To get everything approved we had to survey the land and get a detailed plan drawn up by a Civil Engineer - we used Terry Szewczyk and he was helpful, competent and kept the costs to a minimum. The picture below is a detail from one of the drawings, which were produced at 1inch to 20ft scale, and shows the important part where the garage goes. For some reason the contour lines altitude is shown based around 2000ft, whereas the real altitude is about 2400ft, but no-one seems to care if that aspect of it is accurate.
Our first step is to replace the pipe that goes from the septic tank to the diversion valve and the remaining leach field, so we start by getting the tank emptied (which needs to be done every few years anyway). The pipe has to dive down a bit then go across under the concrete "apron" that will lead up to the garage, and it won't be buried very deep, so we will be putting down a 4" pipe that is placed inside a 6" pipe for the part that goes under the driveway, to give it extra protection from being crushed.
The final detailed changes we need on the building design plan are now in hand (the layout plan shown above is already approved), so I'm back to the county office again next week to resubmit them and hopefully get the permit.
The other details you can see on the plan are the electrical connection, which will be a 220V -200Amp dedicated circuit capable of charging electric cars one day. The propane tank will be relocated, and hooked up to a generator and the house. There is also a water connection to a fire sprinkler system.