner design: Environmental Techniques Ltd
• Civils subcontractor: Jacks1 Civil Engineering
• Underpressure connections: Swan Pipelines
• Scaffolding: AHL Scaffolding
• Temporary works/shoring: Groundforce
• Water supply: Enviroclean
• Liner supply: Insituform
• Bypass pipework: Selwood

[caption id="attachment_13073" align="alignnone" width="1200"] Bypass pit showing pipework cut out and a new ‘T’ piece and valve arrangement - Courtesy of Caledonia Water Alliance[/caption]

Temporary bypass

The first part of the work, after establishing the site, was to install the temporary bypass. The bypass utilised a 700mm diameter flanged steel pipe, bolted together. This was strung out from a bypass pit adjacent to Saltcoats Pumping Station, approximately 1km downstream.

This required a tremendous effort to deliver a large quantity of pipework, drop it in place and bolt it together whilst working on both bypass pits at either end of the 1km section of pipe. The team completed the works on the bypass on time before the bathing season. With this now operational, CWA ensured the safety of the first 1km of the main from potential bursts.

Liner installation

The liner chosen was a cured-in-place pipe liner (CIPP) as this would provide the structural capacity of the host pipe. CIPP lining has been extensively used throughout the UK to repair failing sewer pipes, prevent infiltration and to add structural strength where required.

Designing CIPP liners for pressurised pipe systems presents unique challenges that differ significantly from their application in gravity-fed sewers. In pressurised systems, the liner must withstand not only external forces such as soil, groundwater, and traffic loads but also the continuous internal pressure exerted by the fluid within the pipe.

Additionally, the liner must also be able to withstand negative internal pressures, or vacuum conditions, which can cause the liner to experience inward forces, particularly near joints and bends. The design had to account for these vacuum scenarios to ensure that the liner remains stable and securely bonded to the host pipe, preserving the structural integrity of the pipe under varying pressure conditions.

[caption id="attachment_15903" align="alignnone" width="1200"] Liner installation - Courtesy of Caledonia Water Alliance[/caption]

The liner was designed with the operating and supplied test pressures of the existing rising main. The number of known bends, as well as the potential for more unknown bends, meant that the hot water curing was a more suitable process for this project as the liner would invert itself under the pressure of the curing water, navigating around the bends automatically.

A scaffold tower was installed at the installation pits to secure the end of the liner and to ensure enough vertical height to allow the water pressure to invert the liner through the length of pipe required. The hot cure process utilises a hot water boiler to raise the temperature of the curing water which begins the process of hardening the resin.

The liner provides a 60-year design life, similar to installing a new pipework, but with significantly less digging requirements and waste production.

[caption id="attachment_15902" align="alignnone" width="1200"] Drone image showing the scaffold tower and the liner installation operation underway - Courtesy of Paul Milligan, Caledonia Water Alliance[/caption]

No-dig technique

The decision to use trenchless relining methods was primarily driven by the need to minimise the number of excavations, significantly reducing disruption and environmental impact. In Saltcoats, this approach required only five lining pits and two bypass pits along the existing rising main, demonstrating the efficiency of trenchless technology compared to traditional dig-and-replace methods. One of the key benefits of trenchless relining is the reduced need for extensive excavation, which minimises surface disruption to roads, traffic, and the surrounding environment. This is particularly in Saltcoats to minimise disruption to the local communities, golf course and caravan park. By using trenchless techniques, the project can be completed faster with less noise, dust, and inconvenience to residents and visitors to these areas.

For the bypass pits, existing pipe sections were cut out, and new T-piece and valve arrangements were installed. This allowed for the connection of temporary bypass pipes, enabling the flow to be managed through valve operation without interrupting service. The trenchless approach also reduces the risk of encountering unforeseen underground utilities, which can lead to costly delays and repairs.

Overall, trenchless relining offers a safer, more efficient, and less invasive solution for repairing and upgrading pipeline infrastructure.

