Supply Chain - Mapping & Modelling - Modelling
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Case Studies
(left) Base concrete pour and (right) the upper spillway - Courtesy of MMB[/caption]
Armourstone and lower spillway - Courtesy of MMB[/caption]
Finished spillway - Courtesy of MMB[/caption]
(left) Location of new sewage treatment works and tunnel route and (right) Slyfield Regeneration Project area - Courtesy of Adams Hendry[/caption]
RIC 1 and 2 pass areas - Courtesy of BAM Enpure Ltd JV[/caption]
This combined dataset is then used in Leapfrog 3D geological modelling software, which applies intelligent interpolations, and highlights anomalies that can be quickly assessed and removed. The resultant 3D model has then been used to enhance communication in the engineering AutoDesk BIM 360 federated models, and in the proprietary Arcadis SmartAtlas GIS viewer.
Rapid Impact Compaction (RIC) is a method of imparting energy to the ground using a repeated but relatively short drop-weight, where a base plate (or “puck”) is in constant contact with the ground. RIC is preferred over a larger drop-weight technique due to its more progressive and less disturbing impact on the ground it is being used on. The method is also faster and uses smaller scale setups. A challenge for the RIC method was whether the energy it imparts is sufficient to densify the ground, versus other higher energy drop-weight methods. A trial was deemed necessary to demonstrate the suitability of this method. RIC is proposed to be applied over the majority of the site with an expected densification of landfill down to approximately 4.5m. Areas where assets will not be supported on driven full depth piles will undertake a second pass of the RIC method, reducing the long-term settlement of the landfill material. The predicted reduced surface will be levelled as required by the infill of depressions with imported stone or other suitable material.
Improvement of the existing ground by reinforcement through installation of Vertical Rigid Inclusions (VRI) method across the site. Supporting of level sensitive and heavier elements will be on precast driven piles founded below the landfill material. The combination of methods will be designed to achieve Thames Water’s settlement performance values over 40 years, and remain within the allowable values of 50mm and 100mm. This will reduce the need for full depth driven piling which would otherwise be required.
Reduction of infiltration to the landfill materials by ensuring impermeable surfaces drain to the treatment works and are released at the outfall away from the site. Gas and leachate well monitoring is provided along the perimeter of the site to monitor any impact and provide leachate removal points if required.
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(left) Rapid impact compaction rig and (right) pile under test - Courtesy of BAM Enpure Ltd JV[/caption]
(left) inlet pumping station physical model and (right) inlet pump testing physical model - Courtesy of Hydrotec Consultants Ltd[/caption]
The pump design has been developed to fulfil the project brief load requirements (future peak IPS capacity 2585l/s) and some flexibility either side of the requirements is available due to the standard capacity equipment design offered from the supply chain.
The proposed arrangement now consists of a wet well 12.5m diameter, approximately 20m deep. A common inlet will be provided to dissipate any entrained air, and two selectable pumped sections with double isolation will be provided by wall mounted penstocks on full height walls.
The pumping well will be constructed in two halves, hydraulically connected in normal operational mode however each half will be able to be isolated (using motorised penstocks) in accordance with specification requirements surrounding double isolation, to allow person entry into half of the wet well at a time.
Each half of the wet well will have three pumps installed giving a capability to provide full flow to treatment from two pumps with a standby permanently installed.
The pumping station was first modelled by computational fluid dynamics (CFD) to demonstrate the assumed flow patterns that will occur. The pumping station was then physically modelled to comply with the specification and process design requirements particularly with respect to distribution, mixing, settlement, turbulence, dispersion, and freeboard for the full range of flows that each structure is expected to receive.
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Storm overflow physical models - Courtesy of Hydrotec Consultants Ltd[/caption]
Inlet works
The inlet works is being designed to receive all pumped flows from the inlet pumping station (including future peak IPS capacity 2585 l/s), inlet works drainage and screening liquor return flows. Flows will enter the inlet works and then separate across the four escalator screens inclined at an angle of 45°. Each screen will be provided with a local proprietary control panel. Each panel will incorporate a differential ultrasonic level control.
