Supply Chain - Project Planning & Surveying - Wildlife Surveys

Forming part of Southern Water’s (SW) Hampshire supply region, the Isle of Wight (IoW) is located just off the south coast of England and is divided into two water distribution zones (WDZ), namely IoW North and IoW South. The IoW South comprises major towns of Ryde, Sandown, Shanklin and Ventnor with multiple villages and more remote rural areas forming the wider distribution network. The water sources and distribution systems have been brought together, with their origins being from former smaller localised systems developed in the late 19th century, which were added to in the 20th century as the IoW population grew, to form an integrated system. Today, there are five existing small and medium sized water supply works (WSW) with a combined daily output of 18 ML supplying customers via several small water service reservoirs (WSR). The water distribution network totals approximately 547 km of mains, serving a population of approximately 45,000 people. Project driver The Cooks Castle WSR has been identified for replacement based on asset condition and the associated security of supply risks to customers. This project aims to provide a long term solution for storage requirements and enhance the network associated with the removal/replacement of this existing WSR. To validate the need and determine the optimum size, top water level and location of any new WSR, a solution needed to be developed considering a wider, integrated view of water sources, network storage and water distribution now and into the future. The business planning objectives were broadly defined as: Create a more resilient water supply network for future generations (Southern Water Network 2030 rationalisation). Maintain levels of service to customers and mitigate water quality risks. Ensure future growth and proposed new sources can be integrated (Water Resource Management Plan - WRMP) and reduce dependency on the bulk transfer from the mainland via the Cross Solent Mains. Increase operational flexibility through optimisation of existing/new assets. Improve security of supply to customers (zonal storage provided in line with Southern Water Asset Class Policy). Decommission surplus assets to reduce cost of maintenance. [caption id="" align="alignnone" width="1200"] Figure 2: The planning process developed - Courtesy of Southern Water[/caption] Optimisation The Optimatics’ OptimizerTM tool was used, allowing the team to analyse up to 35,0000 plans (the group of assets the Optimizer chose to test) in a single optimisation run (see Figure 1 - top of page). OptimizerTM was allowed to generate plans incorporating both new asset options and removing or retaining existing assets. New options tested included a total of approximately 80km of strategic mains in varying diameters, over 20 WSR configurations in five different locations, decommissioning of existing WSRs and associated rezoning, rationalisation of WSWs and provision of new pumping stations. The OptimizerTM evaluated plans using input ‘design criteria’ which were formulated and aligned with the project planning objectives and Southern Water standards. More complex ‘rule-based adjusters’ were formulated to allow automation of controls and prevent Optimizer from selecting options which conflicted with one another, e.g. to prevent Optimizer’s ability to select multiple sizes of WSR at the same location. The evaluation of these design criteria by the OptimizerTM produced a cost and performance evaluation for each plan. The best performing plans were then compared with each other on a Pareto curve - see Figure 3. [caption id="" align="alignnone" width="1200"] Figure 3: Typical Pareto curve showing best performing plans - Courtesy of Southern Water[/caption] Incorporating environmental performance into the optimisation was a particular challenge. The team approached this by taking the results from a high level environmental feasibility assessment and factoring in WSR and pipe costs proportionally to reflect better and worse performing options. This then carried through into the overall cost/performance results for that plan. In the example, the Pareto curve shows about 216 OptimizerTM plans (from 30,000) from which 10 plans have been identified as feasible options. The OptimizerTM tool is very powerful at testing several configurations (plans) based on the given inputs, design criteria and formulations. Review and validation are critical parts of the process, and this involves the team checking outputs (individual plan performance), tweaking inputs (adjusting costs/penalties/formulations) and refining the optimisation until several tangible plans are derived. Figure 4 shows typical age of water results for several WSRs with shortlisted plan 7639, 8142 & 8041 compared against the existing system performance. This demonstrates how the optimised plans can significantly reduce the age of water meeting one of the projects key objectives. [caption id="" align="alignnone" width="1200"] Figure 4: Age of water optimisation - Courtesy of Southern Water[/caption] Defining outputs: the optimal integrated solution Taking a short list of tangible plans from the optimisation is a starting point which allowed the team to define the pathway to the final integrated solution. Not all factors can be simply incorporated into OptimizerTM therefore these external factors need consideration alongside the optimisation outputs to form the final integrated solution. One important factor was implementation of solutions over several AMP cycles and ensuring that staged development did not detrimentally impact on customer levels of service. Similarly, consideration of outage scenarios, e.g. WSW shutdowns and mains bursts were considered outside of the optimisation, then retrospectively tested against the shortlisted network configurations. The solution The final integrated solution comprised: Network connections to a single rationalised WSW using three input water sources (currently two separate WSW with two sources). This aligns with WRMP and improves IoW drought resilience. Removal of seven existing WSRs reducing asset risk through deterioration, maintenance costs and age of water issues. Provision of one new strategic WSR providing wider security of supply to several district metered areas (DMAs) compared to current configuration. Trunk mains reinforcements and new installation/upgrading of network pumping stations to support strategic transfers from proposed WSWs to WSRs and customers. Increased operational efficiency and lower OPEX by considering rezoning, triad periods and exploiting opportunities to modify the current network via simple valving operations.

