Clean sand is specified as treatment media in many soil treatment areas, such as mounds and media filters. Sand used for these purposes must be clean (typically washed) to prevent system failure.Dirty sand has silt and clay particles, called fines, which collect and form a restrictive layer, reducing the movement of water through the system. When fines are present in the sand media it can cause moisture to wick up by capillary forces. In addition, pores in the sand can be reduced and limit oxygen transfer. The flow of effluent through the sand can cause the fines to migrate and