An emergency bypass will be provided upstream of the screens to accommodate all four screens blinding at the same time. Three 1200mm wide duty screens will be required to screen flows from low flow up to 2585 l/s, screening 6mm in two directions.
The inlet works and grit treatment plant will be covered with odour covers which will be connected to the inlet works and PST odour plant. The inlet works has been classified as a Zone 2 Area under the odour covers and all equipment beneath the odour covers will be ATEX rated.
Storm tanks
Storm flows from the inlet work storm separation chamber will flow into two storm tanks via a 1400mm above-ground pipe. Within the 1400mm pipe between the storm separation chamber and the storm tanks there will be a partial pipe MCERTs certified flow meter to measure the total flow into the storm tanks.
During normal operation the blind tank will fill first, then the spill tank will fill. In the event that both tanks are full to capacity (and still in storm flows) the spill tank will overflow via a weir and the storm tank will discharge to river.
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Elevated inlet works - Courtesy of BAM Enpure Ltd JV[/caption]
The storm tanks contents will automatically return to the inlet pumping station via 700mm gravity pipe when the flow being pumped to the inlet works drops below a predetermined set point. The return flows will be controlled to approximately 0.5 DWF via an automated valve controlled by an electromagnetic flow meter located in the gravity main, returning to the common inlet well of the inlet pumping station.
Storm tank cleaning will be a pumped system with the two pumps located external to the storm tanks. Storm tank cleaning will be initiated during the latter part of the storm tanks draining back to the inlet pumping station and will not operate when the tanks are filling. The pump discharge pipe work will include connections for flushing with washwater.
Ferric storage & dosing
Two 45m3 ferric storage tanks will be located in a concrete bund with the dosing skid packages and control system located within an adjacent kiosk. The bund will be capable of containing 110% of the one of the storage tanks plus 10% allowance for rainwater. A drive-in bunded area for chemical deliveries will be provided and an underground chemical interceptor will contain any local spillages, complete with a Castell interlocked 3-way valve to allow the bunded drainage area either to drain into the interceptor (during a chemical delivery) or to drain into the site drainage (normal operation).
Chemical dosing points will be provided upstream of the PSTs, on the common outlet channel of the ASP, and upstream of the tertiary treatment plant. The dosing points will utilise sparge systems to ensure adequate distribution of chemicals into the channels.
Odour control plant
The odour plant is a 2-stage system. Stage 2 filters will discharge into an 18-metre-high odour stack. The plant has been designed to achieve a minimum removal efficiency of 98% of H2S and 99% removal of odour, based upon a total system duty of 8432 m3/hr (of which 4813 m3/hr is from the inlet works and 3619 m3/hr from the primary settlement tanks).
Service water
A potable water main supplies a service water break tank via a ballcock (float valve). The service water break tank has a working volume of approximately 30m3 which gives a nominal retention of approximately three hours at average throughput. Service water booster pumps draw water from the tank and transfer it to the service water main network where it feeds the polymer make-up system for all thickeners and dewatering belt presses.
Primary settlement distribution chamber
The distribution chamber has been CFD modelled to calculate the flow split to each downstream primary settlement tank from first principles, and assess whether the proposed design would deliver an equal flow split (+/-5%) for seven future flow scenarios. This required the inlet bellmouth to be turned down to improve flow splitting.
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PST distribution chamber CFD models: (left) with four PSTs in service and (right) with six PSTs in service - Courtesy of The Fluid Group[/caption]
Primary settlement
Primary settlement consists of four 47.15m long by 10m wide tanks, with a depth ranging between 6.24m at the hopper end and 5.3m at the outlet length (equating to 1 in 50 floor slope). Each PST tank has three sludge hoppers at the inlet end. The outlet of the PST discharges into a common 1000mm wide outlet channel. From this outlet channel the 1000mm outlet pipe from the drop box combines with the 700mm RAS lines into an above-ground 1200mm pipe.
