Environmental Engineering Reference
In-Depth Information
(e.g., actions generating noise, traffic, or pollutants). It is important to make
these calculations conservative to represent a realistic worse case and also
to compensate for uncertainty. If there are environmental impact standards
or criteria (e.g., air-quality standards) to compare with the calculated results,
the decision can be simplified and validated. If the calculations representing
a realistic worst case show that expected levels of impact or environmental
characteristics (e.g., water-quality concentrations) are well below applicable
standards (e.g., half of allowable noise levels or water-quality standards),
then a full environmental impact analysis may not be necessary. If on the
other hand, predicted levels exceed or even approach the values considered
acceptable, more analysis is probably necessary. This progressive approach
to determine the need for additional analysis was developed, refined, and is
now standard practice in Ecological Risk Assessment (see Chapter 7).
Caution must be exerted when applying preliminary assessment to
determine the need for full environmental impact analysis and all areas of
potential impact must be considered. In the early 2000s when the U.S. Coast
Guard (USCG) was under the umbrella of the newly formed Department of
Homeland Security, they were required to arm even their smaller vessels. The
USCG was concerned that firing from small vessels (as small as 7 meters long)
was substantially different from firing from much more stable platforms
offshore or larger ships which was the more common USCG practice. Thus
they felt extensive training and practice were necessary to maintain safety
and effectiveness for the program of fixed fire arms on small vessels.
As the USCG prepared to institute the training and practice procedures
in the sensitive environment of the Great Lakes, there was concern about
“bullets in the water” resulting in contamination of the aquatic ecosystem,
particularly the sediments from lead and other potentially toxic materials in
the ammunition. In order to determine whether a full environmental impact
analysis was necessary, the USCG commissioned a preliminary assessment
of what they considered to be the primary, if not the only, environmental
concern; the impact of toxic metals originating from the bullets on aquatic
organisms, particularly those associated with sediment. In order to make the
determination, the area of bullet deposition from the live firing was conser-
vatively estimated by tracking the line of fire, the course of the boat, and fir-
ing accuracy (Figure 4.2). For every input parameter, the value which would
result in the smallest deposition area (with the smallest area for a given mass
of material, the concentration, and thus the toxicity of the material in the bul-
lets would be the greatest) was used. Similarly, the greatest realistic mass of
bullets was used and the sediment concentration calculated. The concentra-
tion was then compared with criteria considered to pose no impact to aquatic
organisms, and the values were found to be well below concentrations of con-
cern (Figure 4.3). The calculated risk quotients (i.e., the calculated concentra-
tion divided by the safe concentration so that a quotient of 1.0 represents a
calculated concentration equal to the safe level and less than 1.0 is a concen-
tration below the safe level) were generally 0.5 or less (Figure 4.3).
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