Environmental Engineering Reference
In-Depth Information
information is used to classify a site as “suspect”, and a first investigation measuring
concentration of contaminants is to follow soon. If contaminants are above a trigger
level, site-specific Risk Assessment is performed, usually involving models. If the
site is a risk for human health or the environment in view of its current or planned
new use, an investigation will follow to assess the remediation options.
In some cases, however, it is already known on the basis of historical informa-
tion and experience that a site will need remediation. If there is enough certainty
to construct a conceptual model of the site, that adequately describes the intensity
of the sources and pathways that lead to exposure of the receptors of concern, one
may skip the time-consuming and costly site specific Risk Assessments and proceed
to the remediation phase. It should be noted that juridical requirements concern-
ing the validity of remediation decisions may lead to the use of site specific Risk
Assessments in all cases.
At a general level, the framework for Ecological Risk Assessment may be very
similar to the framework for the assessment of human health risk. The target of the
assessment, which may be defined as “Ecosystem Health”, is however more com-
plex than human health, since it involves a large number of phenomena operating at
various spatial and temporal scales. As far as the ecological risks of contaminated
sites are concerned, it may be important to make a distinction between two types of
ecological risks: those occurring at the contaminated site itself, and the impact of
the site on the surroundings, either by transport of contamination or, for instance, by
the loss of an important habitat within a limited range of habitats of plant or animal
species. The first category is the effect of the contamination on the capacity of the
soil to support plant and animal life at the site. The impact of the site on the sur-
roundings may be addressed by procedures quite similar to an environmental impact
assessment. Instead of assessing the environmental impact of potential contamina-
tion from, for instance, a new industrial site, the impact of the actual contamination
is assessed for a site in its current state. There is, however, also a large difference
between environmental impact assessment and contaminated site Risk Assessment.
Environmental impact assessment is used to choose between locations and preven-
tive approaches, whereas contaminated site Risk Assessment addresses the actual
contamination resulting from “choices” of the past.
23.5.2 Risk Assessment and Risk Management
The use of Risk Assessment in environmental policy probably originated in the
USA. The aim of the methodology was setting priorities for environmental pro-
tection in an objective and scientific way, avoiding political “perceptions” of
the administration (National Academy of Sciences; (NAS 1983 )). The distinction
between Risk Assessment (the objective scientific part) and Risk Management (the
policy driven decisions about risks) was of utmost importance in these early ideas.
Recent discussions, however, seem to question the strict separation of assessment
from management for a number of reasons:
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