When keying, what is the minimum width required?

The correct choice specifies that the minimum width required when keying is one-half the slope height or a minimum of 15 feet. This requirement helps ensure the stability and integrity of slopes during construction. Keying is a technique used to anchor a structure into the soil or to create a notch, which helps prevent sliding and improves overall support.

By having a width that is either one-half the slope height or at least 15 feet, it ensures that the keying extends sufficiently into the ground, allowing for a better distribution of lateral forces. This requirement is essential in maintaining a safe and stable environment in earthworks, protecting against potential erosion or failure of the structure.

Other choices suggest dimensions that do not provide adequate stability for keying. For example, one-third the slope height may not adequately secure a structure, and stating equal to the height of the trench may not take into account the necessary stability required beyond just the vertical depth. A minimum of 10 feet would likely be insufficient for most slopes, especially in varying soil conditions. Thus, the specified alternative ensures a comprehensive approach to keying safety and structural integrity.