The Hazardous Facility Screening Procedure training manual.
Table 5.2 B Example of semi-quantitative risk analysis used for ranking and short listing of risks
(extracted from GCNZ Consultants and H M Tweeddale Consulting Service, 1989, published in Ministry for the Environment 1999: Assessment guide for hazardous facilities – resource for local authorities and hazardous facility operators)
| Product | Quantity (tonnes) |
Facility | Incident type |
Contributing cause |
Type of event |
Type of effect |
|---|---|---|---|---|---|---|
| Aerosols | 15 | Product store | Fire | Smoking or radiator in office |
Firewater runoff | Environment |
| “ | “ | “ | “ | “ | Toxic smoke | People |
| “ | “ | “ | “ | “ | Heat radiation | Property |
| Calcium hypochlorite | 10 | Product store | Fire | Exposure to incompatible materials | Heat radiation | Property |
| Dieldrin | 1 | Unloading bay | Toxic spill | Fork truck accident | Toxic spill to estuary | Environment |
| Solvent drums | 1 | Raw material store | Fire | Ignition of spill | Heat radiation | People |
| “ | “ | “ | “ | Drum fire exposed other drums | Explosion of fumes (bleve) | People |
| Dieldren | 1 | Truck | Toxic spill | Transport accident | Toxic spill to estuary | Environment |
| Toxic material | 1 | Dangerous Goods Store | Toxic spill | Fork truck accident | Toxic spill to estuary | Environment |
| Product | Severity score |
Frequency per million per year |
Protective response |
Probability of failure |
Risk index |
|---|---|---|---|---|---|
| Aerosols | 0.1 | 100,000 | Containment/ clean-up |
0.7 | 7000 |
| “ | 0.05 | “ | Fire service | 0.3 | 1500 |
| “ | 0.1 | “ | Fire protection, fire service | 0.1 | 1000 |
| Calcium hypochlorite | 0.05 | 10,000 | Little possible | 1 | 500 |
| Dieldrin | 0.5 | 10,000 | Contain, mop up with absorbent | 0.05 | 250 |
| Solvent drums | 0.05 | 10,000 | Fire protection, fire service | 0.1 | 50 |
| “ | 0.3 | 2,000 | Fire protection, fire service | 0.1 | 60 |
| Dieldren | 0.5 | 100 | Contain, mop up with absorbent | 0.3 | 15 |
| Toxic material | 0.1 | 10,000 | Container by bund, mop up | 0.001 | 1 |
Explanation:
1. A separate assessment of risk is undertaken for every hazardous substance
and type of environmental effects (e.g. people, environment and property).
2. Risk indices are calculated by multiplying the severity score, frequency
score and failure probability score with each other.
3. Risk indices are ranked to short-list those hazards that present the
greatest risk on the site and which will need the greatest level of attention.