Conclusion/update

The project was completed successfully on site and within the proposed programme, despite coming across some major obstacles on site. Once the lining was completed, it was inspected, tested, and finally put into commission by transferring the flows back into the newly rehabilitated main.

[caption id="attachment_13071" align="alignnone" width="1200"] CCTV output pre and post lining - Courtesy of Caledonia Water Alliance[/caption]

Following successful commissioning, the rising main was run for a period of 48 hours without any defects. After this time, Caledonia Water Alliance was able to start dismantling the bypass pipe, removing it from site and reinstating the area.

Undertaking the Saltcoats Rising Main Rehabilitation Project was a significant effort by all involved to first install and have the bypass pipe operational before the bathing season, and then to have the existing main rehabilitated and working within the timescales which Caledonia Water Alliance provided Scottish Water at the start of the works.

This was particularly impressive given the fast-track nature of the works and getting a large-scale project to site quickly. There is now a Phase 2 and 3 proposed for the remainder of the rising main to Stevenston WwTW to rehabilitate it over its entirety. These will be looked at over the next 2 to 3 years.

Porthcawl in South Wales boasts a rich maritime heritage and attracts over a million visitors a year. The seaside location is a draw for visitors and residents, but rising sea levels and increasing storm intensity coupled with ageing infrastructure, have increased the town’s risk of coastal flooding. As well as threatening properties, this has constrained development opportunities in the area. This project reduces threat of coastal flood and erosion risk to around 700 properties, while supporting tourism and providing greater opportunities for amenity and regeneration. Works include a complex renovation of the Grade II listed Western Breakwater, enhancement of the Eastern Promenade, and protection improvements at Rhych Point and relict dunes.

Building a business case for investment

Bridgend County Borough Council (BCBC) commissioned Arup to develop a business case for investment to reduce coastal flood risk to Sandy Bay, a wide and popular beach in Porthcawl. Analysis revealed that the condition of Porthcawl’s historic Western Breakwater was key to managing coastal risk throughout the bay. As a result, it was agreed with Welsh Government, to include the structure in the project.

The bay is surrounded by more than 100 acres of land identified for regionally significant regeneration. A phased approach was developed so works within the council’s control could be funded without the delay and risk of awaiting future development.

As part of the evidence for the business case, flood inundation modelling, informed by asset condition assessments and wave modelling, showed that 110 homes and 70 businesses were at risk of flooding. However, if the Western Breakwater were to fail, this increased to more than 530 homes and 175 businesses.

[caption id="attachment_14768" align="alignnone" width="1200"] (left) Flood inundation modelling and (right) site location plan - Courtesy of Arup[/caption]

Innovative investigations & restoration of a historic breakwater

Porthcawl’s 182m-long Western Breakwater is 200 years old and Grade II heritage listed. It forms a crucial part of the coastal infrastructure that protects the harbour and Sandy Bay from extreme wave impacts, but a challenging programme of repairs and strengthening measures was needed to maintain its structural integrity.

To protect its legacy, Arup consulted closely with Cadw, the Welsh Government’s historic environment service, as well as BCBC’s heritage specialists, enabling consents to be obtained without programme delay.

The challenge with the Western Breakwater was understanding the existing structural form (as the breakwater had undergone numerous modifications over its lifetime) and the likely failure scenarios associated with that structure. It was essential for the team to uncover its chronological development since its construction in the 1820s and to identify the nature and extent of its defects.

Arup combined historical research with drone, lidar, geophysical and geotechnical survey data to understand its structural weaknesses. Surveys used non-destructive techniques such as ground-penetrating radar, supplemented by trial pits and horizontal cores. Using the information gathered, the team devised a plan to help maintain the breakwater’s original character while reducing flood risk and improving its structural integrity.

The design included repairs to masonry and concrete, raising parapets, installation of a precast concrete cut-off wall and new rock armour. The design thus reduced the risk of voids and the impact of waves. Stone was sourced from the local quarry used in the original construction to replace a failed seaward sloping wall, and the voids were grouted to prevent water leakage and corrosion. A cut-off wall was constructed to provide a protective layer to reduce scour risk and future washout of fine material.

