EXCAVATIONS: Deep well system.

When the depth of excavation is more than 16 m below the water table, deep well drainage system may be used with advantage. The system is also useful where artesian water is present. A 15 to 60 cm diameter hole is bored and a casing with a long screen (5 to 25 cm) is provided. A submeisible pump with a capacity to

push the water upto a height of 30 m or more is installed near the bottom to the well. Each well has its own pump. Along with the deep wells arranged on the outer side of the area under excavation, a row of well points is frequently installed at the toe of the side slopes of the deep excavation.

 FIG  2.39  DEEP WELL SYSTEM.