1) if the species is native to your climate zone, you likely can hibernate it outside
2) if it needs a pond to hibernate, contact local koi pond keepers. They can tell you how they make their ponds suitable for winter (depth, substrates, heaters, bubblers, etc.)
A pond suitable for overwintering koi will meet the turtle's requirements in the right climate. Turtles will benefit from the addition of a substrate to bury in, or containers like pot halfs to hide in while they sleep.