*TM 5-813-1/AFM-88-10, Vol. 1
CHAPTER 8
RAW WATER PUMPING FACILITIES
arrangements, provision must be made for cleaning.
8-1.
Surface water sources
This can be accomplished by backflushing. In general,
a.
Pumping station arrangement. The location
screening should be held to the minimum required for
and arrangement of raw water pumping stations will
protection of the pumps. Excessively fine screens,
depend upon the requirements of the local situation and
strainers or bar racks are sometimes subject to rapid
only general comments can be given. Raw water
clogging and will require frequent cleaning. Debris
pumping stations and intakes are often combined in a
removed by mechanically cleaned screens must be
single structure, but this is not mandatory. The depth of
collected and hauled to a landfill or other acceptable
the structure is a function of the type and arrangement of
disposal site. Screenings may be stored temporarily at
the pumps used. Horizontal centrifugal pumps are often
the station in dump carts from which they are discharged
employed and will give satisfactory performance and
to a truck for transport to a disposal site.
good operating economy. However, if the supply is from
c.
Structural considerations. Substructures will
a variable stream and the pump suctions are to be under
usually be of reinforced concrete.
Superstructures
positive pressure under all operating conditions, a station
should be of incombustible materials such as reinforced
of considerable depth probably will be required. Deep
concrete, brick or other masonry.
Wood frame
stations of the dry-pit type commonly used for horizontal
construction should not be used except for temporary or
centrifugal pumps should be compartmented so that
minor installations. Structural design should include
rupture of pump discharge piping within the station will
consideration of requirements for pump and motor
not flood all other pumps and motors. The depth may be
servicing and removal for major repairs.
reduced, with some loss in reliability, by installing the
d.
Ventilation.
Where a gravity ventilation
pumps at an elevation such that suction lift prevails
system is deemed inadequate to supply fresh air and
under some operating conditions. Equipment for priming
remove fumes and heated air from the pump station, a
is a requirement when suction lift is employed. Use of
forced ventilation system should be provided. The
vertical type wet-pit pumps, which requires less space in
ventilation system should be capable of removing waste
plan, permits a somewhat shallower station and does not
heat from the motors without allowing more than a 10F
require priming, may prove an economical alternative.
rise in the temperature of the air in the pump station. For
Among other pumping arrangements that could be used
occupied areas, the ventilation system will have a
are:
vertical-type pumps or end- or side-suction
capacity of about six air changes per hour. If dust-
centrifugals, with their shafts in a vertical position,
producing chemicals are to be handled at the station,
located on a submerged suction header. The latter
special dust exhaust systems will also be provided.
permits location of the pump drive units at an elevation
Where chemicals are used in the pump station,
where they are protected from flooding and readily
precautions should be taken to ensure that the exhaust
accessible.
from the ventilation system complies with air pollution
b.
Pump protection. Pumps, particularly those
prevention requirements.
located on streams, must have protection against debris.
e.
Pumping equipment. In general, pumping
In order to prevent or at least minimize screen clogging,
equipment shall be sized to conform to the rated capacity
the size of the screen openings should be consistent with
of the water treatment plant and will include a minimum
the capacity of the pump to pass solids. The pump
of three electric motor driven pumps. With the largest of
manufacturer can supply information on the largest
the three pumps out of service, the remaining
sphere that the pump will pass. Plants with flows of 1
mgd or larger and obtaining their water from streams will
use hydraulically cleaned traveling screens. For smaller
installations or those not obtaining water from streams, a
fixed bar screen or strainers can be used. For such
8-1
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