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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