**Abstract**

Critical infrastructures operations significantly affect the triple bottom lines of sustainability. Considering the dynamic nature of infrastructure and its surrounding environment, the interaction between them can dramatically change over time. This results in a deviation from the predictions used in the design and construction of the infrastructure. Therefore, the negative impacts of critical infrastructures on the environment, society, and economy can exacerbate throughout their service life. It is crucial to maintain these impacts within the desired limits. The measures that attempt to perpetuate a facility's adverse effects on the triple bottom lines of sustainability can be called sustainability maintenance. Regular maintenance operations of infrastructure create an opportunity to integrate sustainability maintenance into preventive, corrective, and periodic maintenances. This chapter discusses four categories of sustainability maintenance of critical infrastructures: (1) minimizing adverse impacts of the infrastructure on people through maintenance, (2) keeping the maintenance operations sustainable, (3) sustainable material allocation throughout the maintenance process, and (4) environmental protection and restoration in maintenance operations. In each category, some of the best practices and methods are discussed.

**Keywords:** critical infrastructure, maintenance, sustainability, environment, society, economy
