Supply Chain - Health & Safety - COSHH Assessments

In recent times Seagahan WTW has faced ongoing issues including:

Unaddressed, these deficiencies could pose risks to regulatory compliance, limit future growth capacity, and increase the potential for Cryptosporidium contamination.

The Seagahan WTW Treatability Improvements Project has implemented a series of targeted upgrades to enhance water quality, improve operational resilience and maintain compliance. Key interventions included:

These upgrades are informed by a treatability appraisal conducted by Arup, which identified critical shortfalls and recommended improvements to ensure the facility could meet current and future regulatory standards.

NI Water engaged Arup and Murphy DAWSON-WAM (MDWAM) early in the project through an Early Contractor Involvement (ECI) approach, fostering a collaborative environment that allowed the project to evolve efficiently. As Principal Contractor, Murphy DAWSON-WAM, supported by strong coordination across all parties, successfully delivered the project on time and within budget. Arup played a dual role, providing NEC Project Management and Supervision throughout the construction phase, while also leading design reviews and approvals. Their involvement extended to managing stakeholder engagement within NI Water and liaising with external bodies such as the Department for Infrastructure.

A key success factor was the strong working relationship developed with NI Water’s Operations, which enabled a clear understanding of practical operability challenges. This collaborative approach informed strategic decisions around infrastructure layout, including pump and panel positioning, freeing up space for storage and maximising the use of existing buildings. These efforts not only streamlined project delivery but also ensured the long-term resilience of water treatment at Seagahan WTW.

ECI with MDWAM and Arup enabled a collaborative and informed approach from the outset of the project. Arup provided up-front technical input through treatability studies, which were instrumental in shaping Business Case submissions and developing focused Basis of Design reports. This proactive engagement supported scope progression and ensured a robust design strategy. Throughout the process, NI Water stakeholders were actively involved in decision-making, fostering transparency and alignment across all phases of delivery.

As designs evolved, a number of design review workshops were held which involved the use of walkthrough models to highlight pinch points and process walk-throughs.

Preference was for the new soda ash storage silo to be located indoors, restricted space for which was determined in the existing GAC building. MDWAM introduced innovative methods, including a 3D scan of the existing GAC building, to validate the feasibility of initial design proposals and facilitate the reuse of existing storage space. The volume and design of the storage silo were influenced by these constraints. The 3D scanning of the existing GAC building was instigated in the absence of record drawings, with new equipment designed to fit head height constraints and roller door access for installation.

A key design decision identified during a design review meeting was the introduction of a structural steel mezzanine platform level to locate the new MCC as floor space was limited.

During the initial investigations, the team identified gaps in the existing information relating to original structures, highlighting the need for further exploration. In several instances, monitoring data was unavailable, so dosing pump and process design had to be guided by SCADA trend analysis where possible. Temporary instruments were also set up during ECI to capture critical analytical data that was otherwise missing. These proactive measures ensured that design decisions were grounded in accurate, site-specific information, ultimately enhancing the reliability and efficiency of the final solution.

The project was delivered within a live operational environment, requiring meticulous planning and coordination to ensure continuity of service and safety. Construction on site began in December 2023 and completion was at the beginning of July 2025. The works were sequenced to minimise disruption to ongoing treatment operations, with close collaboration between the design, construction, and operations teams throughout. A key inherent risk exists when interfacing with existing operational works, live instruments and electrical assets, and this collaboration and careful planning helped to ensure no negative effect on network assets or output during the upgrade.

Early challenges included the failure of legacy equipment originally earmarked for reuse, such as manganese blowers and seized valving arrangements. These issues were addressed through rapid redesign and procurement, ensuring the programme remained on track. Spatial constraints within the site presented further complexity, particularly during the construction of the new dosing chamber and associated pipework diversions. Temporary works and phased excavation strategies were implemented to maintain access and operational integrity.

