question about sloping and grading

[1930]

This is gonna be a long thread but in a nutshell what is the dummied down way to figure out if I have x amount of feet to play with how much slope I can expect to have and how much slope is too much slope that a heavy rain will wash it downhill over time?

I E I need to know at what point I should consider a retaining wall

Now for the long version: I have attached a picture which is perfectly clear to me and I hope it will be clear to you.

This is a 5 acre parcel of land

B indicates the area where I will be removing dirt ( pure sand ) because it is a much higher elevation than the proposed slab and I dont want to look at a hill behind my shop/home. I have been moving this material ( D is at least 6 ft higher in elevation to the slab ) down to the area marked C.

The difference at X is approx 6 ft in other words the proposed slab is 6 feet higher at this point than C. As you work your way across and around the slab the slope becomes less pronounced.

R front corner of proposed slab the slope is nearly nonexistent as in I need to create something there for water to run off and away.

I am having a 3 yard loader dropped off to move this material, Ive been moving it with a JD 544 which has done a great job but just isnt quite heavy/big enough. The bigger loader is not cheap, Ive got it for a week and as far as I know I shouldnt need anywhere near that amount of time but considering I have zero experience with grading Im in for a crash course and Ill do the best I can.

My plan is to cut out a line the width of loader bucket 2 feet deeper than the slab area, I plan to cut this out right in the middle of dotted line on my diagram. I then plan to take more out of the B side so as to create a slope up to my driveway.

Again how much slope is too much in that it will need a retaining wall so that my driveway ( which is still nothing more than more sand at this point ) dosent start falling down the hill?

Also there is at some point gonna come a time where there is no more material going into the C area and there is prob. gonna be a very extreme slope which may or may not require some type of retention.

Im attaching a bunch of pictures, maybe they will help a little to explain better.

Thanks

 

[1930]

More pics

 

[1930]

This picture shows D at its best

 

[1930]

This picture shows X at its best

 

[Tractor Seabee]

Some of what you do will depend on what will be planted on the final grade. Grasses and other ground cover will mitigate a lot of slope even in sandy soil. A good nursery can help you choose plantings that hold the soil. Up here you have to hydro-seed graded lane (no or little vegetation left) as soon as rough graded as part of your environmental remediation plan required to get any grading or building permit. Your plan also has to include the final landscape plan. Hydro-seed is a good idea after rough grading if completion is down the road.

Ron