Site-Specific Ecological Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 710

In the second and last integration step, the independent pieces of information
from the three lines of evidence are compared. In this step, it is also evaluated to
what extent the three lines of evidence indicate comparable levels of risks. At this
point, a weight of evidence approach will pay off. Consequently, when all lines of
evidence point in the same direction, it is defendable to calculate a final risk index
based on the outcome of three different lines of evidence, and then compare the
result with a benchmark value to be able to take a decision about the site-specific
ecological risks. The benchmark value is a decided value by the stakeholders, the
local administration and national government, which marks the border between
acceptable and unacceptable effects (see Fig 15.1 : step 5d). When the three dif-
ferent lines of evidence do not point in the same direction, the deviation between
the three lines of evidence should be calculated and used to decide whether more
research is necessary. Jensen and Mesman ( 2006 ) and Mesman et al. ( 2007 )devel-
oped decision tables in order to arrive at these 'go/no-go decision points' to further
harness a Triad approach (Table 15.2 ).
15.6 Embedding ERA in Formal Assessment Frameworks
15.6.1 An Example of a General Framework from the Netherlands
In the Netherlands, the Soil Protection Act was introduced in 1986. Contaminated
sites are first assessed using a set of Soil Quality Standards, i.e. Target Values
and Intervention Values . These values take both human health and ecological risks
into account, and are applied to all kind of land uses and soil types (Rutgers
and Den Besten 2005 ; Swartjes 1999 ). Recently, also so-called Maximum Values
were introduced as remediation objectives, which are land use specific (Dirven-Van
Breemen et al. 2007 , 2008 ). The ecological basis of these Soil Quality Standards
is a SSD, constructed from No-Observed Effect Concentrations (NOEC values)
from the literature (Posthuma et al. 2002 ). At seriously contaminated sites, remedi-
ation or other soil management decisions are required if unacceptable risks cannot
be refuted, based on a site-specific ecological Risk Assessment, a Human Health
Risk Assessment, and the chance for dispersion of the contaminants. For these three
issues, a tiered approach called the Remediation Criterion is used (VROM 2008 ).
The first and second tiers of the ERA in the Remediation Criterion are based on
a judgment of the likely ecological effects from chemical concentrations in gener-
alized models for toxicity and mixture effects. Note that this numbering of tiers is
formal and does not include the numbering of tiers in a Triad approach. In the first
tier of the Remediation Criterion, the Intervention Values are used as Soil Quality
Standards, besides criteria for impacted soil volume. In the second tier, ERA is
performed on the basis of a calculation of the Toxic Pressure of the mixture of con-
taminants and a decision table addressing critical dimensions of the impacted area
(Table 15.3 ) and presumed land use sensitivity for contamination. For a few cases,
the outcome might not at all be satisfactory and sufficiently robust for a decision