Washing vehicles and equipment outdoors or in areas where wastewater flows onto surfaces where it cannot soak in, such as in concrete areas, can cause the wastewater to flow into storm drains. Because some storm drain systems discharge untreated water directly to water bodies such as creeks, rivers, lakes, and wetlands, discharging power wash wastewater into this type of storm drain system is the same as discharging wastewater directly into a water body. Wastewater can contain high concentrations of oil and grease, detergents that may contain phosphates and suspended solids. Detergents, even biodegradable detergents, can be poisonous to fish. Phosphates, an ingredient in some detergents, are plant nutrients that can cause the excessive growth of nuisance plants when the phosphates enter lakes and streams.
Wastewater can also contain dirt and pollutants from vehicles and equipment washing.
Power washing also removes debris that if discharged can clog storm sewer inlets and grates and reduce or even prevent storm water drainage to the sewer. The suggestions listed below for mobile power washing can reduce the amount of pollutants discharged to water bodies through storm sewers. Use a portable containment system or storm sewer manhole insert to catch wastewater from vehicle washing. Both of these methods use submersible pumps that can pump the wastewater to a sanitary sewer or a holding tank to be hauled off site and properly disposed of. Find out if area storm and sanitary sewers are combined or separate systems.