Operation and maintenance (O&M) of permeable pavement

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.

Example of a new retrofit permeable parking lot at the University of Minnesota

This page provides guidance for operation and maintenance (O&M) of permeable pavement.

Supplemental information can be found on the page called Operation and maintenance (O&M) of permeable pavement - supplemental information . Supplemental information includes the following.

• Assessing the performance of permeable pavement
• Periodic vacuuming
• Deicing
• Maintenance agreements
• Additional references

Overview of Typical O&M Issues

Permeable pavement practices are designed to capture, filter and infiltrate stormwater runoff through the surface and into a storage layer. These practices have fewer “green” components than other green stormwater infrastructure, but they offer a stormwater benefit over what would otherwise be impervious area. Permeable pavements are most common in dense urban areas and experience heavy vehicular and pedestrian traffic. These practices require dedicated and regular maintenance to ensure proper and long-lasting operation, but they can operate effectively for up to 30 years if maintained (TRCA, 2016). The most frequently cited O&M concerns for pervious pavement practices include:

• Surface clogging of filter strips and / or sediment traps caused by organic matter and inorganic sediments
• Vegetation growing in the porous surface
• Water ponding or flowing off permeable pavement

The sections below describe best practices to prevent or minimize these common problems.

Design Phase O&M Considerations

Permeable pavement practices may be subject to high public visibility, sedimentation and vegetation growth and load due to vehicular traffic. Designers should design these practices in ways that prevent or minimize O&M issues. Examples include:

• Limiting practice placement to low-traffic areas only.
• Limiting the contributing drainage area to available practice volume and sizing the practice in accordance to its contributing drainage area.
• Accounting for appropriate traffic load when designing the practice (e.g. thickness of base and subbase layers as well as base / subbase thickness).
• Considering the use of impermeable trench berms for sloped practices to minimize lateral flow on the practice surface and allow water to infiltrate.
• Preventing degradation of the subsoil infiltration capacity, if the practice is designed to infiltrate water into the subsoil. This requires preventing sediment laden water from entering the practice.
• Avoiding runoff from pervious areas if possible. Otherwise account for potential practice clogging due to runoff from pervious areas. This could include:
  • Adding a line of vegetative stabilization with native plantings to pervious parts of the drainage area adjacent to the practice
  • Choosing a type practice surface with a lower potential for clogging. e.g. preferring pavers with wider gaps over porous asphalt or pervious concrete.
  • Adjusting cleaning intervals accordingly
• Providing pretreatment for pervious parts of the drainage area to prevent clogging.
• Providing educational signage to increase public awareness.

Designers should consult and include any local requirements regarding green infrastructure. O&M considerations often depend on whether the practice is located on public land, private land, or in the public right of way. For example, permeable pavement in the public right of way should be located where traffic loads are most suitable.

Designers should also recognize the need to perform frequent maintenance to remove trash, check for clogging, and if necessary perform practice cleaning. Designers can incorporate design solutions to facilitate maintenance activities. Examples include:

• Providing easy access for practice maintenance (e.g. drain pipe clean out traps).
• Instructions for snow removal for practices on parking lots.
• Installing observation wells for infiltration performance monitoring.

The designer should also provide a site-specific O&M plan that includes the following:

• Construction inspection schedule and checklists
• Post-construction routine maintenance schedule and checklists
• Operating instructions for the practice (if applicable)

For more information on design criteria for permeable pavements.

Construction Phase O&M Considerations

Proper construction methods and sequencing play a significant role in reducing O&M problems. Some key items during the construction phase include:

• Before construction begins:
  • Ensure that the pervious parts of the contributing drainage area are fully stabilized with native vegetation (see Plants for Stormwater Design) prior to the beginning of construction. If this is not possible, use barriers or diversions to direct stormwater flows from the contributing drainage area away from the practice.
  • Install any needed erosion and sediment controls in your construction site and prepare a storm water pollution prevention plan (SWPPP).
  • Hold a pre-construction meeting to review the construction plans and the sequencing of construction.
• During construction:
  • If permeable pavement is part of a larger project, those practices should be constructed towards the end of the construction sequence to prevent problems due to construction traffic and / or sedimentation.
  • Construct any pretreatment devices first to trap sediments.
  • Ensure heavy equipment does not enter the footprint of the practice to avoid compaction of the infiltration medium.
  • Store any soil or gravel media away from the practice footprint to avoid clogging the infiltration medium.
  • Inspect the practice during construction to ensure that the permeable pavement practice is built in accordance with the approved design and standards and specifications. Use a detailed inspection checklists that include sign-offs by qualified individuals at critical stages of construction, to ensure that the contractor’s interpretation of the plan is acceptable to the professional designer. An example construction phase inspection checklist is provided on the Prince George County website.
• After construction:
  • Verify that the permeable pavement practice was built in accordance with the approved design and standards and specifications.
  • Verify that the contributing drainage area is fully stabilized with vegetation prior to removing any barriers, diversions, or erosion and sediment control measures.
  • Verify that the practice actually captures and infiltrates runoff. Conduct a full facility test to inspect the underdrain and outflow function (filling test and surface infiltration test). All water should drain within 48 hours. **Infiltration rate should not exceed 8.3 inches per hour.
  • Use a detailed inspection checklists that include sign-offs by qualified individuals at the completion of construction, to ensure that the contractor’s interpretation of the plan is acceptable to the professional designer. **An example construction phase inspection checklist is provided on the Prince George County website.
  • The design/construction team should provide the O&M team with the following information to be included in the O&M plan:
    • The plant warranty .
    • The “as-built” plans of the practice
    • A list of conditions that might cause failure of the practice if not properly maintained.