Retractable odour covers will be provided across the PST tanks to allow for future inspection, cleaning and maintenance. The odour covers will be connected via ducting to the inlet works/primary settlement tank odour plant. All mechanical equipment installed below the covers will be constructed from 316 stainless steel or high performance plastics. The primary settlement tanks have been classified as a Zone 2 Area, and all electrical equipment beneath the odour covers will be ATEX rated.
The design of the PST Tanks is based upon a maximum inflow of 3022m3/hr to all four in-service tanks, and a peak flow to each tank of 1007m3/hr with one PST out of service. In normal operation all four PST tanks will be in service.
Within each PST tank a chain and flight scraper system will be provided which will utilise high-tech non-metallic materials as the main materials of construction. Scum from the primary tanks will gravitate via a rotating surface skimmer pipe to the above-ground primary settlement scum tank. The primary scum return pumps are progressive cavity pumps, operating in a duty standby configuration. The pumps are fixed speed pumps operating between a high and low level in the scum tank.
The PST sludge hoppers will desludge based upon a SCADA-adjustable interval and duration. The primary desludge pumps are progressive cavity pumps, operating in a duty/standby configuration. The pumps are variable speed pumps operating to maintain a SCADA-adjustable flow set point.
Once the effluent has flowed through each PST it will enter into a common 1000mm wide outlet channel. From this outlet channel flows transfer to the ASP distribution chamber via a drop box and 1000mm above-ground pipe.
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ASP overview - Courtesy of BAM Enpure Ltd JV[/caption]
Activated sludge plant
The ASP plant will have a distribution chamber using the same general arrangement as the primary settlement distribution chamber.
The activated sludge treatment tank consists of four ASP lanes. Each ASP lane has a selector tank followed by an anoxic zone and then the three aerobic zones. The main aeration lane will be fitted with aeration pipework and fine bubble diffusers. The aeration vessel is 80m long and 6.1m wide with a water depth of 7.05m. The total instantaneous maximum air demand of the ASP is 10,438 m3/h.
The first third of the aerated fraction of each lane will contain 50% of the aeration capacity, the middle third 30%, and the final third 20%. Each aeration lane will have three passes, arranged as channels of 6.15m width. The air for the diffuser grids will be supplied from three ASP air blowers operating on a duty/assist/standby basis. The aeration system will be controlled by an ammonia based real time control (RTC) system utilising a feed forward ammonia load input and a feedback ammonia concentration.
Once the effluent has flowed through each ASP lane it enters into a common 1000mm wide outlet channel. From this outlet channel flows transfer to the FST distribution chamber via a drop box and 1200mm above-ground pipe.
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Anoxic and aeration zones flows - Courtesy of BAM Enpure Ltd JV[/caption]
Final settlement tanks
The FST plant will have a distribution chamber using the same general arrangement as the primary settlement distribution chamber. The four FSTs will consist of 32m diameter flat bottomed circular tanks with a side wall depth of 6.15m. The FST will separate solids from the flow via settlement, producing a clarified effluent which overflows a peripheral weir into a launder channel, before gravitating to the tertiary treatment distribution chamber via a 1000mm below-ground pipe.
The combined clarified outlet flow from the four tanks will be monitored by a common flow meter, as well as suspended solids and phosphorus monitoring instrumentation, all provided on the common line to tertiary treatment.
The design of the FSTs is based upon a maximum inflow to each tank of 1741m3/hr with one FST tank out of service. In normal operation all four FST tanks will be in service. Each tank will have a 700mm inlet pipe, which will flow into a central diffuser drum before entering the FST tank. Each tank features a 600mm outlet pipe fed via a peripheral launder channel, as well as a 400mm RAS gravity outlet pipe. Each of the four tanks features a full bridge rotating scraper system which will run continuously in normal operation.
