Supply Chain - Water Pumping Stations - Technical Documentation

Witches Oak Water is a series of gravel pit lakes south-east of Derby, on the River Trent. The 80 ha site, part of a larger sand and gravel quarry, was acquired by Severn Trent more than 20 years ago to store water as part of a drought resilience project. Severn Trent constructed an intake, pumping station and pipeline to the nearby Church Wilne WTW. Water quality was poor and required more treatment to meet drinking water standards than was originally anticipated, so abstraction ceased and the site mothballed until a solution could be found. Severn Trent is now bringing Witches Oak Water back into operation by recommissioning the existing infrastructure and increasing raw water supplies to a maximum of 93 MLD. The additional water will improve Severn Trent’s resilience to hot and dry summers and secure water resources for future generations.

Solution

Severn Trent is keen to explore the potential of low-carbon, natural, biological water treatment processes in conjunction with conventional, chemical treatment to remove pollutants from the water abstracted from the River Trent. Historic data revealed that nitrate levels in the River Trent have occasionally exceeded the 50 Mg/l concentration value prescribed by the DWI, and regularly breached Seven Trent’s own, more stringent standard.

As a result, a natural, biological solution in the form of floating wetlands to provide preliminary water treatment is being combined with refurbishing the existing abstraction infrastructure at the lakes (called the Raw Project) to supply water to the new water treatment works being constructed in Church Wilne.

[caption id="attachment_14685" align="alignnone" width="1200"] Installing the floating wetlands - Courtesy of Matthew Nichol Photography[/caption]

Floating wetlands

This is the first time in the UK that wetlands have been used for operational water pre-treatment on this scale and in the ‘real world’, but theoretical studies show that, on average, these floating wetlands could remove in the region of 40-60% of both total nitrogen (ammonia, organic and oxidised nitrogen) and total suspended solids (particles >2 microns), helping to considerably reduce the amount of energy and chemicals used in the traditional water treatment process.

Floating wetlands were selected over conventional or static wetlands because Witches Oak floods regularly during the winter.

The pontoons can rise and fall with the water level, so are resilient to changes in load and seasonal fluctuations, whereas a static wetland would be submerged during a flood event, diminishing process benefits provided by the vegetation. This has been thoroughly tested in winter 2023/24 when the site experienced extensive 1 in 100-year flood events. The floating solution also typically requires less maintenance, including no watering or fertilisation.

The Biomatrix floating ecosystems selected for Witches Oak mimic elements of self-sustaining, naturally occurring riparian wetlands. Water quality is improved by the root mass, which provides a large surface area for the microbial communities needed to remove pollutants. Planted with several types of sedge, hard rush and flowering species, including purple loosestrife and meadow sweet, these islands provide biological treatment to reduce the turbidity and nitrates in the raw water.

[caption id="attachment_14682" align="alignnone" width="1200"] Floating wetlands (2023) - Courtesy of Matthew Nichol Photography[/caption]

In December 2022, Mott MacDonald Bentley initially focused on the construction and launch of three trial wetlands in Lake 2, as well as the removal of a redundant man-made wetland from the lake. Since then, a further 28 floating wetlands have been installed on the three northern most lakes during summer 2023.

The 31 floating treatment wetlands were positioned in the natural water flow path in Lakes 1, 2 and 3.

Work is also being undertaken to upgrade of the existing pumping station and river intake, along with the installation of a new fish recovery system and three new transfer pumps.

Undertakings

This is a true ‘One Mott MacDonald’ project with members of the consultancy teams having worked on the feasibility of the wetlands’ abilities to pre-treat water and then their outline design, before handing over to colleagues at Mott MacDonald Bentley through early contractor involvement and then design and build delivering the detailed design, pre-construction and construction activities.

Witches Oak RWPS: Supply chain - key participants

• Client: Severn Trent
• Principal designer & contractor: Mott MacDonald Bentley
• Outline design & specialist input: Mott MacDonald
• Floating wetlands: Biomatrix Water
• Civils installation: Aquatic Engineering Ltd
• Fish recovery: MEM Fisheries Consultants & Services Ltd
• Cofferdam: MGF Ltd
• Piling: Elite Sheet Piling Ltd
• Formwork: Doka UK Formwork Technologies Ltd
• Steelfixers: MTN Structures Ltd
• Electrical: Main Electrical Ltd
• Electrical: BGEN Ltd
• Dewatering: Selwood
• Dewatering: Alba Dewatering Services Ltd
• Pumps: Xylem Water Solutions
• Fish & eel screens: Intralox LLC
• Pipework supply: Freeflow Pipesystems
• Pipework Installation: Utiliqo Ltd
• Valves: AVK UK Ltd
• Penstocks: Waterfront Fluid Controls
• Kiosk: Morgan Marine Ltd

[caption id="attachment_14687" align="alignnone" width="1200"] Pumping station refurbishment - Courtesy of Sky Revolution[/caption]

Environmental measures

To minimise the environmental impact, temporary track mats were used for the base of the works’ compound and launch area at Lake 2, allowing the site to return to managed grassland when the mats were lifted.

A silt curtain was erected in the lake to prevent debris from the old wetland polluting the water. This was important because the wetland was colonised by invasive species, mostly Himalayan balsam on land and zebra mussels below water. The curtain also ensured that sediment disturbed by the removal work did not spread.

The design has also had to accommodate regular site flooding; in particular for the temporary works around the river intake where, as an example, the cofferdam was designed specifically to account for controlled and safe flooding of the excavation to manage the high river levels experienced on-site.

Programme

Launching and anchoring the 31 floating wetlands was the first phase of the Raw Project. Phase two is refurbishing the abstraction pumping station built in the 1990s to enable raw water to be supplied to Witches Oak WTW.

Located on the western shore of Lake 3, the pumping station is undergoing a complete refurbishment, including the installation of three new transfer pumps to deliver up to 96 Ml/d of pre-treated water; enough for a city the size of Derby.

[caption id="attachment_14690" align="alignnone" width="1200"] River intake - Courtesy of Sky Revolution[/caption]

The design layout for the station also includes a new water quality kiosk and a wash-water booster set to clean the fish screens.

The river intake in the north-east corner of Lake 1 is also more than 25 years old and is being modified. The design will help to protect both fish and the gravel lakes. Two new 2.5m x 4m concrete channels will be constructed to create a flow low enough to allow fish and eels to swim back to the river, while two large, actuated intake penstocks will be installed to protect the lakes if there is a river pollution incident.

The introduction of new recirculation pipework will enable water to be pumped back to the river from the pumping station when necessary. Under the proposals, river water quality will in future be monitored upstream of the intake as well as at the intake itself.

Barbel, bream, chub and roach are common fish species found in the River Trent and two new screens will be fitted to filter fish and debris out of the water drawn in by the pumps at Witches Oak Water. The fish recovery system will consist of an above-ground pipe connecting the pumping station intake culverts to Aston Brook, which runs alongside the river, and from where fish can eventually return to the Trent.

Summary

Witches Oak is one of seven projects that form Severn Trent’s Green Recovery Programme, worth more than £700m, which aims to develop low-carbon water resources, improve river water quality, replace redundant lead pipes, install smart metering and make urban areas more resilient.