West Hallington Reservoir is a Northumbrian Water Group (NWG) asset situated 1km to the northeast of the village of Colwell in the Tynedale district of Northumberland. The reservoir was constructed between 1884 and 1890 for Newcastle & Gateshead Water Company for the purpose of municipal water supply. The reservoir was built adjacent to the earlier East Hallington Reservoir and operates as a non-impounding structure. It has a maximum depth of 12.1m, a capacity of 3.3Mm3 and a surface area of 50 hectares at the Full Supply Level (FSL) of 155.1m AOD. Scope of works An inspection carried out under Section 10 of the Reservoirs Act 1975, identified that the reservoir had insufficient drawdown capability, and thus needed to be increased such that the reservoir level can be drawn down by 4.8m in 8 days. Mott MacDonald Bentley (MMB) developed a design solution which utilises two 700mm diameter siphons on the west embankment to operate at a combined flow rate of 3.2m3/s. The new siphon pipeline, alongside a temporary pump arrangement and the existing scour pipes, will meet the required drawdown capacity. The siphon flows will be conveyed across a stretch of adjacent field which NWG has purchased. The flows will then either percolate to ground or gravitate to the Coal Burn and eventually to the River North Tyne. Detailed design and engineering challenges Hydraulic analysis MMB has designed and constructed over 25 siphons for various water companies in the UK. The siphon arrangement was analysed using an in-house design spreadsheet, and demonstrated that the siphon would break when the water level dropped 3m below top water level which was deemed acceptable. The siphon location was moved to the west embankment due to concerns about stability and leakage through the south embankment (the original proposed location of the siphon) and because it was easier to access this area of the site. [caption id="" align="alignnone" width="1200"] Summary chart from the reservoir drawdown hydraulic analysis - Courtesy of MMB[/caption] Pipes and thrust restraint Hoops stresses within the DN700 mild steel siphon pipes were checked and a DWI Regulation 31 coating specified. The stainless steel pipe supports were analysed for bending and shear and concrete thrust blocks were designed for the system test pressures. The pipe wall thickness was reduced from 10mm to 8mm as an efficiency. The pipework arrangement drawing was uploaded into the federated model in BIM360 to check for clashes and when installed on site was found to fit perfectly. Ground investigation and geotechnical analysis Following the original construction of West Hallington Reservoir (between 1884 and 1890) the Resident Engineer Charles Henzell wrote a report to the Institution of Civil Engineers describing the works and detailing a number of challenges which included: Areas of soft book leaf marl overlaying harder boulder clays on the route of the embankment needed to be excavated. Embankments sinking or slipping and the toe of the slope reinforced with concrete walls, sheet piles and additional stepped embankments. Springs in the vicinity of the works. [caption id="" align="alignnone" width="1200"] (left) Cable percussive borehole rig on the crest of the embankment and (right) scaffold decked area required for rotary bore works on the slope - Courtesy of MMB[/caption] A desk study and intrusive in situ ground investigation (cable percussive and rotary bored boreholes, standard penetration tests (SPTs), piezo installation, lab testing) were carried out to classify and determine the thickness of the superficial and solid geology along with groundwater levels, identify any contaminated or aggressive ground and determine the engineering properties of the native soils. Slope stability and ground bearing pressure checks were carried out to ensure large plant would not compromise the stability of the embankments. The clay core and embankment material of the Pennine-type dam was found to be very silty and exhibit poor engineering qualities and so was disposed of, and a source of good quality puddle clay and Series 600-2C material was found locally at a brick factory in Birtley, Gateshead. This was installed in compliance