Road map for full scale implementation of SWS for fractured chalk aquifer

“The test site on the island of Falster, Denmark, was selected to assess whether the subsurface water solutions (SWS) developed for single porosity granular aquifers in the Netherlands may be applied with similar success and designs in dual-porosity fractured carbonate aquifers. Dual-porosity fractured carbonate aquifers occur in many coastal settings around the globe e.g. in the southeastern parts of the UK and northern parts of France. Efficient SWS techniques to control salt water intrusion and improve the access to high quality freshwater resources in such settings are called for globally.
Set-up
The exact location of the test site for assessment of SWS techniques at the Falster site was selected based on two Geoprobe HPT (Hydraulic profiling tool) soundings performed at two existing water supply wells in well field two of the Marielyst Water Works with increasing salinity approaching the drinking water standard. The selected location and design of the test site were agreed between Marielyst Water Works, GEUS, KWR and GEO (the drilling company selected to drill the wells in the test site) based on existing knowledge about the aquifer and previous tracer tests in a similar setting. The developed test site consists of six wells including two multi-level monitoring wells each with seven screens covering sections of one meter between 12 and 26 meter below the surface i.e. the upper 14 meter of the confined Chalk aquifer from where Marielyst Water Works abstracts water. Two potential “freshkeeper wells” screened in three different sections from 15 to 38 meter depths were also installed close to the water supply well. Geophysical borehole logging (including propeller flow logs) were performed in the freshkeeper wells and another well developed for water abstraction in order to design the pumping and tracer tests for assessment of the hydraulic characteristics of the site in a dipole set up with an abstraction and injection well in each end of the test site. The pumping and tracer tests were conducted during two separate field campaigns in December 2016 and April 2017.”

(Citaat: Hinsby, K., Jakobsen, R., Rasmussen, P., et al. (Quality assurance: Raat, K.J., Zuurbier, K.G.) – Road map for full scale implementation of SWS for fractured chalk aquifer – SubSol – D2.2 (2018))