The additional water supply from Witches Oak will help meet demand for water from a growing population and improve the resilience of supplies during hotter, drier summers.

[caption id="attachment_14683" align="alignnone" width="1200"] Installed wetlands - Courtesy of Sky Revolution[/caption] The 31 constructed wetlands use naturally occurring biological processes to contain and treat ammonia, suspended solids and trace metals. Coupled with installing ceramic membranes at Witches Oak WTW (to provide a filtration barrier, reduce turbidity and remove pathogens such as cryptosporidium), the project is a more carbon-friendly treatment solution.

By restoring natural functions to these gravel lake ecosystems, the project is promoting biodiversity recovery and contributing to enhanced ecosystem services. The wetlands provide amazing biodiversity benefits including:

1. Above the water, the planted vegetation is a haven for wildlife, including nesting birds.
2. Below the surface, the floating beds provide habitat for fish, eels and other aquatic species.
3. On the fringes of the lake, retained coppiced woodland from the construction activities has been used to create further wildlife habitat.

In addition, positive social outcomes and community engagement are key elements of Severn Trent Water’s 25-year water resources management plan. The delivery team presented to the local girl guide group to tell them about the work we’re doing, and a visitor engagement centre has been installed to showcase this exciting project to local school and community groups.

Northbridge is a key drinking water supply location with a large amount of upstream habitat available for eels. The intake is located 11km from the tidal limit on the right-hand bankside of the River Exe, Devon and is the intake for Pynes WTW. Abstraction occurs all year round, with typical abstraction rate between 30,000-40,000m³ per day with a maximum licenced flow is 66,450m³/day. Water is abstracted via two inlet lanes each consisting of a course and fine screen which feed a total of four pumps with the two lanes being able to be operated independently. All four pumps can be operated whilst one lane being closed if flow must be diverted around the closed lane using the actuated penstocks.

Background

The existing screening has coarse (9mm aperture) and fine (5mm aperture) screens within the pump house, which discharge debris and eels back to the river via a chute through the side wall.

The current screening will not meet 2025 statutory requirements and South West Water are addressing the issue now to ensure future compliance.

This project will deliver improved screening at the Pynes WTW intake with Eel Regulations compliance, which is required by the end of AMP7, ensuring continued operational abstraction at the site. There is a need to improve the exclusion of the freshwater stages of the critically endangered European eel from river intakes and abstractions allowing lifecycle completion at sea. Additionally, there is need for protection of downstream migrating salmonids. This includes both Atlantic salmon and brown (sea) trout.

[caption id="attachment_12976" align="alignnone" width="1200"] Existing intake structure (external screens at and below river level behind the debris boom with the access platform above) - Courtesy of South West Water & Fishtek ltd[/caption]

Northbridge design considerations

The proposal was to install two 2.352m wide Hydrolox S1800 rotating band screens within the existing bankside infrastructure to replace the existing screening. This will reduce fish and eel entrapment at the intake and ensure compliance for continued operational transfer to Pynes Water Treatment Works. These screens also offer health and safety benefits, as well as OPEX and TOTEX cost benefits.

To allow the planned work to be undertaken, the inlet lanes had to be closed one at a time for the new screens to be installed and the old screens removed whilst still allowing for the 46,000m³/day abstraction. High water demands during the summer months had to be considered along with other consents and approval conditions, so the earliest date restrictions could be imposed was early September 2023. The work was therefore initially planned for a 4-month duration between September 2023 and January 2024.

During the installation period, South West Water had to allow for ‘recharge periods’ where both lanes could be open to allow for the 60,000m³/day abstraction. This would be over a weekend (Friday-Monday), and this allowed for a total of 50% of the installation period where recharge could be undertaken.

To be able to produce a feasible design, various surveys and reports had to be undertaken. These included dive surveys, ecological surveys, protected species surveys, GPR surveys, existing infrastructure surveys, 3D scans of the pump house building and underwater intake bays, and crane lift surveys.

The results of the surveys found the existing intake structure was structurally sound to be re-used for the new Hydrolox screens, which removed the need for using ‘wet’ concrete to construct the work, which would of entailed using a cofferdam. This removed a hazard from the new work within the design stage, benefitting both programme and cost savings.

[caption id="attachment_12977" align="alignnone" width="1200"] New debris return launder chute - Courtesy of South West Water & Fishtek Ltd[/caption]

Hydrolox screen selection

Hydrolox S1800 rotating band screens were chosen for this scheme as they are considered an industry best practice solution by the Environment Agency. Benefits included:

• Through management and coordination between South West Water Operations and the contractor Fishtek ltd, this option carried less programme risks than alternatives because the ability to abstract river water during construction was retained.
• The solution was considered to be ‘riverside’ and therefore applicable for reduced screen sizes compared to the options available if they were to be set back from the riverbank.
• Being installed above-ground, inspection and maintenance of the screens removed the hazard of requiring confined space access.
• Being an accepted best practice solution, notably less consultation would be required with the National Eel Service Helpdesk, so this solution carried significantly less risk towards compliance.

Restricted site

The work site was approximately 330m from an unclassified single vehicle access road, and having to navigate down this road and track with oversize vehicles, along with having to contend with a section of Japanese knotweed was an early challenge. The rutted access track had to be regraded to accommodate the large vehicles and crane attendances along with protection of the knotweed to prevent cross contamination of the area across the area.

The site was extremely restricted and a 90t crane was required and had to be set up in a small area constrained by the existing building, the Network Rail mainline, 11Kva overhead power cables, outbuildings and mature trees.

Because the location was restricted and unsuitable for larger vehicles, the contractor had to change their methodology and bring the new structural elements in as individual components. These components were transferred onto smaller flatbed vehicles away from the site and reassembled in the small working area.

[caption id="attachment_12988" align="alignnone" width="1200"] (top left) Crane setup within restricted location & approach track, (top right) structural steelwork components being fixed ready for lifting and installation, (bottom left) silt removal prior to installation of steelwork, and (bottom right) accommodation work installing new concrete apron at landowners access gate to provide turning for reversing delivery vehicles - Courtesy of South West Water & Fishtek Ltd[/caption]

Construction phase

One of the first tasks was to remove the existing course trash screens and decking area over the River Exe intake in a safe and controlled manner, utilising a dive team to prop open the existing penstocks which remained in place until the scheme was complete and the equipment removed.

Upon successful removal of the existing equipment, the galvanised steel platforms (as required under DWI Regulation 31) were assembled on site and lowered into position within the existing reinforced concrete inlet structures and fixed with galvanised mechanical fixings. The steel platforms would house the two Hydrolox screens.

Other work streams involved mechanical and electrical interfaces, where decommissioning and removal of existing redundant equipment including the two sets of fine and coarse screens, wash water booster set, pipework and obsolete electrical equipment and cabling, all of which had to be phased in agreement with the Operations team.

Electrical scope included the installation of the instrumentation required to control the new screens and four ultrasonics, including a temperature sensor, and temporary isolation and installation of actuators for the external penstocks so that the new steel decking could be installed. This required good communication and agreement with the South West Water Operations team and the control centre.

