Warren Beere, Condition Assessment Engineer at Xylem, takes a look at how taking a data-led approach to rising main management has a key role to play in preventing sewage and wastewater pollution.

Image:SmartBall® a free swimming tool to detect leaks and air pockets

Warren Beere: Water utilities are currently under immense pressure to reduce uncontrolled sewage discharges. Figures from the Environment Agency show there were 301,091 spills in England alone in 2022 – an average of 824 per day. Public outrage over the pollution of our rivers and seas has prompted UK utilities to announce a £10 billion investment plan, on top of the £3.1 billion being spent by 2025.

The potential for financial and reputational damage can be lessened via a simple method – data-driven inspection. By taking a proactive, data-guided approach, water utilities can reduce rising mains failures, cut their costs, boost public trust and goodwill, and remain compliant with the Environment Act 2021.

Prioritising inspection = lower costs

Upgrading the entire sewerage system is not practical for many reasons, one of which being the significant price tag: costs can vary between £400K to over £2 million per kilometre for large pipelines, depending on pipe diameter. However, rising mains rarely develop issues across the full length of the pipeline: in fact, Xylem generally find less than 5% of inspected pipes show signs of deterioration so complete pipeline renewal is often unnecessary.

Pipeline inspections allow asset owners to pinpoint areas of concern and make localised repairs before they fail at less than 10% of the cost of complete pipeline replacement. This targeted approach is the key to managing capital expenditure and making savings on reactive repairs, not to mention avoiding hefty Environment Agency fines.

Consequences of uninspected mains

Ageing mains are extremely vulnerable to failure due to surges in pressure, joint leakage, external corrosion, and internal corrosion – yet often, these are not spotted until disaster has struck. Disaster can take many forms including sewage backing-up into residential buildings or large volumes of wastewater released into the environment.

Emergency repairs are often extremely disruptive to the public and sewer rising main failures can cost water utilities in excess of £1m to repair, as well as causing unwanted media attention and major reputational damage. On top of this, the Environment Agency could soon be given powers to impose unlimited civil penalties – currently capped at £250,000 – meaning the financial implications could be huge. However, this can all be prevented with proper inspection and maintenance programmes which identify problematic areas before they cause bursts.

Challenges of inspecting rising mains

A lot of technology that has been developed for gravity sewer inspections is unsuitable for rising mains, such as smoke testing and traditional crawler CCTV. Even newer technologies may encounter one or more of the following challenges:

1. Lack of redundancy: It is common for rising mains to transport sewage from one region to another along a single pipeline and so dewatering or even stopping flow for any significant period is not feasible.

2. Access issues: Unlocatable or impractical access points to begin the inspection limit the survey length or what can be achieved in a single run.

3. Technology limitations: While some acoustic technologies may be able to locate leaks, they do not all have the functionality to detect gas pockets which are of a bigger concern in terms of accelerated corrosion.

4. Incomplete data: Extrapolating results from localised pipeline samples are unlikely to catch defects. Remember; generally less than 5% of pipe sections show deterioration and so intermittent pipe scans are insufficient to draw conclusions about the overall pipeline condition.

Because of these difficulties, pipeline owners and operators have historically tended to take a reactive approach to rising main maintenance, but the Environment Act 2021 and growing public dissatisfaction over sewage spills are placing pressure on water companies to act - and act fast. Fortunately, advances in technology are revolutionising the task of inspecting rising mains, making it easier and more cost-effective for utilities to take preventative action while overcoming each of the challenges listed above.

Devices to enable data-driven inspection

Rather than waiting for a failure to occur or jumping to complete pipeline renewal as the first port of call, the first step should involve collecting data. Data from desktop studies are useful to identify which mains are high risk however they are insufficient to make multi-million-pound decisions such as which pipelines should be replaced. The money is much better spent collecting inspection data and only making localised repairs to the sections that need it.

It’s important to have a rising main management strategy that balances risk with system performance and cost-efficacy. Asset owners should invest in proven inspection technologies that can identify both leaks and gas pockets as an economical first step for screening rising mains. For the high-risk rising mains, inline electromagnetic inspections overcome the typical inspection challenges and should be accompanied by detailed engineering analyses which enable a deeper understanding of the pipeline condition. A thorough inspection strategy provides a complete picture of rising main health and will give utilities the data necessary to make confident decisions around managing critical assets for years to come.

By carrying out a holistic programme of inspections and targeted repairs, utilities around the world are avoiding failures and extending the lifespan of their critical rising mains for just a fraction of the cost of full replacement. Proactive investment in inspection technologies and the data they provide directly results in fewer sewage spills, reduced capital expenditure, less negative media attention and ultimately a better performing, safer asset.

Visit info.xyleminc.com/smartball-workshop to register your interest in a free Rising Main Management Workshop where Xylem’s engineering experts can provide further information on how to effectively assess the condition of rising mains.