Selection of the soil is a key of chamber underground infiltration system.Soil is a combination of soil-plant-microbial ecosystem which contains rich microorganisms and acts as a natural wastewater treatment plant.The combination ecosystem plays an important role in the purification of sewage through physical interception,chemical precipitation,adsorption,redox,complexation and ion exchange. Natural soil easily causes the clogging for wastewater treatment and affects the operating costs as well as the servi...