I got a call to make a back yard look beter and wanted a recommendation on what could be done. She has a hill with a 35-40 degree angle. Now there are plants that are "mulched" with concrete. Of course the concrete is for holding the soil in place and prevent erosion. The measurements are: Base 175', Highest Point 9', Avg height 6' The kicker is, the hill is very sandy! After i start digging into the side, will the sand fall in? Will i need an engineer to look at it before i do anything? Building pemit? How deep of a foundation should i dig since this is sand? Usually i use #9 limestone about 4" deep and tamp it, but i think i'm gonna have to dig a 6-8" foundation and pour concrete with rebar for this particular wall.