Well points are to be used to dewater a large trench excavation that extends 35 ft below the surface of the water table. Assume that the bottom width of the trench excavation is 70 ft. (a) Develop a...

Well points are to be used to dewater a large trench excavation that extends 35 ft below the surface of the water table. Assume that the bottom width of the trench excavation is 70 ft.

(a) Develop a simple sketch of the necessary two-stage well-point system. Use separate diagrams to show the progress of the necessary stages of installation.

(b) Assume that half the necessary lowering of the water table elevation is achieved with the outer row of well points. If the soil being dewatered is a fine-to-medium sand, approximately at what distance beyond the well-point location is the original groundwater table not affected by well-point pumping?