The economic impact of corrosion and it’s degradation of infrastructure and assets is estimated to be 3 to 5 per cent of GDP each year. This represents an annual cost of many billions of dollars to the Australian and New Zealand economies.
The cost of corrosion to the water industry is one area that has been quantified. The effects on water distribution and sewerage collection pipework and infrastructure impacts many areas of the economy and covers a wide ranging list of assets owned and operated by urban and rural water utilities, industry, agricultural and domestic environments.
During a pipeline failure event, there are also intangible costs that can have a significant effect upon the wider community. These can include disruptions due to flooding, road closures and loss of trade. These costs have been estimated at $91M per annum to the Australian urban water industry.
The total estimated annual cost of corrosion to the industry and the wider community in Australia is $982 Million which equates to an approximate annual cost of $60 for every adult in the country.
The water industry corrosion cost figures are contained in a report entitled Corrosion Challenges – Urban Water Industry by Greg Moore and commissioned by the Australasian Corrosion Association (ACA). The report estimated the corrosion failure costs and identified which might be attributable to industry practices, industry skilling and regulatory frameworks. The report also looked at some potential cost reduction strategies that could be implemented.
The main infrastructure assets owned and operated by water authorities are the pipelines and treatment plants. Moore’s report showed that the Australian water industry faces many challenges, particularly in the areas of asset management of ageing infrastructure and the required training to support the prevention and remediation of corrosion. The cost attributable to the maintenance and repair of sewage treatment plants is also considerable.
The failure of a major pipeline or reservoir could have far reaching consequences. Not only could such an event have immediate catastrophic impacts to the surrounding area, there would also be long term economic impact on water, and possibly power, supplies to cities and towns. Repair and rebuilding costs would also be high.
As most pipelines are buried “out of sight and mind,” the water industry has had a reactive approach to maintenance whereby the pipes are run to failure, with individual pipe failures repaired until the failure rate reaches a predetermined level, at which point the entire section of pipeline is replaced. For smaller pipes this is still considered “best practice” for the industry, but for larger critical pipelines a more proactive approach is being adopted.
One recommendation of the report was for water authorities to increase pipeline condition assessment to predict when failures might occur. Pipe materials such as grey cast iron and asbestos cement make up a large proportion of reticulation pipes in Australia and many of these are reaching a time where replacement will be required. In some cases, where the consequence of failure is very high, condition assessment is used to evaluate replacing the pipeline before any failures occur. However, there will always be difficulties in any proactive approach to manage buried assets where there is limited technology to carry out condition assessments. Most water utilities have active CCTV inspection programs where internal corrosion of non-pressure sewer pipes can be assessed and repairs, renovations or replacements of these sewers implemented before major collapses occur.
Almost immediately after the establishment of European colonies in Australia during the mid-1800s, a water industry started to evolve. Construction of the infrastructure to deliver fresh water for domestic and commercial consumption, and to remove and treat waste water and sewage, slowly developed up to the end of World War 1. In the years following both World Wars there were periods of rapid development, but the greatest expansion occurred during the 1970s, when approximately 5000 kilometres of pipeline were installed.
Pipelines are the largest group of assets and consist of pressure pipes used for the conveyance of water and sewage, and non-pressure pipes for the conveyance of sewage. Pipelines are made of a variety of materials. Plastic pipes are not subjected to corrosion but the other pressure pipe materials such as cast iron, ductile iron, steel, concrete and asbestos cement, are all susceptible to both internal and external corrosion to varying degrees.
The performance of all pressure pipes is reported in the Water Services Association of Australia (WSAA) National Performance report as the number of water main breaks per 100km per year. The average reported number of 19 per 100 km, which, over the more than 139,000 km of water mains in Australia, is approximately 26,700 breaks per year. This is an enormous problem for the water companies, even though a reported ‘break’ might be a major pipe failure or a minor leak.
The WSAA is the peak body representing the Australian urban water industry which provides innovative, sustainable and cost effective delivery of water services. Some activities undertaken are the facilitation of strategic standardisation, industry performance monitoring for 73 water utilities across Australia serving approximately 75 per cent of population. The water utilities are required to report costs and performance to the WSAA each year.
Major urban water utilities also operate 260 water treatment plants and 442 sewage treatment plants. While some water supplies are only disinfected, the majority of supplies are also filtered and treated to remove impurities so to ensure the water quality meets the Australian Drinking Water Guidelines (ADWG). The consequences of failure of a water treatment plant are usually not as serious as a pipeline failure, but the facilities still require ongoing maintenance and repair.
Sewage treatment plants deal with raw sewage and are subjected in most cases to more aggressive environments than water treatment plants, primarily due to the presence of hydrogen sulphide which forms the weak, though still corrosive, hydrosulfuric acid when mixed with water.
In addition to the pipelines and treatment facilities, there are many other assets such as manholes, sewer vents, tanks, reservoirs, and pumping stations associated with water and sewerage systems which also have costs associated with corrosion. These costs can be high, especially where repairs and recoating of steel water tanks and other complex steel structures are required.
Civil assets comprised approximately 87 per cent of the reported depreciation costs for the water treatment plants discussed in Moore’s study. Using this data and the premise that all of the civil depreciation was due to corrosion, an average annual depreciation figure of $600,000 per plant was estimated.
In all treatment facilities there is an ongoing programme of replacement and repair to the infrastructure of the plant. It can be assumed, therefore, that this figure, or a proportion of it, could be used as a representative annual cost of corrosion.
Sewage treatment plants are considered to be exposed to a more corrosive environment than water treatment plants due to the presence of hydrogen sulphide gas. Many sewage treatment plants are also coastal, or close to the coast, so the marine environment adds to the increased corrosiveness of the sewage treatment plant environment. Both these factors are aggressive to concrete structures.
Studies conducted in the US show similar percentages but the actual amounts are higher due to the fact the much larger population lives in a wider range of geographies and infrastructure has been built to suit the climatic conditions. Many pipelines are buried much deeper to minimise the impact of freezing and other extremes.
The water industry utilises the skills of a wide range of staff to manage, operate and design water and sewerage systems but there are very few training courses available to teach corrosion and its impact on the water industry.
The remit of the ACA includes educational activities such as seminars and training courses to inform and guide organisations and practitioners about topics including the latest protective technologies and processes.
A recommendation in Moore’s report was to implement accredited training courses designed for water industry personnel. Such courses would cover topics such as corrosion basics for the water industry; materials and corrosion control for use in conjunction with the Water Supply Code of Australia and the Sewerage Code of Australia; and identification and assessment of pipeline failures in the water industry. In particular, there should also be increased training in cathodic protection technologies, especially as applied to aging steel water mains, tanks and towers.
The ACA is a not-for-profit, membership Association which disseminates information on corrosion and its prevention or control, by providing training, seminars, conferences, publications and other activities. The industry association was formed in 1955 and represents companies, organisations and individuals involved in the fight against corrosion and promotes cooperation between academic, industrial, commercial and governmental organisations.