When is dirt soil?

Neighbor had new dry wells put in for leach field on new septic system. Five holes, 2 1/2 ft diameter, 30 ft were bored down. When you handle the soil it feels good, there are no rocks, none, but it does not smell as rich as my garden soil. Currently all of this sits in a pile, about 25 -30 yds. When I look around I can see that this is old bottom land, explains the no rocks. My question, is the soil that was 10ft. 20ft, 30ft down soil or is it dirt? If I haul it home and expand my garden will it have enough life as it is or will I need to doctor it up for a year or two to be able to support plants? Add, manure from neighbors, old forgotten hay bales, put it on the side and plant nitrogen fixers, ... Thoughts?

Thank you

My guess would be that is a pile of dirt.

Is it dirt or is it soil? how to know what you're starting with so you can make it what you want it to become.

https://permies.com/t/63914/Soil

Form Dr. RedHawk's Epic Soil Series Threads:

https://permies.com/wiki/redhawk-soil