MIL-HDBK-1164
7.4.1.1
Ground Storage Reservoirs
a)
Covered reservoirs or tanks should be vented to allow the passage
of air to and from the reservoir as the water level changes. Use fine screens on the
vents to prevent entrance of animals and insects, and keep the screens in good repair.
Keep access manhole covers in place to prevent accidents and contamination. Slope
the ground away from the reservoir in all directions so no surface water can flow
towards it. Leaks in the cover or walls that permit the entrance of surface water or
shallow groundwater are dangerous. Repair leaks at once.
b)
In freezing areas, inspect vent screens frequently to keep them
clear of ice and frost. Where ground storage tanks are used only for fire protection,
operate fire pumps and recirculate tank contents as frequently as required to prevent or
reduce ice formation. The construction of earth banks around storage tanks will help
insulate the tanks and prevent freezing. Where these measures do not stop freezing,
install steam or hot water coils or paint the tanks a dark, energy-absorbent color.
7.4.1.2
Underground Reservoirs. If storage tanks are constructed below ground
level, or are surrounded by an earthen embankment, the inspection and repair includes
only the interior walls, roofs, appurtenances, and embankment. If the earthen
embankment, surrounding soil, or interior of the tank shows evidence of tank leakage,
the earth may need to be excavated and repairs made on the walls. Signs of leakage
include the following:
a)
Water streams
b)
Wet, soggy earth that does not dry
c)
Sinkholes
d)
Erosion
7.4.1.3
Elevated Storage
a)
Freezing Prevention. Cover the elevated-tank riser pipe with
insulating material to guard against frozen water. In climates where insulation alone
may not give adequate protection, install steam coils in the riser and pipe stream into
the coils from a nearby boiler plant. Alternatively, connect a circulating hot-water
heater to the rise to take water about 15 to 20 feet (5 to 6 m) above the riser base and
return it near the base. In the latter case, adding a small recirculating pump is
desirable because it provides a large amount of recirculation with limited heat rise.
Inspect vent screens frequently throughout the winter and keep them clear of frost. An
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