Maintenance involves activities that help keep the assets in good working order, so it will operate as intended. Maintenance falls into the broad categories described here. Examples of the different types of maintenance are provided below.
Routine or Planned Maintenance Examples:
An example of this type of activity is a planned sewer cleaning program. The system may decide to clean 1 mile of sewer every month, and a plan can be developed to move through the sewer system to get this work completed.
Cleaning the forebay after a rain event is another example of a planned maintenance activity.
Predictive Maintenance Examples:
Machine vibration is continually monitored through sensors that are attached to the machine. The sensors gather data to assess and monitor machine health quickly and accurately. Sensors are used to quantify and report how smooth or rough the machine is running. Vibration analysis and monitoring can be used to discover and diagnose a wide range of problems related to rotating equipment.
Another example is close-circuit televising (CCTV) of sewer line or placing a condition monitor insied a pipeline to determine wall thickness or the presence of holes in the pipe.
Preventive Maintenance Example:
For example, if the system examines a sewer with a camera and it shows significant corrosion of a concrete pipe, the system may wish to add a chemical to reduce sewer gas build up. Another example is a pump that is showing signs of wear in the bearings. The system can replace the bearings before they fail so that the work may be performed when it is advantageous for the system (e.g., during business hours, when an operator is on duty, and when spare parts can be ordered ahead of time.) Watering plants at the beginning of the asset’s life in a green infrastructure project could also be considered preventive maintenance.
Warranty-Related Maintenance Example:
Warranty maintenance is often the systems responsibility. However, in the case of Johnson County, KS the contractor has to sign a maintenance bond for the first three years and then responsibility is turned over to the city. Before the maintenance can be turned over, it needs to be certified that it is working by an engineer.
Proactive maintenance activities are those that are carried out in a planned fashion. Reactive maintenance activities are those that are completed after the asset fails to meet the desired level of service or fails to function at all. Different types of assets need different ratios of proactive and reactive maintenance. For gray assets, there is enough historical information to establish a best management practice of 80 percent planned maintenance (including the categories of planned, preventive, and warranty-related) and 20 percent reactionary (corrective) maintenance. For green infrastructure, data is still needed to define best management practices. However, for both green and gray assets, the type of asset, its risk level, and its replacement cost must be considered when optimizing maintenance funds.
For low-risk assets, the most economical option might be to allow the asset to fail. This allows the full life span of the asset to be achieved. This management strategy is called “run to failure,” or managed failure. In this case, the operations staff are choosing to let the asset run until it fails, at which time it is repaired, rehabilitated, or replaced.
Green assets can become more self-sustaining over time, so staff might be able to reduce the frequency of planned maintenance. Gray assets typically need higher levels of planned maintenance over time. When considering full life-cycle costs, consider these differences in planned maintenance costs, as it might impact the comparison of a green asset to a gray asset intended to perform the same function.
Risk should be a factor in determining how much to invest in maintenance for each asset. The maintenance needs for green assets are often highly dependent on the specific location, rather than the asset type. Therefore, risk might need to consider asset location, not just asset type, for green infrastructure.
A companion activity to maintenance is monitoring, which includes inspection. Monitoring can help determine when maintenance should be performed. Monitoring can be ongoing and permanent using continuous read equipment, or it can be intermittent. Monitoring might also allow the asset’s operation and maintenance to be adjusted and improved over time. Permanent monitoring might also be called predictive maintenance, which is conducted to monitor specific condition attributes used to predict when asset failure might occur. Asset temperature, vibration, and oil quality are some attributes that can be permanently monitored. Intermittent monitoring might also be called inspection. During the inspection of an asset, staff might check specific attributes, such as oil levels, or review the overall condition of the asset. Green assets likely require more frequent inspection in early stages of the asset’s life, while a gray asset might require more frequent inspection at the later stages of the asset’s life. Monitoring might allow an asset to be adjusted and improved over time.
To know the best way to maintain the asset, it is important to collect maintenance data. This data should include the costs for any maintenance activities conducted. Maintenance data can aid informed decision-making. Data can also be used to improve decision-making after failures. WRFThe Water Research Foundation’s Asset Management Framework for Forested and Natural Assets provides example of maintenance activities required for natural assets as shown below.
WRFThe Water Research Foundation‘s Asset Management Framework for Forested and Natural Assets: Table 9-3. Examples of Specific Maintenance Activities for Different Natural Assets.
Natural Asset Type
Asset Stressor or Hazard
Predictive and preventative maintenance – Jim Smith, Director, Infrastructure Planning, Louisville Water Company, Louisville, KY
The importance of maintenance – David Montgomery, SCADA Manager, Albuquerque Bernalillo County Water Utility Authority, Albuquerque, NM