boy I couldn't read it with the highlighting
Take two long metal rods, coat hanger wires, welding rods, (I have seen it done with paper clips) and bend them so that you have a "L" shaped rod, one long side, one short side about 3:1, or 4:1 long to short. Hold the short leg in your hands right out in front of you, such that the two rods' long side are pointing forward. Slowly walk across the area that you thing the cables to be buried in. When you cross the cables, the rods will change direction so as to line up with the buried cables. The alignment will indicate the direction of the cables. That is to say if you are not crossing the cables at right angles, the rods will show the angle at which you are crossing the cables.
The theory (as I remember what I saw later) is that there is a magnetic field associated with the electrical cables which is an anomoly in the magnetic field of the earth around them, and the fields of the rods will tend to align with this anomoly. This is simplistically put, but that is the basics.
This also works with pipes filled wit water. I work for a Cable company and I use them to doublecheck my cable locating machine the is worth over 4,000.00.
Start at the house where your sewer pipe exits. keep going back and forth until the wire do not cross any more along the line that you were following and you will have probably found one edge of the septic tank. and the line show the middle of the tank the two covers are usually in line with the pipe coming in. then do it on the other side to find your outlet of the tank and you should know exactly where your tank is then measure the lenght of the tank. there is a cover in the middle of both sides of the tank?? not sure if I explained it properly?? Then for the septic bed just start at the house and walk towards the septic bed ( you probably have an idea by this time where the bed is.) The wires will cross whenever you cross one of the septic beds run. just mark it and keep on going. The most important part is not to hold the wires too tight.