Integrating GIS with risk assessment
Rich McGregor
Great Lakes Gas Transmission.
Troy, MI
John Beets
M. J. Harden Associates, Inc.
Kansas City MO
Greg Morris
Kiefner and Associates, Inc.
Worthington, OH
Introduction
Geographic Information Systems (GIS), if implemented correctly, provide a solid information
management base for pipeline companies to undertake myriad applications in which geographic location is
a basic component. Examples include basic query analysis, alignment sheet generation, facility
maintenance, tax analysis, and risk or integrity management related functions. With the increased
regulatory emphasis on pipeline integrity, operators are under pressure to find better, more efficient ways to
safely operate their pipeline systems. One of the most important applications for this system-wide high-resolution
data is risk assessment. This paper outlines the experiences of one operator in implementing a
new software application that uses GIS information to conduct risk assessment.
The GIS
Driven by the typical motivations
Great Lakes Gas Transmission Company (GLGT) began to develop their system-wide GIS
application in 1995. The motivations for undertaking the effort were typical of other companies in the
industry, which include:
- Consolidate data into a single database resource for the corporation, which alleviates duplicate and
conflicting data and centralizes the data for downstream applications
- Spatially reference the data to provide a link between the database and mapping applications,
which aid in moving the data to the field
- Develop automated alignment sheet generation capabilities
- Easier updating and sharing of resources within the company – employees have access to
continually updated data, maps, and alignment sheets.
Designed to achieve long-term goals
GLGT had spent considerable time and resources researching the experiences of other operators in
the development and implementation of GIS applications and had developed a good understanding of the
ways in which the GIS could be used to assist other work functions within the company. Since this
research was done before the GIS was developed, modifications were incorporated into the database and/or
downstream applications at the outset of the project rather than later, when the costs of these changes could
compromise the project. This is not to say that there were not hurdles to overcome as the project
proceeded, but simply that through planning and awareness, the number of setbacks that were encountered
was greatly reduced.
The GLGT pipeline system is relatively new, with the first of its pipelines constructed in 1967.
Because of its age and the availability of records, a vast amount of data about the pipe material, the
construction practices, the hydrostatic test history and service performance were readily available. GLGT
recognized the value of these data and sought a system which could best utilize what they had available to
them.
Prior to the development of the GIS, GLGT had begun to collect and store pipeline data
electronically. A number of downstream applications were researched, including risk assessment, to
determine the type of data often used in such applications. A suitable format was selected for each data set,
consistent with the intended use or uses of these data, before existing data were migrated into or new data
were added to their GIS.
Built with the ISAT model database design
The GLGT GIS application is based on the ISAT data model. The ISAT data model was
developed under contract for the Gas Research Institute (GRI) by M.J. Harden Associates, Inc. and
representatives from numerous operating companies. The ISAT data model represents an industry
consensus data model that can be used as the core structure for a GIS. Since its creation in 1994, the ISAT
data model has been used by a number of different operators for GIS. GLGT used the ISAT data model as
the core database, but customized the database design to include additional data tables used in other
downstream applications, including risk assessment.
Risk assessment model
The early model
GLGT began development of an in-house relative risk ranking model in 1998. The primary
purpose for developing the model was to use it to prioritize sections of the pipeline for maintenance. The
initial model consisted of 11 variables describing primarily 3 failure modes and 3 consequence
components. Data representing the pipeline attributes for each segment were collected and entered into an
Excel spreadsheet. This spreadsheet contained the algorithms required to exercise the model and produce
output.
GLGT divided the pipeline into predefined segments for conducting risk assessment. A
“segment” is defined as a portion of the pipeline system that can be treated as a single unit because all of
the pipeline attributes (or at least those used in risk assessment) are the same throughout its length. In the
initial model, GLGT chose to treat each valve section as a segment, a practice common in the industry.
Valve sections represented a convenient breaking point and resulted in manageable segment lengths
ranging from a few miles to almost twenty miles long. Thus, the pipeline attribute data in the risk
spreadsheet was used to represent each valve section in the system.
A redesigned model
The risk spreadsheet had been in place only a short time before GLGT assembled a team of
consultants to assist them in revising the model. The team consisted of pipeline specialists from Kiefner
and Associates, Inc. (KAI), M.J. Harden Associates, Inc. (MJH), and CC Technologies, Inc. (CCT). CCT
focused on the Corrosion Probability and the Stress Corrosion Cracking (SCC) Probability algorithms,
while KAI focused on the comprehensive model, which included probability algorithms for other failure
modes and consequences. MJH installed a new software program, PipeView Risk, to replace the risk
spreadsheet. The PipeView Risk software was chosen because it was designed to interface directly with
GIS as well as other databases for the purposes of conducting risk assessment.
A number of significant benefits were realized with the implementation of the new risk assessment
model and new software, including:
- Dynamic Segmentation is used to define smaller, more manageable segments
- Probability of Exceedance (POE) Analysis is used in the Corrosion Probability Algorithm
- Segments and risk results are geo-referenced (compatible with GIS for display/mapping)
Each of these changes will be discussed in more detail below.
The new model was rolled out in late 1999 and has been in use since that time. However,
development of the model continues, refining algorithms whenever possible with new information.