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32m final settlement tanks & sludge return (RAS pumping station) - Courtesy of BAM Enpure Ltd JV[/caption]
Sludge return (RAS/SAS pumping station)
Sludge from each pair of FSTs will enter one of two RAS/SAS desludge chambers. The two chambers will be located side by side and will share a set of three duty/duty/standby RAS transfer pumps, which will recycle the settled sludge from both RAS/SAS desludge chambers to the activated sludge plant distribution chamber feed line.
The variable speed centrifugal RAS transfer pumps will be capable of pumping 2200m3/hr at a maximum head of 8.9mhd. The pumps will operate between high and low level in the duty RAS/SAS desludging chamber, with both chambers provisioned.
A pair of duty/standby SAS pumps is provided, which will facilitate wastage of surplus sludge, with each pump drawing from a single RAS/SAS desludge chamber. The fixed speed centrifugal pumps will transfer sludge to the SAS buffer tank. Control of the SAS pumps will be carried out either on a timer or based on the level in the SAS buffer tank, with the common discharge line featuring flow monitoring.
Tertiary treatment
Clarified effluent flow from the FSTs will pass to the tertiary ferric mixing and flocculation (post-precipitation) stage, where the option will exist to dose ferric sulphate solution into the flow in order to encourage flocculation of remaining solids. This stage will be split into two parallel streams, with flow from the FSTs initially entering via a single bellmouth inlet into a common inlet channel, before passing via twin overflow weirs into two rapid mix chambers, and subsequently overflowing into two flocculation chambers. The design of the rapid mixer chambers will ensure complete mixing (>95% CoV) of chemical in less than 4 seconds.
Flow from the flocculation chambers will weir into a common outlet channel leading to a flow distribution chamber feeding the tertiary treatment stage.
The distribution chamber has been CFD modelled to calculate the flow split to each downstream cloth pile filter from first principles, and assess whether the proposed design would deliver an equal flow split (+/-5%) for seven future flow scenarios.
The tertiary treatment stage will comprise six cloth pile filters, which will operate with all filters in service - however the peak flow will be able to be treated with only five filters in service. The filters will be sized to accommodate a peak flow of 840 l/s, producing a final effluent of 20 mg/l TSS (95%ile) and 0.2mg/l TP (average).
Bypass pipework is to be provided adjacent to the cloth pile filter structure, by which clarified effluent from the FSTs may bypass the tertiary ferric dosing/flocculation and cloth pile filter stage.
Each of the six cloth pile filters will feature a central rotor drum onto which filter discs are attached. The rotor and discs will be fully submerged within the tank, with the discs supporting the physical cloth filter media. Flow entering the filters will flow from outside the discs through the cloth into the discs’ interior, with solids collecting on the external surface of the cloth pile, creating a headloss. As this headloss increases, the water level in the tank will rise and at a pre-set water level (as detected by an ultrasonic level sensor) a cleaning cycle will be initiated.
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Tertiary treatment flocculation chambers: Eliquo Hydrok Mecana cloth pile filters - Courtesy of BAM Enpure Ltd JV[/caption]
Filtered final effluent (FFE) from the inside of the filter disc and rotor drum assembly will pass forward through the unit via a low-level aperture to an outlet chamber, from which flow will weir into the common final effluent outfall chamber. An emergency overflow weir is to be provided, allowing unfiltered effluent from the filter tank (external to the discs) to weir over into the outlet chamber.
Backwash liquors from the backwash pumps will exit the filters via a common manifold, draining by gravity to the grit plant liquor PS. Eight backwash pumps will be provided per machine, giving a total of 48 pumps across all six machines. The pumps will be submersible units placed within the tank, with each pump being dedicated to three filter discs. The backwash flow rate is rated for 10 l/s (subject to the installed pipework design/headloss).
Each of the six filter tanks will see some solids settlement occurring (and potential accumulation of other debris), which will create a build-up of sludge in the bottom of the tank. This sludge will be periodically removed by a set of two duty/standby sludge pumps per machine (i.e. 12 sludge pumps installed in total). The discharge from each sludge pump will be connected to the common backwash manifold, leading to the grit plant liquor pumping station.