Modifications to the clean water tanks (CWT1 and CWT2) were carried out under confined space protocols. The installation of actuated valves and bell mouth fittings required innovative approaches due to restricted access openings. Sequencing was critical, with CWT2 brought back into service prior to converting CWT1 into a dedicated un-chlorinated backwash tank.

All works were delivered on a live site, with embargo periods and planned maintenance activities carefully managed. Temporary dosing systems were installed to facilitate safe changeovers, and effective stakeholder engagement with NI Water operations teams ensured that risks were mitigated and service continuity maintained. The new soda ash plant was commissioned in April 2025 and has since been used as the pH controlling process, taking over from the old system.

The project also included the installation of a new potable water supply to the site, with future-proofing measures incorporated to support additional connections. Engagement with DfI Roads and NI Water Distribution Teams ensured compliance and coordination with wider infrastructure planning.

As part of the project, several process-driven improvements were implemented to enhance operational reliability, chemical dosing accuracy, and overall treatment efficiency.

Soda ash system upgrade: The existing soda ash silo was experiencing structural issues and material bridging, leading to inconsistent dosing. A new soda ash system was installed, comprising a silo with integrated shakers, blowers, and a batch tank. A third mixing/maturation tank was introduced to stabilise pH levels and eliminate dosing spikes. Strategically positioned at the opposite end of the building, it also shortens suction lines and improves soda ash solubility. This upgrade ensures consistent material flow and improved pH control, particularly important given the variable pH levels observed due to temperature fluctuations in Seagahan Reservoir.

Potable water protection measures: To prevent back siphonage and protect potable water quality, the supply to the backwash tank was removed following its conversion to an un-chlorinated backwash tank. A new supply line was established from the main distribution network, ensuring compliance with water safety standards.

Centralised control via MCC panels: Motor Control Centre (MCC) panels were installed to provide centralised control of all newly commissioned equipment. This integration enhances operational oversight and simplifies maintenance procedures.

Efficiency gains in backwashing: The transition to unchlorinated water for backwashing has led to reduced chemical wastage and improved backwash efficiency, especially during periods of poor water quality. This required careful reconfiguration of valving arrangements and blanking off interconnections between tanks to prevent contamination of clean water leaving the site.

Flow monitoring & chemical dosing control: A dedicated flow meter chamber was constructed to monitor flow rates of orthophosphate and chlorine dosing. The flowmeter also interfaces with an actuated valve to regulate the filling of CWT1, now designated as the backwash tank. This setup allows for precise control of chemical dosing and tank filling operations.

To protect operatives, the chlorine and orthophosphate are installed in separate chambers to reduce the risk during leaks. This item was identified during a hazard identification meeting.

Hydraulic improvements: The upstand level of CWT2 was increased to enhance hydraulic head, supporting improved flow dynamics across the system. An actuated valve was installed to prioritise flow between the backwash line and CWT2, ensuring that neither system is starved during simultaneous operations.

Water recovery gains: The backwash system was previously a bottleneck to reliable output, following review a hydraulic restriction in the lamellas was identified and addressed which allowed a greater flow to pass through them to reach their design capacity. This improved the overall efficiency and removed the bottleneck, providing headroom in the dirty wash water system and ultimately providing the works with more frequent backwashing facilities.

The Seagahan WTW Treatability Improvements Project incorporated a range of innovative and sustainable measures that enhanced delivery and long-term operational performance. By maximising existing assets and deploying efficient technologies, substantial carbon and financial savings were achieved, both in construction and ongoing operation.

A 3D scan of the GAC building was undertaken to address the absence of reliable as-built records. This enabled accurate coordination with the BIM model and informed the design of new equipment, including a bespoke mezzanine platform for the MCC panels, optimising use of available space.

Sustainability was embedded throughout the project. Excavated material was reused on-site for landscaping and reprofiling, eliminating disposal costs and reducing carbon emissions. Modular blocks were re-purposed for use on other sites, supporting circular economy principles.

