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Pressure washing is often used to clean buildings, paved surfaces and equipment on campus. However, pressure washing can negatively impact water quality if not done correctly.

Printable Handout for Pressure Washing

Site Preparation

Use dry methods such as brooms, blowers or street sweepers to clean the area before using a pressure washer on any surface. Block off storm drains first to prevent debris from entering.

Testing the Surface: Plain Water or Chemical Additive?

Before using soap or other chemicals, test the surface using plain, high pressure water to see if the results are adequate. EHS has often found that the use of chemicals does not improve the result. Cost savings can be significant without the use of chemicals, since the wastewater usually does not need to be captured and transported to a disposal facility.

Using Chemical Cleaners

If a chemical cleaner must be used for pressure washing, take the following steps:

  1. Contact EHS to get a map of the storm drains around the project site.
  2. Develop a plan to contain and collect the wastewater from the pressure washing. This can involve tarps, berms, storm drain covers or mats, pipe plugs, pumps, etc.
  3. Notify EHS of the process for disposal of the wastewater. Wastewater can be pumped into the sanitary sewer only with OWASA approval. The other option is to collect the wastewater in a drum or tank and remove offsite for disposal at an authorized wastewater facility.

Biodegradable and “Green” Detergents

Despite the promise of environmental benefits, biodegradable and “green” soaps and chemicals must not be discharged to the storm drain. Biodegradable soap is designed to protect bacteria in sewage treatment plants because the soap breaks down faster than conventional soaps. Some green products use creative labeling and have been found to be toxic to aquatic life despite advertising promises. Biodegradable and green products can cause fish kills as easily as non-environmentally friendly products.

Spot Cleaning

Some projects may need an additional chemical treatment on small sections. Try using scrub brushes first, and if chemicals are still needed, wipe-on-wipe-off products are acceptable. If a large area requires chemical treatment, see the requirements in the “Using Chemical Cleaners” section above.

Special Circumstances

Pressure washing in some locations require extra precautions to ensure that the materials being washed do not enter the storm drain system.

  • Rooftops over concession booths and restaurants: The ventilation fans located over frying stations still allow grease particles to escape into the environment, causing rooftops to become coated with grease. Runoff from those areas must be captured and not allowed to discharge into storm drains.
  • Food and grease spills, concession booths and outdoor kitchens: Grease and food waste that spills or splashes onto the ground must be cleaned using dry methods such as absorbent materials or shop vacs. If degreaser will be required, contact EHS for help with a clean-up plan that will include blocking the storm drains and collecting wastewater.
  • Loading docks, restaurant locations:
    • Trench drains and floor drains connected to the sanitary sewer: These docks may be pressure-washed as needed with no additional measures under normal operations.
    • Loading dock trench drains and floor drains connected to the storm drain system: Do not pressure wash grease or food waste off of these loading docks. If pressure washing is needed to clean spills, contact EHS for a clean-up plan that will involve blocking the drains and collecting wastewater.
  • Loading docks, all other locations and parking lots: Check for leaking dumpsters or vehicle fluid spills or leaks. If there are spills, contact EHS for a clean-up plan. If the loading dock is otherwise free from liquid contamination, follow the pressure washing steps outlined above.
  • Construction sediment: Sediment tracked off construction sites of any size must not be washed into storm drains. Sediment must be cleaned using only dry methods (street sweeper, brooms, shovels, etc.).