Condition Assessment on the U.S.’ Aging Sewer Systems
Sewer infrastructure in the U.S. needs replacement and rehabilitation.
In 2016, the EPA estimated $271 billion is needed for wastewater infrastructure over the next 25 years, only $51.2 billion of which “to rehabilitate and repair conveyance systems.”
The conveyance systems currently installed are expected to last well beyond their design life. However, as these systems continue to age, they continue to deteriorate and the need for funding continues to grow.
Utilities and collection system owners are charged with acquiring funding (when possible), prioritizing projects, and allocating resources wisely to best preserve their system’s integrity.
This means understanding the condition of their sewer systems, where the most pressing needs are, and taking informed action – the fundamental purpose of condition assessment.
The Importance of Condition Assessment
Condition assessment is the first step in addressing these replacement and rehabilitation needs.
Condition assessment provides owners an understanding of the overall risk of the collection system, where replacement and rehabilitation needs are greatest, and what type of intervention is necessary.
For a gravity sewer system the condition assessment is low cost compared to the inevitable rehabilitation or replacement of the same pipe. Pipeline CCTV for an 8-in. pipe could cost as low as $0.80/linear foot (LF) while a pipe burst of the same diameter could be at least $80/LF. Using condition assessment to drive later rehabilitation activities and funding allows a utility to use its budget to its fullest extent and prioritize higher risk projects.
Collection system risk is made up of two components: consequence of failure and likelihood of failure. The consequence of failure is difficult to change – a pipeline with large flow volumes cannot be addressed through replacement and rehabilitation – making likelihood of failure an easier component to address.
Consequence of failure and likelihood of failure are built into risk models that are developed specific to each utility’s needs, asset classes, and goals. By understanding the internal condition of collection systems, likelihood of failure can be accurately measured and effectively mitigated.
As utilities begin the process of condition assessment, there are several steps that guide how to gain a full picture of a utility’s system based on their goals and the unique situation.
Selecting the Right Technology
Pairing the right condition assessment technology with system assets is key to generating useful data.
For gravity sewer condition assessment, there are a few core technologies that have been around for decades.
Closed-circuit television (CCTV) equipment has evolved from only a standard pan-and-tilt setup to high-definition digital and panoramic capabilities. CCTV provides a snapshot of the pipe’s current condition. However, CCTV alone might not be the right solution for all pipe sizes or the current condition of the pipe.
A CCTV inspection may need to be paired with pipeline cleaning to ensure debris and other objects are clear from the pipe and allow water levels to be suitable for a CCTV crawler.
Optimizing the maintenance needed on a pipeline, allows the sewers to flow freely and does not add excess strain to the walls of the pipe. On the other end of the technology spectrum, laser, sonar, or additional sensors may be paired with CCTV to measure vertical and horizontal deflections, hydrogen sulfide and many more parameters.
Managing the Data
Managing condition assessment data allows for critical insights into your system. To keep up with the evolving digital age, the way we manage and analyze condition assessment data has to change too.
There are dozens of options for asset and data management through computerized maintenance management software, data collection software, artificial intelligence integrations, and mapping solutions.
Finding ways to integrate the proper tools and processes to simplify workflows can help to ease unnecessary burdens on utilities. Selected software should be able to easily integrate new and historical data, exchange data with other software, and allow the end user to access their data as needed.
Using dashboarding tools, these data sets can be transformed into key performance indicators which allow stakeholders at all levels to break down the data into easily digestible pieces.
For example, all pipes with collapses or voids can be displayed on a map with charts beside them showing estimated cost of replacement and other historical information about the pipe. This empowers teams to make data-driven decisions to power their future planning.
As these technologies continue to evolve, artificial intelligence (AI) has been carving a space into the condition assessment and management world.
Largely, AI companies have been working to support CCTV data collection through automated defect recognition (ADR) software. Using the National Sewer Services Companies’ (NASSCO) Pipeline Assessment and Certification Program, AI software are trained to code defects and observations in a pipe.
While NASSCO does not currently certify any ADR software, this software can be used to aid in the condition assessment process to provide more consistent and accurate defect identification. This in turn drives a more consistent recommendation for rehabilitation and future funding needs.
Establishing Replacement, Rehabilitation Programs
System insights are used to drive replacement and rehabilitation actions that maximize benefits for owners.
Using accurate and consistent condition assessment data provides a solid foundation for a robust replacement and rehabilitation program. Condition assessment data can be processed through risk models, as mentioned earlier, that drive rehabilitation decision algorithms to provide a starting point for next steps to remediation.
These results can be prioritized based on different likelihood of failure and consequence of failure values to determine the highest risk assets within the system. Projects can be packaged to allow design and construction to be efficient and target hot spots across a utility.
The condition assessment data, prioritization results, and project packaging are best served in dashboards or other map driven tools to provide stakeholders with easy to understand and accessible data to keep up to date on project progress.
Condition assessment is vital to maintaining and operating a collection system. Whether a sanitary, storm, or combined system, it’s important to understand the inner workings, plan for asset aging and retirement, and implement smart strategies using different technologies to boost a utilities’ workforce.
