The following numbers are critical when excavatng:

2 feet         Materials and equipment must be kept at least 2 feet from then edge.         

4 feet         An exit must be provided if the excavation is 4 feet deep or greater.

5 feet         A protective system is not needed if the excavation is less than 5 feet deep and the competent person determines there is no potential of a cave-in.

6 feet         Guardrails must be provided on walkways 6 feet or more above the bottom of the excavation.

25 feet       Exits must be within 25 feet of worker horizontally.