I am wanting to run a water line about 250 feet to my shed where I have
a garden. The problem is, between my house and garden are my spetic
tank field lines. Any suggestions on how to properly do this or how I
can water my garden without digging a new line?

Cheap and dirty - get a coil (or two) of flexible black plastic water
line, and find someone with a trencher (vibrating type) to bury the
line. Cable TV companies use trenchers to install underground drops
and cables everywhere - and the trenchers can be used to put it a
couple of feet down (if that's what you want) or just 6" or so. The
PVC waterline will feed right down through the throat of the trencher
blade and you would only have a little bit of hand work to do at each
end. Hope this helps.
Ken.