Final effluent discharge
Flows leaving the cloth pile filters will pass out from the main filter chamber via a low level aperture into a small outlet chamber, from which flows will weir over into the common outfall channel. The final effluent (FE) will flow under gravity through an FE flow measurement flume, with an ultrasonic instrument for measurement of final effluent flows discharged to outfall.
The FE outfall channel will feature a pipe leading to the FE washwater system, with a further line branching off this pipe servings as the suction line for FE Meteorburst Analyser. On exiting the FE outfall channel, flows will enter a dedicated FE outfall main, which will drain by gravity, discharging to the river north of the STW site.
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New Guildford STW: 3D model night-time overview - Courtesy of BAM Enpure Ltd JV[/caption]
Thickened sludge blending tanks - Courtesy of BAM Enpure Ltd JV[/caption]
Each tank will feature separate inlet connections for the three types of sludge being received, with actuated valves and crossover lines allowing all sludges to be directed to either of the two tanks. The tanks will also feature outlet actuated valves, which will allow either tank to be isolated from the sludge belt press feed pumps downstream, thereby ensuring the pumps only draw from a single tank at any given time.
A set of three duty/duty/standby sludge belt press feed pumps will be provided, which will transfer blended thickened and imported sludge from the thickened sludge blending tanks to the sludge belt presses. The pumps will be variable speed progressive cavity units, with a peak capacity of 30m3/h (i.e. 15m3/h per pump) at a maximum head of 48.5m, based on sludge of up to 7.0%DS.
Dewatered cake leaving each belt press will enter a discharge cake hopper leading to the suction end of a sludge cake pump. Three pumps will be provided, with a single pump dedicated to a single machine; each pump will operate in conjunction with the associated belt press upstream.
The pumps will be variable speed progressive cavity units, with a peak capacity of 7.4m3/h of sludge (up to 30%DS). The pumps will transfer the cake via individual discharge lines to the sludge cake silos, with manual discharge crossover facilities allowing sludge from the pumps to be directed to either of the two silos as required.
Cake silo storage & discharge
Dewatered sludge cake will be pumped to two truck-loading cake silos, with a combined storage capacity of 600m3, sized to provide 7-days of storage at average cake production. Each silo will feature a discharge screw conveyor (with a sliding frame ‘anti-bridging’ device) which will discharge the cake through a hydraulically operated slide gate valve.
Odour control plant
The odour plant will be a 2-stage system. Stage 2 filters will discharge into an 18-metre-high odour stack.
The plant has been designed to achieve a minimum removal efficiency of 98% of H2S and 99% removal of odour, based upon a total system duty of 6629m3/hr, extracted from the various tanks and thickening/dewatering machines in the sludge plant area.
(left) Outfall route plan - Courtesy of Bam Enpure Ltd JV, and (right) outfall low flow scenario CFD model - Courtesy of Arcadis[/caption]
Outfall structure
The outfall structure will consist of a reinforced concrete headwall, set back from the river channel, to be founded in the river terrace deposits and flared to direct flows downstream and minimise the impact of upstream debris from collecting. The headwall will have duckbill valves on the discharging pipes, and erosion control products utilised in the surrounding area to tie the headwall into the natural riverbank and bed.
The erosion mattress employed following the headwall structure will provide a secondary point at which turbulent flows can dissipate energy without eroding the natural bed of the river.
Where the headwall ties into the natural riverbank, the hard/soft interaction between headwall and natural soil will be reduced by the installation of Rock Rolls erosion control and willow stakes at the base, and the installation of a natural hydro-seeded CocoBN blanket or equivalent (to be seeded with local seed varieties) which will retain the slope shape until vegetation establishes and provides an effective natural erosion control. This will also provide a gradual slope to access down to the river.
