The City operates a program to replace a certain number of manholes each year. Those include manholes that have settled, been damaged or where improperly constructed, which can be a problem with traffic and safety. They are routinely checked to make sure they are properly seated, so they won't rattle or dislodge becoming a safety issue.
Staff also use the Vacon to clean problem area manholes, which collect grit or paper that could lead to a potential spill. The City also uses locking type manhole lids in problem areas where vandalism occurs.