Headwall Installation Case Study:
Environment Agency Innovation Case Study 6 – Using the Permashutter System to replace the Great Stambridge No. 2 sluice on the Roach Estuary, Essex.
Essex Operations Delivery – Thameside and Technical Support Teams.
The tidal outfall at Great Stambridge No. 2 sluice, on the Roach Estuary, was in such poor condition there was a real possibility of it failing. This could have lead to flooding of Great Stambridge, near Rochford, Essex. The importance of replacing this sluice outfall was recognised and funding was secured for the 2010/11 financial year. Replacing the outfall would reduce the flood risk in this community, bring the sluice up to its required condition grade and allow the tidal system to pass a key KPI target.
With this in mind Essex Operations Delivery Technical Support and Thameside teams set to work to design a replacement outfall. An internal ‘Innovations Briefing*’ email caught the eye of Tom Wallace, Technical Support Team Member, as it featured a plastic sluice headwall system called Permashutter. This product was a hollow sluice headwall that was quick and easy to move into position and simply fitted to the end of the existing sluice pipe. Once in place it could be filled with concrete to provide a solid structure that is resistant to saline water and UV rays.
Using the Permashutter headwall system provided a significant saving, both in terms of cost and time, over installing a traditional pre-cast headwall or constructing a cast in-situ concrete structure. Both these traditional methods of replacing a sluice outfall are likely to require a construction period of several weeks, whereas the Permashutter headwall was fitted in less than three days, once the site had been prepared. Other advantages included the lightweight nature of the headwall, meaning no heavy lifting equipment was required, and the fact it came with its own hand railing system which bolted neatly to the headwall.
The sluice outfall was in a difficult to reach location, meaning the team had to construct a ditch crossing and build access ramps over the seawall, before they could reach the site to remove and rebuild the outfall. The lightweight nature of the HDPE structure and its manoeuvrability, helped to make installation on this difficult site easier. Another benefit, was that the Permashutter system only required relatively simple foundations. This enabled the team to reuse concrete from the demolition of the old headwall, which was crushed and recycled to provide the new base.
Installation was straight forward, the existing pipe was connected to the rear of the headwall using an extension pipe, and a new flap valve bolted straight to the face of new headwall using the pre located sockets. The headwall was then filled with concrete and the hand railing installed.
Peter Downes, Field Team Leader for the Thameside Operations Delivery Team, said: “My team have successfully and safely completed this project during cold and icy conditions. The Permashutter headwall solution provided an efficient and effective means of replacing a tidal outfall, using new technologies to provide cost and time savings, as well as significantly reducing health and safety risks when compared with installing traditional concrete headwalls. The lack of any heavy lifting is a real bonus as it means less plant and equipment is required on site. By successfully completing this project on time and to budget we have significantly reduced the risk of tidal flooding in this location”.
Summary of Benefits
- Greatly reduced installation times (from weeks to days) which means reduced plant and labour costs.
- Lightweight and easier to handle which reduces plant and equipment required.
- Health and Safety risks significantly reduced compared to traditional methods.
- Reduced carbon footprint compared to reinforced concrete.