Existing contact tank - Courtesy of MMB[/caption]
3D model showing the four pressurised contact tank vessels - Courtesy of MMB[/caption]
CFD modelling - Courtesy of MMD CFD Team (Spain)[/caption]
The purpose of the model was to provide evidence that the water has a minimum t5 retention time of 20 minutes to comply with the standard if the raw groundwater is considered unstable, or 15 minutes if considered stable. A non-reactive tracer was added to the model at the primary dosing point and measured at the outlet through time to obtain its exit age distribution. The model was run as a worst-case scenario with one of the furthest of the four tanks taken out of service; meaning only three were modelled including interconnecting pipework. The model was also based on a 15 MLD design horizon which is conservative as it is 1.5 MLD beyond the abstraction limit and capability of the existing borehole pumps.
It was agreed with the client that the groundwater was considered stable such that a 15-minute t5 was the target figure, and the model showed an 18.2-minute t5 with 21m long contact tanks. This offered a saving of approximately £230k by having shorter tanks because the CFD modelling showed that 25m long tanks would have been required for a 20-minute t5. This would have made delivery of the tanks down Ufton Lane even more challenging. Even so, Autotrack analysis was completed to confirm in theory there was a route to the site, which was viable for delivery of the 21m tanks, which the tank suppliers’ delivery management company confirmed was possible during a pre-delivery survey. This was considered to be the right balance of resilience and affordability because it is unlikely the unstable groundwater events would occur at peak design horizon demand whilst one of the contact tanks is out of service.
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Exit age distribution of tracer measured at the outlet - Courtesy of MMD CFD Team (Spain)[/caption]
Use of SYNCRO to hold a digital construction rehearsal to de-risk programme: A P6 programme has been produced which lists numerous construction activities and outages limited to eight hours due to the island zone constraint, and a 3D model has been produced to illustrate the physical space each asset needs when installed. As part of MMB’s Digital Delivery Plan SYNCRO (one of the digital tools utilised by MMB) was used to hold a construction rehearsal which led to the following benefits; a better understanding of the space constraints, engaged client stakeholders for programme buy-in, improved safety and a de-risked programme.
By combining the P6 programme with the 3D model and reviewing it via SYNCHRO software allowed a better understanding of the concurrent activities and the ability to spot where there could have been potential space constraints. The digital rehearsal revealed that the design was proposing to install precast pipe support plinths and the access metalwork at the same time as the contact tanks were being installed, so SYNCHRO was used to update the P6 programme live to re-sequence the work.
This rehearsal simulated the contract lift of the contact tanks and illustrated just how much space was needed to have a safe working area to complete a lift of a 21m long 10t tank on a 20m radius. This again led to a change in the construction sequence of the mechanical installation of pipework and access metalwork.
Focusing on safety and being prepared to challenge programme where there looked to be too much concurrent working, should ensure a right first-time approach before committing to starting on site, reducing the risk to quality or safety and having to abortively re-plan works, which may end up increasing costs.
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MMB SYNCHRO digital rehearsal - Courtesy of MMB[/caption]
The digital rehearsal review coincided with a change in a key construction assurance client team member, so the above process sought their buy-in and confidence in the construction programme and occurred at a significate project milestone (contractual solution review) where the client can make a go/no-go decision on whether the project goes ahead into detailed design and construction. The review received positive feedback from the client that the session proved to be a valuable and more engaging way to bring them up to speed with the scheme and the construction programme.
The project will revisit SYNCHO to plan in more detail at other key milestones like works outages, or whilst on site as a more visual way of completing 5-week-look-ahead planning sessions. MMB has a Digital Delivery Network which is a community of people who can support projects with tools like SYNCHRO and others which can be found on the MMB Digital Delivery Hub.
The benefits of this digital rehearsal were more cost/risk mitigation rather than direct cost reduction on a project. The estimated consequence of not having realised the space constraints and programme concurrent working is 10-weeks lost time meaning £148k cost increase ‘saved’ (avoided). It is difficult to estimate the cost saved/benefit of having a happy engaged client stakeholder like a construction assurance engineer. This is assumed as saving/mitigated a potential two-week delay resulting in a approximately £30k saving.
