Civil Engineering Reference
In-Depth Information
Operations and maintenance restrictions
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Capital and maintenance costs, durability, and service life
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The capital cost of covering existing open reservoirs has often been a deterrent. Some
utilities have added treatment on the outflow of large, uncovered reservoirs in lieu of
covering the reservoir. The acceptance of floating covers has substantially reduced
costs of covering reservoirs. Floating covers are generally lower in first cost than rigid
covers, require little maintenance, are resistant to seismic loads, and can be quickly
installed. A floating cover can be installed on a reservoir of nearly any size or
shape.
11,12
Refer to the latest edition of AWWA Manual M25, ''Flexible-Membrane
Covers and Linings for Potable-Water Reservoirs'' for more information.
The all-aluminum geodesic dome is a frequently used cover for smaller circular
reservoirs. The dome consists of a skeleton of aluminum trusses and a skin of alu-
minum panels. Although the aluminum geodesic dome has a higher initial cost than
other covers, it also provides several advantages: a long service life, minimal main-
tenance, no painting, light weight, a bottom tension ring that transmits only vertical
forces to the reservoir walls, easy reservoir access, fast construction while an existing
reservoir is in service, and no interior columns or supports. Figure 27-4 illustrates the
use of a geodesic dome cover on a water storage reservoir.
Protection from Trespassers
Fencing, locks on access manholes, and other nec-
essary precautions should be installed to deter trespassing, vandalism, and sabotage.
Drains
Drains on water storage structures should, if possible, drain to daylight and
not have direct connections to a sewer or storm drain. Drain surface outlets should be
designed to prevent soil erosion downstream of the discharge. Although a drain con-
Fig. 27-4.
Geodesic dome (Courtesy of Northwest Permastore Systems, Inc.)
