"Weep Holes" may be utilized in which method of site grading?

Weep holes play a crucial role in the functionality of retaining walls. These small openings facilitate the drainage of water from behind the wall, preventing the buildup of hydrostatic pressure that can lead to structural failure or displacement of the wall. When water seeps into the soil behind the retaining wall, it needs to be effectively drained to maintain the integrity of the structure. Without weep holes, excessive water can create a saturated condition, which may compromise the wall's stability and lead to erosion or even collapse.

In contrast, weep holes are not typically relevant in excavation, fill placement, or drainage trenches in the same manner. Excavation primarily involves removing soil, while fill placement deals with adding soil or material to an area. Drainage trenches are designed to direct water away from certain areas, but they are not associated with retaining structures in the same way weep holes are. Thus, the use of weep holes is specifically aligned with the context of retaining walls, making this the correct choice.