MGF Ltd
We have a vast experience in delivering shoring solutions to the water and utilities sectors including a wide range of shoring and safety equipment, trench sheets and sheet piles as well as providing bankside retention solutions on UK canals, riverbanks, and marinas.
Our bespoke waler and tie back system is a versatile solution that can be used in a range of configurations to suit different ground conditions, we also hold an extensive range of overlapping and interlocking trench sheets and sheet piles with galvanised or sealant options.
Headquartered in Ashton in Makerfield, near Wigan, we are committed to providing our customers with complete engineered solutions and promoting current best practice for all types of excavation works.
The company now employs over 400 people with a proud record of sponsoring and employing local engineering graduates and has 14 different depots around the UK from Dartford to West Lothian, Scotland. We also have an in-house transport fleet of over 60 vehicles giving us the flexibility to meet our customers needs.
With a vast product range from UniShore® systems to gantries and lifting beams, the hire and sale of our products is fully supported by our team of qualified engineers, experienced representatives, hire desk and operational staff. Providing national coverage, our depots hold extensive fleet stock, modern handling equipment and dedicated transport ensuring operational efficiency.
The hire and sale of our products is fully supported by our team of qualified engineers, experienced representatives, hire desk and operational staff.
Our values of commitment, innovation, and sustainability have guided us well in the last 35 years and will take us in to the future along with our mission which is to be the most trusted supplier of excavation safety solutions.
For more information on our products and services visit our website mgf.ltd.uk
Photogallery
Press Releases & Case Studies
MGF celebrates turning 40!
Bridgwater Water Supply
Hyndburn WTW
Hurleston WTW
Walton le Dale WwTW
Vyrnwy Large Diameter Trunk Main
Sewer Replacement in Shallow Trench
Hornsey WTW
MGF is now open in Scotland!
MGF Launch New Lifting Equipment Division
Alleviating Flooding at Beaumaris Castle
Derby Hydro Power House
Installation of New Foul Pumping Station in Jersey
Major Sewer Upgrades in New Zealand
Major Supply Grid Upgrades, Somerset
River Humber Pipeline Replacement

Brook Street (Dawlish) CSO (2023)

Durleigh WTC (2023)

Marhamchurch SPS (2023)

Meadow Road Stormwater Tank (2023)

Niagara Weir Stabilisation & Fish Pass (2023)

Burnley WwTW Catchment Strategy (2022)

Chippenham Gateway Sewer (2022)

Fontburn WTW (2022)

Johnson Street Storm Overflow Screening Project (2022)

Plas Uchaf Reservoir (2022)
MGF celebrates turning 40!

Reaching this milestone is significant for any business and one that we are immensely grateful to have achieved. It wouldn’t have been possible without the support of our loyal customers and the dedication of our staff, we can’t thank you all enough.
MGF has grown from a very small business into a 400 strong team based across 14 locations, with a multitude of skills and experience. Our founder and Chairman, Michael O’Hara who set up the company in 1981 says “MGF started from very humble beginnings. We imported one load of trench boxes from a German manufacturer, whose name and logo we adopted. We hired them out using a corner of a builder’s yard in Rochdale. Now, forty years later we have ten trading centres covering the UK in our core business, and a major manufacturing and distribution centre at Lockett Road, Ashton in Makerfield.”
After a few years of trading at our first Astley depot, the business expanded, moving into the Midlands, Durham and then Bristol. With the expansion, came a greater demand for temporary works designs (justified by calculations) and so too came the development of the engineering department, which now stands at a 39 strong team of highly qualified team of civil, mechanical and structural engineers.

MGF is celebrating 40 years!
As the business grew, we moved into Yorkshire, London and the South East and expanded further into East Anglia and Exeter before moving up to Scotland early last year.
A key aspect to the success of the business over the 40 years has been the ongoing development of the in-house manufacturing and transport capability, allowing us the logistical control and freedom to innovate required to facilitate increasingly complex customer requirements whilst still providing a quality service.
Our latest development into the area of structural support, UniShore®, has been a tremendous success and has seen two depots opening within their first year of trading – at Warrington and Tring. Branching into this industry has been a natural progression for our business. We have designed and manufactured the equipment in-house and in consultation with customers and experienced market specialists – allowing us to deliver a product that minimises component weight whilst giving market leading performance. We have plenty more plans for growth and innovation ahead too.

