You need to look at how much time you have to work. I would say 1 cu. yd. per man hour. For me 280 works out to 280 man hours maybe more if its a long way from the pile to where you want to spread it. If you've got infinite time, go ahead and do it by hand. However, if you consider that even at minimum wage, 280 hours is $1,442.00 worth of work, I would suggest you blow that much. For me, I would blow most jobs over 20 yards.