Visual display of the Transportation of reagent materials : off-site risk related issues : Crandon Project

				
4.0 PROBABILITIES OF HAZARDOUS MATERIAL TRANSPORT ACCIDENTS
4.1 ACCIDENT RATES
The accident rate data discussed in Sections 3.4 and 3.5 are
judged to be comparable. As discussed in Section 4.4, the
uncertainties in these accident rate data can range from factors
of 1.5 to more than 5. Consequently, the accident rate data
presented in Table 3-1 are adopted for use in this evaluation.
4.2 ANNUAL TRANSPORT DISTANCES
The data presented in Tables 2-2 and 2-3 can be combined to
estimate the total annual mileages for transport of the four
reagents chosen for this study. A shipment distance of 290 miles
is chosen for both rail and truck transport. There would be 29
truck shipments and 24 rail shipments annually if sulfur dioxide
is moved by rail. If truck transport is used for sulfur dioxide,
there would be 70 truck shipments annually for these four
reagents. The annual mileages involved would be 15,370 or 20,300
for the two options. If some other split of rail and truck
transport of sulfur dioxide were chosen, the annual mileages would
fall between these estimates.
4.3 ACCIDENT PROBABILITIES
The data in Sections 4.1 and 4.2 are combined with the accident
rate data in Table 3-1 to estimate accident grobabilities. For
truck transport, an accident rate of 2 x 10    accidents/vehicle6
mile is used. For rail transport, an accident rate of 1.5 x 10
accidents/car-mile is used. The accident rate (acc/mi) is
multiplied by the transport distance to yield the probability. The
combined estimates for all 4 reagents are given in Table 4-1.
TABLE 4-1
ANNUAL ACCIDENT PROBABILITIES
MODE    NUMBER OF         MILEAGE             PROBABILITY
SHIPMENTS
Truck   70                 20,300             4.1 x 10-2
29                  8,410             1.7 x 10-2
Rail    24                  6,960             1.0 x 10-2
These estimates- ay be combined to yield over-all probabilities of
2.7 to 4.1 x 10   accidents/year for the off-site transport of
these four reagents to the Crandon Project.

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4.4 UNCERTAINTIES

The uncertainties associated with the accident rates, the shipment
distances and the probabilities are varied and may be interactive.
The accident- rates are based upon combinations of records and
estimates from different sources. The records were often kept for
purposes much different than their use in this study. There are
no known records of actual mileages accumulated in the transport
of these four reagents, or for hazardous material in general. For
this reason, the estimated uncertainties for other studies
[Refs.7&15] may be slightly low for this study.
The uncertainties associated with shipment distances for the
Crandon Project have been addressed by increasing the estimated
distances for major shipment corridors by 20%. This should
conservatively overestimate the distances in all but the most
unusual routes through Wisconsin. In such cases, the economics of
shipping will help assure that the shortest, less time consuming
route is taken by the transporter.
It is difficult to estimate accurately the overall uncertainties
associated with the probabilities derived in this study. Care has
been taken to use estimates that tended to result in increased
calculated probabilities of accidents. Consequently, it is
believed that the derived probabilities are over-estimates of the
likelihood of the accidents.

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