Thanks for all the great answers. Yeah, this looks to be a BIG job. ...
I'm just wondering, why did he make the flower bed so deep!? It's not
just 30 feet long, and 1-2 feet wide, but deep as well, about 1-2 feet!!
I assume he must have dug out all the soil, and probably used it for his
garden in the backyard??
Sound more like there must have been something larger there that was
removed/transplanted or somesuch. There's no reason a flower bed would
be below grade--it would end up drowning the flowers w/ decent probability.
Are you sure this isn't/wasn't a drainage-related feature? Where is the
water going to go that is being collected by the depression now--be sure
you don't all of a sudden have water running into the garage or
something after you fill this up.
As a practical matter assuming the above is resolved, if the
measurements are close to accurate this is between 2 and 3 cubic _yards_
of material required to fill it. That's going to be 30-40+ of those 2
cu-ft bags if you go the retail route which is ridiculously expensive.
Your only practical solution is have some topsoil delivered. if the
logistics of a large truck are indeed too cumbersome to deal with, find
a neighbor/friend w/ a pickup and go get a couple loads a weekend until