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

8.3 Guidance for Establishing a Comprehensive System Rehabilitation Program
Many questions remain unanswered and Tables 7-1 and 8-1 identify the key issues and what
additional information is necessary. However, 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, are:
inspection; assessment; maintenance; and rehabilitation. These will support a decision-making
process that ensures cost-effective maintenance of a desired service level for the force mains within a
wastewater collection and conveyance system.
When this framework is established, decisions concerning individual elements of the program can be
made. The scope of this report is rehabilitation so this section will focus on rehabilitation and not on
the bigger picture. When rehabilitation has been identified as a potential solution, three questions
must be answered in reaching a decision as to method:
(1) What is necessary? (i.e., What problem is to be solved and what performance is required
in service, including service life?)
(2) What is feasible? (i.e., What methods can achieve the performance level identified as
necessary?)
(3) What is cost-effective? (i.e., Of the feasible options, which achieves the performance
required at least cost, including alternatives such as replacement?)
When these decisions have been made, aspects such as material selection, testing, and QA can be
developed and included in individual project specifications. The specifications should require test
data or testing to be carried out to verify that the desired performance through the service life can be
met. It should also set out a QA regime to ensure that the material and its installation conform to the
specification requirements.
The type of specification used is also important. It may be prescriptive or performance-based. A
prescriptive specification identifies what must be done and also how it must be achieved. A
performance specification sets out what must be done and the required performance level, but leaves
the “how” to the contractor. A prescriptive specification places greater risk on the owner whereas a
performance specification shares risk more evenly between owner and contractor.
8.4 Guidance for Maintenance Programs
Maintenance also comes under an asset management plan and framework and contributes to costeffective
operation of force mains through their service life. Often poor or non-existent maintenance
is a contributory factor in the need for rehabilitation, so development and implementation of efficient
maintenance can reduce or delay the need for rehabilitation or replacement of a main, with significant
financial benefit.
The key elements of force main maintenance are: regular cleaning; maintenance of cathodic
protection systems; and maintenance of air release valves. Operational indicators such as power
consumption and frequency and volume of air release valve operation can identify when and where
maintenance is required. Linking these indicators to a maintenance program will make it more costeffective.
Using maintenance data can also contribute to condition assessment and decisions on
timing of rehabilitation or replacement of force mains.
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