Wastewater Discharges from Vehicle Washing

Water used in washing cars, trucks, and other vehicles may contain a wide range of contaminants —especially oil, other hydrocarbons, metals, detergents, road salt and grit. Discharged into surface waters, these contaminants can degrade water quality and harm aquatic life. Discharged into groundwater, they can make it unfit for drinking. To avoid these problems, and the legal consequences that may result, the following guidelines apply to facilities where vehicles are washed on a regular basis and the wash water is collected by a conveyance such as a drain, catch basin, ditch, or swale.^* Owners of a car wash or a commercial establishment that offers vehicle washing have four options for their wastewater discharges:

1. Operate a closed system with wastewater recycling (no discharge of wastewater).
2. Discharge to a municipal sanitary sewer.
3. Obtain a groundwater discharge permit.
4. Wash fewer than 30 vehicles per week and discharge to the ground surface only.

1. Closed System with No Discharge
This does not require a permit; however, it may require a “Holding Tank Registration” if the treatment system has a grit and oil tank that is pumped out. The residual that is pumped from the tank must be collected and disposed of at an approved disposal facility, i.e., a wastewater treatment plant or hazardous waste disposal facility, depending on the nature of the material.

2. Discharge to Municipal Sanitary Sewer
Connections to your municipal sanitary sewer are controlled by the local sewer authority. Contact the local authority regarding restrictions. Some local sewer authorities do not allow connection of floor drains, while others allow connection only with adequate pretreatment (e.g., an oil/grit separator) or other controls. If you connect an existing floor drain to a municipal sanitary sewer, you still need to notify DES.

3. Obtain a Groundwater Discharge Permit
You may discharge vehicle wash water directly to the ground if both of the following are true:

1. A groundwater discharge permit is obtained in accordance with Env-Ws 1504; and
2. The wash water is treated to ambient groundwater quality standards (Env-Ws 1503.03) using best available technology (typically granular activated carbon).

4. Wash Fewer than 30 Vehicles per Week
If you wash fewer than 30 vehicles per week, you may be able to discharge indirectly to groundwater without obtaining a groundwater discharge permit. However, you need to follow Best Management Practices (BMP) for Groundwater Protection (Env-Wq 401) to avoid contamination of your wash water with regulated substances. You also need to register your discharge and floor drain, if any. To avoid having to obtain a groundwater discharge permit, you must meet all of the following conditions:

1. Best Management Practices for Groundwater Protection are followed.
2. The floor drain is not in an area where regulated contaminants are used or stored.
3. The wastewater:
   • Is not from power washing, steam cleaning, engine cleaning, or undercarriage cleaning.
   • Does not contain soaps or other products which contain regulated contaminants.
   • Does not result in a surface water discharge.
   • Discharges to the ground surface.
   • Contains only approved detergents.
   • Leads to an oil-water separator or other pretreatment method prior to infiltration.
   • Is registered with DES in accordance with Env-Ws 1508.01.

Owners of facilities with these discharges are responsible for ensuring that regulated contaminants are not discharged and that groundwater is suitable for drinking without treatment.

Surface Water Discharges
In order to adequately protect the quality of surface water in New Hampshire, direct discharges of wastewater derived from car washing into surface water is prohibited. For more information about permitting of discharges to surface water, contact the DES Wastewater Engineering Bureau at (603) 271-3908.

For Additional Information
For more information about groundwater discharges, holding tank registration, floor drain registrations, and rules, please visit the DES Drinking Water Source Protection webpage at www.des.nh.gov/dwspp, or call (603) 271-2858.

For additional information, please contact the Drinking Water and Groundwater Bureau at (603) 271-2513 or dwgbinfo@des.state.nh.us or visit our website at www.des.nh.gov/dwgb. All of the bureau’s fact sheets are on-line at www.des.nh.gov/dwg.htm.

Note: This fact sheet is accurate as of January 2007. Statutory or regulatory changes, or the availability of additional information after this date may render this information inaccurate or incomplete.

*These restrictions do not apply to occasional vehicle washing, such as at residences or occasional events such as fund-raising car washes. For more information on community car washes and water quality see fact sheet WD-WMD-14 “Community Car Washes and Water Quality.”