Civil Engineering Reference
In-Depth Information
TYPES OF STORAGE RESERVOIRS
Conventional storage reservoirs can be classified with respect to their configuration:
Underground
•
Ground level
•
Elevated
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An alternative to these conventional reservoirs, using a groundwater aquifer for storage,
is commonly referred to as aquifer storage and recovery (ASR). ASR provide capacity
to store a large volume of water during peak available supply periods to improve
aquifer yields during peak seasonal demands.
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Where groundwater conditions are fa-
vorable, ASR can provide a viable method of storing large volumes of water. Treated
drinking water is stored in a suitable underground aquifer when surplus source water
is available (typically during winter months in northern climates), then recovered when
needed during peak demand periods (typically during summer months). Most of the
applications of ASR have been for seasonal, long-term, or emergency storage appli-
cations.
Selection of the best type of conventional storage for a particular situation depends
upon topography, foundation conditions, hydraulic grade lines, economics, freezing
conditions, environmental and visual impacts, aviation hazards, and sabotage potential.
Where the bottom of a conventional storage reservoir is below normal ground sur-
face, it should be placed above the groundwater table. Sewers, drains, standing water,
and similar sources of contamination should be kept at least 50 feet (15.3 m) from the
reservoir or as required by the local regulating agency. The top of a ground-level
reservoir should be at least two feet (0.61 m) above flood level.
Large storage requirements may favor ground level, underground tanks, or aquifer
storage. Siting a reservoir on a hill at the right location and elevation may provide the
benefits of elevated storage at the cost of ground-level reservoirs. In level terrain,
consideration should be given to standpipes, elevated tanks, or ground-level or under-
ground tanks with provisions for booster pumping out of the reservoir to maintain
system pressures. Elevated tanks are rarely sited in areas that experience significant
seismic activity.
Standby emergency power would likely be required in booster-pumping stations to
consider some ground-level reservoirs in level terrain as firm sources of water during
emergency conditions. Standby emergency power can be in the form of a secondary
independent power feed, engine-driven pumps, or an automated gas- or diesel-fueled
generator.
Underground tanks may be used when it is necessary to conceal the tanks. This
may be done for aesthetic reasons or to facilitate multiple uses of the site, such as for
athletics or park activities. Figure 27-3 illustrates the combined use of a tank site for
recreational purposes.
DESIGN CONSIDERATIONS FOR CONVENTIONAL STORAGE
General
Finished water storage reservoirs are typically constructed of steel, conventional re-
inforced concrete, post-tensioned concrete, or wrapped prestressed concrete. High-
