D07.1 Porous Pavement
D07.1.1 Porous Pavement Vacuuming
Porous pavement vacuuming is done in order to remove sediment that may lead to a clogging of the porous surface, preventing water from infiltrating through the pavement into the stone reservoir. Porous pavement vacuuming applies to several types of porous pavements described below.
Porous Pavers: An alternative to traditional hardscape paving that allows water to infiltrate between the pavers and through permeable layers below ground. When vacuuming porous pavers, adjust the setting to a lower power in order to prevent complete removal of aggregate between voids (unless more intensive vacuuming is required to alleviate clogged areas).
Porous Concrete: A type of concrete that has a high porosity due to an increased void space to facilitate water infiltration through the porous concrete into a stone reservoir and then into the ground.
Porous Asphalt: A type of asphalt that has a high porosity due to an increased void space to facilitate water infiltration through the porous asphalt into a stone reservoir and then into the ground.
Frequency: Annually - Vacuum porous concrete, porous asphalt, and for porous pavers each spring.
Porous Pavement Vacuuming Maintenance Procedure
- Safety set-up: Set up safety perimeter. Ensure no vehicles are parked in the vicinity of the location and that area is closed to the public. Public notice announcing area closing needs to be posted per base standards of notification.
- Inspect: Visually inspect porous pavement for damage, including holes, cracks, excessive scuffing, settlement, and areas of standing water. Inspect status of aggregate between voids in porous pavers before and after vacuuming to see if additional replacement aggregate is needed. Record observations/damage in the Maintenance Report Log, include photos if possible, and report as necessary.
- Prepare site for vacuuming: Remove (by hand) bulky debris and waste materials from surface of porous pavement that may be too large to be picked up and/or block/clog the vacuum hose (litter, tree branches, wire, car parts) prior to using vacuum. Use a rigid street broom to loosen debris as needed. Pay attention to pavement edges and heavily loaded areas.
- Vacuum: Vacuum porous pavement per the vacuum manufacturer recommendations. If vacuuming porous pavers, set the vacuum at a lower power in order to prevent complete removal of aggregate between voids (unless more intensive vacuuming is required to alleviate clogged areas). Adjust the vacuum machine speed so the vacuum draws out the first inch or so of stone and dirt in the openings between porous pavers, because this is where most unwanted sediment/debris typically collects. Follow all steps in the Manufacturer’s Operation Checklist for the specified vacuum. Engage the Water Feature/ Water Dust Control Option of the vacuum (or equivalent on specific vacuum model). Drive the vacuum over the porous pavement, operating at a slow speed setting not greater than 5 miles per hour. Overlap the edges of the vacuum runs and make two passes over the entire porous pavement area. Frequently check and empty the filter bag (located above the debris bag) when vacuuming areas with excessive sediment.
- Post-vacuuming inspection: After two passes, visually inspect porous pavement to ensure adequate debris removal. Any areas with visible debris/ sediment still present must be vacuumed again until debris is removed. If the surface of the porous pavement becomes clogged with fine dirt or sand, follow maintenance tasks outlined in Section D07.1.2, Porous Pavement Power Washing. Record observations in the Maintenance Report Log.
- Review checklist: Follow all steps in the post-operation checklist for the specified vacuum.
- Measure debris removal prior to disposal: Remove material/debris from vacuum bag and hopper and put into a labeled trash bag. Label bag with date and project location and note the weight on the Maintenance
Report Log. - Clean up: Clean work area and vacuum equipment (per Manufacturer’s Operation Manual).
D07.1.2 Porous Pavement Power Washing
Porous pavement power washing applies to several types of porous pavements described below. Power wash if porous pavement surfaces become clogged with fine dirt or sand. Power washing the pavement surface allows partial restoration of the original void space and, therefore, permeability and must immediately follow the porous pavement vacuum task (once every three years or more often as necessary). Never power wash of porous pavers because it may damage the pavers and/or remove aggregate between pavers.
Porous Concrete: A type of concrete that has a high porosity due to an increased void space to facilitate water infiltration through the porous concrete into a stone reservoir and then into the ground.
