Supply Chain - Reservoirs - Raw Water - Valves & Gates

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.

Kerse lies in open countryside approximately 3.5km from the former mining village of Patna in East Ayrshire, some 15km from the county town of Ayr. The newly constructed 3 megalitre capacity, twin cell, treated water storage (TWS) tank serves a local population of 6,500 private customers and businesses. It is situated immediately adjacent to the existing facility and is fed from the nearby Afton Water Treatment Works. Scottish Water’s Non-Infrastructure Alliance Partner, ESD JV (a joint venture comprising MWH Treatment, Binnies and Galliford Try) commenced construction in July 2022.  Water into supply was achieved on schedule on 21 May 2024. Existing facility

The existing single cell, below ground 4.5 ML clear water storage tank dates from the 1930s. It is, therefore, an ageing asset whose deterioration has recently led to some failures in water quality and general lack of resilience in the system. These drivers led to a decision by Scottish Water to commission a £6.5m replacement. Forecast modest rises in local population numbers was a secondary consideration.

Challenges

The principal challenges were:

How to build the new underground tank in a position immediately adjacent to the existing, still operating, facility. Non-interruption to the operation of the existing asset was a primary consideration. Working on the existing ageing network to fulfil the new process pipework. Undertaking testing and commissioning of the new asset whilst keeping the existing asset live and ensuring no negative impact on the network. How to stabilise the ground during excavations to ensure the continued, uninterrupted operation of the to-be-replaced tank and network pipelines. How to mitigate against poor soil conditions - mainly heavy clay - during two winter and spring seasons of heavy rain leading to severe drainage issues. The site was also located adjacent to a number of disused open-cast mines which were situated under a sludge restoration scheme, so continual coordination around access was key. Scope

The contract specified the replacement of the existing almost 90 year-old tank with a 3 ML, twin-celled treated water storage tank to be constructed on the same site, contiguous with the structure of the old tank.

The dimensions of the new asset are 29m x 21.5m x 7m to be covered by a reinforced concrete roof with waterproof membrane.

All aspects of the design of the new tank were undertaken by ESD JV’s design and engineering department. Work started on-site in July 2022. In total, approximately 850m3 of concrete was poured to construct the new structure.

[caption id="attachment_13133" align="alignnone" width="1200"] View of tank with backfill almost completed. Pedestrian crane on the left - Courtesy of ESD JV[/caption] Kerse Treated Water Storage Tank: Supply chain: key participants Client: Scottish Water Delivery contractor: ESD JV Binnies Galliford Try MWH Treatment Geotech design: Stantec UK Tower crane base design: Noble Works Ltd Mechanical design/installation: Dustacco Engineering Ltd Electrical installation: RRC Project Solutions Ltd Soil nailing: Albion Drilling Group Ltd Waterproofing: Concrete Repairs Ltd Underpressure connections: Swan Pipelines Pressure testing: Pressure Test Scotland Ltd Tank disinfection: Panton McLeod Ltd Telemetry: ID Systems UK Formwork: Peri UK Ltd FRC: AJ McAlpine Instrumentation: Processplus Ltd Control valve: CLA-VAL UK Ltd DI pipework: Saint Gobain PAM UK PE pipework: FPP Scotland Ltd Metalwork: HK Gillies Scaffolding: JD Scaffolding Ltd Tower crane: Ladybird Crane Hire Security system: Pointer Access covers: Technocover Ltd Rebar: Midland Steel Reinforcement Supplier UK Ltd Concrete & aggregates: Breedon Group Aggregates: Hillhouse Quarry Group Groundworks

In order to protect the viability of the existing tank, and as a consequence of above average rainfall in the winters and springs of 2022, 2023 and 2024, a complex bulk excavation operation was undertaken which included the extensive use of soil anchors to stabilise the ground.

This solution included some in-depth collaboration from the site team and specialist sub-contractor to design a solution to ensure no current live network pipes (which were only 6m from the top of the batter of the excavation) were damaged during the installation of the anchors. In order to achieve this, the site team undertook a survey of the existing network to establish the precise coordinates of each pipeline.

