Well points are to be used to dewater a large trench excavation that

extends 10 m below the surface of the water table. Assume that the

bottom width of the trench excavation is 20 m.

(1) Develop a simple sketch of the necessary two-stage well point sys-

tem. Use separate diagrams to show the progress of the necessary

stages of installation.

(2) Assume that half of the necessary lowering of the water table eleva-

tion is achieved using the outer row of well points. If the soil being

dewatered is a fine-to-medium sand, approximately at what dis-

tance beyond the well point location is the original groundwater

table that is not affected by well point dewatering?