Full text: The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 
is, 27-31 
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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. 
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. 
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 
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

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