I had to re-read the question at first I though it was 57 inches long Just be prepared for the unknowns your digging along and who knows what has been buried under the ground if the are has been developed over the years. I don't know what a RC-30 is but a skid steer with a backhoe attachment will be slower than what a mini would be. I would count on atleast 1.5 hours you can only dig so far then you got to back the machine up dig some more. Then your spending extra time re-adjusting the machine so you get a straight trench. For guys like me that are so used to minis digging trenches its quck easy and does a clean job your not limited to how far you can put the spoils out of the trench. Good luck and hopefully the homeowner doesn't get pizzed off with you that it cost more for you to do the job over a person with a mini excavator.