Page 280 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

SITE UTILITY SYSTEMS

6.2 CHAPTER SIX

FIGURE 6.1 The basic hydrologic cycle. (Courtesy of U.S. Army Corps of Engineers.)

FIGURE 6.2 Basic geological formations.

The term groundwater is classically defined by geologists as water found below the
water table or in a geological formation that is fully saturated. Subsurface water is defined
as near surface water that infiltrates the soil but is not absorbed into the ground at a lower
level. It is primarily subsurface water that requires draining from excavations.
Groundwater and subsurface water are part of the hydrologic cycle and have two impor-
tant applications. The first is using groundwater to obtain a supply of domestic water. The
second is the necessity of collecting and removing subsurface water when required.
The lithosphere is the geological term for Earth’s crust. All earth materials are known
collectively as rock. Consolidated rock is the common hard rock such as granite or lime-
stone, which will be called simply rock in this book. It is classified by origin into three
main groups: igneous, sedimentary, and metamorphic. Unconsolidated rock is made up of
small particles created from rock and composed of soils such as gravel, clay, and sand. It is
classified into groups described in Table 6.20.
Water falling on the ground either collects on or near the surface or infiltrates downward
into the subsurface. Subsurface water exists in pores and occurs in two distinct zones. The

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