The introduction of a third process tank and the use of un-chlorinated water for backwashing improved chemical efficiency and reduced waste, particularly during periods of algal blooms. Additional measures included the installation of a spill tank with integrated safety features and the design of dosing skids with enhanced access and flushing capabilities.

These innovations supported efficient delivery, reduced environmental impact, and aligned with NI Water’s long-term sustainability goals.

The project exemplifies sustainable infrastructure delivery, with substantial environmental and financial benefits realised through three key initiatives:

Overall, the combined impact of these measures in the first year is estimated to deliver a total carbon saving of 64 to 105 tonnes of Co2e and a cost saving of between £351,216 to £502,432.

The Seagahan WTW Treatability Improvements Project was successfully delivered on time and within budget driven by early contractor involvement, innovative design solutions, and a shared commitment to operational excellence and sustainability. With this project NI Water has been able to enhance operational efficiency, enable real-time monitoring via advanced SCADA telemetry, and has future-proofed the system for further instrumentation upgrades. Collaboration between the client, project manager, contractor and other key stakeholders was central to the execution of the project and its overall success.

Due to the scheduling and repetition of work being undertaken within the four-project portfolio, there was a strategic approach to the appointment of specific sub-contractors to maximise programme benefits and acceleration across the projects.

The primary area that was focused upon was the supply of chemical dosing kiosks with a DfMA approach and the mechanical and electrical installation services.

The Thorne STW scheme has a quality driver to reduce phosphorus concentrations in the final effluent to 2.0 mg/l without exceeding iron concentrations of 4 mg/l.

The new ferric sulphate dosing unit will run automatically, and the operator will only be required to ensure that there is a constant supply of chemicals.

A new liquid polymer plant will be installed to replace the existing powder polymer system which feeds the existing gravity belt thickener. To facilitate the replacement a temporary containerised rig was installed and commissioned prior to the removal of the existing plant which removed the existing H&S risk associated with powdered polymer.

The scope also included a full clean up of the existing polymer plant to help facilitate the safe installation and construction works.

The Aldwarke STW P scheme project has a quality driver to reduce phosphorus concentrations in the final effluent to 0.7 mg/l without exceeding iron concentrations of 4 mg/l (2.5 mg/l Al).

The proposed solution is to chemically remove the phosphorus with a primary and secondary ferric sulphate dose upstream of the primary settlement tanks and upstream of FSTs 1-4 respectively.

A new standard ferric dosing kiosk was provided with two dosing pumps and two 10m3 storage tanks complete with a remote fill point panel and remote wash system installed as a single DfMA off-site fabricated kiosk. This feeds two duty/standby POAs at the inlet works facilitated by a newly installed air mixing system as well as two duty/standby POAs at the RAS distribution chamber.

The FST A & B scum removal boxes were also replaced as well as isolation penstock installation. The existing scum pump was replaced and new MLSS probes were installed on the ASP outlet channels.

At Lundwood STW the quality driver is to reduce phosphorus concentrations in the final effluent to 2.0 mg/l without exceeding iron concentrations of 4.0 mg/l.

The solution was to convert the existing secondary treatment activated sludge plant (ASP) to a RAS anoxic configuration. This process will change the existing ASP into an enhanced biological phosphorus removal (EBPR) plant. To limit recycling of phosphorus from the dewatering process back into the EBPR plant, the project will provide ferric sulphate for P removal and caustic soda dosing to the settled sewage to mitigate against the impact of ferric sulphate dosing on the final effluent alkalinity.

Standard 7.5m3 ferric sulphate and sodium hydroxide (caustic) storage tanks and dosing kiosks were to be delivered and installed in a single DfMA off-site fabricated SR4 rated kiosk (due to site security classification). Both chemicals are pumped to their designated POAs and dosed into the PST distribution channel via a bespoke designed V-notch brackets positioned above the top water level of the channel, with the mixing in the channel facilitated by air-mixing provided by newly installed blowers.

