Green Infrastructure benefits of permeable pavement

Schematic illustrating typical permeable interlocking concrete pavement cross section and basic components of a pervious concrete system.

Permeable pavement is a stormwater management technology beneficial for long term soil and water preservation. It has significant water quality impact for downstream receiving waters such as lakes, rivers, and ponds. Permeable pavement allows water to infiltrate quickly through the porous pavement and underlying media. As it infiltrates this water is filtered before passing into the ground underneath or to an underdrain.

When designing a system, it is recommended to determine if permeable pavement would be feasible. This design consideration allows a site to benefit by changing the pervious to impervious surface ratios on a location. Permeable pavement can be used in conjunction with other stormwater measures to ensure maximum benefit. Examples include

• permeable pavement built with underground cisterns, vaults, or other treatment devices;
• permeable pavement used with harvest and reuse systems for irrigation;
• increased vegetation options at a site due to increased groundwater accessibility; and
• systems in which other infiltration methods are difficult to achieve or may cause detrimental effects.

Different types of permeable pavement include

• interlocking pavers,
• pervious concrete,
• porous asphalt, and
• plastic grid pavers

Permeable pavement can also be used to increase the safety of a site as it has been shown to increase traction and prevent ice accumulation on roadways during adverse weather. (USGS)

For more information on how permeable pavements work please click here.

Green infrastructure and multiple benefits

Green infrastructure (GI) encompasses a wide array of practices, including stormwater management. Green stormwater infrastructure (GSI) encompasses a variety of practices primarily designed for managing stormwater runoff but that provide additional benefits such as habitat or aesthetic value.

There is no universal definition of GI or GSI (link here fore more information). Consequently, the terms are often interchanged, leading to confusion and misinterpretation. GSI practices are designed to function as stormwater practices first (e.g. flood control, treatment of runoff, volume control), but they can provide additional benefits. Though designed for stormwater function, GSI practices, where appropriate, should be designed to deliver multiple benefits (often termed "multiple stacked benefits". For more information on green infrastructure, ecosystem services, and sustainability, link to Multiple benefits of green infrastructure and role of green infrastructure in sustainability and ecosystem services.

Benefit	Effectiveness	Notes
Water quality	◕	Benefits are maximized for bioinfiltration. Biofiltration may export phosphorus if not designed properly.
Water quantity/supply	◕	Bioinfiltration helps mimic natural hydrology. Some rate control benefit.
Energy savings	◯
Climate resiliency	◔	Provides some rate control. Impacts on carbon sequestration are uncertain.
Air quality	◔
Habitat improvement	◯	Use of perennial vegetation and certain media mixes promote invertebrate communities.
Community livability	◔	Aesthetically pleasing and can be incorporated into a wide range of land use settings.
Health benefits	◔
Economic savings	◔	Generally provide cost savings vs. conventional practices over the life of the practice.
Macroscale benefits	◔	Individual bioretention practices are typically microscale, but multiple bioretention practices, when incorporated into a landscape design, provide macroscale benefits such as wildlife corridors.
Level of benefit: ◯ - none; ◔; - small; ◑ - moderate; ◕ - large; ● - very high

Green Infrastructure benefits of infiltration practices

• Water quality: Pollutants are removed through stormwater runoff reduction when permeable pavement is used. This allows for vegetation and biota growth, vegetative filtering, and soil adsorption when rainfall events occur at the site.
• Water quantity and hydrology: Reduction in total water volume movement and retardation of peak flow from rainfall events. Helps protect from downstream flooding and can be used in conjunction with reuse systems to reduce required water consumption for onsite irrigation. Infiltration also will recharge local groundwater.
• Energy: Main energy savings comes from reduced energy requirements for wastewater treatment.
• Air quality: Benefits are largely indirect, such as carbon sequestration.
• Climate resiliency: Alleviates the impact on flooding, saves water through reuse systems, reduction of downstream pollutant loading
• Habitat improvement: Reduction of soil erosion and increased soil stability promotes vegetation growth. Reduction in water temperature changes as a result of volume flow reduction. Retention of water on site helps ensure available water for vegetation and wildlife.
• Community livability: Well designed permeable pavement practices helps to protect recreation sites for people by ensuring safe and healthy access to water sources. Water quality benefits from permeable pavement promote healthy water sources for diverse vegetation growth. This diversity allows for more heterogeneous plant growth and if the water quality is good enough, gardening practices of the local community may not be impacted. Reduction in water on surface ways helps improve safety for driving and human use.
• Health benefits: Reduction of nutrients, pathogens, metals, TSS, and phosphorus among others. Increased longevity for fish and wildlife in the area through the reduction of compounds that would be washed into waterways as rain runoff.
• Economic savings: and savings: In addition to water quality and flood control benefits, properly installed permeable pavers can prevent downstream cleanup needs. Permeable pavement that benefits vegetation can increase property aesthetics that increase property value.

Design considerations

Maximizing specific green infrastructure (GI) benefits of constructed areas requires design considerations prior to installation. While site limitations cannot always be overcome, the following recommendations are given to maximize the GI benefit.

Note: Permeable pavement SHOULD NOT be used in areas of high traffic volume, with heavy equipment, or with frequent start and stopping.

Caution: The following discussion focuses on design considerations. All benefits delivered by the practice require appropriate construction, operation, and maintenance of the practice. O&M considerations should be included during the design phase of a project. For information on O&M for GSI practices, see Operation and maintenance of green stormwater infrastructure best management practices

• Water quality
  • Place the permeable pavement in a location where the majority of water flows through or to
  • Design to maximize retention time and prevent short-circuiting
  • Plan for the expected loading on the permeable pavement and ensure capabilities versus use line up
  • Use in conjunction with other treatments to establish a treatment train or reuse water on site
• Water quantity and hydrology:
  • Permeable pavement can significantly reduce the runoff and can be used to meet the water quality volume treatment requirement per the Construction Stormwater Permit
• Climate resiliency:
  • Established systems using permeable pavement reduces the runoff impact on surrounding waterways through decreased pollutant loads and increased infiltration
  • Permeable pavement systems can be established to support vegetation through water reuse systems, promoting further enhancement of water
• Habitat improvement:
  • Reduction in chlorides needed as water infiltrates through relatively quickly when melted
• Community livability:
  • Community members, depending on the system used, will likely not even realize the system is in place
  • Development of permeable systems can promote mental health through better vegetation from the increased water storage and erosion reduction on site
  • Develop conveyance systems in such a way to minimize changes in temperature that can be detrimental to wildlife populations
• Health benefits:
  • Safety of community is improved by water infiltrating quickly through the pavement, less pooling of water and ice means less slipping hazards
  • Minimizes mosquito by reducing standing water on site that impermeable pavement would otherwise offer
• Economic benefits and savings:
  • Reduction in maintenance cost for vegetation if water reuse system is used in conjunction with permeable pavement
  • Reduction in land space required as the pervious area can serve a dual purpose for cement and treatment that would otherwise be ineligible for water quality volume treatment
  • Integrates infiltration into landscape design, including creating habitat, pathways, picnic areas, etc.

Information regarding types of permeable pavement can be found here.

Additional general information on permeable pavement can be found here.

Additional considerations for permeable pavement can be found here.

NOTE: It is highly recommended that permeable pavement should NOT be used in areas of high traffic volume, high speed traffic, areas frequented by heavy equipment, or with frequent start and stopping.