pacity out of service, or from the water-treatment
rate to sustain lawn-type turf. Irrigation require-
plant with one filter out of service. Normally the
ments for Air Force installations should be sub-
capacity of the clearwell storage at the treatment
stantiated by a local or regional Soil Conservation
plant will not be considered part of the required
Service or recognized local authority as the mini-
storage.
mum rate to sustain lawn-type turf.
(2) Where the water supply is obtained from
3-2. Elevated Storage Capacity
wells, all of which are equipped with standby
The total elevated storage capacity at all military
power and located within the distribution system,
installations, except plant and special projects,
the emergency supply will be considered as the
should not be less than the amount determined in
quantity available from all but one of the wells.
paragraph 3-la Item 2, nor less than 50 percent of
Where one well has a capacity greater than the
the total required storage, unless special condi-
others, that one will be assumed out of service.
tions prevail which would negate the need for such
Where only 50 percent of the wells have standby
storage. For projects with design populations of
power, the emergency supply will reconsidered as
10,000 or less, consideration will be given to pro-
the quantity available from the wells having
viding all elevated storage where the storage will
standby power.
result in an economical and reliable system. For
(3) Where the project is supplied from a de-
projects such as storage depots or aircraft hangers
pendable existing source, such as a municipal
with deluge sprinkler systems, ground storage res-
system with adequate storage and standby facili-
ervoirs with booster pumps will generally be the
ties, through supply lines not subject to damage by
more economical method of supplying large vol-
floods, high pressure, or other unusual conditions,
umes of water for fire protection. Elevated tanks
the amount of water available under emergency
will normally be provided for initial sprinkler
conditions is that obtainable with the largest con-
demand in storage warehouses. Water storage can
nection inoperative.
be most economically provided by constructing
(4) Where the supply is delivered through a
ground storage reservoirs on high ground. Howev-
single supply main, the maximum amount of stor-
er, in the absence of suitable terrain, elevated
age as determined in paragraph 3-la will be pro-
tanks will be required.
vided.
(5) Where the peak demand for water is avail-
3-3. Economic Analyses
able at adequate residual pressure through two or
a. General. Economic analyses of storage re-
more lines while the line having the greatest ca-
quirements could guide decisions on the imple-
pacity is out of service, no storage will be required.
menting or postponing of expenditures for new
(6) Where the peak demand for water is avail-
transmission mains, the constructing of booster
able through two or more lines but is not available
pumping facilities to increase transmission main
if the line having the greatest capacity is out of
capacities instead of adding new mains, the in-
service, storage will be required. The quantity of
creasing of the quantity of storage within a distri-
water available under emergency conditions with
bution system, and the providing of elevated stor-
the line of greatest capacity out of service will be
age or ground storage with booster pumping facili-
considered in calculating the amount of storage re-
ties.
quired.
b. Distribution storage. Distribution storage is in-
d. Irrigation requirements. Where irrigation re-
tended to meet peak flow requirements or emer-
quirements, are justified in arid or semi-arid re-
gency needs, maintain system pressures, and thus
gions, such irrigation quantities will be included as
reduce the required capacities of the treatment
an industrial requirement of Items 1, 2, and 3 of
plant and pump stations. The design of storage fa-
subparagraph 3-la and not as a domestic require-
cilities, in accordance with paragraphs 3-1 and 3
ment. Water requirements may be increased above
2, will be determined by feasibility studies which
those indicated in TM 5-630 for Army installations
take into account all engineering, economic,
provided that the increased rates can be substanti-
energy, and environmental factors. Analysis will
ated by a local or regional Soil Conservation Serv-
be in accordance with AFR 178-1 for Air Force
ice or recognized local authority as the minimum
projects and AR 11-28 for Army projects.
3-2
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