An electrical contractor is preparing to place the duct bank concrete encasement for the high voltage feeders between manhole # 11 and # 12, total distance is 323-ft. The duct bank is 2-ft x 3-ft and holds nine 4.5-in Schedule 80 PVC conduits. The amount of concrete to be ordered is most nearly: 

Solution:

Nominal 4-in Schedule 80 PVC pipe is 4.5-in O.D. 

Total Volume = 2' x 3' x 323' = 1938-ft³ / 27-ft³/CY = 71.77-yd³

 Total Deduct = 9 x (π ((4.5"/12")/ft)²)/4 x 323' = 321-ft³ / 27-ft³/CY = 11.89-yd³

Total Concrete = 71.77-yd³ - 11.89-yd³ = 59.88-yds³