Soil drilling company Haitjema, water company Vitens and KWR have together, within TKI Water Technology, developed a drilling method for drilling large diameter groundwater wells. Using conventional mechanical drilling techniques groundwater wells with diameters up to 1.2 m can be drilled; with the new drilling technique – Expanded Diameter Gravel Well (EDGW) – a groundwater well with a diameter of 1.7 m has already been drilled successfully.
Washing away and extracting sand
Large diameter wells are needed to achieve a high abstraction rate in fine-sand aquifers and to increase the lifespan of the sources. In October 2015 the first well was drilled using the EDGW technique at Vitens. This involved drilling conventionally at first and then using the new technique to achieve a diameter of 1.7 m from a depth of 53 to 68 m below ground level. The diameter increase is achieved by washing sand away over the desired depth with a special drill head and extracting it up through the drill hole.
Commissioning and monitoring
The new drilling method proved to be technically viable and the EDGW capacity tests were promising. The drilling process was further improved to obtain an even better source. In February 2016, a second test well was therefore drilled, with a diameter of approximately 3 m.
The EDGW groundwater well has been put into use by Vitens and is being monitored extensively. Analysis of the measurements will show whether the lifespan of the source is greater than that of conventional wells of far smaller diameter.
TKI Water Technology
The project is part of TKI Water Technology’s ‘Water to the Greenhouse’ (Freshwater Provision and Well Technology) project, which is itself a component of the ‘Circular Water Provision for Greenhouse Horticulture’ cluster project.