For a geometry exercise only, draw a plane sloping downward and outward at 45 degrees from a footing edge. A trench bottom is 18 inches horizontally outward from that edge and 14 inches below it. Where is the bottom relative to the stated plane?
- AIt is 4 inches below the plane
- BIt is exactly on the plane
- It is 4 inches above the plane
- DIt is 18 inches above the plane
Where to look it up
Explicit exercise assumptions; not a universal code requirement.
Why C is correct
A 45-degree plane drops one inch per horizontal inch. At 18 inches outward it is 18 inches below the edge; the trench bottom is only 14 inches below. The bottom is therefore 18 − 14 = 4 inches above the plane. This checks a hypothetical geometry model, not actual soil stability, excavation clearance or code compliance.