Quote:
Originally Posted by Unregistered
We are running ten, 120 Yard drains at a depth of 2ft. We are using a 4inch drain tile and leaving the gravel 2inches below the surface for soil and seed. How many tons of gravel will we need to be ordered to fill these lines.

We need to know the width of the trench in which the pipe and gravel are installed. Also will be there be any sidespurs, filled with gravel, perpendicular to the drain lines? If so we would need details on them. Is 4" the outer diameter of the drain pipe?
The easiest way to proceed is to calculate the volume of the trench, then subtract the volume of the drain pipe. You need consistent units for all dimensions.
The trenches are 10*360 ft * (22/12 ft) *(W/12 ft), where W is the width in inches. W has to be greater than 4, the width of the pipe you lay, but depends on your trencher. That result will be in cubic feet. (The above simplifies to 550*W, where W is given in inches, but the volume in cubic feet.)
The drain pipe is (pi/4)* (4/12 ft) * (4/12 ft) * 3600 ft = 314 ft³
The gravel is delivered loose. I would allow an extra 15% and then tamp it well before covering with dirt and seed. If you need to convert to cubic yards, divide the the number of cubic feet by 27 ft³/yd³.