State of Technology Report for Force Main Rehabilitation, Final ...

terms, or both. A second step is to consider prioritization for external data collection. A method for
identifying high risk locations in terms of likelihood of failure based on environment and operating
characteristics could pinpoint high risk locations, which would be selected for direct inspection.
There is a clear need for assessment methodologies that can work with limited data. These could
potentially be based on Bayesian belief networks. There is also a need for inspection technologies that
can provide data more cost-effectively to support these assessment methodologies.
A gap exists in terms of a design procedure for CIPP in pressure applications to ensure that long-term
performance requirements can be met. Little data are available on the long-term performance of
rehabilitation solutions in real environments, which a designer can use to predict the remaining life of an
asset that incorporates one of these rehabilitation methods. Another capability gap is the access needed to
the main and the need to shut down, dewater, and clean the main for rehabilitation. This is an inevitable
feature of any internal rehabilitation technology, as it is for inspection technologies. This also places a
limitation on the use of rehabilitation in force mains.
Findings and Recommendations
Most of the renewal activity has been outright replacement of the force main either by open cut or
trenchless means. New products and technologies are now emerging for carrying out a direct condition
assessment on a buried force main, as well as rehabilitation methods for those found in distress.
One method of assisting owners in their efforts to apply some of these emerging technologies will be in
the publication of demonstration projects and case studies. Also, setting up a decision support system that
helps a utility ask the right questions so that a viable rehabilitation solution emerges is paramount.
It is clear that a system rehabilitation program needs to integrate several aspects and to have a broader
vision than merely the rehabilitation technology and its implementation. The elements that need to be
integrated within the scope of an asset management approach include inspection, assessment,
maintenance, and rehabilitation.
Key elements of force main maintenance are regular cleaning, maintenance of cathodic protection
systems, and maintenance of air release valves. Inclusion of corrosion monitoring, pressure monitoring,
and leak monitoring should be considered.
The decision-making process relies on data from inspection to assess risk levels and to decide on
necessary actions. Determining the level of data or information required to support effective decisions is
a key aspect of the process. Too little data and the wrong decisions may be made; too much data and the
cost of obtaining the data may exceed its value in the process. Neither scenario is cost-effective. One of
the key data elements needed is verification of the long-term performance of pressure rehabilitation
systems. This should be a major objective of the demonstration project.
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