Utilities are required to mark their lines when anyone is doing excavation work and has requested a locate ticket from Tennessee 811. The APWA color codes to the right are the various colors of markings used by utilities to mark their underground lines. The lines may be marked on the ground in either paint, stakes or flags. Be familiar with them so you are aware of what is marked. Markings do not necessarily mean that is the type work being done. Click here for more information.