Most wastewater companies face an ongoing problem of meeting the demand for maintaining and replacing their pipes and sewers as required. The press frequently carries stories on the very high cost of this backlog, and exhorts companies to make inroads into infrastructure improvements.
Companies approach the backlog by looking at the most pressing problems with the best cost/benefit returns, because that is generally all they can afford to work on in terms of both money and manpower. The question then becomes - which assets have the highest priority for maintenance work and replacement?
There are two ways of approaching the issue. One is to look at the assets most likely to fail, which is those most in need of maintenance or replacement, the most damaged or in the worst state of maintenance. The more sophisticated approach is first to use this measure but then to look beyond it to ask the further question - what would be the impact if any of these assets failed? Risk is a product of both the probability of failure and the impact of that failure, where the impact of failure is often measured using a concept known as criticality.
There are trusted methodologies to define criticality, including the WRC criticality calculation, but the problem of applying them is the availability of data - they require a number of input parameters which, even if they exist in a company, are usually held in a number of different systems. Their computation is a considerable task.
The use of InfoNet
InfoNet specifically addresses each stage in the building of risk measures to automate the process, gathering the data from its own database and other linked databases, and undertaking the computations to produce lists of critical assets and proposed replacement and maintenance schedules. This is achieved in a number of steps, namely:
- Capturing survey data
- Automated condition grading of pipes
- Calculating criticality and risk
- Producing maintenance schedules.
Capturing survey data The key survey data for sewers comes from CCTV surveys, although surveys of manholes and other assets also play their part. In using CCTV data in an InfoNet environment, each pipe survey is viewed in order to record two types of observations - inventory observations and defect observations. Inventory observations are not necessarily adverse - sewer material for example. Defect observations record problems such as a crack, a tree root, or an obstruction, and InfoNet can be set up to use any one of four standard grading systems: PACP (USA), WRc (UK and Europe), WSAA (Australia), and CH2M HILL SCREAM TM - Sewer Condition, a CH2MHill Technology developed for use in the USA.
It is worth noting as an aside that the process of entering the data into InfoNet also gives every observation an immediate geographic reference, and allows it to be related to nearby assets or other features as required.
Automated condition grading Once each pipe or sewer has every observation recorded in InfoNet, the pipe can be automatically given a condition grading, again following the specification of one of the four standard grading schemes. There are two condition gradings that are relevant: the Structural Condition, specifying the soundness of the structure, and the Maintenance Condition, specifying the level of need for maintenance work.
Calculating risk The second element in the risk equation is the impact of failure. That can be based on any combination of:
- the impact on customers of failure - typically failure affecting high priority customers such as hospitals scores highly for example
- the cost of repair - a deep sewer for example will score highly for its higher cost of repair
- the disruption caused by failure - the impact on non-customers, such as road users in the event of a failure under a highway, can also be factored into the impact equation.
Because InfoNet has links to other systems, such as customer records and the location of the assets of other utilities, and geographic referencing can identify the area of impact of failure, the calculation of the impact and risk can be automated using the tools provided by InfoNet, according to the methodology the user chooses. The output of this analysis is a list of assets ordered by risk.
Producing maintenance schedules Although criticality is an essential measure, the final question is - which of the critical assets are running at an unacceptable level of risk of failure. Therefore the final output required is a list of those assets that have both a high level of criticality and a high probability of failure. InfoNet can produce this list as an essential start point to planning maintenance and replacement schedules.
In summary, the main problem with risk analysis is not the methodology but the practical issues of handling CCTV survey data, collating all the other data required for the analysis, and undertaking the calculations. InfoNet is specifically designed to automate this process with standard methodologies that are being used successfully in the US, Europe, Australia, and elsewhere around the world.