Washing vehicles on hard, impervious surfaces such as concrete areas can cause wash wastewater flow into storm drains. It is necessary to find out if area storm and sanitary sewers are combined or separate systems. Many storm and s a n i t a ry sewers in the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) are combined before the final discharge point; therefore, most wastewater is treated before it is discharged to surface water bodies such as rivers, lakes, and streams. Many newer areas and other cities have separate sewer systems; therefore, wastewater discharged to storm sewers is discharged directly to water bodies without treatment to remove pollutants. Car wash wastewater can be harmful to humans, plants, and animals if released untreated to surface water bodies. Additionally, allowing wash wastewater to soak into the ground can be harmful because the wastewater may contaminate soil and groundwater. More information on how to prevent soil and groundwater contamination is presented later