Mix Soils Together or Get Rid of Soil Interfaces

Q. I dug an area about  5 feet by 8 feet at around 12” deep. I removed all the bigger rocks and mixed remaining soil at around 70% native dirt to 30% soil pro compost and put it back in area that I dug. Native soil has lots of clay because it is was very hard to dig. 

Fill is used in many subdivisions. Sometimes this fill contains alot of rocks of different sizes. Landscape fill is extremely variable in quality in Las Vegas.

Because most of the soil that I removed contained very large rocks, I lost a lot of volume. I need to raised level of this area by about 5” to be in line with surrounded soil. Therefore I need to raise the level by approximately 40 sq ft x 5” high which I am reading to be about 3/4 of a yard of topsoil.

I still have about 1/2 a yard of Rejuvenate soil that I purchased from Viragrow. I also have about 1/2 ton of washed concrete sand left over in another pile that I was planning on discarding. 

What is your opinion on  using the Rejuvenate garden soil to raise the level on top of the mix of native soil and compost? Or even using the washed concrete sand (paver level sand) and mix it with native soils to give it volume? I am not sure exactly what I am going to be planting. Can be a deciduous fruit trees or some bushes . I just wanted to get the ground nice ready for future planting and removing the large rocks that I mostly have in backyard.

A. You can mix the two together with no problem. I am looking for two possible problems when reading what you are planning to do. It's best to never use reject sand. True reject sand may have a lot of very small particles that can slow down or plug drainage. The second is creating an interface problem between pure sand and the soil mix. For this reason, either mix the two ingredients together or layer them. If you decide to layer them, be careful of creating an interface between the two layers which can affect drainage. To get around this interface problem, mix the two layers together where they come together and then finish filling the hole.

A.