For several years, AECOM has worked with water and sewerage utility asset-owning organisations, sharing knowledge globally to prioritise, optimise, and deliver national sewer rehabilitation programmes to extend infrastructure lifespans. Ryan Clarke and Keith Bingham outline the challenges and solutions Pollution of our seas, rivers and waterways is a huge challenge. Sewage overflows discharge wet wipes, microplastics, human waste and industrial chemicals into precious water resources. Blockages in pipelines result in street and property pollution urban runoff, which finds its way to watercourses. Infiltration to and exfiltration from sewerage systems present many problems, including additional unnecessary pumping and treatment costs, with associated extra carbon impacts. Work to build new and fix old sewerage assets has taken place around the world for centuries, but with a huge asset base to maintain, and limited budgets, it is a struggle to keep up with current rehabilitation demands. Urban sewerage rehabilitation can be expensive and disruptive. If works are put in place without sound evidence for the level of investment, they can undermine asset management approaches. Good asset stewardship requires a culture of proactivity and consistent improvement, which allows for the creation of sustainable, high-quality sewerage infrastructure. The technical aspects of sewer rehabilitation can be complex, such as pipe condition assessment, hydraulic flows, material quality and the generation (and handling) of large amounts of data. The social aspects present many challenges: dealing with real-world out-of-sewer or internal flooding, public health concerns, odour and septicity issues, client reputational damage, and concerns about data-gathering. The real-world challenges of traditional digging and sewer replacement methods include: road closures and reinstatements; health and safety issues; disruption to businesses and peoples lives; expensive and deep excavations; and large quantities of waste disposal with associated carbon implications. Sewer rehabilitation avoids open-cut works, although accessibility preparation works may be required at access points. Sewer rehabilitation process An organisational approach Organisations are currently tasked with delivering sustainable approaches despite the oft-conflicting pressures of finance, social attitudes and environmental concerns. With billions of buried infrastructure assets around the globe, the goal of asset stewardship is to provide a sustainable legacy for those assets to leave a positive, lasting impact for communities and our planet. For example, Irish Water and Northern Ireland Water (NI Water) are under ever growing strain to find capital investment to maintain Irelands 50,000 km+ sewerage network. It is a challenge to extend the life expectancy of existing assets rather than constructing new ones. This requires an organisational approach to realise value from assets in the achievement of objectives to derive value. Asset management embodies this approach. PERFORMANCE l soc ia Sustainability eco COST RISK enta l nm ro en vi Figure 1: The need to balance sustainability with performance, risk and cost n om i c The challenge of the net zero goal The UN Sustainable Development Goals and Net Zero by 2050 have become strategic priorities for many organisations as they seek to realise the benefit of demonstrating social responsibility by reducing emissions, conserving resources, and demonstrating socially responsible stewardship. Sewer rehabilitation works are usually completed in a trenchless manner with minimal disruption, often through existing access openings and with the help of robotics. This eliminates the need to dig ground (reducing thousands of tons of excavation). Removal of waste materials from site is also limited thereby eliminating transportation emissions. The rehabilitation work seals sewerage systems, thereby significantly reducing infiltration to and exfiltration from networks. The resultant savings in downstream pumping and treatment electricity costs (and associated emissions) are tangible. To retain pollutants within the sewerage network and prevent outof-sewer flooding incidents is also of significant reputational enhancement. Constrained by the challenge of capital investment budgets, an assetstewardship approach demonstrates social responsibility by delivering the maximum amount of rehabilitated assets while using the minimum amount of resources. Sewer rehabilitation programmes seek to leave a legacy of assets with as small a carbon footprint as possible. Purpose and context Review and continual improvement Op er Value and outcomes Life-cycle delivery dis pos e nt ain Asset management decision-making / ew Ren Leadership, people and culture te a re c / e at Strategy and planning Acq uir e Governance i a M Risk management Information management Figure 2: IAM Framework for Maturity Assessment Optimising decision-making to drive maximum value Physical infrastructure has a lifespan: it operates in a dynamic environment where it is exposed to dead and live load variability in ambient environmental conditions. This means that being able to anticipate where a short-term fix, long-term rehabilitation or decommissioning is needed makes decision-making more effective, optimises investment and focuses finite resources where required. The establishment of asset management decision-making processes that both reflect customer and stakeholder needs and define value is one of the biggest challenges that organisations face. The asset management decision-making spectrum is wide, and considers whether to defer action, rehabilitate, replace, or build a new asset based on current and future (long-term) business and regulatory drivers. It also must encompass maintenance strategies and mechanisms for identifying failure modes and time-based interventions. Effective decision-making processes enable the optimisation of maintenance intervals for a cost-effective level of reliability and risk. Decision-making using prioritisation and optimisation tools is invaluable: when combined with engineering judgement it is powerful, ensuring capital, operational and maintenance decisions align with asset management strategies and organisational objectives. To become better asset stewards requires addressing the challenge of incorporating non-financial information such as natural, social and human capital in a way that recognises risks while also creating opportunities for efficiency and resilience. Robust infrastructure management processes improve performance and minimise disruption to customers from real-world hazards. They also offer assurance through the knowledge that assets will continue to operate in the best way possible. Asset stewardship is about understanding the bigger picture, enabling organisations to make informed decisions about asset risk, cost, and performance in the pursuit of maximum value. The benefits of sewer rehabilitation lockages removed and structural defects fixed B Improved condition and performance level of the sewer system Likelihood of sewer collapses and blockages reduced Potential for sewer flooding and odour issues reduced Reduced disruption to stakeholders because of ongoing maintenance and trenchless techniques Reduced maintenance costs because of ongoing proactive maintenance over unplanned reactive Cleaner and greener waste disposal Trenchless rehabilitation allows quicker, cheaper, and less invasive rehabilitation over open cut. Future thinking Sewer rehabilitation programmes endeavour to meet organisational objectives in response to pressures from customers, shareholders, and regulators through finding ways of delivering the services more efficiently and sustainably doing more for less while addressing environmental, financial, social and health and safety pressures. Asset stewardship is about safeguarding physical infrastructure assets for tomorrow by what is done today every project matters and every individual matters. Tackling climate change is possible by delivering truly sustainable solutions and taking care of the assets society already has. For true change to be implemented on macro and micro scales, asset stewardship is about applying good asset management principles to invoke a proactive, continual improvement culture and refinement of capability to build a sustainable sewerage infrastructure legacy across Ireland for future generations. A sustainable approach to safeguarding today will secure physical infrastructure assets for tomorrow. Sewer rehabilitation process I nitial planning by asset planning teams using workshops with operational teams to gather information, and the sewer rehabilitation prioritisation tool, to create a scope of works Cleansing the sewer network to undertake an accurate inspection and remove any blockages Condition assessment by CCTV surveys of the sewer networks Collating information followed by a risk and criticality assessment, requiring data concerning asset definition, condition, installation year, age, decay curve and estimated replacement cost Costbenefit analysis and conceptual and detailed design with contracting partners to form a delivery programme Further cleaning and preparatory works for rehabilitation using lining techniques Repairing the asset through installation of liners, followed by associated repairs where defects are identified using ultraviolet light, steam or air Final survey of the asset for quality assurance, after which data is returned to the asset management team for timestamped cyclical review with the processes cycled to reprioritise future works Continual improvement throughout using lessons learned. A sewer pipe before rehabilitation (left) and after (right)