[caption id="attachment_12980" align="alignnone" width="1200"] (left to right) Hydrolox screen installation, (i) steel support frame, (ii & iii) screen being lowered into position (note proximity to the building), and (iv) final positioning of the Hydrolox screen - Courtesy of South West Water & Fishtek ltd[/caption]

Northbridge Eel Regulations Compliance Project: Supply chain - key participants

• Client: South West Water
• Principal designer & contractor: Fishtek Ltd
• Diving & civils contractor: Teignmouth Marine Services
• Ecological supervision: Colmer Ecology
• Supplier of eel screens: Intralox Ltd
• Instrumentation & controls contractor: SWW O&T Dept
• M&E contractor: A&T Electrical
• Structural steel supplier: Milestone Communications Ltd
• Wash water booster pumps: Xylem Water Solutions
• Trash screens, launder chute & deflector boom: TWS Ltd
• Lifting contractor: Spence Crane Hire Ltd
• Transportation contractor: ACE Crane & Transport Ltd

Value engineering

The contractor, Fishtek Ltd, worked efficiently, continually keeping the project team informed with progress and any issues that arose to agree a solution to keep the project momentum. During the time that the contractor was on site, value engineering principals were applied. Examples of this include the reuse of existing equipment such as the launder chute where a partial section was manufactured and installed which reduced the material usage by some 80%.

Another example of the value engineering approach was to take most of the removed equipment to Pynes WTW, which would be available to be re-used for spares and parts replacement.

This benefitted South West Water from disposal costs and the costs of new parts.

Another positive outcome of the project was that Fishtek Ltd, engaged South West Water’s O&T team to undertake the instrumentation and controls scope. This worked extremely well to the benefit of all parties, setting a precedent for future collaborative working.

Third party relationships

Good engagement with all stakeholders (EA, Network Rail, National Grid, landowners and South West Water’s Asset & Operational team) was maintained throughout the programme and there were zero complaints.

To get equipment and cranes onto site, the team required access via a landowner’s property so good relationship was developed and maintained throughout the project. By way of thanks, a new reinforced concrete slab was constructed at the field entrance as a good gesture for the landowner’s cooperation. Upon project completion, a final re-grading of the 330m track was undertaken, and the Japanese knotweed protection was kept in place.

[caption id="attachment_12979" align="alignnone" width="1200"] (left) Complete Installation of the S1800 Hydrolox screens and decking system, and (right) new wash water booster set which provides high pressure cleaning of the screens removing debris - Courtesy of South West Water & Fishtek Ltd[/caption]

Conclusion & successes

Though the project was completed in an agreed revised programme due to several issues outside of the contractor’s control, the scheme was still completed almost one year ahead of the regulatory compliance date (March 2025).

The contractor demobilised from site in April 2024, with all that remains to be undertaken being the removal of one fine screen which was left in place at the request of the South West Water Operations team until the new screens had sufficient bedding in time, and after five river spate conditions of the River Exe had been experienced.

While on site, the contractor adopted a ‘see it, sort it’ ethos and several site operational safety improvements were identified and acted upon. Despite this additional work, the project scheme still came in 9% under budget.

Good health and safety was managed throughout the programme and the project was delivered with zero incidents or accidents.

The overall objective of the project was achieved and exceeded, gaining valuable lessons learnt for all involved so future schemes can be optimised throughout the project life cycle from conception through to construction and handover. This will allow for improved programme durations and activities, increased risk identification, improved tender scope and work information, as well as logistical restrictions and operational interface requirements.

Northumbrian Water’s Ovingham Raw Water Pumping Station (RWPS) is an abstraction station located on the north bank of the River Tyne in South Northumberland between the towns of Wylam and Ovingham. The station provides raw water from the River Tyne to Horsley Water Treatment Works (WTW) and the Great Southern Reservoir at Whittle Dene WTW. Treated water is then pumped to Birney Hill Reservoir and supplies the City of Newcastle upon Tyne and Tyneside with a population in excess of 800,000.

Background

There are two delivery mains to Horsley WTW (eastern and western mains), and the pumping station currently contains six pumps (four fixed speed Pleuger pumps and two pumps on variable speed drives). In the recent years these pumps have suffered multiple failures which puts at risk the supply of raw water to the WTW. A feasibility report completed in March 2016 stated that the root cause of historical mechanical failures of the existing pumps is a large volume of silt being carried over into the pump bays when the river is in flood. There are also operational and maintenance issues around the current high voltage inverters and drives. Northumbrian Water Group (NWG) appointed Mott MacDonald Bentley (MMB) to investigate viable options for pump replacement in 2018 and the pump options returned by suppliers were for submersible pumps, submersible borehole pumps, axially split casing pumps, and vertical turbine pumps. MMB and NWG agreed that vertical turbine pumps (VTPs) were the most appropriate pump option for the site and the pumping station was designed to the following duty requirements:

• Deliver 110.7 MLD (1280 l/s) with a standby pump available.
• Deliver 154.7 MLD (1791 l/s) with all pumps running, including the standby pumps.
• Be capable of a minimum station flow of 40 MLD (462 l/s).
• Be capable of feeding Horsley and Whittle Dene simultaneously.
• Provide the full range of flows between these figures, whether the river is at LWL, HWL, or anywhere in between, and irrespective of whether delivering up the east main, the west main or both.
• Be most efficient at 106 MLD (1226 l/s).

Following a tender process Bedford Pumps Ltd were chosen to supply the new VTPs. [caption id="" align="alignnone" width="1200"] Ovingham RWPS - Courtesy of MMB[/caption]

Scope of the works

1. The replacement of two existing variable speed pumps with a duty of 384 l/s with two Bedford Pumps VTPs c/w 680kW IP 68 motors capable of pumping 452 l/s and minimum solids handling capacity of 25mm to improve the pumping and solids handling capability of the station.
2. The installation of two floor-mounted high efficiency 3.3kV 680kW drives air cooled variable speed drives and a new PLC control system.
3. Associated heating, ventilation and air conditioning (HVAC), steel support beams, platforms and electrical/instrumentation works.

Ovingham RWPS: Supply chain - key participants

• Client: Northumbrian Water
• Construction delivery partners: MMB
• Hydraulic modelling: Mott MacDonald
• Topographic surveys: Atlantic Geomatics
• Geotechnical & environment Investigation: Dunelm Geotechnical & Environmental Ltd
• Vertical turbine pumps: Bedford Pumps Ltd
• Electrical installation: Intelect Ltd
• Local control panels: Blackburn Starling Ltd
• Systems integration: IDEC Technical Services
• VSD design & installation: Quantum Controls
• VSD construction: Schneider Electric
• Metalwork: JHT Fabrications
• Kiosks: Morgan Marine
• Surge system integration: Quantum Engineering Developments Ltd
• HV Cabling: Integrated Utility Services
• Pump refurbishment: Fluid Sealing & Engineering Ltd

[caption id="" align="alignnone" width="1200"] Hydraulic model schematic extract from Ovingham RWPS Refurbishment Technical Note - Courtesy of MMB[/caption]

Detailed design and engineering challenges

Hydraulic analysis: A hydraulic model of the delivery mains (eastern and western mains) was built in Deltares WANDA v4.5 to calculate the steady state and transient pressures for a number of different operating scenarios. The maximum operation flows are 165 MLD (eastern main) and 180 MLD (western main). The subsequent technical note recommended the following:

• Ten existing air valves should be refurbished and four new air valves should be installed to the eastern and western main (completed).
• The 35.98m³ surge vessel on the eastern main should be replaced (future works).
• A surge vessel should be installed on the western main (completed).
• Fast acting double plate non-return valves should be installed on the pump outlet pipes (future works).

