I need help with a swale design, I had a new house built and the property had been graded. The building inspector did not like the grade, because he felt the property wasn't self contained and he wants a swale dug along property line. How deep and wide should the swale be? The length of the swale will be 100 feet and I would like to grow grass in swale. Property is only 60 feet wide and house is about 15 feet away from property line (fence). Thanks.