AirBurst significantly increases hydraulic performance of groundwater borehole
11 November 2011, News release from Cirrus Aqua Ltd
As part of a project investigating proposals to provide a mains water supply for the wider community in the Orkney Islands, Cirrus remediated and developed an existing groundwater source borehole.
AirBurst rehabilitation of the water well combined with CCTV surveys and hydraulic step drawdown testing was completed to determine whether the post-treatment yield of this borehole would be suitable for further source development.
The pre-AirBurst CCTV survey revealed numerous partially open fissures, fractures and mineralised veins as well as extensive zones of fibrous, cottonwool-like black-grey coloured biofouling.
AirBurst rehabilitation, and subsequent airlifting of dislodged fines, sediments and biofouling from the water well took under half a day.
Post-AirBurst CCTV inspection confirmed the presence of a greater number of fissures and cavities than observed pre-AirBurst. Very clear water was observed at depths between 42 to 49m.This zone of clear water is thought to have been sourced from the wider aquifer environment via inflows through enlarged fissures during the post AirBurst step drawdown testing, when over 5000 litres was pumped from the borehole. Little remaining bio-fouling was observed.
Comparing pre- and post-treatment step drawdown testing, there was a significant increase in specific capacity from 0.83 to 12.83m3/day/m for yields of 1.43 and 1.5m3/hr respectively. Additionally, post-AirBurst well efficiency increased by 87.0%, and estimates of hydraulic conductivity at 0.279 to 0.366m/d generally an order of magnitude greater than for the pre-AirBurst results.
These results demonstrate that AirBurst rehabilitation of the groundwater source borehole has significantly improved the hydraulic performance of the well and its hydraulic connectivity with the wider aquifer. This was achieved by opening up new and existing fissure/ fracture groundwater flow pathways and by the removal of observed biofouling/encrustation from the walls of fractures, fissures and the borehole.
From this work, it was considered that a post-AirBurst sustainable yield exceeding 100m3/day could be achieved for a predicted groundwater level drawdown of between 6.35m to 12.23m at the abstraction borehole. This predicted yield far exceeds the pre-remediation expected increase in yield (to 15 to 20m3/day), and indicates that this groundwater borehole is suitable for further source development.
Commenting after reviewing the write-up of the completed work, Peter Dupen, hydrogeologist with Jacobs acting on behalf of the client declared this was "the most detailed and thorough post-rehabilitation report ever submitted in the history of Scottish Water".
Cirrus' managing director Craig Somerville says "After winning a contract to clean over 50 boreholes for Scottish Water we have been very busy. Our achievements with this led to additional successful work with our partners, Prime Pumps Ltd and Scottish Water Solutions representing Scottish Water. Interest in the AirBurst technology is now very high following a recent shift by borehole and water well managers to look more closely at this cost-effective and proven remediation technology to extend the operational capacity and lifespan of their groundwater assets".
Airburst has also recently been used in the successful rehabilitation of a Scottish Water groundwater borehole source on Fair Isle, available here. In the news section.