There are several ways to classify the hazard potential of a dam based on the various risks.
Hazards relate to impact of dam failure on:
(1) loss human life
(2) economic cost
(3) damage to the environment
(4) damage to lifelines (roads, rails, bridges, utilities, etc)
A classification used by FEMA is:
Loss of Human Life
Other Losses
Hazard
none
low, generally limited to owner
low
none
Yes
significant
>= 1
NA
high
Classifications vary by state. Connecticut uses the following hazard classification:
Loss of Life
Damage to Structures
Damage to Roadways
Economic Loss
Class
probable
major to habitable structures
main roadways
great
C
possible
minor to habitable structures
damage to utilities, railroads or primary roads
significant
B
none
unoccupied storage
low volume
moderate
BB
none
none
minor roads
minimal
A
none
none
none
neglible
AA
Another variable is the estimated annual failure rate probability. As this drops below 1 in 1,000 there is some tolerance of potential risk versus alternative benefits. However, at some point even minimal risk is judged unacceptable if the potential loss of life is too great.
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