This allowed for the design to be altered to a smaller length of anchors with a revised slope angle ensuring no pipes would be damaged as part of the TW solution. All excavated material (spoil) was used as backfill for the new asset and also for the existing asset which is scheduled to be de-commissioned and removed with minimal excess being removed from site. In total, circa 10,500 tonnes of material were excavated to construct the new asset.

[caption id="attachment_13134" align="alignnone" width="1200"] (top left) Groundworks nearing completion, (bottom left) tank construction underway, and (right) view of tank interior - Courtesy of ESD JV[/caption] Innovative construction

A hydraulic assessment to decide the level of the tank resulted in the need to bury it underground. Given the damp ground conditions on-site, a water impermeable concrete was used to construct the base and walls. This maximises the lifespan of the asset and represents the best carbon solution.

The heavy clay soil resulted in the rapid build-up of water within the excavated area leading to significant drainage issues. This resulted in some pre-excavation cut off drainage ditches being constructed at the high level of the excavation along with gravel filled silt ditches and fencing installed around the site to mitigate the impact of any run-off. Due to the inclement weather encountered throughout the winter of 2022, this led to some initial delays to the programme.

However, any delays were mitigated by innovative solutions to other tasks. The team at Kerse are proud of their ‘championing’ of the use of an electric pedestrian tower crane. Operated at ground level, this led directly to accelerating the construction programme and a significant cost reduction. The selection of the pedestrian crane, which was initially proposed to be an operated crane via operator at high level, brought significant health and safety benefits by removing the need for working at height.

Also, the site team installed cameras at critical inspection points on the crane which meant all daily inspections could be carried out at ground level by the operator, again eliminating the requirement to work at height. All statutory inspections were undertaken by a third party under a safe system of work which was included as part of the sub-contracted scope.

The additional benefit from selecting this method came from a reduction in carbon output with the initial temporary works reinforced concrete pads (which were due to be in excess of 95m3) and the selection of the pedestrian ground operated crane reducing this concrete requirement to only 8m3 to fulfil the temporary works requirement.

A rechargeable electric mobile elevated working platform (MEWP) was employed, providing further benefits. The use of the pedestrian crane and MEWP significantly reduced the carbon footprint on the project in comparison to using alternative options such as mobile cranes and access scaffold which are commonly used on this type of project. The use of the tower crane to facilitate lifting operations throughout the project, along with the MEWP for high level access, proved to be a time saving, cost effective and carbon friendly solution to our buildability requirements on site.

Another innovation was the temporary works wall truss system employed.

Reinforcement for the walls of the new tank was prefabricated on-site. In itself, this produced significant cost, time and safety benefits. This solution reduced the requirement for access scaffolding to be erected, this being substituted by the MEWP system. In addition, personnel did not have to construct the reinforcement whilst working at height or manually handle the reinforcement and place it into position. Instead, this was achieved via pre-fabrication at low level, subsequently allowing full panel reinforcements to be lifted and installed into position providing further safety, time and cost benefits to the project. Another reason for employing this system was that no additional temporary support system was required to support the reinforcement.

[caption id="attachment_13132" align="alignnone" width="1200"] The almost completed structure before backfill operations - Courtesy of ESD JV[/caption] Telemetry

Throughout the project, there was regular liaison between ESD JV and Scottish Water with weekly and monthly collaboration meetings held leading to a close and productive working relationship on the project mitigating potential delays. All issues and challenges have been met in a collaborative environment.

At Kerse, Scottish Water have introduced a new telecoms telemetry system using 4G connectivity monitoring all instrumentation, including water level sensors, alarms and floats, which replaces the old PSTN line.

This option was the result of a business approach change from Scottish Water to provide either VDSL (fixed line) or LTE (4G mobile) for IP enabled communications. In order to prevent the time and cost involved in installing a VDSL line, a decision was made following a successful survey to utilise a new 4G solution for the project’s telemetry communications.

Current status

Water into supply was achieved on schedule in May 2024. This was followed by reliability testing and sampling by Scottish Water before the facility was declared fit for operation which was achieved on 30 May 2024, with the old asset now drained and ready for de-commissioning.

