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Minnesota Stormwater Manual

Operation and maintenance (O&M) of permeable pavement - supplemental information

Green Infrastructure: Permeable pavement can be an important tool for retention and detention of stormwater runoff. Permeable pavement may provide additional benefits, including reducing the need for de-icing chemicals, and providing a durable and aesthetically pleasing surface.
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a photo illustrating porous concrete
Example of a new retrofit permeable parking lot at the University of Minnesota

This page provides supplemental information on operation and maintenance (O&M) of permeable pavement. To see information on design phase, construction phase, and post-construction phase O&M, including inspection checklists, see the page called Operation and maintenance (O&M) of permeable pavement.

Assessing the performance of permeable pavement

Maintenance of permeable pavement includes a review of its condition and performance. A spring maintenance inspection is recommended and cleanup conducted as needed. The following are recommended annual maintenance inspection points for permeable pavements:

  • The drawdown rate should be measured at the observation well for three (3) days following a storm event in excess of 1/2 inch in depth. If standing water is still observed in the well after two days, this is a clear sign the system is not performing as desired and subgrade soil clogging is a problem.
  • Inspect the surface for evidence of sediment deposition, organic debris, water staining, or ponding that may indicate surface clogging. If any signs of clogging are noted, schedule a vacuum sweeper to remove deposited material. Then test sections using ASTM C1701 to ensure that the surface attains an infiltration rate of at least 10 inches per hour.
  • Check inlets, pretreatment cells and any flow diversion structures for sediment buildup and structural damage. Remove the sediment.
  • Inspect any contributing drainage area for any controllable sources of sediment or erosion
  • Inspect the condition of the observation well and make sure it is capped.
  • Inspect the structural integrity of the pavement surface, looking for signs of surface deterioration, such as slumping, cracking, spalling, or broken pavers. Replacement to rectify a damaged surface or one removed for access to utility repairs should be done per industry recommendations. After base compaction, small areas of pervious concrete and porous asphalt can be replaced with conventional (impervious) asphalt or concrete up to 10 percent of the total permeable pavement area. For PICP, paving units are removed for reinstatement later. The remaining undisturbed pavers at the perimeter of the opening are typically held in place with temporary wood or metal braces. Once the base is replaced and compacted, new bedding material and pavers are reinstated and compacted over the base.

Periodic vacuuming

The pavement surface is the first line of defense in trapping and eliminating sediment that may otherwise enter the stone base and soil subgrade. The rate of sediment deposition should be monitored and vacuuming done at least two times per year. A typical vacuum cleaning schedule may include the end of winter (April) and after autumn leaf-fall (November). Maintenance records should be maintained by the owner. The vacuuming frequency should be adjusted according to the intensity of use and deposition rate on the permeable pavement surface. At least one pass should occur at the end of winter. Regenerative air vacuum sweepers are the suggested means for regular surface cleaning. For neglected surfaces (i.e., those with no surface cleaning over several years) true vacuum sweepers have the most efficient removal of debris and fine particulates when compared with regenerative air or mechanical sweepers. However, areas on steep slopes or near curbs may limit vacuum sweeper performance (Brown 2013). If a true vacuum sweeper is used on PICP the removed aggregate in the joints should be replaced with the same material.

Deicing

Minimizing salt use or sand for de-icing and traction in the winter, keeping the landscaping areas well maintained and preventing soil from being washed onto the pavement helps increase its life. Less salt will be needed. However, such water should not be directed to irrigation uses.

Maintenance agreements

Maintenance agreements should note which conventional parking lot maintenance tasks must be avoided (e.g., sanding, re-sealing, re-surfacing, power-washing). Signs should be posted on parking lots to indicate their stormwater function and special maintenance requirements. When permeable pavements are installed on private residential or commercial property, owners must understand routine maintenance requirements. These requirements can be enforced via a deed restriction, drainage easement, maintenance agreement, performance bond, letter of credit or other mechanism enforceable by the local authority to help ensure that the permeable pavement is maintained and continues functioning. The local authority should use this MIDS guideline to establish measurable performance criteria for enforcing maintenance procedures. The mechanism should, if possible, grant authority for local agencies to enter the property for inspection or corrective action.

Additional references


Related articles

Permeable pavement

Green Infrastructure

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This page was last edited on 30 December 2022, at 14:02.