Which factor is NOT a primary contributor to construction site erosion?

The correct choice indicates that building materials are not a primary contributor to construction site erosion. When assessing erosion processes, the primary factors typically involve natural elements and site conditions that directly affect soil stability and loss.

Rainfall is a significant contributing factor, as the intensity and volume of precipitation can lead to surface runoff and increased soil erosion. Different soil types also play a critical role; for example, sandy soils are more susceptible to erosion than clay soils due to their structure and moisture retention capabilities. Runoff is another key element, as it can transport eroded soil particles away from the site, exacerbating erosion issues.

In contrast, while building materials are integral to construction practices and can influence site stability indirectly, they do not actively contribute to the erosion process in the same way that environmental factors do. Thus, they are not considered a primary factor contributing to erosion at a construction site.