MGF is celebrating 40 years!
Despite the growth, MGF has maintained a family business ethos – based on the same values that Michael started with 40 years ago – commitment to excellent customer service, innovation through the reiterative pursuit of betterment and long-term sustainability for the business.
Join us in celebrating and catching up about the memories.
Submit your photos and anecdotes to [email protected]
Bridgwater Water Supply

Excavation works began in early 2017 at the Dancing Hill Reservoir site as part of a £6 million project to upgrade the water supply grid for Bridgwater and the surrounding areas. Major upgrades are required due to large-scale developments in the area.
The project has four connected cofferdams in place allowing safe working space to combine new pipeworks to the main reservoir tank. Multiple back-to-back 203UC tank braces with special alignment of bracing has been key in the design, combined with KKD 600 sheets to secure the trench. Several Lightweight DavitSafe systems allow safe access into the 10-metre-deep cofferdams.
The design was particularly challenging due to the complicated nature of the ground surrounding the reservoir tank. A sizeable berm was built on the ground profile around Cofferdam 4 to ensure a safe and stable excavation.
This exaction also had to accept other loadings from Cofferdams 1, 2 and 3. Multiple 203UC tank brace frames were used due to the strict lift plan limit of 1 tonne. Larger or heavier brace systems could risk the collapse of existing foundations.
Vibration pile driving was not permitted due to the detrimental effect it could have on the high-pressure water mains that supplies customers. There was also a HV cable running through the site that had to be avoided. The exact location of other services created additional challenges and ongoing surveys had to be monitored throughout the duration of works.
“Once these works are completed then the new upgraded line will be tested and commissioned and will link up with another reservoir. It will ensure the reservoir will be able to cope with the increased demand that is required in the coming years ahead and allow us to move water around our water supply network.”
Paul Chedzoy, Construction Manager, Wessex Water
Hyndburn WTW

In 2003 the HMB Alliance were upgrading Hyndburn WTW at Great Harwood, as part of a £10 million water treatment project. This required a 14.0m long, 3.0m wide, 10.0m deep trench to carry large pipe runs from the main settlement tank.
Aside from the high loadings generated by the fairly poor ground conditions (granular fill with a mid-level water table) and the huge depth, the excavation had another problem – it took a turn through 45° at the centre.
HMB Alliance had come up with a sheet pile design utilising Larssen piles and had intended to design and install bespoke welded steel frames to accommodate the bend in the trench. However, the cost implications and anticipated difficulty of installation of a welded frame – particularly on such a short time scale – urged HMB to seek a better option.
MGF used HMB’s frame loads to design ‘back to back’ bays of hydraulic Heavy Duty Tank Brace. The pinned joints at the corners meant that the usual internal angle of 90° for rectangular frames could be articulated and increased to 112.5° thus accommodating the overall bend of 45°. As the frame loads at lower levels were very high, the lower frames were twinned up, but there was no need for any additional cross strutting and the customer had almost 7.5m of clear working room in the pit.
The sheet piles were pre-driven to full depth by a specialist piling contractor. Excavation commenced to the underside of the top frame, approximately 1.0m below commencing level.
The first ‘back to back’ frames were installed at approximately 0.7m below commencing level. Excavation continued further to the next level, where the middle ‘twin’ frame was installed.
The same sequence was repeated for the bottom ‘twin frame’. Excavation was complete at 10.0m deep and the pipework commenced.
Once all pipework was complete and satisfactory, the excavation was backfilled, gradually removing the frames one at a time, from the bottom upwards.
The equipment was easy to install and, due to its available adjustment, it allowed for slight deviations in actual on site dimensions compared with those designed. The solution was much safer and more cost effective than a welded frame option and also greatly reduced the risk and magnitude of any deflections or ground movement. Working space was kept to a maximum, with the only obstructions being the return legs of Heavy Duty Tank Brace cutting across the bend.
Hurleston WTW

