Bill was one of those people every organisation used to have: involved with the system for most of his working life, with an encyclopaedic memory and always able to pull up a file from somewhere in his garage which nobody else could seem to locate in the filing system. If you let Bill keep talking he could tell you the overall condition of most of the major parts of the system and the location of most problem areas.
Times have changed, some may argue not necessarily always for the better, as a result of new technology, the availability of electronic storage and retrieval of data, and changing organisation practices on human resources management that has increased the focus on specialist outsourcing and job flexibility resulting in a reduction of specific job permanence.
Under this current regime, it is possible to assess the condition of a buried pipe system the information available can be used to develop a rehabilitation and maintenance strategy. Given the magnitude of the subject, this article will be restricted to several key areas.
There needs to be a purpose behind any program set up for the condition assessment of buried pipe assets, and it must be more specific than: “It would be nice to know what sort of general condition our pipes are in”. In terms of asset maintenance the process should look at two key areas. The first is the criticality of the pipes in terms of what happens if something goes wrong and the second are those areas where pipes are causing a continuous drain on the maintenance and operation of the system. There may be other drivers for undertaking a condition assessment such as the reduction of inflows during wet weather, elimination of dry weather exfiltration or even the prevention of salt water ingress in tidal areas. The focus and the method of undertaking the condition assessment and the intended objectives will differ in each case.
The value of a pipe asset to an organisation is related to what it does, how long it will last and how much it costs to replace. Typically the most critical assets are those that are large, deeply buried, located under other important infrastructure, crucial to the operation of the network, or could have major social or environmental impacts if they fail. A typical way of categorising assets to develop a condition assessment program is shown in Table 1.
Even without a Bill Goodman it is always amazing how much useful information can be obtained from existing data records with some effort and perseverance. It may only be a desk job but its importance and value should not be overlooked. It is often possible to identify the most critical assets by simply obtaining records on basic pipe and site data. Maintenance records often record call-out locations and details for collapses and blockages. Hydraulic performance can be obtained from catchment flow patterns, surcharge locations and overflow frequency data. If you are lucky it may even be possible to find results of previous inspections which can assist in the assessment of deterioration rates and the prediction of life expectancy. It is important that the data is not gathered simply because it is available. The data needs to be relevant to the objective of the condition assessment and rehabilitation strategy.
There will always be a need to fill some gaps resulting from missing or out-of-date information on the current condition of a buried pipeline. Pipe inspection and condition assessment techniques have improved markedly over the last 10 years and there is now a broad range of different devices, methods and support services that can be used to obtain and simplify interrogation of data. It is important not to lose sight of the reasons behind the gathering of missing information, otherwise there is the risk of spending more than is required for the privilege of being buried in data. Often the information required to assess the condition is in the simplistic terms of: “How big and how bad?” The obvious corollary of this is a decision on the spending required to fix the problem, and equates to: “How much do I need to spend and how soon?”
For large bore pipelines, direct survey by means of internal inspection by traverse is still the preferred option, although the definition of the size of a large pipe is increasing as the resolution of remote techniques improves. This method will inherently involve some risk to the traverse party, but good planning and reliable support crews can minimise this risk. An internal inspection can be of pipe lengths or of manholes. Observations made during the inspection and locations of deterioration need to be carefully reported in a systematic manner and supported by photographs, and in recent times video records, to ensure repeatability of the interpretation of the results.
The most common type of equipment used for determining the condition of small and medium sized pipes by remote survey is CCTV. The old days of black and white, blurred images and single focus are well and truly passed, with full colour cameras and heads that can tilt, rotate and zoom to produce high quality images. Data quality is now often governed by the level of the cleaning of the pipe and the ability of the operator to accurately code what is seen. The cameras have become an even more powerful diagnostic tool through the piggy backing of assessment software that can store, score and analyse inspection codes and can produce summaries that can assist in decisions on rehabilitation.
Other techniques are also available for use in gravity pipes as an alternative or supplement to CCTV. Sonar allows the mapping of the pipe surface and the location of defects below flow. The ‘Lightline’ technology allows the mapping of pipe deformation and deterioration by measuring any deformation in a circle of light projected onto the pipe’s internal surface. High resolution digital imaging with data recognition systems to identify defect types have recently become available overseas and may one day replace CCTV as the tool for condition assessment. There are also techniques such as ground penetrating radar that are available to examine the condition of the bedding conditions outside the pipe.
Irrespective of how or how much information is obtained, in most cases the picture obtained of the condition of the pipe is only a snapshot in time, unless previous information is available. A major defect in a pipe may have been the result of poor original construction which once formed has been stable ever since. Conversely a minor defect may have formed very recently and is increasingly allowing the influx of bedding support materials that could lead to rapid degradation. For this reason the ranking of defect codes using what is observed will always be at best a probabilistic approach. However in the absence of an alternative it at least allows a systematic basis for the assessment of pipe networks and the development of rehabilitation programs.
Condition assessment must be followed by a decision making process. In simplistic terms the decision process should be predominantly black or white - do I fix it or do I leave it? Obviously there will be some cases of grey, where the decision is not clear cut, in which instance the response may be to keep an eye on it an review it again so many years time.
Unfortunately, it is all too often the case that the money required to rehabilitate a pipe network exceeds the amount of funds available. In such cases, it is necessary to prioritise work so the assets with the highest risk obtain funding first. Modern data interrogation software is very good at identifying assets with the highest defect rating. When reviewed in conjunction with other factors that relate the criticality of the pipe, as mentioned above, a sensible ongoing program can be developed for rehabilitation.
Ideally it would be nice if in the future it was possible to sit down at a terminal and obtain all the information on a pipe network system including hydraulic, structural, and operational performance and maintenance together with the current condition assessment and details on site constraints that relate to the criticality, sort of like the electronic version of the Bill Goodman’s of the past. A new response to such queries as they may arise might be “Ask PC Bill Goodman”.