CFD modelling: Computational fluid dynamics (CFD) was carried out to assess the most suitable wet well location to install the VTPs to minimise potential adverse hydraulic effects that could be induced by the joint operation of the VTP and Pleuger pumps. The modelling report recommended that the VTPs should be installed in wet wells No. 3 and 4. [caption id="" align="alignnone" width="1200"] Extract from Ovingham RWPS CFD modelling report - Courtesy of MMB[/caption] Cooling water: The motors installed on the new pumps needed to be IP68 due to the high likelihood that the RWPS would flood up to roof level, therefore fan-cooled motors were not suitable. The motors were supplied with a helical design cooling water jacket which was extensively tested in the motor supplier’s works. A number of options were considered to provide cooling water to the VTPs:

• Automatic changeover duplex strainers using rising main pressure.
• Potable water closed loop or ‘once through’ systems.
• Duty/standby automatic flushing filters.
• Duty automatic flushing filter with static filter standby.

Due to the lack of spare low voltage capacity within the station and the lack of a nearby potable water supply Option 2 was ruled out. Option 3 was discounted due to lack of space but will probably be installed in the future when MMB complete the design of new eel screens at the site. Option 4 was discounted due to the amount of maintenance intervention. Option 1 was therefore designed and installed with automatic switch over between baskets on high pressure drop to enable a basket to be cleaned while the pump is in service. A pressure reducing valve was required to reduce the pressure from 10 bar down to 5 bar and this fitting has experienced pressure drops due to leaf debris passing through the inlet screens and so the layout will be modified. Electrical and instrumentation works: This element of the works included:

• Design, supply and installation of two off high efficiency, air cooled 3.3kV 680kW variable speed drives. This involved the de-commissioning and removal of the existing drives.
• Design and implementation of modifications to the existing 3.3kV Switchboard to allow the new VSDs to interface with the control circuit within the switchboard.
• Upgraded ventilation to the MV switch room to ensure the new VSDs operate at a suitable temperature.
• Bespoke local instrumentation/monitoring panels for the new pumps. Rather than adopt the standard panel offered by Bedford Pumps, bespoke panels were designed to integrate both the pump instrumentation and external instrumentation.
• A new PLC and remote I/O panel were installed to accommodate all of the new I/O associated with the systems being installed. Fibre optic cabling was employed to reduce long lengths of traditional cabling being installed.
• Systems Integration at site level and full SCADA integration at Horsley to provide the client with local and remote operation.

[caption id="" align="alignnone" width="1200"] Vertical turbine pumps from Bedford Pumps - Courtesy of MMB[/caption] Heating ventilation air conditioning (HVAC): Heat gain within the building due to pumps, MCCs, screen motors etc. was modelled to ensure that during the summer the temperature within the building did not exceed 40° C when the external temperature was 30°C and during the winter the temperature within the building exceeded 5°C when the external air temperature was -5°C. Side wall mounted LPCB SR4 security rated aluminium louvres with a 30% free area were specified to the east and west of the building along with a 370W fan to extract warm air. Noise assessment: A pre-works noise survey was carried out to give a base line. The subsequent report found that plant noise breaking out of the station was low and so recommended that the design target noise levels for the replacement plant should be to achieve the same output noise level. Achieving these noise levels would ensure the adjacent properties would not be detrimentally affected.

Construction

Site works commenced March 2021 and ran through until October 2022. The client insisted that as the pumping station was a key operational asset it must stay operational throughout the works and so a big challenge was to complete the works whilst providing critical raw water supplies up to Horsley WTW. The pumping station which is situated in a rural location in Northumberland brought its own logistical challenges. Site staff had to consider that any plant used for lifting operations could be demobilized and moved from site prior to a flood event at short notice. Access to the pumps was via six large openings in the roof and covered by heavy concrete slabs. All lifts were done ‘blind’ and planned to precision to ensure everything ran smoothly with some complex lifts carried out. An adjacent HV building supplied power to the pumping station and required the installation of new VSDs. An environmental survey confirmed the presence of bats and so site staff ensured a qualified ecologist was on hand to make sure the bats and their roosting spots were not disturbed. The works were monitored and carried out during selective working hours. Following the successful completion of the works the ecologist confirmed the bats had not been affected. [caption id="" align="alignnone" width="1200"] Ovingham RWPS east elevation - Courtesy of MMB[/caption]

Customer

NWG are very keen on community projects and ‘leaving a legacy’. MMB carried out works to refurbish park benches at Wylam Village and to refurbish the sports pavilion at Ovingham as a thank you to the local community for any disruption during the works.

Looking ahead

MMB were asked to design and construct a new surge vessel for the western main. This work was completed in September 2022 alongside the VTP works. New travelling band screens compliant with The Eels (England and Wales) Regulations 2009 are also required and MMB are currently at the design stage with a view to starting on site May 2023. New non return valves (NRVs) and replacement of the eastern main surge vessel is also expected to start in 2023.

Located in the heart of the picturesque Scottish Borders, the towns of Galashiels and Selkirk are central to a significant upgrade of the region’s water infrastructure. Galashiels, situated approximately 38 miles south-east of Edinburgh, serves as a vital hub for the surrounding rural communities. In line with Scottish Water’s vision, the £30m Borders Central Strategy focuses on improving water quality and reliability in these communities by transforming Galashiels’ Manse Street Water Treatment Works into a Distribution Service Reservoir site only and enhancing Selkirk’s Howden WTW’s borehole supply and treatment output to serve over 20,000 houses and business premises. The construction includes a new 12 ML clear water tank, 7 miles of 400 mm HPPE main, and significant upgrades to Howden WTW; promising to support the region’s growth and resilience for years to come.

The need for improvement

Manse Street WTW was built in 1964 and has a capacity of 5 ML/D; equivalent to two Olympic sized swimming pools. The process consisted of an inlet clarifier, four RGFs and associated backwash equipment (backwash pumps, blowers and dirty wash water system), and poly, caustic and sodium hypochlorite dosing. Since the 1960s there has been no significant capital maintenance and plant operation is reliant upon significant manual and knowledgeable operator input. Manse Street WTW has eight outputs with risk concerns of contaminant breakthrough due to process issues with the filter backwashing, flocculation formation, and clarification.

