J Murphy Group awarded Aarsleff the contract to install a temporary sheet piled cofferdam on the River Severn, as part of the £300 million Birmingham Resilience Project. The scheme is one of Severn Trent’s largest ever infrastructure projects, specifically to develop an alternative water supply for Birmingham to complement the Elan Valley Aqueduct (EVA). The Birmingham Resilience Project will create a new abstraction point and pumping station on the River Severn, at Lickhill Quarry near Stourport, to which water will then be pumped along a new 25km pipeline, through pipes with a 1.0m diameter, to the water treatment works in Birmingham. Aarsleff’s sheet piling works allowed a dry working area for J Murphy to construct the secant piling to the intake structure. Sheet piles will then be subsequently removed and the entire structure submerged. Water is to be taken from the River Severn which will provide a new source for the aqueduct, while maintenance takes place on the original EVA. When the resilience plan is in operation, the city of Birmingham will be drawing water from at least four sources, rather than just one

Early contractor engagement between J Murphy and Aarsleff identified significant technical deficiencies in the early engineering proposals for the temporary works cofferdam. Aarsleff’s proposed design was safer, quicker and cheaper with significantly less risk to the environment, their clients program and operatives. Aarsleff installed the bespoke temporary sheet piled cofferdam which comprised 154 (No.) AZ26-700 steel sheet piles, with an integral enhanced toe support system comprising of 53 (No.) H-Section piles. These were required due to the very shallow underlying bedrock, which only allowed for a limited sheet pile penetration. Access was provided by a temporary access works platform allowing safe working over water. Aarsleff employed a high frequency vibratory hammer and an impact hammer to drive its piles (using panel driving techniques) and employed a 110-tonne capacity mobile crane operating at a maximum 25m radius to unload and handle piles and hammers.

Senior technical estimator Ashley Carter said:

“This was a technically challenging scheme to be involved with requiring a lateral thinking approach to resolving the challenging problems. The prestigious project demonstrates the high level of experience and expertise Aarsleff’s sheet piling department can offer to its clients”.

Aside from delivering the project on time and within budget, Aarsleff were also able to reduce risk and environmental damage. Risk reduction through application of practical construction methodology, and Reduction in Environmental impact, (as the original scheme involved drilling underwater and spoil flushed directly into the watercourse). Steel sheet piles will also be recovered for re-use making this element of the scheme carbon neutral. Aarsleff Ground Engineering took the technical challenge and applied sense and reason to develop a practical, constructible and engineered solution, which benefitted all parties for the aforementioned Environmental, Commercial and Safety aspects. Meeting a tight construction programme at the front end of a long complex scheme gives Aarsleff great satisfaction.

Scope of works

• 154 (No.) AZ26 steel sheet piles (section modulus 2600cm³/m of max length 8.0m)
• Integral enhanced toe support system comprising of 53 (No.) 254/254/132 S355 JO H-Section piles
• Prefabricated box section connection detailing at 1.26m centre to centre

Construction period

• 21st July 2017 - 13th Sep 2017

Aarsleff Ground Engineering has completed the CFA and Sheet piling works for a major new scheme that will protect homes in Newark from sewer flooding and provide a reliable water supply for decades to come. In 2016, Nick Wallace from Severn Trent explained that £60 million would be spent to replace more than 12 miles of old pipes with new, larger ones.

Aarsleff worked on Queens Road to facilitate the replacement of a tunnel with a 1.5 metre diameter one. We employed an ABI TM13 /16SL with a Hydropress to pre-auger,and further installed 28 (No.) PU22- 12m long sheet piles.

Due to being in a residential and restricted area, Aarsleff employed a Silent Hydropress to drive in the sheet piles to reduce the vibration.

Scope of works

• CFA -  28 (No.) sheets

Equipment

• ABI TM13/16SL with Hydropress

Construction period

• 10th May 2017 - 25th May 2017

Severn Trent is investing £60 million to upgrade Newark’s sewerage and water system to help protect homes from sewer flooding. The scheme will provide a reliable water source for decades to come. In 2016, Nick Wallace from Severn Trent explained that more than 12 miles of old piles will be replaced with new, larger ones.