with the test and inspection plan (T&IP) to a good standard. Thankfully the three springs in the west embankment mentioned in the Henzell report were not encountered. [caption id="" align="alignnone" width="1200"] Extreme weather conditions during the construction stages: (left) winter 2022 and (right) flooding from Storm Babet (October 2023) - Courtesy of MMB[/caption] Temporary works A borehole at the toe of the embankment on the dry side indicated the presence of water-bearing sands and gravels and so interlocking sheet piles were specified that punched through the sands and gravels into the underlying clays and so cut off groundwater flows into the excavation. A Portadam supplied and installed by OnSite Central was employed to provide a dry area to construct the intake bay. The Portadam was erected in the wet by operatives wearing buoyancy suits, and then pumped out and an excellent seal was achieved. The Portadam also allowed plant access around the pipework whilst the stone pitching was reinstated. Flood risk assessment A flood risk assessment (FRA) was carried out to support the planning permission and, as due diligence, to ensure MMB would not flood a property by accident. The assessment looked at the extent of flooding during operation of the siphon along with fluvial, surface water, groundwater and finally reservoir flood risk due to an uncontrolled release (which of course the siphon is designed to help prevent). The FRA concluded that:

The maximum modelled flood extent from a drawdown of Hallington Reservoir is in agreement with the flow path identified by the Environment Agency in the long-term flood risk map and no communities are shown to be at risk due to the proposed drawdown. As periodic testing of the reservoir drawdown will occur during dry periods, it is not considered that a drawdown of West Hallington Reservoir at this location would increase flood risk elsewhere.

Synchro 4D MMB chose SYNCHRO 4D from Bentley Systems during the latter stages of the design process. SYNCHRO 4D is software that enables MSP/P6Programme to be linked with a Revit model and to run a construction simulation. [caption id="" align="alignnone" width="1200"] A screen dump from the SYNCHRO 4D simulation - Courtesy of MMB[/caption] The simulation highlighted a number of pinch points when materials must be delivered or when water levels must be lowered or raised and helped drive efficiencies. SYNCHRO 4D was also useful for explaining the construction process to the client, to site operatives and to visitors. Solar power The mechanical equipment associated with the siphon is housed within a high security kiosk. Due to the remote site location, the cost of a permanent power supply for the kiosk building services was prohibitive. A solar powered solution has been installed utilising roof mounted PV cells, DC/AC converter and battery storage. This sustainable solution provides sufficient energy for lighting and heating within the kiosk with negligible running costs. West Hallington Reservoir: Supply chain - key participants Construction delivery partners: Mott MacDonald Bentley Feasibility study & ARPE: Stantec UK Ecological surveys: OS Ecology Ltd Temporary water barrier (Portadam): OnSite Central Ltd Large diameter pipes: Powerrun Pipe-Mech Ltd Electrical/instrumentation installation: Intelect (UK) Ltd Large diameter valves: AVK UK Ltd Large diameter valves: Glenfield Invicta Valve actuators: Varley Hydraulics Ltd Stonemasons: Stuart Marley Ltd Steelwork fabrication: AJ Engineering & Construction Services Ltd Steel fixing: D&N Reinforcements Ltd Kiosks: Technocover Ltd Bespoke steel access cover: EJ Solar panels: Green Leaf Engineering [caption id="attachment_9915" align="alignnone" width="1200"] Solar panel display - Courtesy of MMB[/caption] Construction: Problems, successes and lessons learned? Intake bay The intake bay was located along the Small Burn which originally ran across the middle of the reservoir and was diverted into the adjacent Coal Burn in the 1880s via a DN375 clay gravity drain. The ground around the intake bay was found to be poor and was excavated down to competent sub-grade and reinstated with 340 tonnes of gabion stone and 60 