Power Washing at UNC
The potential for generating water pollution as part of power washing activities requires that extra attention be given to how these activities are conducted. Because these activities are conducted outside with water (and sometimes chemicals) for the purpose of removing residues, dirt and debris, this material can negatively impact water quality.
Surface cleaning wash water that enters the storm drain system flows directly into campus streams and ultimately into Jordan Lake without any treatment. State and Federal water quality regulations prohibit the discharge of polluted wash waters to the storm drainage system. Adherence to stormwater pollution prevention best management practices as described in this document will reduce the discharge of pollution to campus streams.
UNC requires that power washers adopt the following four-step approach:
- Do dry cleanup before washing down
- Wash without soaps or solvents when possible
- Keep polluted wash waters out of storm drains
- Dispose of wash waters properly
Wash waters containing biodegradable soaps can not be discharged to the storm drain. The term biodegradable simply means that the product will not harm bacteria in sewage treatment plants, and that the soap will break down faster than conventional soaps. Biodegradable soap can cause fish kills in creeks as fast as any other types of detergents. UNC does appreciate the use of biodegradable products because they are gentler on the local sewage treatment plant when they are disposed to the sanitary sewer.
Avoid using soaps and other cleaning chemicals whenever possible. Before using soap, test to see whether warm water under pressure will do the job. Wash waters containing soaps and/or other cleaning chemicals must be collected and discharged to the sanitary sewer.
Stormwater Best Management Practices for UNC Pressure Washing
Outdoor power washing can negatively impact water quality if not done correctly. In addition, State and Federal laws dictate the use and disposal of certain cleaning chemicals. Failure to do so can lead to significant fines for both the University and contractors. The following guidelines clarify the correct way to power wash outdoor surfaces.
|Type of Surface||Cleaning Method||Proper Disposal|
|Sidewalks, plazas||Without Soap: Dry cleanup first (broom), then wash.||Screen wash water, if needed, to catch debris, then discharge water to landscaping, gutter, street or storm drain.|
|With Soap: Dry cleanup first (broom), then block storm drains and contain runoff.||Collect water, screen water to remove solids, and pump wastewater to the sanitary sewer. Make sure pH is between 6 and 10 before disposing of the water into the sanitary sewer. (Contact EHS if you need help verifying the pH.)|
|Parking lots, Driveways, Restaurant/Food Handling Areas, Dumpster Areas, Loading Docks, Grease Storage||With or Without Soap: Clean up any oil, grease, or dumpster discharge using absorbents. Sweep and bag absorbents for disposal. Block storm drains and contain runoff.||Collect water, screen water to remove solids, make sure pH is between 6 and 10, and pump wastewater to sanitary sewer.
Contact EHS for assistance with alternative disposal options if there is a high concentration of petroleum products.
|Unpainted Building Surfaces, Exterior Brick and Masonry Walls, Wood Decks, etc.||Without Soap: Screen runoff for solids.||Discharge water to landscaping, gutter, street, or storm drain.|
|With Soap: Block storm drains and contain runoff.||Collect water, screen to remove solids, make sure pH is between 6 and 10, and pump wastewater to sanitary sewer.|
|Painted surfaces without loose paint (call EHS for assistance to determine paint’s lead content).||Without Soap: Use high-pressure water, no soap.||Lead-free paint: Screen wash water, if needed, to catch debris, then discharge water to landscaping, gutter, street or storm drain.
Paint contains lead: Collect water, screen to remove lead and solids, make sure pH is between 6 and 10, and pump to sanitary sewer.
|Painted surfaces being cleaned to remove paint or graffiti (call EHS for assistance to determine paint’s lead content).||With or Without Soap: Block the storm drain and contain runoff.||Collect water, screen to remove solids, make sure pH is between 6 and 10, and pump to sanitary sewer.|
Please note that biodegradable soap is subject to the same disposal procedures as any other soap.
Contact EHS at 919-962-5507 if you have questions or need assistance setting up a power washing operation on campus.
Methods of Collecting Power Washing Wash Water
The following are example of devices that may be used to contain and collect wastewater during pressure washing activities. The collection devices that are described are not the only containment devices that are available.
- Berms may be used to prevent wash water from entering a storm drain by placing a protective barrier around a storm drain inlet. This allows wash water to pool around an inlet prior to proper collection and disposal. This type of containment may be less effective or ineffective when a storm drain is located at the bottom of a slope or when a large amount of wash water is generated.
- Storm Drain Covers/Mats
- These devices are placed on top of a storm drain grate to create a seal and prevent wash water from entering the storm drain system. Storm drain covers/mats (magnetic vinyl mats, PVC drain covers, polyurethane mats, and others) allow wash water to accumulate on top of the inlet until the power washing is complete and the wash water can be collected for proper disposal. Storm drain covers/mats are frequently used along with a vacuum device that allows wash water to be pumped into a sanitary sewer.
- Containment Pools
- A portable or temporary containment pool is another option which may be used to collect wash water. Containment pools are easy to assemble, provide an immediate work area, and allow wash water to be collected in a manner that prevents pollutants from entering the storm drain system. Containment pools vary in size and material and can be used for washing equipment and vehicles. Containment pools may also be constructed on site by using plastic sheeting and sand bags or framing wood.
- Devices such as wet/dry vacuums, sump pumps, and vacuum pumps may be used to collect and dispose of wash water after power washing. Vacuum devices typically have an extension (vacuum boom) that allows water to be collected efficiently. In addition, many vacuum devices are equipped with a discharge hose that can be run from the pump to the sanitary sewer.
- Vacuum Boom
- A vacuum booms is an attachment for a vacuum device. The boom typically rests flush on the ground and draws wash water through small holes in the bottom of the boom. In addition, different varieties of vacuum booms are available for areas with steep slopes or rough terrain.
- Inflatable Pipe Plug
- Inflatable pipe plugs prevent wash water from entering a storm drain system by blocking the pipe leading from a drain inlet. Unlike the storm drain mats/covers that block storm drain grates, the inflatable pipe plug is inserted into the storm drain pipe and uses the inlet structure beneath the grate to collect the wash water. Once inserted, the plug is inflated to make a snug fit. Once the wash water has been contained in the inlet structure, it can be collected and disposed to the sanitary sewer by using a portable pumping device.
Equipment and Supplies
|Name||Web Address||Phone Number|
|Lab Safety Supply||www.grainger.com||800-356-0783|
|C & H||https://www.globalindustrial.com/||800-558-9966|
|W. W. Grainger||www.grainger.com||888-361-8649|
|Name||Web Address||Phone Number|
|Power Washers of North America||https://www.pwna.org/||800-393-7962|
|Cleaning Equipment Trade Association||https://ceta.org/||800-441-0111|