To strengthen the slender parapets without damaging the heritage-listed historic masonry, Cintec reinforcing anchors were added. This is a system that uses grout contained in a fabric sock mesh, combined with steel anchors. It helped to preserve the breakwater’s original character, as well as minimising carbon impacts and overall project costs.

By repairing the existing breakwater, rather than building a new one, the project reduced embodied carbon, and using locally quarried materials reduced transport impacts. The choice of prefabricated mass concrete blocks instead of reinforced concrete for the cutoff wall reduces future maintenance needs for the Western Breakwater. During construction it also reduced the health and safety risks of deep-water working, as the blocks acted as permanent shuttering.

Early engagement with Knights Brown contractors providing early supplier engagement was key; it ensured that the team’s designs could be safely implemented during periods of low tide and in challenging coastal working conditions.

[caption id="attachment_14767" align="alignnone" width="1200"] Western Breakwater Point Cloud model - Courtesy of Arup[/caption]

Placemaking public realm enhancements

As well as repairing and improving the listed breakwater, the project extended to the Eastern Promenade, located on the west side of the popular Sandy Bay beach. Initially, a secondary wall to stop waves overtopping the promenade was planned, but Arup’s placemaking design sought to ensure the promenade would be attractive for visitors and residents in years to come, and overtopping studies showed that the wall could be replaced with multifunctional planters. This added more green space, integrated terraced seating and minimised service diversions and disruption to the public.

The team also improved cycling and walking routes, ensuring the promenade was more functional and appealing for visitors and locals.

Preserving the dunes

Where previous proposals would have seen the sand dune habitat protected by concrete terraced defences, ABPmer’s study for Arup into coastal processes showed that the dunes could be preserved and restored using nature-based solutions, minimising costs and carbon emissions. For the restoration of the dunes to create a natural buffer, the team proposed 285m of low-level fencing to encourage the build-up of new dunes. These simple measures, combined with a growth and stability monitoring plan, will help maintain the coastal pathway. This approach has enhanced coastal resilience and revitalised the beach ecosystem, benefiting both residents and tourists.

Supporting marine biodiversity

To help support marine biodiversity, the team worked with CubeX Industries Ltd/BlueCube Marine and Swansea University to test innovative modular textured panels used to form an artificial reef and rock pools.

The hexagonal panels featured 13 distinct patterns made from ultra-high-performance concrete, with three different concrete mixes tested, including one incorporating local crushed cockle shells and ash. These were affixed in a beehive arrangement on the horizontal toe of the breakwater, to evaluate pattern colonisation by fauna and seaweeds under varying submergence times and wave exposures. The panels aimed to mimic natural habitats and foster marine life such as the protected honeycomb worm. [caption id="attachment_14773" align="alignnone" width="1200"] Settlers of Porthcawl - Courtesy of BlueCube Marine[/caption]

The project, known locally as the Settlers of Porthcawl, gained community support for eco-engineering interventions. Through questionnaires, the team established the public’s preferences for patterns imitating natural textures, and for a mixture of designs on the seawall. The project gained popularity among local schools and hosted over 200 students to teach them about climate change, biodiversity and sea-level rise.

Monitoring for a year revealed colonisation disparities across the sites due to wave exposure. This emphasised the significance of submergence and exposure. It was found that the most successful patterns to help foster colonisation were those with protruding ledges and rough microstructures, as opposed to smooth designs.

