This method is used when the depth of excavation is more. Installation of deepwells shall be carried out from the reduced ground level. The required number of bored holes of 800 or 900 mm dia., with a sufficient depth shall be made for the deepwell installation.

Care must be taken to ensure that the location is not infringing with any pile cap, water tank, staircase etc . Screened casings, 400/450mm dia. will be inserted into the bored holes and the annular space will be filled with aggregates to act as filter media. Electric Submersible pumps will be placed in the wells and purging will be carried out by intermittent pumping so that the discharge is clear and free from silt. The discharge will then be connected to main discharge line and the pump will be started.

(Slotted well casing)

As the excavation advances the retaining surface water, if any, at the excavation area shall be channelised to the nearest well. Cross drains/trenches shall be made.

During excavation the system shall be cared effectively to avoid any disruption to the system. As the excavation advances, the wells will be shortened until reaching the final excavation level

   (Deep well being installed)