The contractor must excavate a site to a final elevation of 6 feet. The site has varying existing elevations across three areas - A, B, and C. By calculating the existing and required final elevations for each area, and determining cut/fill volumes, the total excavation needed is 324.1 cubic yards of additional backfill material.

1. A contractor must excavate the
site shown in the following
sketch to a final elevation of
6.0’. Based on the site layout
and elevations given, the total
amount of excavation or backfill
would be ____cy.

2. N

4. Calculate elevation at 100’ & 200’

5. 22.0’
Δ = +14.0’ – (-8.0’) = 22.0’
Δ/lf = 22’/400’ = 0.055’

6. Δ/lf = 22’/400’ = 0.055’
Δ@100’ = 100’ x 0.055’ = 5.5’
El100 = 14.0’ – 5.5’ = 8.5’
El200 = 14.0’ – (200’ x 0.055) = 3.0’

7. EL 8.5’
EL 3.0’

8. EL 8.5’
EL 3.0’

9. C B
EL 8.5’
A
EL 3.0’

10. Area A
Finish El 6.0’
Ex El = {2(+14.0’) + 2(-8.0’)} / 4
Ex El = 12.0’ / 4 = 3.0’

11. Area A
Finish El 6.0’
Depth Excav = Ex El – Finish El
D = 3.0’ – 6.0’ = -3.0’
B’fill = (125’ x 400’ x 3’) / 27
B’fill = 5,555.6 cy

12. Area B
Finish El 6.0’
EL 8.5’
Ex El = {2(+14.0’) + 2(8.5’)} / 4
Ex El = 45.0’ / 4 = 11.25’

13. Area B
Finish El 6.0’
EL 8.5’
Depth Excav = Ex El – Finish El
D = 11.25’ – 6.0’ = +5.25’
Excav = (150’ x 100’ x 5.25’) / 27
Excav = 2,916.7 cy

14. Area C
Ex El = {2(+14.0’) + 2(3.0’)} / 4
Ex El = 34.0’ / 4 = 8.5’
Depth Excav = Ex El – Finish El
D = 8.5’ – 6.0’ = +2.5’
Excav = (125’ x 200’ x 2.5’) / 27
Excav = 2,314.8 cy

15. Vol = Area A + Area B + Area C
Area A Backfill
Area B & C Excavation
V = (-5,555.6) + 2,916.7 + 2,314.8
V = -324.1 cy
Or you need 324.1 cy of additional backfill