Geologic Vulnerability - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 219

6.6 Summary and Conclusion
Through the construction of a vulnerability map, we have combined the knowledge
gained from Chapters 2 through 5 to explain the relationship between the natural envi-
ronment and human influence in urban areas. As stated in the introduction of Chapter
2, the arrangement, thickness, and composition of the sediment layers beneath our feet
have a profound influence on where cities are located, how buildings are constructed,
where roads are built—and perhaps most important to the development and redevelop-
ment of our urban centers—how contaminants behave and how they affect the environ-
ment and people. The two case studies presented in this chapter have highlighted this
relationship—but they are a just a small subset of the thousands of examples of this
important concept and its multifaceted connections.
As demonstrated by comparing the two sites in this chapter and as we shall see in the
next section of this topic—once the environment has been contaminated at levels that pose a
human or ecological risk—it is often very expensive to remediate, especially when ground-
water is affected. Furthermore, it may be impossible to fully remediate some sites even with
the most advanced technology. Therefore, minimizing wastes and preventing pollution have
proven to be the most effective methods for reducing costs, and ultimately, preserving our
environment. The two examples highlighted in this chapter are not uncommon. Tens of thou-
sands of industrial and even commercial and residential sites in the United States have con-
taminated soil and groundwater to levels requiring one or more expensive remedial actions.
The realization that certain locations or areas within urban regions are especially vul-
nerable to contamination offers even greater promise for resolving future environmental
issues. Geologic vulnerability analysis of urban regions produces essential information
for evaluating the environmental and financial risks associated with development and
redevelopment. By minimizing the impact of pollution once a release has occurred, certain
geological features may play, if we so choose, a central role in the development and rede-
velopment of an urban area.
However, the story does not end here because geology alone is not responsible for dic-
tating the environmental risks and the costs of remediating contamination. The physical
chemistry of contaminants themselves also plays a central role. Until now the focus has
been on learning the geology of urban areas and how the geology of a particular area
or watershed inluences environmental risk. The next section of this topic introduces the
next piece of the environmental risk puzzle—the contaminants themselves. And as will be
demonstrated, the physical chemistry of specific contaminants shares top billing with the
existing environmental geology when estimating the environmental risk.
References
Albinet, M. and J. Margat. 1970. Cartographie de la vulnerabilite a la pollution des nappes d”neau
souterrians. Bulletin BRGM (2nd Series) 3:13-22.
Aller L., T. Bennett, J.H. Lehr et al. 1987. DRASTIC: A Standardized System for Evaluating Ground Water
Pollution Potential Using Hydrogeologic Settings . United States Environmental Protection Agency
USEPA-600/2-87-35. Ada, OK: USEPA.