It seems unreasonable to me that anyone would ever have a Jet A contamination as low as 10%. In my Legacy that would mean that the line person would have put only 3.3 gallons of Jet A in a wing tank that already had 29.7 gallons of 100LL  The Legacy wing holds 33 gallons per side.  A more likely contamination would be adding 10 gallons of Jet A to a wing that had 23 gallons of 100LL in it.  This would result in a mixture that is 30% (by volume) Jet A.  Therefore, it would seem to me the contamination would be obvious, either by checking the smell, feel, color, or vaporization of a fuel sample.

Jim Thomas
Legacy