Project details

• Programme overview: Welsh Government
• Client: Bridgend County Borough Council
• Project cost: £6m
• Design start: October 2016
• Construction period: April 2021 - June 2023

Porthcawl Coastal Scheme: Supply chain - key participants

• Designer: Arup
• Construction supervisor: WSP
• Marine specialist: ABPmer
• Geophysical survey specialists: TerraDat (UK) Ltd
• Land surveys: Azimuth Land Surveys
• Archaeology: Glamorgan-Gwent Archaeological Trust
• Surveys: Tetra Tech
• Maritime structural engineering sub-consultant: Steve Hold Consulting
• Main contractor: Knights Brown
• Groundworks: McCarthy Contractors Bridgend Ltd
• Concrete repairs & grout: Beton Bauen Ltd
• Scaffolding: PSS Scaffolding Ltd
• Fabrication: Total Fabrication
• Precast: Macrete (Ireland) Ltd
• Green infrastructure pilot: Swansea University
• Architectural concrete: CubeX Industries Ltd
• Artificial reef & rockpools: BlueCube Marine
• Handrailing: Broxap Ltd
• Cintec anchors: Celtest Company Ltd
• Masonry: Dawson Stone Masonry Ltd
• Surfacing: Asphalt Surfacing Ltd

[caption id="attachment_14769" align="alignnone" width="1200"] Western Breakwater construction works - Courtesy of Knights Brown[/caption]

Challenging, collaborative construction

Knights Brown was appointed principal contractor under a NEC3 Engineering and Construction Option A contract, reflecting a commitment to cost acuity and risk mitigation.

In the high-risk environment, reducing construction risks meant minimising drilling, concreting and grout injection times to suit three-hour tide windows. Design and construction teams worked collaboratively on site, for example to minimize grout loss due to residual post-survey uncertainty around structural void volumes and locations. Cradle solutions extended working times. Precast standardised mass concrete blocks and redesigned Cintec anchor applications all supported installation.

Extensive consultation with users of the infrastructure and development of a phasing plan (including measures such as avoiding construction at Rhych Point during peak tourist season and phasing construction to retain public access to Eastern Promenade) was crucial to mitigate negative impacts during construction. This enabled community and sporting groups to access the promenade and maintained RNLI lifeboat access to the slipway. Project information boards and use of local media raised awareness of the scheme and kept users informed of progress.

Community benefits emphasised local employment and training opportunities, including five new-entry apprenticeships, engagement with local supply chain and support of local initiatives for young people not in education, employment or training. A bespoke schools engagement programme based on ‘The Tale of the Sea Monster’ educated and raised awareness of the need for improvements in a child-friendly, engaging way.

Construction was hit by several large and powerful storms; evidenced by modelling to be impacted by climate change. In response to damage from a May 2021 storm, repairs employed hydro-demolition of concrete around reinforcement bars, repairing the corroded bars and spraying concrete to repair panels. The resilience of these repairs was proven in December 2021 when Storm Barra halted construction work but caused no damage to repairs.

[caption id="attachment_14776" align="alignnone" width="1200"] Western Breakwater during Storm Diana - Courtesy of Keith Jones[/caption]

Conclusion

Despite the impact of the COVID-19 pandemic, as well as multiple severe storms, the Porthcawl Sandy Bay Coastal Scheme was completed in the agreed time-frame and within budget in Summer 2023.

Beyond its primary objective of reducing flood risk, the scheme has delivered substantial economic benefits to the local community and the wider region. By safeguarding critical infrastructure, residential properties and commercial assets, the scheme protects livelihoods and preserves the vitality of the coastal economy. Moreover, the enhanced recreational opportunities and improved coastal aesthetics will attract tourists and investors, stimulating economic growth and enhancing the town’s resilience to future shocks.

Janine Nightingale, Director of Communities, Bridgend County Borough Council commented:

“... [the scheme] forms a vital part of the infrastructure for defending the town against flooding and will also help to secure future development in the area.”

The scheme was highly commended for the Environmental Project of the Year and shortlisted for the National Infrastructure Commission’s Design Principles Project of the Year at the British Construction Industry Awards 2023.