Porous Asphalt: A type of asphalt that has a high porosity due to an increased void space to facilitate water infiltration through the porous asphalt into a stone reservoir and then into the ground.
Frequency: Once every three years (perform immediately after thorough vacuuming) or more frequently if necessary. Spring is the recommended time.
Porous Pavement Power Washing Maintenance Procedure
- Safety set-up: Set up safety perimeter. Ensure no vehicles are parked in the vicinity of the location and that area is closed to the public. Public notice announcing area closing needs to be posted per City/County standards of notification.
- Inspect: Visually inspect porous pavement for damage, including holes, cracks, settlement, excessive scuffing/raveling and areas of standing water. Record observations/damage in the Maintenance Report Log, include photos, if possible, and report as necessary.
- Prepare site for power washing: Remove (by hand) bulky debris and waste materials from surface of porous pavement that may block or impede power washer access to the surface (litter, tree branches, wire, car parts). Use a rigid street broom to loosen debris as needed. Pay particular attention to pavement edges and heavily loaded areas.
- Power wash: Follow manufacturer’s recommendations for use of the power washer unit with the clarifications noted below. Ensure the water inlet
valve and pump are both on. Set the pressure levels to be no greater than 500 pounds per square inch. Perform two passes over surface of pavement, with wand spraying at a 45-degree angle. Do not keep water flow on one location for longer than 5 seconds. - Vacuuming: Power washing may need to be followed immediately by vacuuming. Refer to Porous Pavement Vacuuming for detailed instructions. If sediment is exposed (brought to the surface) during power washing, this sediment must be immediately removed through vacuuming instead of allowing the sediment to migrate and re-enter the porous pavement.
- Post-power washing inspection: Visually inspect porous pavement to ensure adequate sediment/debris removal. Any areas with visible debris/sediment still present must be washed again until debris is removed. Note if water remains ponded in any areas of the porous pavement. Record observations in the Maintenance Report Log.
- Safety completion: Remove safety perimeter and re-open lot for parking/public access.
D07.1.3 Porous Paver Aggregate Maintenance (Restoring Aggregate)
Safety set-up: Set up safety perimeter. Porous pavers are an alternative to traditional hardscape paving which allows water to infiltrate between the pavers and through the permeable layers below them. Pavers are laid out on the surface and clean-washed aggregate material (also called screening or gravel) are placed in the spaces (voids) between paver units to provide stability and surface drainage while keeping unwanted debris out of the system. Refill the voids between pavers with additional aggregate material to replace any material that has been lost by vacuuming and/or due to natural migration, settlement and erosion.
Frequency: As needed and when gravel infill is not within 1/2 inch of the paver surface. Immediately after vacuuming.
Porous Paver Aggregate Maintenance Procedure
- Safety set-up: Ensure no vehicles are parked in the vicinity of the location and that area is closed to the public. Public notice announcing area closing needs to be posted per City/County standards of notification.
- Inspect: Visually inspect porous pavers for damage, including broken pavers, cracks, settlement, and any areas of standing water or evidence of standing water. Inspect status of aggregate infill material in the voids between porous pavers to see if additional replacement aggregate is needed. Evaluate if voids (joints) between porous pavers are clogged or not. Inspect to see if pavers themselves are missing from any areas and note need for replacement pavers. Record observations/ damage in the Maintenance Report Log, include photos if possible, and report as necessary.
- Prepare site: Remove (by hand) bulky debris and waste materials from surface of pavers.
- Cleaning Clogged Voids: If voids (joints) between porous pavers are still clogged even after area has been vacuumed (Porous Pavement Vacuuming), use a manhole pick to tool out joint until clean aggregate is found. Follow aggregate replacement instructions below.
- Add aggregate: Using a shovel, spread aggregate over the surface of the pavers. Using a broom, sweep aggregate into the voids between porous paves, taking care to fill in any obvious holes. Once the aggregate has been added to the pavers, and the voids have been filled, perform a final
sweeping pass with the hand broom to remove any excess gravel from the paver surface. - Clean up: Clean-up work area.
- Safety completion: Remove safety perimeter and re-open area for parking/public access.