Pit and related covered filter tube

A method to make an underground water well in an aquifer containing a mixture of ground water and undesired particles, at a distance below the ground surface, for the withdrawal of ground water, filtered from said undesired particles, from said aquifer, wherein:

• above the ground a filter tube, having a tube wall provided with water passage pores, is treated to become completely enveloped by a tightly fitting, rigid layer of porous coherent material, comprising a mixture of granules and binder, provided with water passage pores, to produce a prefabricated sheathed filter tube containing a rigid envelope of porous coherent material;
• and by means of horizontal directional drilling at a distance below the ground surface a substantially horizontal bore hole having a bore hole wall and filled with drill fluid supporting the bore hole wall, is made in the ground below the ground surface, such that said bore hole extends a predetermined distance within said aquifer;
• and said sheathed filter tube is threaded into and advanced through said bore hole to become installed into said aquifer to extend a predetermined distance within said aquifer, after which the material of said envelope around said filter tube within said aquifer looses its coherent nature such that said envelope becomes a layer of loose laying granules tightly fitting around said filter tube within said aquifer and providing said water passage pores;
• and subsequently ground water from said aquifer, containing undesired particles, flows through said pores inwards into said filter tube while said pores filter said ground water from said undesired particles, to produce filtered ground water, while said filtered ground water flows through said filter tube towards and above the ground surface, such that said well is developed.

A method to make an underground water well in an aquifer containing a mixture of ground water and undesired particles, at a distance below the ground surface, for the withdrawal of ground water, filtered from said undesired particles, from said aquifer, wherein:

• above the ground a filter tube, having a tube wall provided with water passage pores, is located into a wrapping such that said wrapping concentrically surrounds said filter tube and delimits a free annular space around said filter tube, which annular space has a thickness between 0.5 and 10 centimetre and is subsequently completely filled by pouring into it a curable mixture of binder and granules which provides, after curing, completely around said filter tube a tightly fitting, rigid layer of porous coherent material, provided with water passage pores, such that a prefabricated sheathed filter tube is produced containing a wrapped envelope of porous coherent material;
• and by means of horizontal directional drilling at a distance below the ground surface a substantially horizontal bore hole having a bore hole wall and filled with drill fluid supporting the bore hole wall, is made in the ground below the ground surface, such that said bore hole extends a predetermined distance within said aquifer;
• and said wrapping is removed from said prefabricated sheathed filter tube which is subsequently threaded into and advanced through said bore hole to become installed into said aquifer to extend a predetermined distance within said aquifer, after which a fluid at a pressure between 5 and 400 bar is pressed from said filter tube into said envelope such that the material of said envelope around said filter tube within said aquifer looses its coherent nature such that said envelope is transferred into a layer of loose laying granules tightly fitting around said filter tube within said aquifer and providing said water passage pores;
• and subsequently ground water from said aquifer, containing undesired particles, flows through said pores inwards into said filter tube while said pores filter said ground water from said undesired particles, to produce filtered ground water, while said filtered ground water flows through said filter tube towards and above the ground surface, such that said well is developed.