[caption id="attachment_14780" align="alignnone" width="1200"] Completed access road to new CWT - Courtesy of ESD[/caption]

Howden WTW was built in 2000 and in 2009 a membrane stage was added. The setup is comprised of four abstraction boreholes (duty/assist/assist/standby), a membrane package plant including six membranes, CIP cleaning plant and equipment, sodium hypochlorite and orthosphoric acid dosing, contact tank and four high lift pumps. Howden’s design capacity was 16 ML/D although it only ever managed a peak flow of 12.5 ML/D due to issues with raw water quality and limitations of membranes performance.

The average demand is 8-9 ML/D and the clear water tank (CWT) was undersized at only 5 ML and required significant repairs.

The Central Borders Strategy Project aims to address these issues by upgrading Howden WTW to meet a demand of 16.2 ML/D that will enable a main out of Manse Street WTW in addition to providing additional capacity in the Central Borders Supply Network for the 25-year growth design horizon that is anticipated.

Scottish Water’s Non-Infrastructure Alliance Partner, ESD (a joint venture between MWH Treatment, Binnies, and Galliford Try), started the design of the £30m project started in June 2018 and work commenced on site in February 2020.

Process selection

Studies to assess and identify potential solutions to tackle the issues and optimise delivery demand were undertaken, with each scenario also considering the optimum solution for neighbouring areas. The following were considered for Howden and Manse Street:

1. Maintain and enhance Manse Street and Howden.
2. Main out Manse Street from upgraded Howden.
3. Main out of all WTWs from new Peebles works.
4. St Mary’s Loch.
5. Main out Howden from new enhanced Manse Street.

Options 1 and 5 were deemed too costly and had significantly more risks for a successful outcome, while Option 3 was discounted due to negative impact on Edinburgh and Lothian yield. Option 4 had a lower yield of only 13 ML/d versus demand of 16 ML/d for Howden and Manse Street.

Option 2 was selected as it best fit the demands of Scottish Water’s SR15 framework drivers, being able to deliver the capacity needed with a lower anticipated cost.

[caption id="attachment_14779" align="alignnone" width="1200"] (left) Geographic extent overview and (right) Option 2: the chosen solution - Courtesy of Scottish Water[/caption]

Central Borders Strategy: Supply chain - key participants

• Client: Scottish Water
• Principal designer & contractor: ESD
  • Binnies
  • Galliford Try
  • MWH Treatment
• Pipeline & tunnel design: Caledonia Water Alliance
  • MGroup
  • AECOM
• Excavation works: RJT Excavations
• Construction: Careys
• Pipe construction: AG Wilson
• Borehole pump changeover & pipework: Dustacco Engineering Ltd
• Pipework: Alpha Plus Ltd
• Borehole pumps: Wilo
• Actuators: Rotork Controls
• Air compressors: Kerr Compressors
• Membranes: DuPont
• Membrane feed pumps: Grundfos
• Systems integrator: IDS
• Systems integrator: Lintott Control Systems
• Systems integrator: Saftronics
• Electrical: ICL
• Electrical: Main Electrical Ltd
• Pipework & metalwork (Howden CWT): AJ Engineering & Construction Services Ltd
• Cryptosporidium unit: Watercare Systems Ltd
• GRP kiosks: Kingsley Plastics
• MCC: Lintott Control Systems Ltd
• PE pipes: FPP Ltd
• Gate valves & pipe fittings: AVK UK Ltd
• Metalwork (Howden WTW): Archibald McAulay & Son Ltd
• Metalwork (Manse Street): GT Fabrications
• Metalwork (Manse Street): Homer Burgess Ltd
• Security & fire systems: Pointer Ltd

Overview of process and scope

The existing treatment works at Manse Street, Galashiels is to be closed and decommissioned to create a Distribution Service Reservoir (DSR) site only. Meanwhile an increased borehole and treatment output being installed at Howden WTW, means larger sections of the customer network will be fed from the Howden WTW into a new clear water tank to replace the 5 ML Thornbush Quarry tank. This project will be supported by upgraded infrastructure, including new main laying from Howden-to-Howden new tank to Manse Street.

[caption id="attachment_14778" align="alignnone" width="1200"] New water tank at Howden WTW - Courtesy of ESD[/caption]

The Borders strategy was split into 4 key projects outlined below:

Galashiels WTW

At Galashiels, the existing works, including the raw water source, will be decommissioned and abandoned along with the nearby Thornbush CWT once the new upgrades at Howden and Manse Street are operational and fully integrated. The following tasks to accomplish this at Galashiels, undertaken by ESD, are outlined below:

• New MCC and standby power generator to replace ageing asset.
• Construction of a new twin compartment 12 ML CWT nearby Galashiels and Howden replacing Thornbush CWT, known as the new Howden CWT. With the CWT compliant with all security requirements.
• Installation of associated valves and overflows, scour pipework, flow meters, and connections into three transfer/distribution mains.
• Installation of a new kiosk housing quality instruments, level instruments, flowmeter display, telemetry
• Install a new power supply to the instrument/telemetry kiosk.
• Decommission the existing Thornbush Quarry CWT, TWS power, instrumentation and existing security
• Conversion of Manse Street WTW to a DSR within the existing treatment site a new standby, decommissioning of the supply transformer, generator and telemetry.

Improving resilience of supplies

The pipework installation to tie all the works together and deliver the Central Borders Strategy was led by Caledonia Water Alliance; Scottish Water Alliance’s Partner. The works included:

• Pipelaying 11.55km of 400mm HPPE main from Howden to Manse Street Clear Water Tank/Distribution Service Reservoir.
• Upsize 400m of the Central Borders Trunk Main from upstream of Melrose DSR to 350mm HPPE.
• Lay new gravity fed 400mm HPPE main to cater for a 5.56 ML/D (3.24 M/LD from current Manse Street site plus an additional 2.12 ML/D for the re-zoned).
• Abandon the existing 300mm supply pipe from Manse Street.

[caption id="attachment_14783" align="alignnone" width="1200"] (left) Borehole set up and (right) CWT valve chamber - Courtesy of ESD[/caption]

Howden WTW upgrades

At Howden WTW, the following improvements to upgrade the existing WTW capacity from 12.5 ML to 16.2 ML were undertaken by ESD:

• Replacing a pump in Borehole No. 2 with a 10 ML/D pump.
• Replacement of the existing scour and supply valves on each borehole wellhead and the installation of electronic actuators to enable automated scouring of the boreholes.
• Construction of new brick built walk-in enclosures over each wellhead to replace the existing chambers.
• Installation of a 300m³ raw water tank to buffer flows from the borehole pumps to the membrane plant. The borehole pumps are to operate on level control.
• Installation of three membrane feed pumps in a duty/assist/standby arrangement to feed the membrane plant from the raw water tank.
• Construction of a new membrane treatment building to house additional membrane units.
• Installation of three additional membrane units (3 x 48 (No.) L20N modules) to increase the current number of units to nine.
• Alterations to the membrane plants ancillary components to include increasing the capacity of the air system by installing an additional compressor, installing sodium hydroxide and sodium bisulphate for chemical neutralisation removal of the existing GAC neutralisation system, and increasing the heating capacity of the existing CIP tank.
• Installation of flow meters, relocation of the site boundary security fencing, alterations to power and control cabling PLC and SCADA modifications.

