Unless facts exist which would reasonably cause an excavator to believe that an underground facility exists within the depth of the intended excavation, a permit shall not be required for the following excavations:
A. The tilling of soil to a depth of less than fifteen inches (15") for agricultural purposes;
B. For replacement of highway guardrail posts, signposts, delineator posts, culverts, electric poles, telephone poles and traffic control device supports in the same location and depth of the replaced item within a public highway right of way. (2003 Code § 8-06-03)