Just a caution that the weather forecasters keep saying they're worried about more flooding if it gets warm fast and rains a lot because there's a lot of snow up in thar them hills and mountains.

I had to put in umpteen creeks and dams and erosion control groundcovers and pound in vertical stones throughout my yard to stop the flooding from carrying away the very expensive 4-way blend topsoil I had imported.

Don't know about de-germifying dirt -- I just planted a lot of swamp trees, nothing to eat!

Looking forward to reading the answer ...

It would have to be tested to have any idea. Nearest Cooperative Extension office will be acquainted with local issues, may offer some appropriate testing or information about it.

Depends on what was upstream of you when it flooded. Most of the floodwaters came from commercial timber and agricultural land, the latter mainly dairy and vegetables as far as I know. Not much industrial! but there'd be some diesel and gasoline from all the flooded farm machinery and vehicles. Plus raw sewage, both livestock and human.

The current would probably have kept most contaminants moving. Petroleum products tend to float on top of water, and things like pathogens and pesticides are so small that the water would have to stop before they'd settle out. Particle setting in water is dependent on the weight of the particle and the velocity of the water. Some contaminants could be expected to be stuck on sediment and debris, but if you didn't get sediment settling out, you probably didn't get much contaminants either.

All in all I'd say you wouldn't have any contamination that you didn't have before.