To limit impacts to downstream waters, municipalities should contain, treat or reuse vehicle and equipment wash water.

• For containment, a municipality can build drainage features that direct wash water to containers, sumps or a treatment system.
• Treatment systems (which regulations often require if a facility discharges wash water to sanitary sewers and subsequently municipal treatment plants) generally include oil/water separators or some type of filtration.
• Sometimes a facility can use more advanced treatment practices if it intends to reuse wash water on-site—a practice that not only limits discharge impacts but also reduces water consumption. For all practices, municipalities should consider local regulatory requirements. These may include pretreatment requirements from the local sewer authority or specific containment requirements for wash areas in wellheads or water supply protection areas.