tonnes of Type 1 capping material. As this area is normally under a 5m depth of water it was inaccessible during the ground investigation stage. Pressure testing As the DN700 pipes are fabricated from coated mild steel, a Type 1 pressure test (water loss method) was required. All bolts had been tightened using Hytorc© equipment and the torque readings recorded in the T&IP, but achieving a pass proved difficult due to sunny weather. A temperature rise on the above -ground pipework led to a pressure loss of more than 0.2 bar in the water filled pipe voiding the test on a number of occasions. Eventually cloud cover enabled a valid test; one of the only times a site team has prayed for the sun to go in! [caption id="" align="alignnone" width="1200"] Siphon intake bay constructed within a Portadam barrier supplied and installed by OnSite Central - Courtesy of MMB[/caption] Stone pitching Reinstatement of the original stone pitching (to resist wave action) took seven weeks longer than planned; mainly down to availability of stone masons. Productivity increased as the works progressed and the three man gang went from replacing 3 to 5m2 per day. The stone pitching was reinstated to a good standard, but it was felt that the detailing around one of the pipe supports would be built differently next time. The 2,500m perimeter of the reservoir had been faced with stone pitching down to original ground level; installation of which in the 1880s without an excavator and selector grab must have been a job and a half! Ecology Prior to the construction works, NWG employed OS Ecology to undertake trapping for white clawed crayfish, a native species that is in decline due to the introduced North American signal crayfish. No white clawed crayfish were found within West Hallington Reservoir but three were trapped within the adjacent East Hallington Reservoir. A pied wagtail nest was spotted by eagle-eyed site workers next to the engine of an excavator. The excavator was withdrawn from service until the eggs had hatched and the fledglings left the nest. [caption id="" align="alignnone" width="1200"] Reinstatement of the stone pitching - Courtesy of MMB[/caption] Testing, commissioning & conclusions The siphon is designed to operate above a water level of 152.5m AOD and to self prime above a level of 154.1m AOD (TWL = 155.1m AOD) and so the All Reservoirs Panel Engineer (ARPE) requested that during the testing and commissioning stage, MMB should demonstrate the following: That the siphon can be primed between the water levels 152.5m AOD and 154.1m AOD. That the siphon can self-prime above a water level of 154.1m AOD. That the Full Supply Level of 155.1m AOD can be achieved. The water level rate was restricted to 300mm/week and any seepage through the clay core will be monitored in future via a flow measurement chamber. During operation of the siphon, receiving watercourses and culverts were monitored at a number of locations to ensure scour or carriageway flooding were recorded and the test halted if required. The works were completed within budget (final NEC3 contract value £3.3m, £60k gain pot) and on time. The original compliance date of 31 September 2023 was extended to incorporate obtaining the Section 166 agreement and a new date of 30 June 2024 was agreed with the ARPE. [caption id="" align="alignnone" width="1200"] DN700 siphon pipework during installation - Courtesy of MMB[/caption] Leaving a legacy Northumbrian Water is very keen on creating community projects and “leaving a legacy”. MMB widened the access from the main road and provided three passing places as the access route is used by both residents and members of the fishing club. Looking ahead Northumbrian Water are investigating another 10 reservoir sites that potentially require siphons, and so Mott MacDonald Bentley hope to use the good practice and experience learned at West Hallington Reservoir on other schemes in the future. A Northumbrian Water Engineering Briefing Note for siphon design and construction is also underway, which captures all the learning and good practise and will sit alongside the newly published CIRIA 813 Siphons in Dams: Design, Installation, Operation, Management and Testing.

