Under most farm conditions a safe place for the disposal of wastes
is in the upper 3-foot layer of soil, where the action of bacteria
tends to render it harmless. Tile disposal fields, such as are used
with septic tanks, and earth-pit privies accomplish this if the water
table remains several feet below the surface and if the location is
remote from water supplies. Cesspools and other types of pits do not
ordinarily confine contamination to their immediate vicinity and are
not recommended except for special conditions.
Sewage or other wastes discharged into abandoned wells or other pits
that reach to the water table or below it are almost certain to
contaminate the ground water.
It is generally poor practice, and often illegal, to discharge wastes
into surface streams. Streams do not necessarily purify themselves
in 50 feet, 100 feet, or some other stated distance, as is commonly
believed. They do tend to purify themselves over long distances through
the action of sunlight, aeration, and other factors but may not be
safe for domestic use for many miles below the source of pollution.
Clear, sparkling water is not always safe drinking water. Streams in
agricultural communities are subject to many sources of pollution and
they are likely to become more contaminated as they merge into larger
streams.