Environmental Engineering Reference
In-Depth Information
Pilot test
Figure 13.2
Aerial photograph of contaminated lagoon.
13.2.2 Illustrative example: remediation of contaminated lagoon
An example illustrating the value of information framework is for the remediation of a
contaminated lagoon (
Figure 13.2
).
Two approaches are considered to remediate this site:
Alternative A is a conventional approach to pump and treat the contaminated groundwa-
ter on-site, effectively containing the contamination to prevent it from migrating off-site;
Alternative B is an innovative approach to remove the source of contamination by breaking
down the volatile organic compound contaminants in the lagoon into benign by-products
with
in situ
bioremediation. The decision tree for these two approaches based on existing
information is shown in
Figure 13.3
;
this step is referred to as a
Prior
decision since it is
analyzed prior to obtaining any additional information. The probabilities for different out-
comes are based on the available information, including historical information about opera-
tion of the site, geologic and hydrogeologic models, and site investigation and monitoring
data. On the basis of the available information, the preferred alternative is the conventional
approach, Alternative A (
Figure 13.3
).
An alternative to consider before deciding the best approach for remediating the site is to
obtain additional information about the innovative bioremediation approach. Specifically,
a pilot test of the
in situ
bioremediation process could be performed in one corner of the
lagoon. Since this pilot test is implementing the approach at a smaller scale and shorter
duration than it will be implemented in the lagoon itself, the results are not perfectly reli-
able. Three test outcomes are possible: a successful result (
S
), a questionable result (
Q
)
Probability
Consequence
W
A
=
A works
Alternative A:
conventional
pump and treat
0.8
-$20 mm
E
(
C
)
=
-20*0.8
+
-40*0.2
=
-$24 mm
0.2
-$40 mm
F
A
=
A fails
W
B
=
B works
0.5
-$15 mm
E
(
C
)
=
-15*0.5
+
-35*0.5
=
-$25 mm
Alternative B:
innovative
in situ treatment
0.5
-$35 mm
F
B
=
B fails
Figure 13.3
Decision tree to select preferred alternative to remediate contaminated lagoon based on exist-
ing information.
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