Combine all ingredients EXCEPT ice and last quart of water in a very large bowl that will hold a gallon of liquid. Stir well. Transfer to a 4-quart saucepan and bring just to a rolling boil. Immediately turn off heat. Return to original bowl and add ice and remaining water. Stir to thoroughly chill.

Place cleaned turkey in large, clean garbage bag. Carefully add brine to bag, seal and put in the refrigerator. After 6 hours, turn the bird over and continue to refrigerate until ready to cook.