Soil Horizons, can conduct site assessments of small or large tracts of land for septic system suitability and map soil types and classify them for the various types of septic systems. Soils can be very uniform or highly variable across a landform. Some soil types are usable for septic systems and others are not. If you plan on building a house or developing a subdivision that will require on-site septic sytems, you will have to know the soil suitability for septic systems so you can plan the project.