St Augustines Road is a busy thoroughfare in Chesterfield linking the town to Matlock and the south-eastern edge of the Peak District. Lying within the Yorkshire Water (YW) waste catchment area, the road is steep in its nature with gradients often exceeding 7%. Due to the local hydraulic catchment and topography, during heavy rainfall events flooding occurred at the road’s intersection with Derby Road (A6). The flooding lifted manhole covers from their frames which caused significant damage to the highway. It also caused internal and external damage to the surrounding properties. To combat this, mitigation was carried out by Yorkshire Water and Chesterfield Borough Council (CBC), including the implementation of mitigation measures such as non-return air bricks and flood gates, however, this had limited success. CBC also commissioned the construction of a detention basin to the rear of the flooding properties; but again with limited success. Hydraulic study As a result of the mitigation’s limited success, a hydraulic study was commissioned by Yorkshire Water. This confirmed the root cause of the flooding was hydraulic overloading of both the foul and surface water sewers. A notional solution was developed by Yorkshire Water which included the upsizing of these sewers, with some form of temporary storage for the foul system to retain flows in a rainfall event. Later iterations of the hydraulic model revealed that improvements to the surface water network would in fact also reduce the frequency of flooding on the foul water network due to interactions between the two systems during storm conditions. In light of this information, in May 2021 Yorkshire Water secured funding to implement a series of significant improvements on St Augustines Road. Preferred solution The preferred solution included the construction of a new outfall into the River Rother and the transfer of all flows from the surface water sewer in Derby Road. This would provide a much greater flooding resilience in the existing system. The existing 225mm surface water sewer was to be upsized to Ø750mm along its 320m length. It would then be diverted via a tunnel underneath Derby Road into the wetland area immediately adjacent into the River Rother. Here, a new outfall would be constructed to discharge the surface water sewer into the river network. [caption id="" align="alignnone" width="1200"] (left) The preferred option and (right) flooding on St Augustines Road - Courtesy of Galliford Try[/caption] Constraints and engineering challenges The preferred solution progressed to detailed design with several technical challenges to be overcome. Several of these challenges were exacerbated by the need to construct the outfall into the River Rother outside of the salmonoid spawning season. An Environment Agency (EA) bespoke Flood Risk Assessment Permit, (FRAP) was required to construct the outfall and all in-channel activities were required to be undertaken before 1 October 2021 in order to mitigate the impact on any spawning salmon. A significant flow rate of up to 0.89m3/s would be discharged into the river during storm events and river scour was a concern. In order to combat the scour on the riverbed and riverbanks, there was a requirement to reduce the velocity of the flow before it interacted with the River Rother, causing excessive turbulence. To achieve this, box culverts were selected due their unique cross section and significant channel width. This slowed velocities down to near 1m/s, which is widely regarded to have negligible effects on turbulence and thus reducing scour. The headwall was also designed to allow flows to enter the River Rother at a 45° angle, as per EA Standard Rules SR2015 guidelines, further reducing the risk of scour on the opposite riverbank and riverbed. Outfall design This design however did not come without complications, such as the need to carry out the structural design, build and installation of a bespoke outfall within a few months. BSP Consulting was commissioned to carry out the structural design of the outfall which was to be precast, reducing the need for in situ concrete handling adjacent to the sensitive receptor. Off-site build (OSB) also reduced the construction programme and allowed the headwall to be manufactured concurrently within the determination period of the FRAP. [caption id="" align="alignnone" width="1200"] Outfall under construction - Courtesy of Galliford Try[/caption] Poor ground and underfoot conditions adjacent to the River Rother proved too risky and problematic for traditional mobile crane lifts, so all lifts of the precast sections were to be undertaken with a tracked excavator. This further constrained the design and restricted the maximum mass of each section to 13 tonnes. Consequently, in its final iteration the precast headwall was designed in two sections and was combined with an in situ toe and infill slab/wall which completed the structural design. Design During the design stages, extensive ground investigation was carried out. This identified water