Currently, a new site access road is being completed and various measures of landscaping, including grass seeding, are underway. A new perimeter fence will also be installed as per SW security requirements.

Towards the end of the project, ESD JV was asked by Scottish Water to undertake the decommissioning and demolition of the now-replaced clear water tank. This was not part of the original scope of the contract. These works will be completed in the summer of 2024.

The village of Longwood is located in south-west County Meath, Ireland, approximately 15km south of the town of Trim and 50km north-west of Dublin. In March 2023, construction started on a 500m3 above-ground treated water storage tank at the site of the existing Longwood Water Treatment Plant, which will ensure that Uisce Éireann can secure supplies to over 1,244 customers in the Longwood Water Supply Zone; providing a safe and sustainable source of drinking water. Project background

The Longwood Water Supply Zone (WSZ) had been identified as having insufficient capacity and before the construction of the new treated water storage tank, there were no storage facilities for the Longwood WSZ. To ensure security of supply, it was necessary for Longwood WTP to be upgraded to provide 24-hours of storage, more flexibility and network management.

Ensuring the additional storage required constructing a new 500m3 treated water storage reservoir, replacing the two existing borehole pumps to improve efficiency and longevity of the units, and constructing a high-lift network pumping station designed to maximise the efficiency of the pumping system.

[caption id="attachment_21002" align="alignnone" width="1200"] The existing water treatment plant prior to the construction of the clean water storage tank - Courtesy of Uisce Éireann[/caption] Project design

The detailed design works included the following for the structural works, drainage, mechanical and electrical installation, and the photovoltaic system:

A 500m3 capacity drinking water storage reservoir at the Longwood WTP, including pipework connections, scour and overflow. Replacement of two number existing borehole pumps (both boreholes were in operational use on a duty/standby rota system; programmed to change duty every 12 hours). High-lift network pumping station kiosk for the Longwood WSZ, containing three booster pumps (duty/duty/standby). Integration into the existing Longwood WSZ Distribution Network. Modifications to the existing chlorine dosing and control system to ensure adequate disinfection contact time is provided within the new storage reservoir in compliance with Uisce Éireann’s Primary Disinfection Specification (IW-TEC-900-05 & IW-TEC-900-05-01) and Uisce Éireann’s Design Specification: Disinfection: Secondary Chlorination (Document No: IW-TEC-900-05-02). Provision of free chlorine residual monitoring system. Provision for emergency generator connection. All automation and control including modifications to the existing SCADA/HMI system. Design of a de-chlorination chamber. Design of a photovoltaic system. Associated site works including landscaping, site fencing and surface water drainage system. [caption id="attachment_21000" align="alignnone" width="1200"] Kiosk housing three booster pumps - Courtesy of Uisce Éireann[/caption] Longwood Treated Water Storage Tank: Supply chain - key participants Client: Uisce Éireann Employer representative: Nicholas O’Dwyer Ltd Civils designers: McAdam Principal contractor: BSG Civil Engineering Ltd Mechanical & electrical design/construction: EPS Water PV system: Solmatix Renewables Ltd Concrete testing: Mattest Ireland Ltd CBR plate bearing tests: Construction Testing Services Ltd Control system programming: ECN Technologies Control panel: Motrol Steel fixing, formwork and concrete: ONCCE Ltd Davit sockets: Columbus McKinnon Corp Ltd Booster pumps: DP Pumps Borehole pumps: Xylem Water Solutions Pump & control panel kiosk: Shanette Sheds Ltd Ductile iron pipework: APP Fusion Group Oil interceptor: Kingspan Klargester Precast manholes: FP McCann Ltd Drainage & manhole covers: J McAleer & Sons Ltd Handrails & access system: MEGS Fabrication Ltd Haulage & disposal: J Ryan Haulage Ltd Access covers: Technocover Ltd Rebar: Walter Watson Concrete & stone: Kilsaran Tarmacadam: Mitchell Macadam Ltd General hardware: Murdocks Builders Merchants Sustainability measures - PV system and carbon reduction

The photovoltaic system was designed to provide around 10% of the Longwood Water Treatment Plant’s annual power consumption. The system, supplied by Solmatix Renewables Ltd, is expected to generate approximately 5,168 kWh per annum; resulting in Uisce Éireann reducing the carbon emissions generated from the Longwood WTP by approximately 1,170 kg annually.

