Trenches have a maximum allowable slope of 1/5 horizontal to 1 vertical in ___________________.

The correct answer pertains to the safety and stability standards for trench excavation within different soil types. Type C soil is classified as the least stable among the three types of soil classifications (A, B, and C) established by OSHA, which means it poses a higher risk of collapse. Due to its instability, Type C soil requires a more cautious approach to excavation, specifically a maximum allowable slope of 1/5 (or 20%) for trench walls.

This slope means that for every 5 horizontal units, the trench can only go down 1 vertical unit. The reasoning behind this guideline is to minimize the risk of trench collapses, as Type C soil is more prone to shifting and is less able to support vertical walls without additional support systems. Understanding these standards is vital for maintaining safety on job sites where trenching operations take place.