[caption id="attachment_14781" align="alignnone" width="1200"] (left) Membrane feed pumps and (right) expansion to membrane plant - Courtesy of ESD[/caption]

Howden WTW chloramination

Another project to ensure quality at Howden WTW was installation of an ammonia sulphate dosing skid. This system will be housed in a walk-in kiosk. The chemical will be dosed downstream of the chlorine contact tank (CCT) and upstream of the high lift pumps. The overall components of the chloramination dosing plant include:

• Storage tanks.
• Dosing pump skid.
• Fill point.
• Carrier water header tank.
• Carrier water pumps.
• Motor control center (MCC).
• Dual-contained dosing lines (duty/standby).
• Dosing static mixer.
• Sampling equipment.
• Chemical spill tank.
• Associated pipework and instrumentation.

Project challenges

Howden’s construction phase began just before the onset of the COVID-19 pandemic, which brought unprecedented challenges.

With the implementation of social distancing measures, lockdowns, and restrictions on workforce movement, the project faced significant delays and disruptions. The team had to quickly adapt to new health and safety protocols to ensure the safety of all workers, which included staggered shifts, remote coordination, and strict sanitation practices.

Implementing the SCADA system posed substantial difficulties as the existing chip needed to be replaced due to incompatibility issues with the new installations due to age. Ensuring seamless communication between various components and achieving real-time data acquisition was challenging. The technical intricacies and need for precise calibration and testing led to additional time and resource investments. Following this, there was a 12-month delay for the Siemens’ chip needed for the new system, due to the Ukraine-Russia war. This delay significantly impacted the project’s timeline, necessitating adjustments in the scheduling and prioritisation of other project activities.

[caption id="attachment_14782" align="alignnone" width="1200"] New South Common CWT and valve chamber - Courtesy of ESD[/caption]

Successes

• The new clear water tank stores water and monitors the quality before it goes into the supply. It also provides additional resilience to the network by providing additional storage to supply the area.
• The Howden Membrane upgrades increased membrane plant surface area allowing for increased treatment and production capacity from 12 ML/D to 16 ML/D.
• Leveraging off-site construction, when possible, allowed for precise, high-quality prefabrication of components in a controlled environment. This minimised on-site disruptions, reduced construction time and enhanced safety. Prefabricated elements were seamlessly integrated into the site, improving efficiency and sustainability by lowering emissions and waste.
• Weekly coordination meetings between Scottish Water (the client), ESD (for Galashiels and Howden WTWs), Caledonian Water Alliance (for infrastructure and pipe implementation) and other stakeholders were instrumental in ensuring the project’s smooth progression. These meetings facilitated effective communication, timely resolution of issues, and alignment of project goals, contributing to the overall success of the water infrastructure upgrade.
• The groundworks at the CWT site demonstrated exemplary resource utilisation. Materials excavated during construction were crushed, regraded into different sizes, and reused effectively. This not only reduced waste but also minimised the environmental impact and lowered material costs.
• At the Galashiels Manse Street site, the installation of a Hush Pod for the generator significantly reduced noise pollution. This implementation was particularly important for maintaining community relations and adhering to noise regulations. The Hush Pod ensured that the generator operated efficiently without disturbing the surrounding residential areas.
• Adherence to Scottish Water’s DOMS and TOMS Protocols, and working closely with Scottish Water’s Public Health Team ensured water quality compliance and avoidance of any issues while interfacing with a live water treatment works (Howden WTW) and distribution network (Howden CWT including inlet and outlet pipework).

[caption id="attachment_14785" align="alignnone" width="1200"] The completed Howden CWT - Courtesy of ESD[/caption]

Status

Howden’s chloramination project began in 2016 and was completed in 2019. The additional enhancements at Howden WTW, which commenced in 2020 alongside the Galashiels project, are both expected to be completed and operational by winter 2024.

The pipeline is currently undergoing the final stages of commissioning with the aim to commence the final flushing and sterilisation in November 2024 to allow the main out of manse street water treatment works.

• Client: Scottish Water
• Project delivery (WTWs, CWTs, pumping stations etc): ESD
• Project delivery (pipelines and tie-ins): Caledonia Water Alliance
• Project cost: £30m
• Design start date: June 2018
• Construction start: February 2020
• Completion: October 2024

Northern Ireland Water’s Cushendall Water Pumping Station (WPS) is housed on the outer perimeter of Dundonnell Water Treatment Works (WTW) situated on the outskirts of Cargan village in the middle of County Antrim. The WPS solely supplies Parkmore Service Reservoir (SR) with potable drinking water, which in turn gravity feeds three other downstream SRs (Knockans, Mullarts and Knockenny), which provide for the surrounding Glen’s of Antrim district. Parkmore SR has a capacity of 1.3 ML suppling a population equivalent of approximately 2000 with an average day demand in peak week (ADPW) of 17.6 l/s.

The existing trunk main

The Cushendall Water Pumping Station to Parkmore Service Reservoir Trunk Main was constructed back in the 1970s using 6” PVC pipeline across bog land on mountainous terrain outside Cargan village. This has posed operational problems over the years when locating and repairing any leakages or bursts. Repair machinery has become stuck and unable to navigate the poor ground conditions raising access issues and Health & Safety concerns for staff and operatives attending repair works. Some bursts in the off-road pipeline have caused expensive tankering operations to keep the ~2000 customers with a reliable supply of potable drinking water to the villages of Cushendall, Cushendun and Glenariff. In addition, the existing Cushendall WPS has been difficult to maintain due to the age of the surge vessel, panels and pumps.

Project scope

NI Water, as part of the IF105 Integrated Partnerships Framework, identified the need to relocate the Cushendall WPS and associated trunk main due to the ongoing operational problems and supply outages. The new scheme included the following scope:

1. A new modular, prefabricated, modular, plug and play water pumping station located in the verge close to a picnic area off the Glenravel Road, approximately 0.5km south of Cargan Village, Co. Antrim.
2. Connection to the existing 18” trunk main in the same picnic area, and approximately 400m of new suction main to deliver water to the new pumping station.
3. Approximately 2km of new 225mm HDPE rising main to deliver water to Parkmore SR installed in the carriageway for improved access.
4. Alternative connections to live tanks at Parkmore SR (non-siphoning), including baffle curtain works and the addition of a 200mm bypass and meter.
5. Civil and MEICA abandonment works of existing Cushendall WPS, and re-tapping the existing chlorine residual pump.

[caption id="" align="alignnone" width="1200"] Dual lay pipework inside steel sleeves - Courtesy of WSP[/caption]

Detailed design and engineering challenges

Following ECI works in October 2021 by the Farrans/Glanua Group Joint Venture under a NEC4 option ‘A’ contract, engineering designs were undertaken comprising of a range of elements including:

• Proposed trunk main route, longitudinal sections, and connection details.
• Scheme plans with details on bridge crossing and new water pumping station location.
• Reinforced concrete slab drainage and ducting detail for modular pumping station.
• Surge analysis report and proposals.
• Hydraulic assessment of the new trunk main with total head loss, average flow, and peak flow information.