Through design of the landscaping and planting elements, a biodiversity net-gain was achieved at the site. This included the planting of approximately 65m of mixed native hedgerow to bolster an existing hedgerow and to protect an existing open drain at the rear of the site.

[caption id="attachment_20999" align="alignnone" width="1200"] Photovoltaic system on the roof of the new treated water tank - Courtesy of Uisce Éireann[/caption] Project construction

BSG Civil Engineering Ltd was employed as the main contractor and construction started on site in March 2023. The construction works included:

Construction of in situ concrete 500m3 capacity dual cell water storage reservoir. Installation of the inlet and outlet pipework to each of the storage reservoir cells, overflow and scour pipework into each cell linking it to the existing outfall, and interconnecting pipework and pressure regulating valves linking the storage reservoir to the Longwood WSZ. Installation and construction of four openings to the new storage reservoir, two for each cell. One opening in each cell is provided with a davit socket and a permanent internal access ladder. Construction of a de-chlorination chamber. Installation of a secured external staircase for access to the roof of the storage reservoir. Installation of a high-lift network pumping station kiosk for the Longwood WSZ. Installation of three booster pumps (duty/duty/standby within a new pumping station kiosk. Site drainage pipework including seven manholes, an oil interceptor, a de-chlorination chamber and a new headwall to allow discharge to existing outfall. Replacement of two existing borehole pumps along with associated pipework, sensors and cabling. Installation of a photovoltaic system and associated electrical works. Installation and upgrade of external generator connection point. Construction of roadway, footpaths and landscaping around the site. [caption id="attachment_21025" align="alignnone" width="1200"] The completed water treatment plant site - Courtesy of Uisce Éireann[/caption] Final considerations

The project was successfully completed and handed back to Uisce Éireann in December 2024 and was a testament to the skill of all involved.

Nicholas O’Dwyer’s initial design concept, which was carried forward by BSG Civil Engineering Ltd, met all of Uisce Éireann requirements and the upgrades at the water treatment plant provide a safe, secure and sustainable source of drinking water to the Longwood Water Supply Zone for years to come.

Utilising a photovoltaic system will ensure a continued reduction of Uisce Éireann’s carbon footprint, and reusing all the excavated materials generated from the construction at a local sports facility for use in future development works has benefited the local community by enhancing the sports facility and the community as a whole, due to the fact the excavated material is not going to landfill.

Scope of works Excavation works began in 2017 at the Dancing Hill Reservoir site as part of a £6 million project to upgrade the Water Supply GRID for Bridgwater and the surrounding areas. Major upgrades are required due to large-scale developments in the area. Issues & solutions The design was particularly challenging due to the complicated nature of the ground surrounding the reservoir tank. A sizeable berm was built on the ground profile around Cofferdam 4 to ensure a safe and stable excavation. This exaction also had to accept other loadings from Cofferdams 1, 2 and 3. Multiple 203UC tank brace frames were used due to the strict lift plan limit of 1 tonne. Larger or heavier brace systems could risk the collapse of existing foundations. Vibration pile driving was not permitted due to the detrimental effect it could have on the high-pressure water mains that supplies customers. There was also a HV cable running through the site that had to be avoided. The exact location of other services created additional challenges and ongoing surveys had to be monitored throughout the duration of works. As of 2017 there are four connected cofferdams in place allowing safe working space to combine new pipeworks to the main reservoir tank. Multiple back-to-back 203UC tank braces with special alignment of bracing has been key in the design, combined with KKD 600 sheets to secure the trench. Several Lightweight DavitSafe systems allow safe access into the 10m deep cofferdams. Sector: Water & Utilities Client: Wessex Water Location: Bridgewater, Somerset Scheme: Water Supply GRID Upgrade MGF depot: Bristol Products hired: Multiple 203UC brace, KKD 600 sheets, lightweight davit [caption id="" align="alignnone" width="1200"] Dancing Hill - Courtesy of MGF Ltd[/caption] For more information: MGF Ltd | +44 (0)1942 402700 | www.mgf.co.uk    

