If the walkway was there first? Using a trencher to dig close as you can without damaging anything. Then use a Hilti TE 74 with especially fabbed chisel bit to drive a piece of 1" RMC under the walkpath. Then use the RMC as a sleeve for the pvc. I would think that you would be able to get the pvc stalks to bend enough so that the only factory or short radius ninetys in the run would be at the stub ups.
