Weirside Mill
Bradford on Avon, Wiltshire
In 2015, we won a national award for Project of the Year (highly commended) from the Property Care Association for the Weirside Mill flood prevention and remediation project.
The people of Bradford on Avon in West Wiltshire are used to the River Avon (which runs through the town) bursting its banks. The water usually rises and spills onto the local floodplain with minimal disruption.
But on Christmas Eve 2013 the town was brought to a standstill when the main bridge flooded. And by the end of the wettest January on record, the Avon had burst its banks 10 times in six weeks.
During this time the workshop area of Weirside Mill flooded badly and at its worst the water levels rose to 2 metres, leaving all equipment and workbenches floating in the flood water causing considerable damage. To make matters worse the owners, Mr & Mrs Johnston, were away on holiday and therefore did not see or hear about the effects of the flooding until it was too late.
What we
Did
Within four hours of the flood beginning, water levels inside the workshop were measuring two metres high and around 80,000 litres of water were passing through the building each hour.We were on site within 24 hours and after an inspection we decided to help clear the water out. We needed to install two pumps, plus two battery packs and installed a drainage channel and two gullies.
The Technical
Version
Our brief was to design a flood remediation system that would help combat large amounts of water ingress during flooding whilst keeping the original natural stone walls and concrete floor exposed.
Once the flooding had started it had taken approximately four hours for the water to reach the highest point of 2m within the workshop and we would therefore work to this being the maximum possible height due to the river reaching a record height. The following calculations were used to establish rate of water ingress:
| WORKSHOP DIMENSIONS | 20m x 8m | 160m² |
| VOL. OF FLOOD WATER | 160m² x 2m | 320,000 litres |
| TIME TAKEN TO FULLY FLOOD | 4 hours | |
| INGRESS PER HOUR | 320,000 litres / 4 hours | 80,000 litres / hour 1,333 litres / min |
We therefore needed a solution to prevent the potentially huge amounts of water entering the building and we turned to our extensive background in Type C structural waterproofing used successfully for many years to waterproof basements and cellars for the answer. The basic principle we adopted for keeping the area free from flooding would be to evacuate the water faster than the ingress via a drainage system controlled by mechanical means i.e. pumping stations, until such time as the water level receded by natural means i.e. existing land drainage and reduction in the high river levels.
We looked through the various arsenal of pumping equipment available to us and after careful consideration chose the NP750 range due to their impressive discharge rate:
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From the above we established that 4 x NP750’s would give us the required discharge rate, with an additional 6,400.00 litres per hour (should this be needed). We then required sump chambers to house the pumping equipment and we selected the Titan Pro, which is fully compatible with 2 x NP750 pumps and also allows the benefit of a large diameter of discharge pipework (63mm) per pump.
Following the necessary site survey we established that the walls were over a metre thick of solid natural stone and the concrete floor slab was heavily reinforced and over 500mm in thickness. We therefore concluded that the bulk of the water had entered the structure at the base of the walls (wall/floor junction) with only some minor seepage through the walls themselves.
The design and positioning of the pumps and drainage system was critical. We therefore decided to cut recesses into the concrete slab adjacent to all perimeter walls and link them at 5 metre intervals. Plastic drainage channels were installed within the recesses and connected to the sump chambers. We then chose to use a channel with pre-drilled holes in both the rear and top so that in the unlikely event of water breaching the channels the water could be brushed/pushed back into the system. In addition we installed trapped gullies in the floor connected to the sump chamber which would serve the same purpose.
Finally 2 x battery backup systems were installed to ensure that 1 x pump within each sump chamber will continue to operate even during a power outage. 2 x high levels alarms were also installed which would warn the client (or designated representative) that the system may become overwhelmed and in which case the client had a 3kva generator which could simply be connected to the 2 x pumps which are not connected to the battery backup systems, ensuring that the system is working to its full potential at all times.
Links
Would your business stay afloat? A guide to preparing your business for flooding.
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/410606/LIT_5284.pdf
Sources
What’s happened
since?
The River Avon continues to burst its banks regularly. But the workshop remains bone dry. It’s also fully protected by our design and installation Guardian Watertight 10 year guarantee.
In 2015 we were awarded the national award for Project of the Year (highly commended) from the Property Care Association for this flood prevention and remediation project.
Testimonial
"Guardian produced a well thought out and thorough proposal to deal with flooding in our workshop. All work was carried out efficiently, within schedule and budget."
If you would like to meet up and discuss how we could help you to complete projects on time and to high quality specifications, please get in touch. We’d love to hear from you.
