For excavations less than 20 feet deep in type C soil, what is the maximum allowable slope?

In excavations involving type C soil, the regulations specify that for depths less than 20 feet, the maximum allowable slope is 1.5:1. This means that for every 1.5 units of horizontal distance, there should be a vertical drop of 1 unit. This slope ratio is deemed safe for workers to minimize the risk of soil collapse, as type C soil is classified as the least stable and most susceptible to erosion and failure under various conditions.

The choice of this particular slope rule is driven by safety concerns; ensuring the right slope can significantly reduce the hazards associated with tunneling and excavation work in unstable soil. A 1.5:1 slope allows for better stability and less likelihood of sudden soil movement compared to steeper slopes that could increase the potential for cave-ins.

Other slope ratios indicated in the options either exceed the maximum safety requirements for type C soils or are not practical for the conditions stated, thereby reinforcing the importance of adhering to standardized safety practices in plumbing and excavation work.