In 2003, Balfour Beatty Construction were in the process of upgrading Hurleston WTW, located just north of Nantwich off the A51, as part of a £6 million design & build contract. A major part of the contract was the construction of a new Clean Backwash/Interstage Pump/Sump Tank, alongside an existing 2-storey Control Building.
This required the installation of a temporary cofferdam, 25.2m x 14.4m x 5.0m deep. The soil profile was predominantly medium dense sand with a high water table, which, combined with the close proximity of the Control Building (1.75m from the face of the excavation) created extremely high soil pressures.
The decision was made to reduce the water table to below formation level using a well pointing system in order to alleviate some of the forces acting on the cofferdam. MGF designed a temporary cofferdam with a nominal sheet pile toe-in of 1.0m and two levels of frame. The frames were designed to leave as much clear working space as possible, whilst also minimising deflection and movement of the supported soil to protect the integrity of the Control Building. For ease of construction, the upper frame was positioned above commencing level and the design allowed for the lower frame to be removed after the basic slab was cast, thus giving the customer a completely unobstructed working area to construct the RC Tank and Roof.
Prior to any excavation, 7.0m long L601 Sheet piles were pre-driven driven 6.0m by Dew Construction using a leader rig.
The upper frame was installed at 0.3m above commencing level. The frame consisted of MGF Heavy Duty Tank Brace / MGF Titan Brace with Mechanical 54Te Superstruts across the width.
Once the frame was in position, excavation continued to the underside of the next frame level (approx. 3.7m below existing ground level) in preparation for the next stage.
The lower frame was then installed at 3.4m below commencing level. The frame consisted of MGF Heavy Duty Tank Brace with 5184Te Mechanical Superstruts (as cross struts) and Twin Mechanical 54Te Knee Braces in all four corners.
The frame was supplied with shear stop already welded in place to accommodate the knee braces. Excavation then continued down to formation level, 5.0m below existing ground. The basic slab was poured and the construction the permanent works commenced.
As the slab now took loading from the temporary works, the lower frame could be removed to provide even more clear working room. Once construction of the RC Tank was complete, the rest of the excavation was gradually backfilled and remainder of the shoring equipment removed.
The MGF scheme enabled the customer to complete the job very quickly with the temporary works being installed in little over 2 weeks. The vast working room provided and quality of service meant that progression with the permanent structure was unhindered.
The RC Tank and roof slab were successfully completed for the required water test to be carried out in time for the deadline of an upcoming shutdown period.
Walton le Dale WwTW

The Walton le Dale Waste Water Treatment Works was a large and challenging site with multiple excavations which required a range of safety solutions. Throughout the scheme MGF delivered:
- A dedicated design engineer providing; comprehensive technical support, temporary works design coordination and project management.
- Innovative, bespoke excavation safety solutions.
- On site shoring and safety tuition.
United Utilities commissioned a major upgrade to the existing WwTW.
The upgrade to the works was approved a £23.5m budget. Due to the large scale of the site and the complexity of the construction and commissioning sequence it was recognised that the scheme would prove one of the most demanding in the AMP5 programme.
The site itself delivered some challenges – an area of land to the south east was designated as an ancient woodland and site of biological interest with further fields south west of the site said to be of biodiverse value. The site was partly located on a flood plain with high water tables and the risk of flooding had to be considered from the out-set of planning.
With multiple, deep excavations taking place on the site KMI Plus identified the need for extensive shoring solutions in order to create a safe working environment. Based on previous experience with the contractor and the ability to provide complete engineering solutions, contract management and temporary works coordination, MGF were appointed to provide excavation safety solutions.
On the site there were a number of small, shallow, ductile and concrete pipe excavations which required simple shoring solutions such as manhole boxes and trench boxes. Other excavations were larger and deeper and required precision planning and innovative solutions.
The three most notable excavations and the equipment MGF delivered to support these were as follows:
- Humus Tank Excavation: 30 diameter and 1.8m deep. MGF provided a bespoke, circular, cantilevered, Larsen sheet piled cofferdam.
- Cross Over Weir Excavation: 18m x 10m and 4.5m deep. MGF provided MGF 400 Series Struts, MGF 406 UC Braces and trench sheets. The shoring of this excavation was complex with changing requirements which MGF were able to accommodate.
- Outfall Pumping Station Excavation: 17m diameter and 8m deep. MGF provided bespoke designed, octagonal shaped MGF 406 UC Brace hydraulic systems complete with inter-locking Larsen sheet piles to help minimise groundwater ingress. The octagonal design was developed to accommodate existing structures on site and keep access roads open. The outfall pumping station was positioned close to another structure and extra care was taken to ensure that neither excavation affected the other.
“In addition to the shoring equipment, MGF provided a dedicated Project Manager, Antony Birchall and Temporary Works Engineer, Emma Hewitt to support the project throughout the duration of the temporary works. They gave us the support we needed to create a safe working environment on such a large and complex site. Regular contact and consultation of the temporary works designs, combined with their knowledge, experience and understanding of our requirements and the site, enabled us to safely deliver the shoring elements of this demanding project at Walton Le Dale Waste Water Treatment Works.”
Desmond Donnelly, Project Manager, KMI Plus
MGF provided KMI Plus with made to measure systems that were easy to install and remove whilst providing a safe working environment and optimum working space. The solutions allowed site access to remain open and reduced the levels and flows of ingress water from the flood plains.
MGF conducted site checks and soil inspections and offered on site training in shoring and safety awareness. The designation of a single design engineer to the scheme ensured that the contractors temporary works design requirements were fulfilled.
Vyrnwy Large Diameter Trunk Main

