Culvert size | Avg. rock diameter | Apron width1 | Apron length2 | Apron length3 |
---|---|---|---|---|
8" | 3" | 2–3 ft. | 3–5 ft. | 5–7 ft. |
12" | 5" | 3–4 ft | 4–6 ft. | 8–12 ft. |
18" | 8" | 4–6 ft. | 6–8 ft. | 12–18 ft. |
24" | 10" | 6–8 ft. | 8–12 ft. | 18–22 ft. |
30" | 12" | 8–10 ft. | 12–14 ft. | 22–28 ft. |
36" | 14" | 10–12 ft. | 14–16 ft. | 28–32 ft. |
42" | 16" | 12–14 ft. | 16–18 ft. | 32–38 ft. |
48" | 20" | 14–16 ft. | 18–25 ft. | 38–44 ft. |
Source: Kentucky Division of Water