Providing maintainable assets vs keeping flood plain impact negligible: The existing site not only feeds an ‘island zone’ network; it also becomes an island during flood events and is surrounded by drainage ditches.
Relocating the entire site would be uneconomical and too intrusive so expanding the treatment works into the adjacent field is the best whole life cost solution even if that field is a flood plain. This meant any new assets needed to have as small a footprint as possible to ensure it had negligible impact on the flood plain, and yet still needed to be assessable for the planned maintenance and main driver for the scheme; to be able to take one contact tank out of service for quality and structural inspections.
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Flood plain location of contact tanks - Courtesy of MMB[/caption]
The solution is to install the steel contact tanks on slim 2m tall concrete plinths, with the inlet/outlet stainless steel pipework supported off steel pipe supports founded on Legato blocks or strip foundations. Precast units were selected where practical and economical to speed up the install to reduce the risk of needing to poor concrete into a floodplain as part of the 10-month long construction programme.
The outlet pipework was looped back to join the inlet pipework such that all the isolation and air valves can be operated from the same common access platform, which is 21m long by 6m wide and stands 2.8m above ground level, which saved approximately £400k in metalwork and civil plinths The platform then bridges over the ditch between the treatment works and adjacent field to provide operational access.
To ensure all the new assets didn’t have a negative impact on the floodplain a flood model and flood risk assessment was completed based on the volume of new assets to be installed in the field, which showed negligible impact to the flood plain.
The contact tanks can be accessed at ground level outside of flood events via a new Grasscrete access road, which removed the need for road drainage which saved £37k. Foundations would have the existing underlying alluvium layer of soft organic clay replaced to target the medium dense gravels layer with stone to allow for better drainage during periods of rainfall and reduce the risk of settlement.
The alternative to the elevated assets would have been to bund the entire area which would have had significant cost, carbon and floodplain offset impact which was calculated using the Mott MacDonald Moata Carbon Portal.
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Ufton Nervet WTW 3D models - Courtesy of MMB[/caption]
Biodiversity net gain (BNG): Approximately 2m of the existing ditch will be disturbed to install the new headwall, so another section approximately 10m long will be enhanced from poor to moderate condition equating in a 13.3% BNG in river units. The 0.1ha of agricultural grassland will be enhanced from poor to moderate condition to achieve a net gain of 10% to account for that lost from installing the new assets.
Approximately 88 urban trees are proposed to be planted and maintained to moderate condition along the 180m boundary fence line to achieve a net gain of approximately 40%. To achieve a net gain of 10% would mean only 22 small trees needing to be planted, but this would of only provided a visual screening along 25% of the fence line. Therefore a hedgerow will also be planted along approximately 125m of the inside of the fence line to provide further visual screening and offer at least a 27% net gain in BNG hedgerow units.
Melton Mowbray STW before the start of works - Google Earth image[/caption]
(top left) Groundworks underway, (right) SMR UK ASP area soil stabilisation, and (bottom left) stabilised ASP area with piling and ASP base construction ongoing - Courtesy of MWH Treatment[/caption]
The net carbon reduction profile of these activities[/caption]
(left) Inlet works physical model at Hydrotec and (right) inlet works screen baffles and dye test - Courtesy of MWH Treatment[/caption]
Refurbished inlet works with three screens & bypass pipework and (inset) the inlet works prior to the upgrade with two screens - Courtesy of MWH Treatment[/caption]
Refurbished inlet works with three screens & bypass pipework and (inset) the inlet works prior to the upgrade with two screens - Courtesy of MWH Treatment
(left) Flood inundation modelling and (right) site location plan - Courtesy of Arup[/caption]
Western Breakwater Point Cloud model - Courtesy of Arup[/caption]
Settlers of Porthcawl - Courtesy of BlueCube Marine[/caption]
Western Breakwater construction works - Courtesy of Knights Brown[/caption]
Western Breakwater during Storm Diana - Courtesy of Keith Jones[/caption]
A screenshot of the 3D model used for design and construction - Courtesy of Bam Nuttall Ltd[/caption]
Construction of the high level inlet works structure - Courtesy of Bam Nuttall Ltd[/caption]
(left) Rapid impact compaction underway and (right) a selection of site plant in use - Courtesy of Bam Nuttall Ltd[/caption]
(left) Driving precast concrete piles and (right) vertical rigid inclusion installation - Courtesy of Bam Nuttall Ltd[/caption]
2. Precast driven piling: The main structures and pipelines are founded on precast driven piles. These are end-bearing into the London Clay, approximately 10m below ground level. Precast driven piles were chosen as the solution as the operation does not bring any landfill to the surface. Various size piles were driven to various depths and tested with both dynamic and static tests. Borehole monitoring showed that there was no discernible change to leachate and ground gas levels and that there was no dispersal of leachate happening throughout the landfill.