The Vyrnwy Large Diameter Trunk Main (LDTM) consists of three parallel pipelines with a total combined length of around 240km. These large mains carry up to 210 million litres of water a day from, Lake Vyrnwy, to 900,000 people in Cheshire and Merseyside.
Over the project, MGF teams across multiple locations have demonstrated the ‘one team’ service excellence to deliver the temporary works design for two phases totalling over 100 excavations spanning from Oswestry to Malpas. Over 2000 KKD trench sheets were supported by MGF modular frames.
Our Technical Sales and Engineering Teams provided daily project support for United Utilities which all combined to successfully deliver on this technical challenging project.
View our animated video guide developed for Balfour Beatty on the Vyrnwy project to demonstrate the safe installation of MGF excavation support equipment using the push and dig technique.
Sewer Replacement in Shallow Trench

R&M Utility and Civil Engineering Services were contracted by Balfour Beatty to replace a 140m sewer run in Exmouth, Devon. The works required a full road closure and the route was highly congested with services. R&M were having difficulty identifying a shoring solution that could provide a safe working environment for operatives needing to enter the excavation. Traditional shoring methods were deemed inappropriate as they were not flexible enough to work around the multitude of crossing services.
The 140m long scheme was divided into sections, the first being the excavation of a 2m deep, 1.1m wide trench in the most congested section. MGF provided 20 sets of 500mm GRP Vertishore rails from the GRiPSHORE range along with hydraulic struts, bucket pump and required ancillaries together with a variety of larger boards and walers.
Operatives were able to reduce safety risk without compromising cost or time by using the GRP Vertishore rails. The lightweight shoring enabled them to progress the works safely where a traditional shoring system would have further congested the working area.
Through the lightweight nature of the GRP components, operatives sped up the install process by handling and installing them manually without reliance on an excavator.
They optimised the working space in which to thread the 600mm diameter plastic pipe which enabled them to focus on the sewer replacements works, reducing the time the road was closed causing less disruption to the public.
Hornsey WTW

As part of their AMP4 programme Costain asked MGF to design and supply numerous temporary works solutions for seven schemes on a large WTW improvement scheme. The largest and perhaps most challenging schemes on the site was the Lamella Building excavation. The 7.4m deep excavation measured 58.3m x 17.4m and was adjacent to a river and reservoir, therefore is was essential that ground movement was kept to a minimum and had to be monitored continuously throughout the works.
MGF provided a solution comprising two frames of MGF 406UC Brace complete with MGF 1200kN and 2500kN Hydraulic Struts, combined with MGF 400 Series Strut Extensions configured as cross struts and knee braces to support a sheet piled wall cofferdam. Additional struts were required in the lower frame where a greater depth was required locally.
Through careful co-ordination with Costain Engineering Services, Thames Water and the piling subcontractors throughout the project, MGF’s excavation support system successfully managed ground movement during the works. Hornsey represented the largest single site supply of equipment for MGF in 2007.
MGF is now open in Scotland!

