Soil Quality Concerns - Past Burned Garbage

I recently moved into a new house and was wondering what everyone's levels of concern would be with soil quality. I know past residents burned their trash based on evidence I've found in a couple different places around the yard. What has me even more worried is that I threw a couple boards and steps on the burn pile and it wasn't until afterword I considered they were probably treated. After reading the horror stories about the arsenic I potentially released, I was worried about any damage I may have done. It's about 75 yards from the house, but I was also worried about it entering the water supply. The ground is pretty much frozen and I dug out all of the ash and some underlying soil for proper disposal. There also hasn't been any precipitation to wash it down into the soil. I plan on taking some tests and would appreciate if anyone could offer a recommendation. Should I test now, spring thaw? Am I being overly paranoid (wouldn't be the first time). Thanks for your help!

Welcome to Permies billy, first off; what sort of residues from the burning have you found? Usually not everything burns completely up, no matter how hot the fire. Finding bits of plastics could be a concern as would bits of aluminum.
I'd recommend some soil testing in the burn areas, especially if you found wood fragments or charcoals.

AS for the leaching of arsenic from the boards you laid down. It is probably not a huge concern at this point, just remove them if you decide to.
Research in Volume 36 of Wood and Fibre Science shows that soil contamination due to the presence of CCA-treated wood after 45 years is minimal.
Should any chemicals leach from the wood they are likely to bind to soil particles, especially in soils with clay or soils that are more alkaline than neutral.
In any case, it is always preferable to err on the side of being conservative in matters like this.

Thanks for the reply, Bryant. They had an old barrel and what seems to be a couple random spots where there's all kinds of left off trash. Melted plastic, metal remnants, cans, etc. To be clear, I actually burned that wood in the pit. It then hit me I should probably check into it. It was a set of about 3 steps from a porch and 2 2x8s about 8 feet long. I panicked when I found the following:

Incineration of CCA wood does not destroy arsenic. It is incredible, but a single 12 foot 2 x 6 contains about 27 grams of Arsenic - enough arsenic to kill 250 adults. Burning CCA wood releases the chemical bond holding Arsenic in the wood, and just one Tablespoon of ash from a CCA wood fire contains a lethal dose of Arsenic. Worse yet, Arsenic gives no warning: it does not have a specific taste or odor to warn you of its presence. No one disputes that the ash from burning CCA wood is highly toxic: It is illegal to burn CCA wood in all 50 states. This has serious implications for firefighters, cleanup and landfill operations.
Even more astonishing, minute amounts of 'fly ash' from burning CCA pressure treated wood, can have serious health consequences. The Journal of the American Medical Association reported on a family that burned CCA in a wood stove for winter heating. Their hair fell out, all family members suffered severe, recurring nosebleeds, extreme fatigue and debilitating headaches. The parents complained about 'blacking out' for periods of several hours, followed by long periods of extreme disorientation. Both children suffered frequent seizures described as 'grand mal'. The symptoms were finally traced to breathing minute amounts of arsenic laden dust leaking from the furnace as fly ash. The family's houseplants and fish died, too, victims of copper poisoning from the same dust.

yeah, burning "green wood" is not something to do.

While the amounts of arsenic released from such treated wood from laying on the ground or in ground contact has been shown to be minimal, the amount released by burning is as you mention, catastrophic in scope.
When I first tested our land I found some traces of arsenic where the previous house had stood. Apparently when it burned down, the arsenic was released, the land surrounding the "burn area" showed normal or below normal levels (.0002ppm), while the burn area showed .0015ppm, enough difference that I scraped the surface down one foot and used that for the road bed instead of leaving it where it lay. I have since then added back new soil which has acclimated nicely and is continuing to get better every year.
The weird thing to me is that the previous home was a double wide Mobile home, I would not expect lots of treated wood to be used in something like that that would not be close to the ground when set up.

I have used some "anti-fungal" treated wood for the floor sections of our buildings but I get it from a local sawmill that uses a Borate treatment.
Their treatment is only to prevent fungi, termites and molds from gaining a foot hold.
We have some floors that are only 12" above the soil level.
Our humidity is so high that non treated wood that close to the ground would end up with fungi growing on it or be infested with termites in a year or two.
The anti-fungal treated wood is holding up very nicely with out any arsenic in the treatment.

Good to know. With plans of adding a deck in the spring, I'll keep that in mind. Thanks again.