The Forgotten Step of Criticality

Defining critical assets

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February 26, 2021 | David Totman

In this era of amazing new technologies, I get the feeling that organizations are sometimes forgetting the important asset management step of defining critical assets. Do not get me wrong, I absolutely love all the innovation coming through in the condition assessment world. Other innovative companies like WinCan, IT Pipes, VAPAR, Sewer AI and others are making Condition Assessment more efficient than ever. Our most recent partnership with Electro Scan has shown me how effective they are in sewer main condition assessment and now they have a potable water solution as well!

However, most utilities and municipalities cannot afford to visit and assess every foot of their entire system. When you are asked to “Do more with less”, you need to prioritize. The first step of prioritization should be identifying critical assets. THEN follow through with a condition assessment on the most critical assets first.


Asset management 101 says:

Risk=Consequence of Failure (COF)*Likelihood of Failure(LOF)

Consequence we know as impact. The impact is a function of the criticality of the asset and/or event. A highly critical asset with low probability of failure still has HIGH RISK.

Defining asset criticality can be as simple as setting an attribute in your CMMS or GIS to CRITICAL = ‘Y’ based on institutional knowledge, or as complex as the asset’s functional role from engineering design specifications. An asset hierarchy in plant asset management typically has an inherent criticality built into the asset’s placement in a parent/child relationship. The higher up the hierarchy the more “critical” the asset from a roll up perspective. Yet understanding the weakest link of failure in an asset hierarchy is very important in understanding the causal relationships underpinning the definition of critical assets that could bring down the entire hierarchy should any one asset fail.

Network Criticality

Defining criticality in a pipe network can be a bit more complicated. Yet just like plants, by design it follows a hydraulic hierarchy. You have heard these before, the “skeleton” or “backbone” of the network. Sewer systems follow an inherent design hierarchy: 1 (highest) Interceptors, 2) Trunks, 3) Collectors, and 4 (lowest) Local Collectors. Typically, these are in order of decreasing pipe diameter. I have seen too many utilities declare critical assets based on diameter. It is a good estimate, yet you really do need to look at the hydraulics.

Many sewer pipes in flat lands have incredibly low slopes, less than 1%. In this case, diameter can be a good surrogate for criticality simply based on cost. In areas of undulating topography, you give me a 6 to 8-inch pipe with 5 to 7% slope and it will act more like a Collector or Trunk than its Local Collector designation due to the volume, or potential d/D capacity. In potable systems, transmission lines that carry water from one pressure zone to another should always be defined as critical regardless of their diameter. No one wants to lose treated water before it even gets distributed to the customers. This assumes that “critical” assets are then prioritized in the condition assessment program to mitigate potential failure.

Geospatial Criticality

Borrowing from my own phrase that “Assets have Intent to serve,” geospatial proximity of assets to other assets and or unique topographic conditions can increase criticality regardless of engineering design parameters. Hydrant criticality models immediately come to mind. Fire hydrants next to critical facilities such as hospitals, schools, nursing homes, etc. are typically deemed “critical”. Hydrants along a natural wildland fire corridor can be deemed critical. My favorite that I used at my former utility was using the GIS to calculate any fire hydrant that did NOT have a fellow hydrant within 500 feet of it, because it was then VERY critical should a fire break out, as our local fire department didn’t have hoses that could reach more than 500 feet. You get the idea.

In sewer systems, gravity mains collect sewage and take it downhill, just like rivers. Therefore, you see a lot of sewer mains near/in riverbeds. If you are trying to implement a program to reduce total system Inflow and Infiltration (I/I), maybe the lowest lying gravity mains in the area (near the river) should be deemed critical with respect to the program intent. Throw in a Consent Decree and I guarantee any sewer main near a US Navigable Water Body becomes highly critical due to Sanitary Sewer Overflow (SSO) discharge requirements.

Cart before the Horse

I applaud any organization beginning the journey to asset management, yet I ask that you perform a criticality assessment prior to any condition assessment. I know the cool toys are in the latest condition assessment technologies, but with a sound criticality assessment, you will know where best to deploy those cool new gadgets saving you time and money. And that is what asset management is all about.

PS: asset criticality is a built-in object behavior of the Asset Twin supporting our Info360 platform. Please stay tuned for more information as we roll this out in 2021.

If this did not make any sense or you have questions, feel free to contact me at



Tags: asset management, asset twin, critiicality, risk, condition assessment

About the Authors

David Totman

David Totman

VP of Asset Management


Having been a public servant for many years, David's passion for infrastructure is exemplified throughout his experience as the VP of Asset Management at Innovyze and advisory Past-President for the Utility Engineering & Surveying Institute in the ASCE. 

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