Hmmm, I'm drawing on old knowledge here from farms back in SA.
Drainage is the key, you'd have to have perimiter drains to prevent a washout of both your orchard and your neighbours property.
The trees of the orchard would be planted in rows with furrows, the trees elevated slightly. This was to also help with irrigating.
Look at these images.
orchard rows drainage - Google Image Search
What sort of soil do you have? If clay careful to not compact it and ripping/furrows is best way to decompact for large acreage ... rotary hoeing compacts it.