Potential Contamination to the Environment Exposure Screening Guidelines.

DOE-STD-3014-96

APPENDIX A

onsite guidelines are not needed. Thus, the analyst's obligation is to

justify why they should be used in a specific case, not why they are not

being used. In particular, it should be noted that, because of the

differences between the offsite and onsite guidelines and the way the

exposure calculations are performed, the onsite guidelines are totally

useless when the site boundary is within 300 m (984 ft) of the facility and

are very likely to be useless when the site boundary is within 1000 m

(3280 ft) of the facility.

A.1.3 Potential Contamination to the Environment Exposure Screening Guidelines.

The final topic considered in developing the exposure screening guidelines was

potential contamination of the environment. In most cases, it was felt that

exposure to the general public was a sufficient surrogate for offsite

environmental contamination. Similarly, if onsite contamination were an issue,

then exposure to onsite workers was considered a sufficient surrogate. Although

it was recognized that this may not always be the case, there was no obvious set

of accidental contamination guidelines readily available for incorporation into this

standard. This is in large part due to the fact that there are many different types

of environmental receptors (as opposed to only one, a human, for health and

safety), and these receptors vary in their sensitivity to different hazards. For this

reason, providing specific guidelines for environmental contamination was felt to

be impractical. As stated in Section 1.3, "Applicability," it is left to the analyst to

determine whether special conditions exist that would warrant a specific

evaluation of environmental impacts in those cases where such analysis is not

warranted by health and safety concerns. Again, the default position is that such

analyses are not needed, and the burden is on the analyst to justify their

inclusion.

Frequency Screening Guidelines. The DOE has issued a standard, DOE-STD-3009-94

A.2

(Reference 1), providing guidance for the preparation of Safety Analysis Reports (SARs).

This standard states that an external event should be analyzed as a design basis

accident (DBA) if its frequency of occurrence exceeds 1E-6/y conservatively estimated,

or 1E-7/y, realistically estimated. Aircraft crash impacts are human-caused external

A-6