Project overview
The Avonmouth Water Treatment Works project involves the construction of four Primary Settlement Tanks as part of the facility’s wider expansion. Each tank has a 41.6m radius and 3.5m-high walls, forming a major element of the site’s future treatment capacity.
Key info
- 4 Primary Settlement Tanks
- 41.6m radius per tank
- 3.5m-high reinforced concrete walls
- 4 bases completed
- Specialist travelling formwork
- 2 tanks complete, 2 progressing
Carney Construction delivered the tank bases and reinforced concrete wall structures using a specialist travelling formwork system. This enabled the main stem wall, launder channel and launder channel wall to be constructed simultaneously, improving sequencing, dimensional control and finish quality across the structures.
Delivery
Tank construction
The works comprise four large Primary Settlement Tanks, each requiring the delivery of a substantial reinforced concrete base, perimeter stem wall and integrated launder channel arrangement.
All four bases were completed to a high standard, providing the foundation for the subsequent wall construction. At the time of the update, two tanks had been completed, with work progressing on the remaining two.
Travelling formwork
A bespoke travelling formwork system, fabricated by Special Formwork, was used to deliver the circular tank walls and launder structures.
The system allowed three key elements to be constructed within the same sequence:
- Main stem wall
- Launder channel
- Launder channel wall
Combining these elements reduced the need for separate formwork operations and helped maintain consistent tolerances and finishes around the full tank perimeter.
Quality and technical delivery
The circular geometry and scale of the tanks required careful control of alignment, levels and concrete finish throughout each construction cycle.
The travelling formwork approach supported repeatable pours and consistent dimensional accuracy, while reducing interfaces between separate construction stages. This contributed to a high-quality finish across the completed tank structures.
Productivity and programme
The project has progressed through a phased construction sequence across all four tanks. Completing the bases first allowed wall construction to move forward systematically, with the travelling formwork transferred and reused as each section advanced.
Two tanks have now been completed, while the remaining two are under construction. The delivery approach has allowed the team to maintain quality and consistency across multiple structures of the same scale and design.
Conclusion and summary
The Avonmouth Primary Settlement Tanks demonstrate Carney Construction’s ability to deliver large-scale circular reinforced concrete structures using specialist formwork and controlled construction sequencing.
The use of travelling formwork has improved efficiency while maintaining the tolerances and finish required across the stem walls and launder structures. With all four bases complete and two tanks delivered, the remaining works are continuing across the final structures.
