Page 279 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

CHAPTER 6

SITE UTILITY SYSTEMS

This chapter will describe various pressurized and gravity flow utility and service systems
that are found outside of buildings on the site. These also include services that extend from
buildings to points of connection or disposal. A common connection point for site work is
considered to be 5 ft from the building wall.
Site utilities discussed here include subsurface drainage, storm water drainage and reten-
tion methods, sanitary drainage, water supply, and industrial and laboratory site drainage
systems. Also included are sections that provide information and fundamentals of hydrol-
ogy and design of buried piping.

BASIC GEOLOGY AND HYDROLOGY

Because of the close relationship of geology and hydrology to site utility work, it is use-
ful to have an elementary knowledge of the hydrological cycle and underlying geological
formations.

HYDROLOGIC CYCLE

The continuous circulation of water through surface water, the atmosphere, and the land is
called the hydrologic cycle. Inflow to the hydrologic system arrives as precipitation (rain or
snowmelt) on the surface. Three things may then happen to this water. It may be pulled into
the soil surface by capillary action, and evaporated back into the atmosphere, be absorbed
by plant roots and evaporated back into the atmosphere by transpiration through leaves and
roots, or infiltrate down through the soil until it reaches the groundwater table. The hydro-
logic cycle is schematically illustrated in Fig. 6.1.
From surface sources, including rainfall, streams, rivers, and lakes, water infiltrates down
into the soil. Basic geological formations are illustrated in Fig. 6.2. By infiltration, capillary
action, and percolation, some portion of that water eventually reaches the groundwater table.
Water in the soil between the surface of the ground and the water table is called subsurface
water. The slow movement of subsurface water through the ground places this water in direct
contact with soluble minerals that make up Earth’s crust. The water, therefore, may have a
wide variation in its chemical character even within small geographic regions.
In some areas, water may accumulate in a local zone of saturation above an impervious
stratum and be prevented from reaching the level of the water table. This is called perched
water, and its free surface is called the perched water table.

6.1
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