A topographic map of the site of a proposed sewage treatment system can be very helpful to both the site evaluator and designer. Information can be obtained about land slope, drainage and depressions by looking at a topographic map.
A topographic map is a scale diagram with lines connecting points of equal elevation. There are different scales of topographic maps available. There are U.S. Geological Survey maps available where the contour interval is a line between 10 and 20 feet in elevation difference. Maps at this scale are of limited use for specific onsite system location. However, they can identify landscape