bearing sand and gravel strata adjacent to the river which transitioned to mudstones and clays towards St Augustines Road. It was this change in strata which posed a significant challenge for the no-dig section of the work beneath Derby Road. This section of work was critical as it linked the outfall to the upsizing work on St Augustines Road. Discussions were held with Active Tunnelling Ltd who proposed the use of the guided auger bore technique to install the sewer in this transitional strata. Although initially designed as a 750mm diameter sewer, this was reduced to 600mm which was the maximum diameter which could be accommodated by the tunnelling contractors. Hydraulic modelling was undertaken by RES Environmental to confirm the viability of this proposal and in order to compensate for this localised throttling, the pipeline had to be upsized locally to 900mm immediately upstream of the tunnel. The alignment of the tunnel was severely limited due to proximity of existing buildings on Derby Road. BSP Consulting was again called into action as pre-condition surveys and settlement calculations were commissioned in order to understand the impact of the tunnelling works on these at-risk properties. [caption id="" align="alignnone" width="1200"] (left) Installation of drive pit on St Augustines Road, (middle) guided auger bore rig, and (right) the transition between 600mm and culverts - Courtesy of Galliford Try[/caption] Settlement calculations were undertaken using the “Guide to best practice for the installation of pipe jacks and microtunnels technique” and a predicted settlement of <3mm was deemed to be acceptable. The pre-condition surveys highlighted only minor cosmetic issues and were used as reference to the state of repair of the properties prior to construction work commencing. The majority of the civil design was undertaken in house. This element included a design coordination role combining and processing the information received from the consultants and stakeholders. An example of the numerous stakeholders which were consulted is that of the Coal Authority. Initial searches indicated the presence of historical coal workings. More detail was sought and records indicated the presence of an adit within 20m of the proposed pipeline. A coal permit was sought from the Coal Authority and the design progressed whilst this was processed. St Augustines Road (Chesterfield) Flood Alleviation: Supply chain: key participants Principal contractor & civils design: Galliford Try Temporary works & headwall design: BSP Consulting Hydraulic modelling: RES Environmental Ltd Ecological consultants: Middlemarch Environmental Traffic management: Amberon Traffic Management GRP & utility mapping: Cloud Conversion Ground investigation: Grange Geo Consulting Ltd Pipelaying & outfall construction: Arthur Civil Engineering Trenchless installation: Active Tunnelling Ltd Cofferdam design & supply: National Trench Safety UK ‘EndSafe’ safety barrier: Groundforce Shorco Cofferdam installation: Ivor King The Piling People Dewatering: Alba De-Watering Services Ltd Precast concrete: Bonna Sabla CCTV, CIPP & cleansing: CPS Drainage Solutions Handrailing & grille design: Galliford Try (Fabrications) Silt curtain: Murlac Land and Marine Environmental Solutions Pumping: Selwood Ltd Ridgistorm pipes: Polypipe Civils Pipe & flap valve supplier: Keyline Civils Specialists Landscaping & site clearance: Landscape Maintenance Services Ltd Reinstatement of traffic signals & street furniture: Swarco Aggregates & muck away: JC Balls & Sons Brickwork: Derwent Joinery & Construction Gates & fencing: SFC (Midlands) Limited Surfacing: BDS (Yorkshire) Ltd [caption id="" align="alignnone" width="1200"] Service detection - Courtesy of Galliford Try[/caption] Installation The Environment Agency granted the FRAP on 13 August 2021, and the detailed design was finalised and submitted to Yorkshire Water’s technical approval committee on 16 August 2021. Work began on site a few days later, leaving just six weeks to construct the headwall and cease all in-channel activities as per the conditions of the FRAP. Work commenced immediately on the enabling works, with particular attention paid to the temporary works. Haul road To provide drainage to the waterlogged land adjacent to the River Rother, a land drainage scheme was commissioned, designed and installed by Lincolnshire Drainage. This provided a more suitable foundation on which to install the haul road and working laydown areas. The haul road was designed by BSP Consulting and was of substantial construction given the underlying strata, at 700mm thickness with geotextile layers to improve longevity. Ground dewatering After the installation of the haul road, wellpoint dewatering was installed around the outfall area and along the proposed culvert alignment. The dewatering was installed by Alba De-Watering Services Ltd at 1.5m centres. However, due to the underlying mudstone, each well had to be pre-augered and was then installed using the more traditional spout method to ensure