Environmental Assessment
Volume D-3.5
Process Plant
Natural Risks
Table 3.5-1 Description of Risk Criteria for the Process Plant
Ranking
Categories
Likelihood of Occurrence
(Probability)
Magnitude of Consequences
Overall
Risk
extremely low
1
negligible chance of
occurrence, <1:10,000 yr
“doubt it will ever happen”
1
no fatalities possible,
minor to no damage beyond
owners property
1-5
low
2
not likely to occur, 1:1,000 to
1:10,000 yr “highly unlikely to
happen”
2
no fatalities anticipated,
minor damages beyond
owners property
6-10
moderate
3
moderate frequency of
occurrence 1:100 to 1:1,000 yr
“it could happen”
3
no fatalities anticipated,
moderate property damages
11-15
high
4
frequent occurrences, 1:10 to
1:100 yr
“it has happened, or it probably
will happen”
4
some fatalities possible,
large property damages
16-20
extremely
high
5
very frequent occurrences,
>1:10 yr
“happens all the time”
5
large number of fatalities
possible,
extreme property damages
21-25
3.5.5.3 Mitigation
A number of risk mitigation measures were identified in the reference report
(Dynatec, 2005). The design basis and criteria for the process plant will be based
on maximum recorded regional natural hazard events to minimize risk to within
recognized acceptable levels for surrounding public and environmental resources.
Risk mitigation measures were identified for all potential natural hazard
scenarios. Mitigation is discussed in the referenced report under the five
principal natural hazards: seismic, hydrologic, wind, geotechnical and tsunami.
These risk mitigation measures include:
,
•
Pipeline is designed for shutdown of several days duration.
•
Plant units will be designed to shut down in safe mode.
•
H
2
S venting from equipment will be burned to SO
2
.
•
Plant structures will be designed for the maximum regional earthquake.
•
Earthquake loads will be considered in piping design. Connections to
rigid equipment such as tanks and pumps will be located in bermed
areas. Following an earthquake, equipment and piping will be
inspected, and any leaks will be isolated.
•
Earthquake loads will be considered in tank and vessel designs. Tanks
will be contained in bermed areas sized for 110% of largest single vessel
in the area.
Ambatovy Project
63
January 2006
