I had to replace my feed line last fall, and it was surprisingly easy to
do using a mattock and a narrow shovel. Dug ~50' of 2' deep trench in
about 3 hours. The crucial tool was a sharp mattock. Since you're going
to drain it in the winter (use an air compressor to clear the line) all
you need to do is get below the surface. I'd go down about 6" and lay
plastic pipe. Fit the turf back on top in order and it will be invisible
after the first rain. Don't know where you are, but here in earthquake
country they recommend you lay a curving line so it will flex a bit and
not sheer at one end in a quake.

Jim (Seattle)