*TM 5-813-1/AFM-88-10, Vol. 1
b.
Sampling and analysis. It is mandatory to
5-4. Water quality evaluation
review the stipulations contained in the current U.S.
Both well location and construction are of major
Environmental Protection Agency's drinking water
importance in protecting the quality of water derived from
standards and state/local regulations as interpreted by
a well.
the Surgeon General of the Army/Air Force and to collect
a.
Sanitary survey. Prior to a decision as to
samples as required for the determination of all
well or well field location, a thorough sanitary survey of
constituents named in the drinking water standards. The
the area should be undertaken.
The following
maximum chemical concentrations mandated in the
information should be obtained and analyzed:
drinking water standards are given in TM 5-813-3/AFM
(1)
Locations and characteristics of
88-10, Vol. 3.
sewage and industrial waste disposal.
Heavy metals are rarely encountered in significant
(2)
Locations of sewers, septic tanks and
concentrations in natural ground waters, but may be a
cesspools.
concern in metamorphic rock areas, along with arsenic.
(3)
Chemical and bacteriological quality of
Radioactive minerals may cause occasional high
ground water, especially the quality of water from
readings in granite wells.
existing wells.
c.
Treatment. Well water generally requires
(4)
Histories of water, oil, or gas wells or
less treatment than water obtained from surface
test holes in area.
supplies. This is because the water has been filtered by
(5)
Industrial and municipal landfills and
the formation through which it passes before being taken
dumps.
up in the well. Normally, sedimentation and filtration are
(6)
Direction and rate of travel of usable
not required. However, softening, iron removal, pH
ground water.
adjustment and disinfection by chlorination are usually
Recommended minimum distances for well sites, under
required. Chlorination is needed to provide residual
favorable geological conditions, from commonly
chloride in the distribution system.
The extent of
encountered potential sources of pollution are as shown
treatment must be based upon the results of the
in table 5-2. It is emphasized that these are minimum
sampling program.
For a detailed discussion of
distances which can serve as rough guides to good
treatment methods, see TM 5813-3/AFM 88-10, Vol. 3,
practice when geological conditions are favorable.
and Water Treatment Plant Design.
Conditions are considered favorable when the earth
materials between the well location and the pollution
5-5.
Well hydraulics
source have the filtering ability of fine sand. Where the
a.
Definitions. The following definitions are
terrain consists of coarse gravel, limestone or
disintegrated rock near the surface, the distance guides
necessary to an understanding of well hydraulics:
given above are insufficient and greater distances will be
-Static Water Level. The distance from the ground
required to provide safety.
Because of the wide
surface to the water level in a well when no water is
geological variations that may be encountered, it is
being pumped.
impossible to specify the distance needed under all
-Pumping Level. The distance from the ground
circumstances. Consultation with local authorities will aid
surface to the water level in a well when water is being
in establishing safe distances consistent with the terrain.
pumped. Also called dynamic water level.
-Drawdown. The difference between static water
Table 5-2. Minimum Distances from Pollution Sources.
level and dynamic water level.
-Cone of Depression. The funnel shape of the
Minimum
water surface or piezometric level which is formed as
Source
Horizontal Distance
water is withdrawn from the well.
Building Sewer
50 ft.
-Radius of Influence. The distance from the well to
Septic Tank
50 ft.
the edge of the cone of depression.
Disposal Field
100 ft.
-Permeability. The rate of flow through a square
Seepage Pit
100 ft.
foot of the cross section of the aquifer under a hydraulic
Dry Well
50 ft.
gradient of 100 percent at a water temperature of 60F.
Cesspool
150 ft.
Note: The above horizontal distances apply to all depths of
wells.
5-6
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