I live in SE Michigan where the frost line is between 3 and 4 feet. I have a house with a basement I'd like to finish and would like to run the water as far away from the house as I can. Clay soil. However, while I have a decent lot of 1/2 acre, the available slope is minimal and there are no storm sewers or culverts in the lot where I can easily send water. Max drop over about 40 feet to the road is 2-3 feet at best. I was hoping to run the water about 20 feet away into a dry well, but most dry well discussion online puts them at least 3 or 4 feet tall, which puts total depth of the well at some 8 feet deep if the line entering it is 4 feet. My question is, do I need to run the whole line from start to finish at 4 feet deep, or if I get sufficient grade, can it finish (after a 20-30 foot run) at about 2-3 feet deep (i.e. water has a fast flow), with an opening to below the frost line, at 4-5 feet bottom. I'm trying to find a way to get the water away with minimal available grade.
This is roughly what I have to work with: