Environmental Engineering Reference
In-Depth Information
Failure risk
Borehole
number
Decade
Structure
Environmental
effects
Human lives
Tall buildings, towers
5-10
10-2,000
Low
1960
Large dams
20-50
>5,000
Moderate
Offshore platforms
1-10
10-300
Very high
1970
Nuclear plants
50-100
50-50,000
Extremely high
Toxic disposal sites
(Panoche, US)
400
?
High
1980
Rocky Mountains arsenal
(US)
1,600
?
High
Table 12.2.
Site characterization from 1960 to 1990 [SHA 99]
In France, annex 6 of the BRGM report [BRG 00] provides various sampling
strategies for contaminated sites.
12.3.2.
Geotechnical site investigation methods
The cost of decontamination is generally high and is often a direct function of
the volume and severity of the contamination, hence the need for high quality and
detailed characterization of the site of interest. In the past, the characterization could
be carried out by performing off-site analysis. Laboratory methods, such as
chromatography and mass spectrometry, were the only reliable techniques for
assessing chemical concentrations in soils. These techniques, although accurate, are
expensive and require the extraction of samples.
As in traditional soil sampling, sample disturbance is still a problem. Collateral
contamination, small changes in temperature, light exposure, and volatilization may
influence the results of chemical analysis. Therefore, off-site chemical analysis
requires strict quality control and careful evaluation to ensure that test results are
truly representative of the site conditions. These highly subjective processes can
often make decontamination decision-making difficult.
The goal of any geoenvironmental characterization is to obtain high quality
information on the nature and spatial distribution of pollutants in an efficient and
economical way. This characterization has evolved from traditional drilling and
sampling used for decades by geotechnical engineers to apply sophisticated
exploratory non-intrusive and intrusive exploratory techniques to provide indirect
and direct quantification of soil properties and the characteristics of contaminants.