In May 2017, Aarsleff worked on Queens Road in Newark, to facilitate the replacement of a tunnel with one at 1.5m diameter. Here, 28 (No.) sheet piles were installed.

As part of the same scheme, and for the same client, Aarsleff was awarded the contract to construct a sheet piled cofferdam on Harcourt Street. Aarsleff installed 46 (No.) sacrificial steel sheet piles, with pile width 600mm and 12.0m in length. There was a retained height of 10.2m, forming the overall cofferdam. Again, Aarsleff’s work will facilitate the replacement of an old water course.

As Aarsleff was piling in the middle of a residential street, it drove the sheet piles using an ABI leader rig with pre-augering taking place in advance of main works where it utilised a Silent Hydro pile press to reduce the noise and vibration. A 50-tonne capacity crawler crane was employed, operating at a maximum 6m radius to unload and handle piles and hammer.

Aarsleff’s Senior Technical Estimator Ashley Carter said: “It is a great endorsement of Aarsleff’s work that we have been awarded our second contract for the same scheme in Newark, just 7 months later. There are around 400 homes in Newark that are currently at risk of flooding, demonstrating just how important sheet piling projects like this are in future-proofing our infrastructure and communities."

Scope of works

• 46 (No.) steel sheet piles
• Pre-auger

Equipment

• ABI rig
• Silent hydro pile press

Contractor

• BNM Alliance (an nmcn PLC and Barhale joint venture)

Construction period

• 11th December 2017 - 20th February 2018

The BNM Alliance (a joint venture between Barhale and North Midland Construction) awarded Aarsleff Ground Engineering the contract to design, supply and install a soil nailed slope to allow, with associated works, the launching of a tunnel boring machine for the Severn Trent Elan Valley Aqueduct Rehabilitation project in Wales.

The original aqueduct was built between 1893 and 1904. Fast forward over 100 years and the aqueduct still provides drinking water from the Elan Valley to Severn Trent’s customers in Birmingham. The aqueduct transports high quality water entirely by gravity. Having supplied water for over 100 years, the aqueduct is beginning to tire in three key locations and offline replacements are necessary.

8 (No.) test nails were installed on the 17th July. These were tested to destruction to confirm the design prior to production works starting. With its Klemm 806 rig, Aarsleff will then installed 670 (No.) 100mm diameter fully galvanised R32 -280 self-drilling soil nails of 6-16m in length.

In addition to the soil nails, approximately 670 (No.) head plate and nut were supplied and fixed. The soil nailed wall has an estimated 1250m² area to which Aarsleff has supplied and fixed a steel mesh and geotextile facing. Aarsleff were on site from 24th July with completion 15th September 2017. Aarsleff showcased its previous work in soil nail projects of similar size to the main contractor before winning the contract to demonstrate its technical capabilities and expertise whilst simultaneously, assuring the client of cost, time and quality. Aarsleff Ground Engineering has sought value engineering primarily through optimisation of the soil nail layout and facing mesh.

The self-drilling soil nails were procured from Barnsley-based Minova and possess a hollow bar, which is used for drilling ether with water flush, air flush or cement grout flush and are extended by using couplers. The standard couplers have a design which ensures end-to-end bearing of the hollow bars to transfer percussive energy from the top hammer to the drill bit whilst a sealing ring in the centre stop, minimised flush spillage during drilling. The soil nails also possesses a sacrificial drill bit.

The rig we employed is designed for the use of powerful double head drilling units, hydrualic drifters or rotary heads. It can also be equipped with drill masts either with feed gear or cylinder feed systems, with the option of fitting lattice mast extensions, the modularity of which, allows the adaption of a variety of options, which makes the drill rig ideal for anchoring, micro piling, jet grouting and even geothermal drilling. After completion, two percent of all working nails will be ‘Acceptance’ tested to validate the design and provide confidence as to the quality of the installation.

Scope of works

• 670 (No.) 100mm soil nails
• 670 (No.) head plate and nut
• 1250m² steel mesh and geotextile facing

Construction period

• 17th July 2017 - 15th September 2017