Ideally located in the central belt, MGF’s depot is able to support the growing needs of the northern UK construction industry by offering national service to Scotland with the support of the other 12 MGF locations.
Cairns Gibson, Regional Manager for Scotland and North East England commented:
“It’s great to now have a full sales team in Livingston, supported by our Regional Engineer. We have been servicing the country for 10 months now to great success and we hope that the team continues to do MGF justice in Scotland.”

MGF Scotland
Based in West Lothian – Livingston, the depot covers 3.5 acres of Houstoun Industrial Estate and will be our main supply to our customers across Scotland.
The depot is now open to trade and has been fully operational since January 2020.
Regional Director, Kevin Clarke commented,
“We have been serving Scotland through our North East – Durham depot for 23 years, but I’m thrilled that we have opened a depot in Scotland as it will allow us to improve and strengthen our offering to our Scottish customers on a regional basis.”
Thank you and congratulations to all those involved in making this happen, and here’s to MGF Scotland!
If you have any future or current excavation project in Scotland, please get in touch.

MGF Scotland
MGF Launch New Lifting Equipment Division

Complementing our existing range of safety and handling equipment, our expansion into the Lifting industry brings new products and services to our offering, allowing us to further benefit our existing customers as well as reaching new businesses and industries.
“In line with our core values of commitment, innovation and sustainability, we are diversifying our product range to supply our customers with a full product solution. Enabling a one stop-shop for all your lifting, safety, shoring and structural support needs on site – ultimately reducing time and suppliers to make the job as easy as possible.” – Chris Whitworth, Operations Manager.
Starting with an initial phase of products featuring slings, loose lifting equipment, hoisting, blocks, winches and crane site equipment; the division will continue to expand to suit the demand of the industry, regularly releasing new products and increasing our coverage to service the nation through our regional teams.
Alongside the new lifting products, we have also introduced our new testing and inspection service to fulfil the legal requirement that all lifting, safety and other work equipment can be inspected on a periodic basis by a qualified person. To facilitate our testing and inspection service, our team of fully qualified technicians are available to visit customers sites or depots.
To facilitate this offering, MGF are full members of the Lifting Equipment Engineers Association (LEEA) – providing our customers with the comfort and knowledge that our products and services conform to the industry standards. With LEEA qualified engineers currently located at our Astley, Rugeley and Durham Depots, we are working to have all regions supported to offer our customers on-site inspections nationwide.
Supported by our existing Technical Sales, Hire Desk and Operational teams, the Lifting department will be headed up by Mark Smith and is the latest development of the MGF Group.
Mark has worked within the lifting industry for 20 years and has a further 10 years’ experience with plant hire. Mark has joined MGF as National Lifting Manager and brings a wealth of knowledge and expertise to enable the business’ success.
Mark is supported by a team of specialist technicians, qualified with LEEA, at our Astley, Rugeley and Durham depots as well as a dedicated engineer and sales team.
Following 6 months of behind-the-scenes preparation, Mark and the team are ready to start servicing the UK with MGF’s lifting equipment and accessories. For more information on the lifting division and to download a copy of the new brochure please visit www.mgf.co.uk.
Alleviating Flooding at Beaumaris Castle

The project required the contractor to excavate within 25m of Beaumaris Castle – a UNESCO World Heritage site and one of the best examples of 13th and 14th century architecture in Europe attracting over 100,000 visitors last year.
Faced with the challenge of installing 600m of 1.5m diameter polypipe in 6m sections between existing manholes, John Kelly Construction spent time researching the products available on the market, before finding that MGF’s High Clearance Trench Boxes were ideal for the job.

The 7m x 2.9m wide High Clearance Trench Boxes coupled with Top Boxes saved time and money to the contractor when compared to sheets and frames. The strength of the box allows suitability and capability of going to 5m depth and having high clearance struts on both ends of the box allows access at both sides – ideal for installing larger diameter pipes.

