Treat the sloping sides as half of a solid
rectangle and subtract their volumn from
you 829 cu yds. ie, for 2:1 slope on sides :
Total yards :
829 - (14 * 80 * 7)/27 = 539 cu yds
Note: the volumn of one sloping side is
1/2 of the (14 * 80 * 7)
If you slope the ends also, then :
Total yards :
539 - (14 * 40 * 7 )/27 + 4*Vc = 410 cu yds
where Vc is the inclusive yardage in the
intersecting corners. This value can be
approximated in your this case at about
4 cu yrds.