York city centre, with its dense network of restaurants, takeaways, pubs, and other commercial establishments, has long faced significant challenges relating to fats, oils and grease (FOG). These businesses contribute substantial FOG loads to the sewage system, leading to issues such as blockages, odour problems, pollution incidents, and infrastructure strain. In 2023, Yorkshire Water (YW) embarked on a groundbreaking initiative to address these FOG challenges. The trial leveraged Cobra Hydro UK’s innovative Cobra Bio Block technology, aiming to enhance wastewater management efficiency, reduce environmental risks, and improve overall network performance. This case study explores the objectives, deployment, technology, outcomes, and industry implications of the trial, showcasing a significant step forward for sustainable utility practices.

Background & objectives

Before the trial, Yorkshire Water regularly encountered FOG discharge into the nearby River Ouse; presenting environmental hazards and regulatory compliance concerns.

The primary objective of the Cobra Bio Block trial was to mitigate FOG accumulation in York’s sewage network while exploring a cost-effective and environmentally friendly alternative to traditional FOG management methods. Specifically, the project sought to:

• Achieve a measurable reduction in FOG levels within the network.
• Eliminate pollution incidents caused by FOG discharge.
• Improve operational efficiency by minimising maintenance requirements and infrastructure stress.
• Assess the financial and environmental benefits of deploying Cobra Bio Block technology.

Project implementation

The trial commenced in September 2023 with the installation of Cobra Bio Blocks in over 40 key manholes across York city centre. The blocks were replaced every two months, ensuring consistent microbial and enzymatic activity. The final replacement occurred in August 2024, marking a full year of continuous operation.

YW provided a robust framework for monitoring the trial’s impact, utilising video footage, photographic evidence, and data collection to assess pre and post implementation conditions. These observations formed the basis for evaluating the effectiveness of the Bio Blocks.

[caption id="attachment_19284" align="alignnone" width="1200"] Bio Block - Courtesy of Cobra Hydro UK[/caption]

Cobra Bio Block technology

The Cobra Bio Block represents a pioneering approach to wastewater management. Designed for durability and simplicity, the Bio Block is a semi-submersible solution engineered to reduce FOG and odours in wastewater systems. Its unique features and mechanisms include:

• Innovative composition: The Bio Block consists of a slowly dissolving matrix enclosed within a durable, porous mesh sleeve. This design ensures gradual erosion and consistent release of active agents over time.
• Biological action: The block contains a blend of naturally occurring microbes and enzymes. As it dissolves, these microbes colonise surfaces within the sewage network, breaking down organic contaminants such as fats, oils, and grease.
• Ease of deployment: Suspended below the waterline in locations such as wet wells, pumping stations, or sewer lines, the Bio Block operates autonomously, requiring no electrical power, additional equipment, or extensive maintenance.
• Eco-friendly design: The non-toxic, environmentally safe composition ensures that the Bio Block poses no risk to aquatic ecosystems or surrounding environments.

Benefits of the Cobra Bio Block

The Cobra Bio Block offers several advantages over traditional FOG management methods:

1. Continuous action: Unlike periodic dosing solutions, the Bio Block provides a steady release of microbes and enzymes, maintaining consistent effectiveness even during heavy rainfall or washout events.
2. Odour and FOG reduction: By breaking down organic matter, the Bio Block significantly reduces unpleasant odours and FOG accumulation.
3. Low maintenance: Operating 24/7 without the need for active intervention, the Bio Block minimises the operational burden on utility providers.
4. Cost efficiency: The elimination of dosing equipment and associated infrastructure reduces both capital and operational expenditures.
5. Environmental safety: The non-toxic formulation supports sustainable wastewater management practices, aligning with environmental regulations and corporate responsibility goals.

Key findings from the trial

Yorkshire Water reported compelling results from the Cobra Bio Block trial, highlighting its effectiveness and transformative potential:

1. FOG reduction: The trial achieved a 90% reduction in FOG levels within the sewage network. This dramatic improvement alleviated blockages, enhanced flow capacity, and reduced infrastructure strain.
2. Elimination of pollution incidents: Prior to the trial, six FOG-related pollution incidents were recoded between 2019 and 2023. During the trial period, no major pollution incidents were reported, marking a significant milestone in environmental protection.
3. Improved network resilience: The absence of FOG-related flooding issues demonstrated the Bio Block’s role in enhancing system reliability and performance.
4. Financial impacts: Although detailed cost analyses were not provided, YW acknowledged the potential for substantial savings through reduced maintenance requirements, lower risk of fines, and improved regulatory compliance.
5. Stakeholder satisfaction: YW praised Cobra Hydro UK’s professionalism and the seamless execution of the trial, emphasising the collaborative effort’s success.

