I just had a septic system installed last week. The installer used a product I didn't know about, and had I known, I might have done the job myself. Here's the link...
http://www.hancor.com/product/ec.html
All the installer had to do was install the tank, dig four lateral lines and place these panels. The output of the tank goes into the top of the center panel of the first row. Each end of the first row has an outlet near the top that loops into the bottom of the next row. When/if this row fills up, the output goes to row three, then onto row four.
The amazing thing about this stuff is... you don't have to use any gravel, pipe or anything other than these panels. The panels are placed directly in the trench, and each lateral line is allowed to be +/- one inch from one end to the other. The panels are about 36" wide and the installer used a 36" bucket on his backhoe, so didn't take long at all to do the job. After the county did their inspection, he used a skid steer to back fill... right over the top of the panels! He told me the crush strength of these panels is 16,000 lbs, so using the tractor over the field will not ever be a problem.
He did such a good job and was very fair in his pricing, I had him go ahead and dig the trenches for my water lines and power. He had to go through a bunch of rock and still only charged $.50/ft for 220 feet. Worked out to the same price it would have cost me to rent a walk-behind trencher for me to do it myself. The trench he dug was 18" wide and 24" deep. Couldn't have done that with a walk-behind.
Anyone interested in pictures, I took many. Just let me know. Each are about 150k.