(foreground) Ferric mixing and flocculation chambers and (background) concrete bases for sludge tanks - Courtesy of Bam Nuttall Ltd[/caption]
Piles and blinding concrete for the four final settlement tanks and (left) temporary ground support for pipelaying into the centre of the tanks - Courtesy of Bam Nuttall Ltd[/caption]
Activated sludge plant precast walls erected, prior to pouring base slab and concrete stitches - Courtesy of Bam Nuttall Ltd[/caption]
(foreground) PST precast walls with concrete stitches and bases and (background) ASP precast walls - Courtesy of Bam Nuttall Ltd[/caption]
Safdar Ali, Andrew Dawes and Izhar Ahmad from the BAM team at the completion of the tunnel - Courtesy of Bam Nuttall Ltd[/caption]
Threading buried process pipework between new structures requires extensive temporary works - Courtesy of Bam Nuttall Ltd[/caption]
(left) Concrete bases for the tertiary treatment plant, (top right) cross-sectional view through the primary settlement tank, showing the piles and gas dispersal layer beneath the base, and (bottom right) precast wall panels are joined with an in situ concrete stitch - Courtesy of Bam Nuttall Ltd[/caption]
Ovingham RWPS - Courtesy of MMB[/caption]
Hydraulic model schematic extract from Ovingham RWPS Refurbishment Technical Note - Courtesy of MMB[/caption]
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:
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.
Ovingham RWPS east elevation - Courtesy of MMB[/caption]
Mini CS & Company News
- Hydro-Logic® Aquator
Hydro-Logic® AquatorHydro International’s Data, Insights and Analysis (DIA) experts have given its Hydro-Logic® Aquator version XV a major upgrade.
Able to run complex models of real-world water resource supply networks and systems, the latest version of Hydro-Logic® Aquator is more flexible and includes new features and components. Based on regulatory guidelines, the updated software has implemented a technique that allows modellers to determine the availability of water supplies during an extreme drought event. This is the new ‘Enhanced Return Period Deployable Output’ analysis feature within the Analysis Control engine. It allows users to combine results from multiple scenarios for the estimation of a single return period deployable output (DO). It has been specially designed for the estimation of DO under stochastic scenarios. A new component has also been added which allows users to set models up to define trigger points for understanding the frequency with which demand saving restrictions may need to be imposed. The ‘Event Group’ component allows modellers to define a set of conditions that trigger an event. For example, one or more reservoirs reaching the drought alert curve. [caption id="attachment_16460" align="alignnone" width="1200"]
The blue line shows the reservoir drawing down through the brown, mint, yellow and purple trigger points. Each time a coloured line is crossed, an intervention/restriction is imposed in the model to reduce demand (and thus to protect limited supplies), with this information captured by the Event Group component for estimating the frequency of imposition.[/caption]
The Event Group can also be used in combination with the ‘Enhanced Return Period Deployable Output’ analysis feature.
Hydro-Logic® Aquator is ideal for modelling public water supplies, river catchments, lakes and reservoirs, hydropower systems, navigation and canal systems, and irrigation resource management.
To find out more about how Hydro-Logic® Aquator can help you manage your vital water supplies, visit: hydro-int.com/aquator.