The challenge The South East Water contact tank has a constant output of 18.1 million litres per day, it contains water which is treated with Sodium Tripolyphosphate and sodium hypochlorite before entering the distribution network. The structure is of a ‘certain’ age and has a number of active leaks that have progressively worsened over time. As the tank is in constant use, it cannot be taken off-line and so a solution was required which could be undertaken against heavy flow of water with the tank still in use. The Xypex solution Xypex not only likes water, but the repair method requires a wet environment therefore an active leaking tank is not a problem. The cracks were chased out in accordance with the DWI Reg. 31 approved Instructions for Use Document i.e. a minimum of 37mm depth and 25mm wide, following the line of the crack. Either side of the crack was cleaned and the laitance removed to expose the capillary and pore network. [caption id="" align="alignnone" width="1200"] The Xypex solution; Concentrate and Patch'n Plug - Courtesy of SMR Projects Ltd - Xypex UK Distributors[/caption] A bleed pipe was installed and secured with Xypex Patch’n Plug at the lowest point of the crack where water flow was at its greatest. Then the base of the crack was plugged using Xypex Patch’n Plug to stop the flow of water. This was then left to see if there were any additional issues that manifested themselves over night. Once the flow was proven to have stopped, the repair was finished using Xypex Concentrate both as a dry pack and a slurry in line with the IFU and Xypex’s standard repair methodology. The results The Xypex methodology using Xypex Patch’n Plug stopped the flow of water instantly and allowed the repair to be undertaken. The crystalline chemistry within the Xypex Concentrate will migrate deep in to the concrete matrix around the repair, driving water out and increasing the life and durability of the tank in those areas. [caption id="" align="alignnone" width="1200"] Courtesy of SMR Projects Ltd - Xypex UK Distributors[/caption] As the original repairs were undertaken, additional pressure was transferred to other cracks that were visible, but not leaking, and these were all repaired using the same method. In all, only 2 materials were used on site and no specialist methods were used. SMR Projects Ltd attended and were on hand for technical help throughout the installation.   For more information: SMR Projects Ltd - XYPEX UK Distributors: +44 (0)1295 279747 | www.smrxypex.co.uk

 

The challenge The reservoir had an estimated 180 meters of cracks that needed repair, as well as the main element of the concrete that required coating to waterproof and add durability to the concrete structure. The reservoir was taken out of commission but it needed to be returned to service as soon as possible. To do this, we looked at the order of the processes to ensure the tight time frames could be met. The Xypex Solution In accordance with the Reg. 31 IFU (Instructions For Use) all cracks were broken out to a minimum depth of 37mm and a width of 25mm. The walls were prepared by removing the laitance and the whole area was saturated. To stem the ingress of water, every crack that showed moisture was sealed with Xypex Patch’n Plug which sets in seconds stemming the flow. To meet the required time frame, the Xypex Concentrate coating work was then undertaken to allow it to air cure for the specified time. Once applied, the crystalline technology takes time to migrate deep into the concrete and become fixed within the concrete matrix as a permanent solution. When the curing is complete the coating could be removed if required, in this instance it remained. During the curing process of the coating, the crack repairs were then filled using Xypex Concentrate as a Dry Pack and then finally topped off with a thin layer of Xypex Patch’n Plug to enable the fast return to service. [caption id="" align="alignnone" width="1200"] The Xypex solution; Concentrate and Patch'n Plug - Courtesy of SMR Projects Ltd - Xypex UK Distributors[/caption] The results The allowed time frame meant undertaking the processes out of the normal sequence, but this allowed the repairs to be to be delivered on time. The coating was undertaken to increase the durability but also to pick up any minor unidentified cracks. The larger cracks were repaired and sealed using the standard Xypex repair methodology, however ultimately over 300 metres of crack repairs were completed.   For more information: SMR Projects Ltd - XYPEX UK Distributors: +44 (0)1295 279747 | www.smrxypex.co.uk