When removing manhole or handhole covers or making excavation, employes shall promptly protect the opening with a barrier, temporary cover, or other suitable guard, and see that danger signals or red lights are displayed in a location conspicuous to the traffic until permanent covers are in place or the excavations are filled.
34 Pa. Code § 39.541
This section cited in 34 Pa. Code § 39.501 (relating to general requirements).