I think you have not had any responses because you are talking about such a monumental project!! The concern is, a 70 degree slope is terribly steep. Supporting that amount of soil really requires engineering design. Especially because the slope doesn't stop at your property line, and anything you do will have to work with the continuing slope. I can understand doing the work yourself, but for a design like that to be SAFE, it really should be designed by a pro. It really sounds like it has the potential to create a hazard.

The first thing I suggest is getting a few books from the library on retaining walls. Then consider calling some landscape architecture firms for design only. They are usually slow this time of year.

Good luck!

Thanks for your response and concern.
If the project is approached in small sections it does become manageable.

I am not looking to do this over a weekend but over years.

My slope is not in danger of falling and my house is not at the edge of the slope..
It is sandy and well drained soil. The base is easily accessible from the top.
I am looking for people who have terraced their own slopes. Their knowledge and experience would be helpful.

In the first place, you do not have a 70 degree slope. Such slopes are a rock cliff or if, of dirt, are falling down with exposed soil, no vegetation of any kind.

Not knowing what your slope really is like makes it impossible to make any suggestion for remediation.

If you care to, the graphic below shows how a home owner can measure slopes that are not too high so you and others can tell what you have to deal with.

You need a pole taller than the slope is high. A 10 ft joint of plastic pipe will do, or use two joined for taller slopes. Tie a string to a point on the pole that will be higher than
the slope. Use one that is light in weight to reduce sag. With the pole at the toe of the slope stretch the string over the top of the slope. Attach a string level to the string as shown and raise or lower that end until it shows level.

Measure dim. Y. Lower the pole and measure pole to string, dim. X. X minus Y = slope height. Next measure the run distance of the slope.

{{gwi:288827}}

If you have to use two pipes and they bow too much, use a second string to brace the top of the pole as shown.

If you don't know what a string level is, go to the link below to see one.

Here is a link that might be useful: string level