For individuals and families who live in rural areas and want to build a home, the land must "perc." This means the soil will allow sewage to be deposited from your house to the surrounding soil. The soil must have good drainage and not have too much clay or be too shallow. The soil must act as a filter so that sewage is not directly deposited into our groundwater.          
The picture to the left shows a soil pit.  A soil evaluator must describe the color, texture and structure of the soil to determine it will "perc."