ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
59
is, 27-31
dynamic
her (eds.),
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behavioral
of the 7 th
ling, Delft,
geographic
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and J Jiang
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gs of 1997,
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403-418.
A GIS-SUPPORTED ENVIRONMENTAL RISK ASSESSMENT FOR PETROLEUM WASTE CONTAMINATED SITE
Su Chen 1 , Gordon Huang 1 , and Jonathan Li 2
1 Environmental System Engineering Program, Faculty of Engineering, University of Regina, Regina, SK, Canada S4S 0A2
Tel: (306) 585-5631, Fax: (306) 585-4095, E-mail: {chenllsu, gordon.huang@uregina.ca
2 Department of Geography, University of Regina, Regina, SK, Canada S4S 0A2
Tel: (306) 585-5273, Fax: (306) 585-4815, E-mail: jun.li@uregina.ca
KEYWORD: GIS, environmental risk assessment, Monte Carlo, fuzzy set theory.
ABSTRACT
Responding to an urgent requirement for effective management and environmental assessment of contaminated petroleum sites, this
paper presents an environmental risk assessment approach for petroleum-contaminated aquifers due to leakage from underground
storage tanks (USTs). It contains two components: environmental risk assessment and geographic information system (GIS). Using the
monitoring data and predicted fate of contaminants concentration under different transportation time and different proportion of
remediation strategies groundwater transportation model software-kit, the risk assessment model can be effectively incorporated with
effects of different contaminants and different remediation techniques within one framework. Extensive uncertainties for a number of
modeling inputs in an exposure-dose model are presented as a series of probability distribution function with a variety of forms, and are
solved using the classic Monte Carlo simulation method. Data originating from the exposure dose model are sequentially incorporated
into a fuzzy risk assessment approach to achieve an integrated risk level for the target location. Results of a case study indicated that
plausible solutions for risk assessment under different system conditions have been generated.
GIS provides comprehensive database of contaminated site conditions, tools for spatial and customized interface of risk assessment,
and visual presentation of modeling results and site natural and spatial characterization. Especially, integration of the risk assessment
results with Geospatial information is very helpful for identifying and assessing pollution impacts on specific receptors. A desktop
ArcView GIS was used in this study for spatial analysis and Microsoft Excel and Access were used for the spreadsheet and relational
database components, respectively.
1. INTRODUCTION
Development of the petroleum industry is currently associated
with a number of environmental concerns. Among them,
severe soil and groundwater contamination phenomenon is
attracting more and more attentions from the public,
governments, and petroleum industries themselves (Mathews
and Donahue 1989). This situation is especially worse in
western Canada where involves extremely active petroleum
production, processing, upgrading procedure. Showing by the
past and recent research, It is recognized that the major
sources causing soil and groundwater contamination are
coming from leaking storage tanks which are used enormously
by commercial, industrial and residential sectors nationwide.
In North America, several hundred thousand of USTs that are
used for storing petroleum products are leaking (Levy et al.,
1990). There are over 70 separate hydrocarbon compounds in
regular gasoline (Bruel and Hoag, 1984), and they are mainly
compounds of aliphatic hydrocarbons and aromatic
hydrocarbons.
The greatest harm caused by a leaking underground storage
tank, which holds petroleum or petroleum bi-products, is the
contamination of groundwater. Petrochemical compounds that
seep down to a groundwater formation will intend to float on
top of the water table according to their lighter specific gravity.
Also, volatile components can exist in gaseous phase and will
escape as fumes or odors. Other components, such as
benzene, toluene, and various xylenes (or BTXs), can attach to
the soil and exist in adsorbed phase. In addition, some
compounds can be in soluble phase contained within the
groundwater (Canter et al., 1988).
Soil and groundwater contamination can lead to a variety of
impacts, risks, and liabilities to the communities and for the
industries themselves. The leakage represents an increasing
danger to groundwater resources and public health (Testa and
Winegardner, 1991; Hayward, 1994). For example, it is proved
that one gallon of gasoline can render one million gallons of
water unsuitable for drinking needs. Since the nation draws
about half of its drinking water from groundwater sources,
there is growing concern that leaking underground storage
tanks will continue to contaminate many drinking water
sources. Exposure to contaminated soil and groundwater can
occur through skin contact, inhalation, or ingestion. Very truly,
even a small leak into an underground water table can be
permanently damaging to the source, since groundwater is
unable to naturally recharge and cleanse itself because
petroleum and its bi-products float on top of the water. The
leakage problem has led to a variety of impacts, risks, and
liabilities. In Canada, about 10% of 200,000 underground
storage tanks are leaking and contaminating the surrounding
environment, causing violent losses of thousands of dollars
annually to petroleum industries and stakeholders. It is
estimated that rendering all of these abandoned drilling sumps
will require a minimum expenditure of 10 billion dollars, what a
shock? Therefore, in-depth and effective environmental risk
assessment of groundwater contamination due to leaking
petroleum contaminants is important and anxiously desired for
evaluating the need for site remediation actions and providing
support for decisions related to prevention, estimation, and
remediation of the leakage and contamination problems
(Huang et al., 1999)
Since 1970 the field of risk assessment has received
widespread attention within both the scientific and regulatory
communities and the legal system (Paustenbach, 1999). In
recent years, risk assessment techniques have become widely
utilized in the decision making process related to contaminated
soil and groundwater problem, it could support managers with
a more rational and scientific base on which kind of decision
should be made.
Generally, the formulation of the environmental risk problem
captures the entire process of identifying the source term of
risk agent, toxicity assessment and exposure assessment and
risk characterization. This process involves a number of
chemical, physical, biological factors regarding to their direct or
indirect relations to the environmental risk problem. The related
parameters generally show high degrees of intrinsic variability
and substantial levels of uncertainty since many system
components in real-world problem many not be known with
certainty (Woodbury et al., 1991). This makes the study