I'm pretty sure chuck resetting requires Admin level access. It may be best to /msg ItsLawrence in game. He is available quite often.

Also take note of which chucks you would like to have reset and who the current owner is of those chunks. While in game type /player [chunk owner] to see when they have last visited the server. If you do this before hand it will make it easier for ItsLawrence to verify their inactivity.

If there are many chucks you are looking to reset as opposed to just a couple, you could make a list with the owners, last active date and coordinates to facilitate the process, provided everything checks out. But either way, contact the admin first to see how he wants to proceed.