Methods and systems for use in the removal of trunnion pin sleeves and the supporting of lock and/or dam gate structures (e.g., tainter or roller gates) are disclosed herein. In one example embodiment, a method of trunnion pin sleeve removal includes causing either a constriction of at least one part of the sleeve or an application of a torque with respect to the at least one part of the sleeve, and subsequently applying a force to the at least one part of the sleeve so as to pull out the sleeve. Also, in another example embodiment, a system for supporting a lock and/or dam gate assembly includes a support assembly having a at least one pedestal assembly. The support assembly further includes a trunnion arm support structure, configured to be supported at least in part by the at least one pedestal assembly and to at least partially support a trunnion arm.