(a) At a minimum, all markings shall conform to the requirements of American Public Works Association (APWA) Uniform Color Code (ANSI Standard Z535.1, Safety Color Code).
(b) Markings shall be valid for an excavation site for 14 days from the time a positive response is given, unless the markings were placed in response to an emergency and the emergency condition has ceased to exist. If a line locate ticket has been refreshed pursuant to §18.3(e) of this title, relating to Excavator Notice to Notification Center, then the operator shall either ensure that markings are still visible and valid or shall re-mark.
(c) If the use of line marking may permanently damage property (driveways, landscaping, historic locations to the extent boundaries are known), a locator shall use spot marking or another suitable marking method or methods.

Source Note: The provisions of this §18.6 adopted to be effective September 1, 2007, 32 TexReg 3545