Supply Chain - Project Planning & Surveying - Hydraulic Analysis
6
results
Related Content
Case Studies
Search
- Water Companies
- Case Studies
- Innovations
- Supply Chain
- Accreditations
- Asset Maintenance & Rehabilitation
- Construction Plant & Equipment
- Contractors
- Control & Automation
- Designers
- Flood Alleviation
- Health & Safety
- Mapping & Modelling
- Programme Management
- Project Planning & Surveying
- Recruitment
- Renewables & Energy Management
- Reservoirs & Storage
- River Work
- Security
- Sewerage
- Site Preparation
- Smart Water
- Stormwater Storage
- Wastewater Pumping Stations
- Wastewater Treatment
- Water Mains
- Water Pumping Stations
- Water Treatment
- Digital Flipbooks
- Jobs Board
- Mini Case Studies
- Company News
- Login
(left) The preferred option and (right) flooding on St Augustines Road - Courtesy of Galliford Try[/caption]
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.
(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.
Service detection - Courtesy of Galliford Try[/caption]
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 Piling 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.
900mm Ridgistorm pipe from Polypipe Civils ready for installation - Courtesy of Galliford Try[/caption]
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:
(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:
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.
Solar panel display - Courtesy of MMB[/caption]
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]
DN700 siphon pipework during installation - Courtesy of MMB[/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]