Water Well Manual (USAID).pdf - The Water, Sanitation and Hygiene

gravel aquifers where water is extracted in close proximity to pollution
sources, such as privies and cesspools. This latter problem has been dealt with
in more detail in Chapter 9, where the sanitary protection of ground-water
supplies is discussed. Poor well construction can also result in the
contamination of ground waters. The reader is referred to the section in
Chapter 4 dealing with the sanitary protection of wells.
The solution of the potable water supply problems of Nebraska City,
Nebraska, U.S.A. in 1957 bears striking testimony to the benefits derived
from percolation of water through the ground and the general advantages of’a
ground-water supply over one from a surface source. For more than 100 years
prior to 1957, Nebraska City depended upon the Missouri River for its
domestic water supply. The quality of the water in the river deteriorated as
the years went by due to the use of the river for sewage and other forms of
waste disposal. To the old problems of high concentrations of suspended
matter, dark coloration from decayed vegetation and highly variable
temperatures (too warn in summer and too cold in winter) was added
bacterial pollution. So bad was this sittration that the Missouri River, in this
region, soon beczrre recognized as a virtual open sewer and the water no
longer met the requirements of the United States Public Health Service
Drinking Watei- Standards for waters suitable to be treated for municipal use.
The search for a new source of supply for Nebraska City led to the use of
wells drilled into the sands that underlie the flood plain of the Missouri River
at depths up to 100 feet. Wells drilled a mere 75 feet from the river’s edge
and drawing a considerable percentage of their water from the river yielded a
very high quality, clear water that showed no evidence of bacterial pollution
or noticeable temperature variation. The lessons of Nebraska City can be put
to beneficiai use in many other areas of the world.
Chemical Quality
The chemical quality of ground water is also considerably influenced by its
relatively slow rate of travel through the ground. Water has always been one
of the best solvents known to man. Its relatively slow rate of percolation
through the earth provides more than am