[caption id="attachment_19285" align="alignnone" width="1200"] Examples of the results after Bio Block dosing – Courtesy of Cobra Hydro UK[/caption]

Additional observations

The trial also uncovered secondary benefits that reinforced its value. Beyond the reduction of FOG and operational challenges, Yorkshire Water noted improvements in system cleanliness.

The microbial action facilitated by the Bio Blocks not only addresses fat and grease but also mitigated other organic contaminants. This broader impact on sewer line hygiene contributed to an overall reduction in maintenance costs and extended the lifecycle of infrastructure components. Additionally, the Bio Blocks’ low maintenance design allowed YW personnel to allocate resources more efficiently, focusing on proactive network management instead of reactive problem-solving.

The public’s perception of YW also benefited from the trial. By deploying environmentally friendly technology, the company demonstrated its commitment to sustainability and community well-being. This enhanced reputation is expected to yield long-term advantages in stakeholder trust and regulatory goodwill.

Implications for the utility industry

The success of the Cobra Bio Block trial offers valuable insights and opportunities for the utility sector:

1. Scalability: The simplicity and versatility of the Bio Block make it suitable for deployment across diverse wastewater systems, from urban centres to rural networks.
2. Sustainability: By prioritising eco-friendly technology, utility providers can align their operations with global sustainability goals, reducing environmental footprints and fostering community trust.
3. Cost management: The financial benefits of reduced maintenance, enhanced network performance, and regulatory compliance create a compelling case for wider adoption of Bio Block technology.
4. Collaborative innovation: The partnership between YW and Cobra Hydro UK underscores the importance of collaboration in driving industry advancements and solving complex challenges.

Testimonials

Kelly Burke, Network Protection Officer at Yorkshire Water, shared her perspective on the trial’s success:

“The trial of the dosing blocks in York has been very successful. The blocks have helped reduce incidents of fats, oils and grease causing blockages in the network and clogging up the pipes under the city to zero. In the last 12 months, we’ve had no pollution incidents linked to fats, oils and grease and no sewage escapes due to fat blockages.”

On 11 December 2024, the groundbreaking success of the product was featured on BBC Morning Live. During the segment, James Harrison, Head of Wastewater Asset Management at Yorkshire Water, highlighted its transformative impact on the utility’s sewer network:

“The thing that’s great about this product is that they’re easy to install, easy to replace. And they don’t just break down fat that is there, they can also prevent it’s built up as well, so it’s a really cost effective, practical, sustainable solution. The difference is incredibly noticeable if you look at the CCTV footage of the cameras down the sewer network, historically you would come back here to do an inspection and you’d see a coating round the pipe and it really starting to layer up, and the difference it has made is phenomenal.”

Clint Jackson, Business Development Director at Cobra Hydro UK, echoed these sentiments:

“Since we began this project in 2023, we have provided a cost-effective solution to reduce the fat, oil, and grease build-up within the sewers under the centre of York. We’re extremely pleased that our enzyme Bio Blocks have achieved the desired results.”

Conclusion

The Cobra Bio Block trial in York city centre represents a significant advancement in wastewater management. By addressing longstanding FOG challenges with an innovative, environmentally friendly solution, Yorkshire Water and Cobra Hydro UK demonstrated the power of technology and collaboration to achieve measurable improvements.

This case study serves as a model for the utility industry, illustrating how innovative solutions can enhance operational efficiency, protect the environment, and deliver tangible benefits to stakeholders. As the sector continues to navigate evolving challenges, the success of the Cobra Bio Block offers a roadmap for sustainable, effective wastewater management practices.