Environmental Engineering Reference
In-Depth Information
can be locked to prevent access to these valves. Valve-specific lockout devices
are available in a variety of colors, which can be useful in distinguishing
different valves. Different colored lockouts can be used to distinguish the
type of liquid passing through the valve (e.g., treated, untreated, potable,
chemical) or to identify the party responsible for maintaining the lockout.
Implementing a system of colored locks on operating valves can increase
system security by reducing the likelihood of an operator inadvertently
opening the wrong valve and causing a problem in the system.
Security for Vents
Vents are installed in aboveground, covered water reservoirs and in under-
ground reservoirs to allow ventilation of the stored water. Specifically, vents
permit the passage of air that is being displaced from, or drawn into, the
reservoir as the water level in the reservoir rises and falls due to system
demands. Small reservoirs may require only one vent, whereas larger res-
ervoirs may have multiple vents throughout the system. The specific vent
design for any given application will vary depending on the design of the
reservoir, but every vent consists of an open-air connection between the res-
ervoir and the outside environment. These air-exchange vents are an inte-
gral part of covered or underground reservoirs, but they also represent a
potential security threat. Improving vent security by making the vents tam-
per resistant or by adding other security features, such as security screens or
security covers, can enhance the security of the entire water system. Many
municipalities already have specifications for vent security at their water
assets. These specifications typically include the following requirements:
• Vent openings are to be angled down or shielded to minimize the
entrance of surface water or rainwater through the opening.
• Vent designs are to include features that exclude insects, birds, ani-
mals, and dust.
• Corrosion-resistant materials are to be used to construct the vents.
Some states have adopted more specific requirements for added vent security
at their water utility assets. The State of Utah's Department of Environmental
Quality, Division of Drinking Water, Division of Administrative Rules (DAR)
provide specific requirements for public drinking-water storage tanks. The
rules for drinking-water storage tanks as they apply to venting are set forth
in R309-545-15 (Venting) and include the following requirements:
• Drinking-water storage tank vents must have an open discharge on
buried structures.
• The vents must be located 24 to 36 inches above the earthen covering.
• The vents must be located and sized to avoid blockage during winter
conditions.
