I thought I knew all I needed to know about plumbing, Dad always said you need to know two things to be a plumber, **** runs downhill, and paycheque is on Friday.  So far that has served my well, but now I need to know what happens if I violate rule # 1?

Installing a lagoon( gravity fed big open hole) sewer for a household, and in order to meet all the setback requirements, I can't find a good downhill location.  The best I can come up with is basically flat from the house to the lagoon, at about 200 feet distance.  The lowest drain in the house will be about 2 to 3 feet off the ground, and I'll bury the pipe about 3 feet deep at the house end and use the minimum 1/4 inch per foot, that will be 7 feet deep at the outlet.  The soil is relatively light, and midway up a slight slope, so water table should be lower than that.  If I install as is, and dig the lagoon a few feet deeper than the outlet, do I have the potential for water backing up in the pipe and freezing closer to the house(where the pipe could be within the frost zone, if the level in the lagoon is much above the outlet?  Or if it is above the water table, should it be OK?  The next best option is to put the lagoon in the middle of a field, with lots of slope, but work around it forever, and need a lot more distance to meet all the setbacks.  Or use in expensive option of a field or mound system.