Borehole Pump & Inject: an Environmentally Sound New Method for Groundwater Lowering

Holzbecher Ekkehard; Jin. Yulan; Ebneth Stefan
Groundwater lowering is usually required at construction sites, and for open pit mining, sometimes for aquifer remediation measures. Conventional methods lower the groundwater table by galleries of pumping wells. The pumped-out water is conducted to a distance place, where it is discharged back into the ground or into a surface water body. The system is criticized due to its environmental impacts, due to the disturbance of the local groundwater budget with negative effects on the eco-systems in the direct surroundings. Moreover, there may be severe problems connected with land subsidence and with groundwater or surface water pollution. In contrast to current and traditional techniques, we propose a novel method (DSI method), which can achieve dewatering without water conveyance above ground. In the method, dewatering is reached by pumping, while groundwater conservation is achieved by re-injecting pumped water back into the deep aquifer in the same borehole. The DSI method aims to avoid environmental problems with water pumped to the surface and meanwhile to reduce the costs. In the paper, the DSI concept, referred to as “borehole pump and inject” is described in detail. Moreover we report the current state of a project with two test sites for field experiments. Numerical models, based on Darcy’s Law as physical principle, are built up in 2D and 3D to evaluate the field experiments. The lowering of the groundwater table is implemented using ALE (Arbitrary Lagrangian-Eulerian) and moving mesh methods. Aquifer parameters are calibrated by inversely matching the modelled result to the measured field data. Our studies show a high potential for a promising future of the DSI method. The challenges are pointed out by discussing the limitations of the new method.
Dewatering; groundwater; wells, pump; injection
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