Environmental Engineering Reference
In-Depth Information
100
80
60
Historic and residual damage
[Loss of 2000 SAY]
40
Total deficit
[Loss of 3600 SAY]
Invasive remediation
[Loss of 1600 SAY]
20
Full recovery
Start
Years
FIGURE 7.13
Environmental deficits from contaminated sediment dredging remediation.
NEBA provided a tool to define a superior approach to remediating the
contamination. A remediation alternative was formulated to dredge a lim-
ited area of only the most contaminated sediment (“hot spot”), which had
a large benefit because almost 90% of the contaminant mass was in only
about 20% of the contaminated area. This activity resulted in a net debit of
2000 SAYs (Figure 7.14). However, the alternative included the restoration of
a rare and ecologically important hardwood wetland habitat that had been
severely damaged by past unrelated activities. This produced a 2500-SAY
credit resulting in a net environmental benefit of 500 SAYs. The responsible
party was happy because they actually achieved a benefit and the cost of
the NEBA-derived alternative (approximately $3 million including the hard-
wood wetland restoration) was only a fraction of the conventional dredging
alternative. The other stakeholders were also pleased with the plan because
of the hardwood wetland restoration that had been an unfunded priority in
their regional plan for years and they could demonstrate to their constituents
the removal of approximately 90% of the contamination.
7.3.4.2
Pollution Abatement in the Green River
In this hypothetical (but reflective of common issues in water resources
management) example, the pollution problems in the Green River resulted
from nutrient overloading from a variety of sources. The responsible state
environmental agency addressed the problem in this impaired water body
through the preparation of a Clean Water Act-mandated program by con-
ducting a total maximum daily load (TMDL) evaluation. This evaluation
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