for slots and wells do not consider the effects of hy-

flow to trenches, French drains, and similar drainage

draulic head losses Hw in wells or wellpoints; proce-

systems. They may also be used where the drainage

dures for accounting for these effects are presented

system consists of closely spaced wells or wellpoints.

separately.

Assuming a well system equivalent to a slot usually

simplifies the analysis; however, corrections must be

drainage systems from a circular seepage source are

made to consider that the drainage system consists of

based on the assumption that the system is centered

wells or wellpoints rather than the more efficient slot.

on an island of radius R. Generally, R is the radius of

These corrections are given with the well formulas dis-

influence that is defined as the radius of a circle be-

cussed in c below. When the well system cannot be

yond which pumping of a dewatering system has no

simulated with a slot, well equations must be used.

significant effect on the original groundwater level or

The figures in which equations for flow to slots and

piezometric surface. The value of R can be estimated

wells appear are indexed in table 4-1. The equations

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