Post-Construction Phase O&M

Effective short and long-term operation of permeable pavement practices requires a dedicated and routine maintenance plan with clear guidelines, expectations, and schedules. Proper maintenance will not only increase the expected lifespan of the facility but will improve aesthetics and property value. A maintenance plan clarifying maintenance responsibilities should be required for all practices.

Some important post-construction considerations are provided below along with recommended maintenance standards.

• A site-specific Operations and Maintenance Plan should be prepared by the designer prior to putting the permeable pavement practice into operation. This plan should provide any operating procedures related to the practices. The plan should also provide clear maintenance expectations, activities, and schedules. Include photos if possible. Be clear about who is responsible for the maintenance and the type of expertise that will be needed for distinct O&M activities. The O&M plan should include an anticipated budget for O&M activities. The O&M plan should also include an example O&M inspection checklist and an example maintenance report. Example O&M plans are provided in the “Useful Resources” section, below.
• Where necessary, a legally binding and enforceable maintenance agreement should be executed between the practice owner and the local review authority. Example maintenance agreements are provided in the “Useful Resources” section.
• Inspection and maintenance activities are distinct and can be done as separate activities or together. Inspection will typically assess the practice for any O&M issues, whereas maintenance will address the O&M issues identified by the inspection. A dedicated inspection effort on a large number of BMPs can help prioritize maintenance activities.
• Maintain pervious parts of the practice drainage area to limit sediment runoff onto the practice. This could include ensuring adequate plantings for the entire pervious area or if this is not feasible, adding a line of vegetative stabilization adjacent to the practice.
• Prevent construction traffic on permeable pavement to limit potential for tracking and spilling dirt onto the practice.
• Provide routine cleaning (vacuuming) of the practice and impervious parts of the drainage area on a biannual basis or a shorter interval if necessary.
• For winter maintenance, avoid using sand or cinder on the practice or within its drainage area. Standard road salts or certain liquid deicers are acceptable, though ice will form less readily than on conventional pavements. Plow blade heights should be set slightly higher than normal (0.5”). Rubber blade tips may also extend the life of the pavement. *Snow storage on permeable pavement should be avoided, because it could lead to clogging due to sediment accumulation.
• Do not allow storage of construction materials, landscaping materials, soil or mulch on any unprotected surfaces of or contributing drainage areas to the permeable pavement practice.
• Inlets draining to the practice storage layer should be cleaned twice per year.
• Do not seal-coat permeable pavement surfaces.

The table below provides an overview and schedule of general maintenance activities.

Overview and schedule of general maintenance activities for permeable pavement practices

Link to this table

First Year of Operation
Activity	Frequency	Time Period	Level of Effort	O&M Benefita
Check pretreatment for proper flow/filtration. If applicable, assess the health of plantings and replant as necessary.	At least twice after storm events > 0.5 inches within 30 minutes of the event, then biannually	Within the first 6 months then during Spring / Fall	2 hours	1
Check that there is no ponding	At least twice after storm events > 0.5 inches within 30 minutes of the event	Within the first 6 months	2 hours	1
Check permeable parts of drainage area to make sure they are clean of debris and evidence of erosion	Biannually	All year long		1,5
Check for accumulation of sediment and organic debris on the permeable pavement surface.	Biannually	All year long		1,5
Check for damaged pavement	Biannually	All year long, especially after winter season		1,5
Replace any joint fill material, if applicable	Annually	As needed		1,5
Practice surface cleaning (vacuuming)	Biannually	Spring / Fall		1
Perform surface infiltration test	Biannually	After practice cleaning		1
Replace any joint fill material, if applicable	Annually	As needed		1,5
Clean underdrain	Biannually	Spring / Fall		1
After First Year of Operation
Activity	Frequency	Time Period	Level of Effort per Visit	O&M Benefita
Check pretreatment for proper flow/filtration. If applicable, assess the health of plantings and replant as necessary.	Biannually	Spring / Fall	2 hours	1
Check that there is no ponding	Biannually	All year long	2 hours	1
Check permeable parts of drainage area to make sure they are clean of debris and evidence of erosion	Biannually	All year long		1,5
Check for accumulation of sediment and organic debris on the permeable pavement surface.	Biannually	All year long		1,5
Check for damaged pavement	Biannually	All year long, especially after winter season		1,5
Replace any joint fill material, if applicable	Annually	As needed		1,5
Practice surface cleaning (vacuuming)	Biannually	Spring / Fall		1
Perform surface infiltration test	Biannually	After practice cleaning		1
Perform surface infiltration test	Biannually	After practice cleaning		1
Clean underdrain	Biannually	Spring / Fall		1
After 5+ Years of Operation (non-routine maintenance)
Activity	Frequency	Time Period	Level of Effort per Visit	O&M Benefita
After long term operation of the practice, some occasional and infrequent maintenance activities might be required, such as bigger repairs, partial rehabilitation, or redesign of key elements of the practice.	As needed	As needed	Could be significant depending on the activity	1,5
aKey to Maintenance Benefits: Proper stormwater flow and infiltration Creation and maintenance of wildlife habitat Creation and maintenance of pollinator habitat Nutrient cycling and storage Aesthetics and public enjoyment Carbon sequestration b. Note that many practitioners are minimizing the use of mulch or using alternatives to mulch to control weeds. Using mulch can cause clogging of inlet, outlet, and bypass pipes, and can introduce invasive species such as jump worms. Alternatives to mulch include ground vegetation such as clover or sedges, or arranging plantings in more dense configurations so as to minimize use of mulch.