that a reasonable well depth was achieved to adequately dewater the working area. A silt curtain was supplied and installed by Murlac Land and Marine Environmental Solutions prior to the channel works to minimise silt and sediment damage downstream from the works. It proved to be very effective during the cofferdam installation. [caption id="" align="alignnone" width="1200"] Cofferdam and silt curtain - Courtesy of Galliford Try[/caption] Cofferdam A cofferdam was required to retain the River Rother and this was designed and supplied by National Trench Safety UK and installed by the primary subcontractor Arthur Civil Engineering. The cofferdam was unique in design in that it utilised Larsson piles in a trapezium shape (plan) to minimise over-dig yet still accommodate the headwall and first culvert. The cofferdam was installed by Ivor King The Piling People using a 35t excavator with a Movax side grip pile driver attachment. The cofferdam was effective but 4” end suction pumps supplied by Selwood Ltd were still required to maintain the cofferdam and keep water levels low. Headwall installation Once the cofferdam was watertight, the headwall toe was cast in situ, after which the precast headwall arrived in two sections as planned. It was lifted into position by Arthur Civil Engineering using a 50t tracked excavator. An administrative issue led to the need to negotiate a 2-week FRAP extension with the EA and the headwall was completed and the cofferdam removed by 14 October in accordance with the conditions of the revised FRAP. Pipeline works Construction works on the remainder of the project continued in March 2022. A temporary one-way system was implemented to provide a safe working area to install the remainder of the pipeline with open cut works commencing on 14 March. The open cut works progressed steadily with over 100 services safely crossed. The later spring and summer months provided excellent conditions for online sewer relay with drought-like conditions, culminating in hosepipe bans for the majority of the UK. [caption id="" align="alignnone" width="1200"] Open cut pipelaying - Courtesy of Galliford Try[/caption] Prior to the tunnelling works commencing, concern was raised over the proximity of the tunnel as it crossed under a 225mm foul water sewer in Derby Road. With a clearance of just 300mm, the existing foul sewer was inspected by CPS Drainage Solutions using CCTV and a precautionary 5m cured-in-place patch liner was installed to strengthen the sewer prior to the guided auger bore operation. No-dig works commenced in early June and progressed well without incident and were completed towards the end of the summer. No settlement was detected during the installation and no visual deformations were reported from the nearby structures. Open cut works continued late into the summer with flooding benefits delivered by 5 October. Significant rainfall events have since occurred and the feedback from residents previously affected by the flooding has been positive. Off-site build Off-site build was utilised heavily without which it would not have possible to abide by the conditions set in the FRAP and achieve the tight programme when constructing the outfall into the River Rother. The headwall and culvert manhole cover slabs were precast by Galliford Try off site and the hand railing and grille were fabricated by Galliford Try (Fabrications). The flap-valve was fabricated off-site by Keyline Civils Specialists. [caption id="" align="alignnone" width="1200"] 900mm Ridgistorm pipe from Polypipe Civils ready for installation - Courtesy of Galliford Try[/caption] Public engagement & community impact Throughout the project customer engagement was a priority for Galliford Try and Yorkshire Water. Although COVID-19 curtailed some of the engagement meetings which were planned at the start of the project, regular communication with residents of St Augustines Road and surrounding area took place. A significant quantity of the communication was made to the local residents Facebook group, which provided timely and accurate updates on progress. Traditional letters were also posted as back up and for those who didn’t have access to Yorkshire Water’s online updates. Towards the end of the project volunteers from Galliford Try and Yorkshire Water spent a day helping out at the local food bank on St Augustines Road and made a donation of £500 to assist with their ongoing charitable cause. Project success The project is considered huge a success for Galliford Try and is the largest single project completed on the Infrastructure Framework for Yorkshire Water within the AMP7 period.

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 Ltd 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 &amp; switchgear: Schneider Electric Eel screens: Andritz Ltd Air-burst compressed air system: Quantum Engineering Developments Ltd Generators: Aggreko UK HV transformer: Wilson Power Solutions Ltd 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 Ltd 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.