Strmchzr

Most engineering firms will have a testing lab. Call a couple and ask.
You need to test the parent material.
Topsoil is first, then you get into your subsoils when they become uniform that is what needs to be testes. The problem is there may not be just one soil to be tested you may have a couple of different soils. If the pond is in a ditch, creek,the soils on one side of the creek may be different from the other side.
Otto