Introduction to Water Infrastructure Asset Management - Global Drinking Water Management and Conservation - page 154

7.2.2.1 Types of Failure

There are three failure categories associated with the provision of water: asset
failure, pathogen intrusion, and service interruption.
Asset failure (Type 1) refers to a piece of equipment that ceases to function to at
least some degree. This includes a break, seize-up or plug in any type of asset that
renders the asset at least partially inoperable. A Type 1 failure may lead to failures
of Type 2 or 3 and subsequently to mass illness or loss of life. Type 1 failures can
be caused by natural disasters, aging or weak infrastructure or poor workmanship.
Pathogen intrusion (Type 2) refers to the infection of the water supply. This type
of failure cannot lead to a Type 1 failure, but may lead to a Type 3 failure and/or
mass illness. Type 2 failures are caused by system contamination, pressure rever-
sals, natural disasters, poor workmanship in pipes or valves, or source contami-
nation and Type 1 failures.
Service interruption (Type 3) refers to a level of service that is suboptimal. This
includes complete or temporary cessation of service or reduced levels of service.
Type 3 failures are caused by, and do not cause, Type 1 or 2 failures. Type 1 and 2
failures lead to Type 3 failures under two circumstances: suboptimal redundancy
and multiple failures of Type 1 and 2. A Type 3 failure may also be a result of a
combination of these two circumstances.

7.2.2.2 Types of Failure Costs

The costs of failure manifest themselves in a number of ways: repair, property
damage, environmental or ecosystem impairment, economic losses due to failure of
delivery, temporary replacement, communication costs, and health costs.
The most obvious and easiest cost of failure to enumerate is that of the
impending repair. Any type of failure must be

fixed. Type 1 failures necessitate the
repair or replacement of the respective asset, disinfection, and cleaning. Repair
costs associated with Type 2 failures refer to pathogen removal, disinfection, and

flushing. Type 3 failures arise from Type 1 or 2 failures. The repair costs of Type 1
and 2 failures must be accounted for appropriately. Therefore, the repair cost of a
Type 3 failure is simply the cost of repairing any damage to the system caused by
the interruption (i.e. pumps running dry, flushing due to pressure reversals, etc.).

All failure types may result in environmental damage. Type 1 failures may result

in flooding that may damage the local ecology. Any time that disinfection and

flushing is undertaken and treatment administered, there are costs. In addition,
infected water needs to be dealt with properly as improper disposal can be envi-
ronmentally dangerous.
Economic costs need to be accounted for as well. Type 1 failures may result in
repairs that necessitate road closures and traf

c diversions. These inconveniences
can disrupt a local economy. Some businesses will experience a loss of patronage;
others may incur staf

ng problems, as employees take longer to get into work.