Water main decision support system seizes advantages
Armlication Models
The custom-developed decision-support application or Pipe Evaluation System (PIPES) consists
of three main models:
The Deterioration Model is derived from a statistical analysis of the pipelines’ break history and
how these data correlates with direct or surrogate parameters associated with each pipeline.
Examples of significant parameters that correlate to breaks include the length and diameter of
pipe, static water pressure, pipe material, age of pipe, and whether a pipe is located on a steep
slope. As a result of the statistical analysis, a number of equations can be generated to calculate
the probability of pipe failure. These equations are built into the PIPES application and will be
accessed when the deterioration model is selected to evaluate the pipelines. Further discussion of
the statistical analysis process is covered in the section on Objective Evaluation.
The Vulnerability Model and Criticality Model consist of a number of parameters that can be
selected and ranked subjectively to evaluate the vulnerability or criticality of the pipelines.
These two models will provide the answer to questions like “Which pipelines are in need of
rehabilitation or replacement and which pipelines will cost the most if a break occurs?’
Examples of vulnerability parameters include soil corrosivity, corrosion protection, pipe
material, age of pipe, type of land use zoning the pipe is in, and whether the pipe is located in
liquefaction zone or steep slope.
Examples of criticality parameters include whether pipes are directly connected to hospitals,
medical facilities, kidney patients, dialysis centers, community centers, schools, major water
users, and whether the pipe is located in flood-prone areas.
The application is designed with the flexibility to allow users to rank or prioritize pipelines from
different points of interest. For example, the application can be used to rank pipelines for capital
improvement program (CIP) improvements, or to prioritize pipelines for corrosion protection, or
to prioritize pipelines to improve seismic reliability. This flexibility is achieved by allowing
users to create “sessions” that are tailored to a specific point of interest. With each new session,
the user can select the models for evaluating the pipelines; within each model, users can select
the parameters. All information generated by a “session” created by one user is available to other
users who want to review the results or create new “sessions” based on those properties.
Figure 2.1 provides an overview of the different levels that users will need to interact within
order to prioritize the pipelines. Figure 2.2 shows the process flow for a user of the PIPES
application.
The application does not store session results in the database; instead, the application stores all
the properties of a session. This includes information on the models, parameters, categories, and
all the ranking points assigned for the particular session. This approach reduces the storage
space required since the potential for multiple sessions being created by multiple users to
evaluate thousands of pipes in the system could quickly take up a lot of disk space should all the
results be saved in a database. The advantage of storing only the session properties is that the
same session can be re-executed periodically when enough changes in the pipeline attributes
have taken place. The most frequent changes would occur as pipelines are rehabilitated or
replaced in the system. Other parameters such as land use zoning, soil type, and neighborhood
areas are less likely to change much over time.
Figure 2.1 PIPE Application-Main components
Figure 2.2 PIPES Process Flow Diagram
