24 ENVIRONMENTAL ENGINEERING
Curve showing
that the standard
Is exceeded1@R lOdR 104R 104R 0.01R 0.1R 1.0R lOR
Release of radioactive material R
Figure 2-2. Release of radioactive materials vs. probability of release.The curved lines are complementary cumulative distribution functions and repre-
sent the risks of releases for three different alternatives being assessed. This is a typical
representation of the probability of release of material from a hazardous or radioactive
waste landfill. The alternatives might be three different sites, three different surface
topographies, or three different engineered barriers to release. In the case of the EPA
standard, the curves represented three different geological formations. Risk analysis
is particularly useful in assessing future or projected impacts and impacts of unlikely
(low-probability) events, like transportation accidents that affect cargo, or earthquakes
and other natural disasters.
Recently much has been written about the difficulty of communicating risk to a
large public, and the perception of risk as it differs from assessed risk (see, for example,
Slovic 1985; Weiner 1994). The engineer must remember that risk assessment, when
used in environmental impact assessment, is independent of risk as perceived by, or
presented to, the public. He or she should assay risk as quantitatively as possible. The
details of performing a risk analysis are presented in Chap. 3.SOCIOECONOMIC IMPACT ASSESSMENTHistorically, the President’s Council on Environmental Quality has been responsible for
overseeing the preparation of environmental assessments, and CEQ regulations have
listed what should be included in all environmental assessments developed by federal
agencies. For the proposed projects discussed earlier in this chapter the primary issues
are public health dangers and environmental degradation. Under original NEPA and
CEQ regulations, both issues must be addressed whenever alternatives are developed
and compared.