Treated wood ash & bonfire site.

webbfish.sw

Hello, recently moved into a new home and am starting to build a veg patch but have discovered ash mounds containing lots of nails, and a bonfire site with all sorts in it. According to neighbour he was a professional gardener and rather than pay at the dump he was burning everything in the back yard and wood burner... So I'm assuming that's treated / preserved wood, varnished items, old furniture, and a fair amount over a number of years. Read that CCA treatment contains arsenic and not been replaced by much better.. anyone got any suggestions; I'm on the side of getting a man with a digger scoop all the topsoil that looks to be impacted. Is this an overreaction, should I just grow veg away from it, if do how far... And anyone know of a reasonable priced place that would do soil testing in words that the average person could make an informed decision on? Any thoughts greatly appreciated. Thanks.