Well, unfortunately, a regular pass with any kind of machine won't really work. Here's a pic from my back yard. The tank (to the right of the dirt pile) sits right in a drainage swale created after we finished the house. I didn't realize at the time exactly where the tank was, unfortunately. To the right is our decomposed granite driveway. About 35-40 ft to the right is a twin trunk eucalyptus tree. I suspect that is the root culprit, but not sure.
http://i110.photobucket.com/albums/n82/handi*****/Septic%20flood2_zpswlrr7kyt.jpg
This is a shot from farther up the back patio. This was taken during our last rain, and you can see where the water runs through the swale.
http://i110.photobucket.com/albums/n82/handi*****/Parking%20spot_zpsfysdgat1.jpg
Here is a closer look at the top of the tank. This has been sitting for 2 days now, AFTER it was pumped. So, as you can see, there is little question of there the ground is saturated.
http://i110.photobucket.com/albums/n82/handi*****/Septic%20flood1_zpspaqhykrq.jpg
Even if it wasn't where it is, with my luck I would rip up the PVC lines, somehow.
Travelover
Thanks, that will be one of the possibilities I will have to consider.
RNeumann
I figured you'd say something like that, once you saw the system.

No real way to scope it either. There are T fittings at each end, inside the tank, and a T cleanout about a foot from the tank, outside. I don't believe there is solids in the leech line. I watched him pump and it looked very fluid on top, and the sludge was only about 12-18" deep. That's a guess, I wasn't about the measure it.

What is not in the system picture, is there was a second line to the left of the one shown (facing from leech line to tank).
Good idea about a marker by the D-box. It will have to be something else, cause a T post would get in my way, but I will mark it. I also plan on adding extensions and a steel lid to the cleanouts on the tank. That way I can drive over them, but not have to dig up every time it needs pumped. This was our first pump in 7 years. Had I done it sooner, I might have caught the roots before they got too bad.