Paul Cowen, Technical Sales for MGF commented:
“Beaumaris’ most recent floods in 2017 was the catalyst that something needed to be done regarding the surface water drainage system. MGF became involved to supply the excavation support equipment to alleviate the threat of flooding to protect the natural beauty and tourism trade in the area”.
MGF’s stock logistics team confirmed availability of the kit at our Dartford depot and coordinated transfer to the Astley depot before delivery to site with three 40ft articulated vehicles and two 15t wagons to ensure the order was met.

John Kelly, Managing Director of John Kelly Construction, stated:
"I was very impressed with MGF as a company as they were very quick to respond to our queries, provided designs and all equipment ordered arrived on site with no delays."
Sector: Water & Utilities
Client: Isle of Anglesey County Council
Contractor: John Kelly Construction
MGF depot: North West - Astley
Products hired: High clearance trench box, top boxes & titan manhole box
Derby Hydro Power House

The purpose of the job was to design and supply temporary and permanent support for a hydro power house and turbine chamber (plus associated inlet channel and tailrace) constructed at the side of an existing weir on the banks of the River Derwent in the centre of Derby.
The design incorporated a single level of modular 406UC Hydraulic Brace system in conjunction with Larssen piles up to 10m in length, toed in mudstone, covering a perimeter of over 150m.
MGF's design allowed early removal of the brace by using a permanent concrete base slab as a low propped cantilever. The design had to take into consideration the complicated construction sequence; and the location of a large crane during installation and removal of the river piles.
During the project Balfour Beatty and MGF collaborated to develop the Stairsafe system (the UK's first temporary steel stair system designed specifically for excavations). The system proved a great success in providing rapid and safe access into excavations leading to greater site productivity. The system is now being used throughout the UK on excavations up to 6.5m in depth.

From early in the tender process MGF have been heavily involved with Balfour Beatty to develop an innovative, cost effective and highly complicated cofferdam design; which helped make Balfour Beatty's tender attractive to the client, Derby City Council.
Michael Rummens, Balfour Beatty Site Agent, commented:
"MGF were brought in at tender stage to assist in the value engineering of the cofferdam and support frames. Upon contract award, MGF's technical team were extremely proactive in producing a workable design in line with the projects requirements. The professional, amenable and expedient attitude continued throughout the process from design, technical support, plant hire and delivery and site assistance."
Sector: Energy & Waste
Client: Derby County Council
Contractor: Balfour Beatty
Consulting Engineer: WS Atkins
MGF Depot: Midlands - Rugeley
Product hired: 406UC Hydraulic Brace, 10M Larssen Piles
Installation of New Foul Pumping Station in Jersey

A support system was required for the installation of a new foul pumping chamber tank and customers D.B Cummins (Jersey) Ltd called for MGF’s assistance to meet a tight construction programme. The report from the sub-contractor, D.B.Cummins Ltd, detailed a 15m x 12m x 3m deep excavation with groundwater at 2m, with poor clay conditions throughout – requiring engineering designs and advice on the most efficient and safe support system.
Managing Director, Pierce Cummins, praised MGF’s efforts here noting:
“... the technical design and information was very helpful to present to our client. I couldn’t have asked for better customer service. Chris and his team looked after us from initial design all the way through to shipping equipment back to the UK."
Chris Whitworth, MGF’s International Sales Manager added:
“... it was important to Pierce to ensure that we met their construction programme. The design was completed and approved by their external consultant and equipment was on site, on time, as assured.”
Equipment was pre-assembled at MGF’s Tring Depot – including 254UC, 203UC braces complete with a 60T cross strut – and delivered to Southampton docks for shipping direct to site.
- Sector: Exports
- Contractor: DB Cummins (Ltd)
- MGF Depot: South East - Tring
- Product hired: 254UC, 203UC with cross struts
Major Sewer Upgrades in New Zealand

