We built a new house 2 years ago, and had a septic field installed by a contractor. We live in Calgary AB in the flat area. We were not in the house 2 months and the field froze up. We pumped above ground until the spring and then back under ground. The second winter came and it froze again. The contractor says this is normal but the others in our area don't have a problem. I dug up the laterals to find the junction point but never found one. They installed the system in a "S" configuration. My investigations told me that this type of configuration is only used on a hill. Is that true? Also I found that the pipes are only 8 to 12 inches down from the surface, is this OK? 
Do you have any suggestions as to what I could do before next winter?
I thought I should add top soil, about 1 to 2 feet worth on top and seed more grass, what do you think?