From these reports it was concluded that surge could occur when the pump flow increased or decreased to suit changing water demands or uncontrolled sudden pump failure. From this the WPS was designed with a 500-litre bladder type surge vessel in accordance with the selected 38Kw pumps chosen for a 35 l/s and 7 bar charge arrangement. The rising main was designed with six air valves to aid high/low pressure spikes or transients during operation. The hydraulic analysis of the new rising main from the picnic area to Parkmore SR, using the average day demand in peak week (ADPW) of 17.7l/s, calculated a total head loss average flow of 1.10m and peak flow 3.09m for the total 4.2km of the 225mm HPPE pipeline.

Construction

The construction contract was awarded under NEC4 Option ‘C’ Target Cost Contract to Farrans/Glanua Group JV. Construction began in December 2022 and took place over a 14-month period at a total cost of £1.3m. The scheme was situated in an Area of Outstanding Natural beauty, this brought its own unique constraints and limitations. Due to ground conditions, opencut excavations was the method of installing the 2km of 225mm HPPE pipe under a DFI Roads approved lane closure using a rolling traffic light system operated and maintained by traffic management company, McVeigh Contracts Ltd. [caption id="" align="alignnone" width="1200"] (top left) traffic management barriers, (bottom left) notice of works and lane closure for pipeline installation and (right) pipeline track excavation - Courtesy of WSP[/caption]

Bridge crossing

Following trail holes and liaison with DFI Roads at ECI stage, two sections of 180mm HPPE pipework were installed inside 250mm steel sleeves and C30 concrete and steel mats used for protection over the span of the 35m bridge structure. A reduced road cover level of 700mm was agreed and approved with DFI Roads to ensure the structural integrity of the underside of the bridge remained unchanged.

Parkmore Service Reservoir works

In tandem with the construction of the pipeline, a specialised company Waterworx Ltd carried out the alteration works to the live Parkmore SR. Each cell was shut off and drained individually to aid the installation of the inlet pipework and repositioning/installation of the new baffle curtains. All of the SR works were undertaking in close liaison with NI Water Operations who ensured stringent drain down and sampling timelines to ensure continuous water supply the local area. [caption id="" align="alignnone" width="1200"] (left) the existing baffle curtain and (right) new anti-siphon inlet pipework and baffle curtain at Parkmore Service Reservoir - Courtesy of WSP[/caption]

Modular pumping station

The new modular ‘plug and play’ WPS included the following elements:

• Pumping system and associated ancillaries.
• Control panels.
• Telemetry.
• Surge suppression.
• Building services.

The kiosk and skid base of modular pumping station was supplied by Morgan Marine Ltd. The assembly of the mechanical and electrical items were completed at Profitec Solutions’ headquarters in Cookstown. Electrical switchgear was built into the kiosk to facilitate an external portable generator in the event of mains supply failure. Following a factory acceptance test, the modular WPS was delivered to site in November 2022 and craned into position on top of the 450mm reinforced concrete base slab. For the inlet supply to the WPS an under-pressure Tee was installed onto a live existing 450mm cast iron trunk main, this allowed for seamless transfer to the new section of trunk main without any disruption to current trunk main supply in the district.

Parkmore Water Pumping Station & Trunk Main: Supply chain - key participants

• Delivery contractor:  Farrans/Glanua Group JV
• Design/project management: WSP
• Civil Design: Jacobs Design
• Main Contractor (Civils): Farrans
• Main Contractor (M&E): Glanua Group
• Civil team: McCormick Contracts Ltd
• Electrical works: Profitec Solutions
• Traffic Management: McVeigh Contracts Ltd
• Kiosk for new WPS: Morgan Marine Ltd
• Pumps: Grundfos
• Under-pressure tee connection: Waterworx Ltd
• Quarry products & reinstatement: Northstone Materials Ltd
• HDPE pipe: APP Fusion Group
• WPS automatic control (PLCs & HMI): Mitsubishi

Mechanical, electrical and instrumentation works

The Parkmore WPS consists of two Grundfos 38 KW CR125 booster pumps working on a duty/standby regime which can be controlled manually or automatically by way of variable speed drives. The duty/standby system is set to switch over after each pump stop its programmed cycle. [caption id="" align="alignnone" width="1200"] (left) The existing Cushendall WPS and (right) the new Grundfos pumps and inlet/outlet pipework - Courtesy of WSP[/caption] The two modes of control available are the primary, level-based control, and the secondary, pump fixed speed mode control. The chosen method by the client is the level-based method, remotely controlled on Telemweb with agreed low and high Parkmore Service Reservoir set-point levels (pumps on at 2.2m and off at 2.8m). The WPS automatic control is achieved using a Mitsubishi iQ-R series Programmable Logic Controller (PLC) system attached to a 12” Mitsubishi GOT Human Machine Interface (HMI). The PLC communicates status/alarms/events and exchanges set-points between the PLC and the telemetry talus unit via Modbus RS232. Critical status, alarms and controls are hardwired to/from the telemetry talus unit. The HMI provides information to the MCC for pumps 1&2 with the following list of options for NIW operatives to manually operate inside the WPS:

• Plant data.
• Plant mimics.
• System screen.
• Control system settings.
• I/O test pages.
• Trends and alarms.

[caption id="" align="alignnone" width="1200"] (left) HMI screen and (right) Parkmore Dungonnell WPS - Courtesy of WSP[/caption]

Project summary

Commissioning of the new pumping station began in early January 2023 and the existing pumps at Cushendall Pumping Station were turned off, allowing the 28 days commissioning period to begin. Following a successful testing period and training of NI Water Operatives, the new Parkmore Pumping Station is solely suppling the strategically important Parkmore Service Reservoir regularly during the day. The redundant Cushendall WPS has been electrically isolated and associated pipework has been sealed and capped off. To date the new pumping station has supplied over 60,000m³ of clean drinking water to Parkmore SR and has proven to be a resilient and reliable trunk main asset to NI Water.

The River Lyd Pumping Station is consented to abstract up to 40 Mld from its intake source at Lifton, Devon during November through to March, pumping raw water approximately 7km to Roadford Reservoir. The pumping station was last used on a full operational basis during the mid-1990s and the original equipment had remained in a shutdown and non-operational state up until the point of the upgrade works. The existing electrical switchgear was deemed to be life-expired and beyond the state of any possible refurbishment. The primary driver for the scheme and the scope of works was to upgrade and re-commission the pumping station for operational use at full output design capacity. During the course of the capital works project, a temporary works scheme was implemented in order to maximise operational use of the available pump sets while the capital build was in progress.

Background

The pumping station is configured with six Pleuger-type QN borehole pumpsets supplied by Flowserve Ltd and which had been previously refurbished by the manufacturer in the intervening period, and the pumps were maintained in storage at Roadford Reservoir. Four pumps are sized at 5 Mld and two at 10 Mld, providing for a combination of flows up to 40 Mld. The discharge from the common pump manifold is to the 900mm diameter rising main to Roadford Reservoir operating with a system pressure at 11 bar. At the works, two surge anticipation valves protect the pipeline in the event of failures and resulting critical surge conditions. Downstream of the common pump discharge manifold, and within the section of pipework that forms the washout connection at the river headwall, are two pressure transducers which have been installed to provide high pressure alarms and initiate pump stop in the event of an adverse operating condition and to afford protection to both pumps and also the rising main. From the common discharge, manifold flows leave the site through the existing 900mm rising main and are measured by a new Siemens electromagnetic flow meter installed as part of the refurbishment works.