MGF have supplied specialist hire company Trench Shoring New Zealand (TSNZ) for the last 8 years during an excellent period of growth. During this time, TSNZ have expanded their fleet and added a variety of MGF equipment, including hydraulic brace systems and the breakthrough range GRiPSHORE®.
TSNZ proposed a temporary works solution for major sewer upgrades in Auckland, New Zealand. General Manager, Frank Swanberg identified hydraulic brace systems as the most effective solution for tank installations. The contractor required an open pit to work on stormwater and sewer diversion upgrades as part of the Waterview Dual 3 Lane Tunnel Project.
TSNZ have found they are recommending hydraulic systems more frequently to local clients due to ease of installation, providing stronger working environments and overall reduction in time.
Chris Whitworth, International Sales Manager at MGF, stated:
"We delivered a 203 series brace system, 200 series struts, 60-tonne cross struts and multiple extensions to suit the specific dimensions of the cofferdam."

Sector: Exports
Contractor: Trench Shoring New Zealand (TSNZ)
Products hired: 203, 200, Cross-Struts & Extensions
Major Supply Grid Upgrades, Somerset

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

Dancing Hill - Courtesy of MGF Ltd
River Humber Pipeline Replacement

National Grid, working with North Lincolnshire Council and East Riding of Yorkshire Council, developed a plan to construct a tunnel under the River Humber to replace the existing pipeline. The three-year project will provide National Grid with a 5km long, 3.65m diameter tunnel bored 30m under the river bed. A single 1200mm concrete-weight coated steel pipe will be inserted into the tunnel in a single string, making it the longest gas pipeline insertion of this kind in the world.
The River Humber pipeline is an important pipeline - connecting an import location for gas at Easington, on the East Yorkshire coast, to the national network – delivering gas supplies to millions of households throughout the UK.
The original pipeline, Feeder 9, is buried in a cut-and-cover trench under the river bed where tidal patterns have eroded the river bed uncovering the pipeline. Remedial work was undertaken to provide a short-term solution while a long-term solution was developed.
Working with the joint venture consisting of Skanska, PORR Bau GmbH and A.Hak, MGF’s in-house design engineers developed and manufactured a bespoke temporary works propping solution for the tunnel boring machine (TBM) launch pit excavation.
The contractor required the design to allow for the following key factors:
- Use of a load monitoring system.
- Design of bespoke connection details to sheet piles or capping beams where steel walers were not used.
- Design of bespoke 'headwall' beam to eliminate knee bracing at the end of the tunnel portal to increase working space.
- Design of prop connections to withstand 10 tonne accidental load.
The excavation was 209m long by 8m at its widest point, ramping from ground level to 11m depth. The deepest section, including the portal wall, was constructed with secant piles with PU32 sheet piles forming the remaining walls. The propping solution consisted of 406UC hydraulic braces with 2500kN 400 series struts. To accommodate the TBM installation the longer, high-level props were twinned with spans of up to 11m between pairs of props. The headwall beam was primarily required for ease of excavation as knee braces are notoriously hard to navigate around with an excavator. This ensured that the temporary works was sufficiently robust whilst maintaining an accessible working space; a technical aspect which separated us from the competition and was completed to Eurocodes.
Additionally, there were concerns that accidental impact of the struts by plant could cause failure of the system, particularly during the TBM lift, as there was only 200mm space between the paired props. To mitigate this risk MGF designed bespoke connections to the capping beam, wailing beams and sheet piles to withstand an impact of 10-tonnes.
MGF used its in-house load monitoring system which actively measured the load and temperature of each individual prop, waler axial loads and bending and axil load in the headwall beam. The data collected during the monitoring regime will have a significant impact on creating efficiencies in the design of hydraulic strutting and support of narrow closed trenches going forward.
Stephen Barker, Major Projects Engineer said:
"This project was particularly challenging due to the multiple levels of framing, high loads and strict robustness criteria. As the design was required to survive the loss or damage of a prop and withstand a 10-tonne impact load more props were required, however we had to balance this with ensuring that the contractor had sufficient space to excavate efficiently. The design of the headwall beam contributed significantly to this as it removed the requirement of having knee bracing at the end of the excavation, opening space and making bulk excavation easier."
The project will take approximately two years to complete and top level of the temporary works will stay in place during this time. In an adjoining field, the pipework is being welded in top strings in readiness for insertion. The tunnelling is currently underway with a slurry TBM.