Page 157 - Water and wastewater engineering

4-12 WATER AND WASTEWATER ENGINEERING

Both gravel-packed wells and those in consolidated formations benefit from well development
because the placement of the rock and the drilling operations tend to smear and seal the surface
of the aquifer material around the well. The development operations will break up this layer. This
effort is worthwhile to obtain the maximum capacity of the well.

Other Sanitary Considerations. Figure 4-6 summarizes several sanitary considerations in

well construction. The sanitary well seal is a gasket to prevent contamination from entering the
top of the casing. It is to be water tight with an air vent to relieve the negative pressure caused
by lowering of the water in the well. Because it keeps the air above the water at atmospheric

Power cable
Plug Discharge
Air, vent
Ground surface sloped
to drain away from well Sanitary well seal Drop pipe connection
Concrete pad
0.6 m
Top soil
Highest
Connection to flood Check valve
source of power
level
Clay Pump casing
Inlet screen
Artesian pressure surface
or piezometer surface
6 m
Cement grout
formation seal
Diffusers & impellers

Dynamic (pumping)
water level Inlet body

Submersible pump
Power leads
Motor shaft
Motor section

Drive shoe
Packer
Lubricant seal
Water-bearing sand
Screen
Submersible pump details
FIGURE 4-6
Drilled well with submersible pump.
( Source: U.S. EPA, 1973.)