21—44.58 (200) Wash water and rinsates. All washing of fertilizer and soil conditioner handling and application equipment at permanent storage sites shall be conducted within an area which drains into a containment structure which complies with rule 21—44.55(200). No fertilizer rinsates or wash waters from fertilizer or soil conditioner equipment shall be disposed of through sanitary or storm sewer systems. Field washing of fertilizer or soil conditioner equipment is permissible and encouraged if performed at the site of final fertilizer or soil conditioner application for a given day and no runoff from the wash site occurs.