Eel screens

Prior to the upgrade and re-commissioning works of the pumping station, a separate contract was undertaken by Galliford Try in 2021 to replace the river eel screens. The scope of works in this respect was to make the connections between each of the eel screens designed and manufactured by Andritz Ltd and a new air-burst cleaning system. The air-burst compressed air system is a self contained package plant designed and built by Quantum Engineering Developments Ltd with its own local control panel and PLC which control the cyclical cleaning of each of the eel screens. Local alarms are initiated at the LCP and key alarms are relayed back to the main plant MCC as required. Duty/standby screw type air compressors are installed, supplying a single air receiver with operating pressure at 9 bar. There are six air lines that connect with its respective screen and the control of air is via electro-pneumatically operated valves installed at the air compressor skid. Flexible 50Nb air hoses are installed in ducts and connect each piped outlet with a connection to the eel screen. Within the pump chamber a piped manifold of manual isolating valves and air hoses has been installed to provide for the connection to each eel screen. [caption id="" align="alignnone" width="1200"] Airburst package plant - Courtesy of Galliford Try[/caption]

HV & LV electrical works

The scope of HV electrical works required the re-establishment of the HV supply to the site and these works have been undertaken by National Grid to provide a new 1250 kVA supply to their existing substation on the site and inclusive of new interconnecting HV cabling from their primary substation. A new transformer of required capacity has been designed and manufactured by Wilson Power Solutions under supply to Enerveo who have completed the site HV installation. The LV side of the transformer is connected to a new form 4A Type 3 MCC which has been designed and manufactured by Galliford Try. The build incorporates the six soft starts for each of the existing 190kW and 110kW pumpsets. The incomer is rated at 2000A and busbar 2500A. Phase failure, surge protection, and transformer protection are incorporated within the build. There are common controls section, distribution board feeders, 110V and 24V supplies. Plant control and surveillance is managed by a Schneider Electric PLC and HMI which are built within the C&I section.

Water quality monitoring

A containerised suite of raw water quality instruments has been installed in accordance with the requirements set out in South West Water’s Technical Standard for Intake Protection & Raw Water Monitoring. The respective quality parameters measured are colour, turbidity, ph/temperature, dissolved oxygen, and ammonia. The sample is drawn from the River Lyd by a pair of duty/standby Grundfos JP sample pumps and which are connected to the river headwall by means of dedicated ducted 25Nb flexible sample pipes. Actuated GF ball valves within the piped discharge local to the pumps allow for the sequencing of the duty/standby changeover, air scour sequence and back wash of the sample lines during the changeover cycle. Flow monitoring to the instruments is by means of inductive type flow meters. The control, monitoring, alarm initiation and operator interface is via a local control panel complete with HMI and PLC.

River Lyd Pumping Station: Supply chain: key participants

• Principal contractor & designer: Galliford Try
• Pumpsets: Flowserve Ltd
• Flow meters: Siemens
• PLCs & HMIs & switchgear: Schneider Electric
• Eel screens: Andritz Ltd
• Air-burst compressed air system: Quantum Engineering Developments Ltd
• Generators: Aggreko UK
• HV transformer: Wilson Power Solutions
• HV installation: Enerveo
• JP sample pumps: Grundfos
• Software development & automation: Galliford Try
• Rising main: Kier Group
• Instrumentation: IFM Electronic
• Instrumentation: Partech Instruments

Capital works delivery

Before any works could be undertaken, significant tree and overgrown vegetation clearance had to be carried out at the entrance to the pumping station and along the lengths of the access paths and tracks that connect with the top of the site and the existing HV substation. GPR, topographical and ecological surveys were undertaken to establish conditions. There then followed a programme of dismantling works to remove the original GRP kiosk housing the 1990s MCC and transformer. The programme of civil works provided for the construction of reinforced concrete bases for the new 1250kVA transformer and air-burst package plant respectively. Installed on these bases are new GRP enclosures that provide the necessary protection for this equipment. A third GRP kiosk has been installed as the enclosure for the new MCC which utilised the original constructed base slab and trench albeit extended for the larger switchgear build. Elevated concrete piers have been constructed for the container housing the raw water quality instruments and with due consideration to the known risk of flooding at the site. The new enclosures required the submission and approval of a planning application. New ducts and drawpits have been installed to provide for the routing of pipework, HV and LV cables. The scope of mechanical installation works principally involved the re-installation of the refurbished Pleuger pumpsets and the associated pipework connections to the existing delivery manifold and rising main; the installation of the new airburst eel screening compressor skid and its hook up requiring a new air distribution system within the pumping chamber to supply each of the individual eel screens. The scope of the electrical installation works has been principally the uprating of the original 1000kVA supply to 1250kVA. This has required two new HV supply cables to be installed from the primary substation to the River Lyd site. A new HV transformer from Wilson Power Solutions and switchgear from Schneider  Electric has been installed to make the HV connection. The new Form 4 MCC has been designed and built as the replacement switchgear incorporating the most up to date electronic components and compliance with SWW Technical Standards. The software development and automation works has been carried out by Galliford Try. [caption id="" align="alignnone" width="1200"] (left) River water sampling container on flood prevention supports, (middle) Aggreko UK duty, primary assist and secondary assist generators, and (right) Generator flood prevention as design by the design team - Courtesy of Galliford Try[/caption]

Temporary works

During the period of the capital works build, and with continued falling level in Roadford Reservoir, Galliford Try was asked to put in place a temporary system of operation for the six installed pump sets using standby generators and temporary switchgear. Working with Kier Group, Galliford Try took charge of the works at the pumping station and Kier Group the rising main to Roadford Reservoir, responsible for checking, filling, flushing and pressure testing the pipeline; mindful that the system was last used in 1996. The original remit was to have the temporary plant installed and connected to allow the existing six pumps to operate by the 1 November 2022. All parties achieved their objectives, however South West Water was unable to obtain approval from the Environment Agency (abstraction permit) in the same timescale. This did however provide more time to allow Galliford Try’s capital works team to incorporate process elements of their capital build into the temporary works (flow meter replacement, air-burst compressed air system, telemetry and online operational water quality instruments). This has provided South West Water and the Environment Agency with a more robust pumping arrangement and water quality monitoring regime. Although the pumps and temporary works operation is scheduled to the end of March 2023, there is the possibility of an extension until the end of May 2023 which is being discussed between South West Water and the Environment Agency.

Completion

At the time of writing (April 2023) the capital works completion has been achieved insofar as it can be until such time as the temporary works operation has finished and the equipment removed off site. Following on from this, final landscaping will be completed along with those works required to complete all permanent connections to enable the pumping station to come back into operation from the beginning of November 2023.