*TM 5-813-1/AFM-88-10, Vol. 1
CHAPTER 5
GROUND WATER SUPPLIES
pumping and storage with a minimum of other treatment.
5-1. General
Surface water supply costs include intake structures,
Ground water is subsurface water occupying the
sedimentation, filtration, disinfection, pumping and
saturation zone. A water bearing geologic formation
storage. Annual operating costs include the costs of
which is composed of permeable rock, gravel, sand,
chemicals for treatment, power supply, utilities and
earth, etc., is called an aquifer. Unconfined ground
maintenance. Each situation must be examined on its
water is found in aquifers above the first impervious layer
merits with due consideration for all factors involved.
of soil or rock. Confined water is found in aquifers in
b.
Coordination with State and Local
which the water is confined by an overlying impervious
Authorities. Some States require that a representative of
bed.
Porous materials such as unconsolidated
the state witness the grouting of the casing and collect
formations of loose sand and gravel may yield large
an uncontaminated biological sample before the well is
quantities of water and, therefore, are the primary target
used as a public water supply. Some States require a
for location of wells. Dense rocks such as granite from
permit to withdraw water from the well and limit the
poor aquifers and wells constructed in them do not yield
amount of water that can be withdrawn.
large quantities of water. However, wells placed in
c.
Artic well considerations. Construction of
fractured rock formations may yield sufficient water for
wells in artic and subartic areas requires special
many purposes.
a.
Economy. The economy of ground water
considerations. The water must be protected from
freezing and the permafrost must be maintained in a
versus surface water supplies needs to be carefully
frozen state. The special details and methods described
examined. The study should include an appraisal of
in TM 5-852-5/AFM 88-19, Chap. 5 should be followed.
operating and maintenance costs as well as capital
costs. No absolute rules can be given for choosing
between ground and surface water sources. Where
5-2. Water availability evaluation
water requirements are within the capacity of an aquifer,
After water demand and water use have been
ground water is nearly always more economical than
determined, the evaluation of water availability and water
surface water. The available yield of an aquifer dictates
quality of ground water resources will be made. The
the number of wells required and thus the capital costs of
following chart is used to illustrate step-by-step
well construction. System operating and maintenance
procedures.
costs will depend upon the number of wells. In general,
ground water capital costs include the wells, disinfection,
5-1
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