Groundwater infiltration with bored wells

Abstract

The installation of groundwater control systems when large building structures are being constructed can have undesirable consequences in the immediate vicinity (e.g. damage to buildings and vegetation). In some areas of the Netherlands restrictions exist on the amount of abstracted groundwater (if any) which may be discharged into surface waters. In such cases one solution consists of returning the water to the aquifer by bored wells (i.e. groundwater recharge). A number of groundwater recharge schemes in the Netherlands ran into problems, for which reason the Tunnel Technology Department appointed a study group on 'Groundwater Infiltration with Bored Welis' with the following terms of reference. a. compilation of a survey of past groundwater recharge schemes in the Netherlands; b. examination of the circumstances in which groundwater recharge is feasible in practice; c. formulation of the requirements which a groundwater recharge system should satisfy. For the first of these a survey was carried out which produced detailed particulars on all major recharge schemes in the Netherlands up to the end of 1977. This amounted to a total of 18 projects, the operating results of which are shown in Table I. The projects to which the numbers used throughout this report refer are listed on p. 6, together with a general description of each project. The location of these projects in the Netherlands is shown in Figure I. Generally speaking the groundwater recharge projects in the Netherlands have been successful. In three of the four cases the cause of the problem was the release of methane gas from the pumped-up water. Experience has shown that this form of obstruction can be prevented by the installation of effective degasification equipment or by maintaining the water under pressure. In one case the clogging was caused by the flocculation of ferrous hydroxides resulting from the mixture of two different types of water. This can only occur in phreatic conditions, i.e. in the absence of a covering clay or peat layer. These circumstances were encountered only in project 8. Clogging up by iron deposits can also occur as a result of the aeration of drainage water in the pumping wells or pipeline system. Although this is a fairly common phenomenon it does not generally result in major problems since the effects can be dealt with by careful groundwater infiltration procedures. Since the survey was carried out further experience has been accumulated in the field of phreatic conditions in which clogging up by iron deposits did not occur, in this case because of the absence of iron-bearing groundwater in the layer in question.