The project benefited from carbon savings and construction efficiencies by reviewing the original proposed site location and relocating it to an area which eliminated the demolition of existing assets.

The driver at Castleford is to reduce phosphorous concentrations in the final effluent to 2.0 mg/l without exceeding iron concentrations of 4.0 mg/l.

The proposed solution is to chemically remove the phosphorus by dosing ferric sulphate dose upstream of the final settlement tanks.

The primary ferric sulphate dosing system includes constructing foundations and support structures, installing a 7.5m3 storage tank with duty/standby dosing pumps, and integrating with the existing SCADA and telemetry systems. Civil works required modifications to access pathways and safety installations. Electrical installation works ensured the new plant was fully integrated into the existing works control systems.

The POAs dosed into a splitter box upstream of the final settlement tanks which ensured even distribution of ferric sulphate within the FST distribution chamber.

In order to best meet the needs of the four sites, the design team needed to develop the most efficient and effective solutions for each individual site and application. A collaborative multidisciplinary approach was taken to produce each solution whilst looking for the efficiencies in the standard elements of the portfolio.

The team engaged with Yorkshire Water in weekly collaborative planning meetings to review design; technical challenges and construction programme together with reviewing project Risk & Value (R&V). By adopting this collaborative approach, we achieved design and delivery consistency while utilising standard solutions delivered by a design team comprising of civil, mechanical, electrical, and process engineers.

At the time of writing (July 2024) the projects are progressing well:

Thorne STW: As the first project in the portfolio and therefore the most advanced, Thorne STW has progressed through to commissioning and the Glanua Group team are preparing to bring the plant online.

Aldwarke STW: Significant progress has been made with the completion of the civil works and installation of the ferric dosing kiosk. The delivery team have now moved on to completing the mechanical and electrical installation. This has included the potable water connections, installation of the secondary dosing lines to kiosk dosing rigs. The team has also installed three VSDs to provide a more flexible control of the replaced ram pumps and the blowers have been installed to facilitate air mixing at the point of application.

Lundwood STW: The civil works are complete and kiosks have been installed on site. We we have also progressed with the mechanical and electrical installation works including the installation of the point of application units as well as air mixing pipework. The electrical installation has progressed and cables are being pulled to allow for the second phase of installation prior to commencement of commissioning.

Castleford STW: The civil works are progressing in line with the programme and this includes the demolition of the roadway prior to piling and kiosk base construction, as well as the integration of the drainage and commencement of roadway reinstatement to form the chemical delivery bunded area.

The primary Common Data Environment (CDE) and information delivery platform used programme is Autodesk’s BIM360 software. Utilising this, Glanua Group has been able to control the flow and dispersal of information throughout the project and delivery teams, enabling the information management workflow process and review to align with the ISO 9001 Quality Management Process.

The information management platform allows us to control how and when the various projects teams see and receive information ensuring the right information is delivered in the most efficient and effective way. This collaborative approach has ensured the right information is received at the right time.

Multiple digital tools were utilised to facilitate the safe design and construction process, this includes the Autodesk Revit suite for the civil structures and all mechanical and electrical equipment which was all modelled in 3D with subsequent sheets produced to facilitate a review and approval process as well as provide construction coordination, assessment, and as-built markups where required. Glanua Group utilised reality capture technology to establish baseline data and monitor progress against this.

Through the asset function of BIM360 Glanua Group has been able to replicate the client’s asset data requirements to collate data prior to submission on to their asset management database.

Within this function the procurement and construction/installation status could be tracked whilst assigning supplier and design information in preparation for the O&M and H&S file information.

Whilst significant progress has been made of all four projects, there is a number of key elements still need completing, a lot of work has been undertaken to help meet the project’s completion dates including completion of civil works, mechanical and electrical installation and wet and dry commissioning.