Common problems and how to troubleshoot them for permeable pavement practices

Link to this table

Troubleshooting Common Problems
Symptom	Possible Causes	Solution
Standing water on permeable pavement area	The surface of the permeable pavement area may become clogged with fine sediment over time. This might be due to high sediment loads from the pervious part of the drainage area or leaf debris in the fall. Vegetation growth in permeable pavement (especially important for interlocking pavers) Inlet clogged due to accumulated debris	Clean the permeable pavement area (vacuuming) Test infiltration capacity of the surface Clean out inlets Check for sediment sources from the pervious part of the drainage area and correct. Check and if necessary correct issues with pretreatment if applicable.

Maintenance Costs

Maintenance costs will vary on a number of factors, including but not limited to:

• Size of the practice and its contributing drainage area
• Type of plantings used
• Site visit frequency
• Level of maintenance needed
• Local weather conditions
• Staffing needs (number of staff, external vs. internal staff, etc)
• Travel time between sites
• Efficiencies of scale (single GI vs. a cluster of GI)
• Equipment needed

Maintenance costs will vary depending on the size of the practice, its contributing drainage area, type of plantings, and whether it is part of a larger GI effort. Preventative maintenance is key to minimizing major costs associated with repairs. A general rule of thumb to estimate annual maintenance costs is 3%-6% of the installation costs. Maintenance costs should account for the number of hours of labor, the cost for different types of labor expertise required, and any equipment needed to successfully complete the maintenance activities.

A study published in 2017 by ASCE shows the range of annual maintenance cost of permeable pavement systems was estimated to be $0.06/sq ft to $0.31/sq ft in 2014 dollars. This translates to costs of $0.07/sq ft to $0.37/sq ft in 2021 dollars, though the estimates were based on data from 2005-2009 (Clary, 2017).

No special equipment is necessary for winter maintenance, however, regenerative air vacuum sweepers and other specialized cleaning equipment may be necessary to remove and prevent clogs.

Useful Resources

Additional Detailed O&M Information

• More detailed information regarding specific maintenance activities are provided in the Assessing the performance of permeable pavement page
  

Topics discussed include:

• • Assessing the performance of permeable pavement
  • Periodic Vacuuming
  • Deicing
  • Maintenance Agreements
  • Additional References

Case Studies

• Minnesota Stormwater Manual - Case Studies for permeable pavement practices
• City of Portland, Oregon - Pervious Pavement Case Study

Maintenance Training Documents and Videos

• Washington, DC - DoEE Riversmart permeable pavement maintenance

O&M Resource Catalog

MPCA has compiled publicly available O&M resources related to green infrastructure. This non-exhaustive catalog is intended as a resource to practitioners. https://docs.google.com/spreadsheets/d/1TNGVghLhudcWPgXKLbLAu2cUWv6O3ZeS7-FIuLSGIPM/edit#gid=0

Example O&M Plans, Checklists, Reports, and Maintenance Agreements

Document	Link
Operation & Maintenance Plan	University of Kentucky, Post Construction Structural BMP Operations and Maintenance Plans
Construction phase inspection checklist	Prince George’s County, MD, Permeable Pavement Construction Inspection Checklist
O&M inspection checklist	Chagrin River Watershed Partners, Chagrin River Watershed Partners Permeable Pavement Inspection and Maintenance Checklist City of Franklin, TN, City of Franklin, Tennessee Stormwater Division Permeable Pavement Inspection and Maintenance Checklist Franklin Township, NJ, Franklin Township, New Jersey, Permeable Pavement Maintenance Inspection Checklist University of New Hampshire, Checklist for inspection of permeable pavement
O&M example report	University of Kentucky, Inspection Report (page 46)
Maintenance Agreements	Mooresville, NC, Maintenance Agreement Fuquay-Varina, NC, Maintenance Agreement

References

Toronto and Region Conservation Authority (TRCA). 2016. Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-7.4-Permeable-Pavements.pdf