Environmental Engineering Reference
In-Depth Information
The covers are constructed from aluminum or some type of steel. This
should provide adequate protection from being pierced or cut through. The
metals are corrosion resistant so they will not corrode or become weakened
due to extreme weather conditions in outdoor applications. The bolts used
to install each of these systems are galvanized steel. In addition, the bolts for
each cover are installed on the inside of the unit so they cannot be removed
from the outside. The important features of ladder access control are the size
and strength of the cover and the ability to lock or otherwise secure the cover
from unauthorized access.
Locks
A lock is a type of physical security device that can be used to delay or pre-
vent the opening, moving, or operation of a door, window, manhole, filing-
cabinet drawer, or some other physical feature. Locks typically operate by
connecting two pieces together, such as connecting a door to a door jamb or
a manhole to its casement. Every lock has two modes: engaged (or locked)
and disengaged (or opened). When a lock is disengaged, the asset on which
the lock is installed can be accessed by anyone, but when the lock is engaged,
only access to the locked asset.
Locks are excellent security features because they have been designed to
function in many ways and to work on many different types of assets. Locks
can also provide different levels of security depending on how they are
designed and implemented. The security provided by a lock is dependent on
several factors, including its ability to withstand physical damage (e.g., being
cut off, broken, or otherwise physically disabled) as well as its requirements
for supervision or operation (e.g., combinations may have to be changed fre-
quently so they are not compromised and the locks remain secure). Although
no agreed-upon rating of lock security exists, locks are often designated as
being minimum, medium, or maximum security. Minimum security locks
are those that can be easily disengaged (or “picked”) without the correct key
or code or those that can be disabled easily (such as small padlocks that can
be cut with bolt cutters). Higher security locks are more complex and thus
are more difficult to pick, or they are sturdier and more resistant to physi-
cal damage. Many locks only have to be unlocked from one side; for exam-
ple, most door locks (single-cylinder locks) can be opened on the outside
by inserting a key in the lock. On the inside, a person can unlock the same
lock by pushing a button or turning a knob or handle. Double-cylinder locks
require a key to be locked or unlocked from both sides.
Manhole Intrusion Sensors
Manholes are located at strategic locations throughout most municipal water,
wastewater, and other underground utility systems. Manholes are designed
to provide access to underground utilities, and they represent potential entry
