A sand filtration system is an option, where the infiltration is not possible e.g. due to heavy clay in the soil. In the sand filtration system, a drainage pipework is installed underneath the infiltration pipework. The water cleaned in ballast and sand layers is collected with the drainage pipework into the collector well, from which it is led further into an open ditch. The collector well can be used as a sampling well, too. If it is desired to completely prevent the water from infiltrating from the drainage pipework into the soil, the bed can be isolated from the surrounding soil using e.g. construction plastic.
