Question for builder, engineer, etc.

[TripleDigitRide]

An area needs to be leveled that will be used to place two shipping containers. I'm sort of assuming the fill will need to consist mostly of rock, if not all. I'm guessing the fill will need to be 5' - 6' deep at its deepest point. The "level" part of the existing ground is actually sloped more to wards the drop-off than the drawing depicts. If I had to guess, the fill area will be roughly 30' or so wide. 

As you can see in my crappy drawing, at the right side of the area is a drop-off. If building a retaining wall to hold the rock in place at the edge of the drop-off isn't necessary, that would be a huge plus. 

As we've all seen many times where rock is used to fill/level an area for a structure, parking lot, etc., the rock gradually slopes, keeping the rock in place and safe(r) from erosion.

My question is this: Is there a general rule of thumb as to how much of a slope and how far the rock need to extend past the leveled fill area? I hope that makes sense. Any input would be greatly appreciated.

Edited March 26, 2018 by TripleDigitRide

[gregintenn]

2:1 minimum slope. If you plan to topsoil and mow it, I'd prefer a 4:1 slope.

[peejman]

I'm sure there are standards or guidelines for site slopes when backfilled with gravel. It's not my forte, but I've got a buddy who does structural concrete so he might know. 

6ft deep x 40 ft long x 30ft wide is a LOT of gravel. Like 2.4 million pounds (1200 tons) of it.  Just off hand, I don't see how that wouldn't require a retaining wall. 

[gregintenn]

If you are able, using existing material from the hill side of the site will be much more economical. Oc course you will still want some stone for leveling beneath the concrete pad.

[gregintenn]

7 minutes ago, peejman said:

I'm sure there are standards or guidelines for site slopes when backfilled with gravel. It's not my forte, but I've got a buddy who does structural concrete so he might know. 

6ft deep x 40 ft long x 30ft wide is a LOT of gravel. Like 2.4 million pounds (1200 tons) of it.  Just off hand, I don't see how that wouldn't require a retaining wall. 

More like 500 tons of shot rock, but still expensive.