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{{alert|The anticipated construction period for this page is January through March, 2013|alert-under-construction}}
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[[File:Pdf image.png|100px|thumb|alt=pdf image|<font size=3>[https://stormwater.pca.state.mn.us/index.php?title=File:Overview_for_permeable_pavement_-_Minnesota_Stormwater_Manual_June_2022.pdf Download pdf]</font size>]]
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[[File:General information page image.png|right|100px|alt=image]]
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[[File:Univ of MN PICP Photograph.jpg|thumb|300px|alt=a photo illustrating porous concrete|<font size=3>Example of a new retrofit permeable parking lot at the University of Minnesota</font size>]]
  
{{alert|The anticipated review period for this page is January through March, 2013|alert-under-review}}
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{{alert|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.|alert-success}}
  
[[File:picture of porous concrete 1.jpg|thumb|300px|alt=illustration of porous concrete|<font size=2>This photo illustrates an example of pervious concrete.</font size>]]
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<span title="Permeable pavements allow stormwater runoff to filter through surface voids into an underlying stone reservoir for temporary storage and/or infiltration. The most commonly used permeable pavement surfaces are pervious concrete, porous asphalt, and permeable interlocking concrete pavers (PICP)."> '''[https://stormwater.pca.state.mn.us/index.php?title=Permeable_pavement Permeable pavements]'''</span> allow stormwater runoff to filter through surface voids into an underlying stone reservoir where it is temporarily stored and/or <span title="Infiltration Best Management Practices (BMPs) treat urban stormwater runoff as it flows through a filtering medium and into underlying soil, where it may eventually percolate into groundwater. The filtering media is typically coarse-textured and may contain organic material, as in the case of bioinfiltration BMPs."> [https://stormwater.pca.state.mn.us/index.php?title=Stormwater_infiltration_Best_Management_Practices '''infiltrated''']</span>. The most commonly used [[Types of permeable pavement|permeable pavement surfaces]] are pervious concrete, porous asphalt, and permeable interlocking concrete pavers (PICP). Permeable pavements have been used for areas with light traffic at commercial and residential sites to replace traditionally impervious surfaces such as low-speed roads, parking lots, driveways, sidewalks, plazas, and patios. While permeable pavements can withstand truck loads, permeable pavement has not been proven in areas exposed to high repetitions of trucks or in high speed areas because its’ structural performance and surface stability have not yet been consistently demonstrated in such applications.
  
Permeable pavements allow stormwater runoff to filter through surface voids into an underlying stone reservoir where it is temporarily stored and/or infiltrated. The most commonly used permeable pavement surfaces are pervious concrete, porous asphalt, and permeable interlocking concrete pavers (PICP). Permeable pavements have been used for areas with light traffic at commercial and residential sites to replace traditionally impervious surfaces such as low-speed roads, parking lots, driveways, sidewalks, plazas, and patios. Permeable pavement is not ideal for high traffic/high speed areas because it has lower load-bearing capacity than conventional pavement.
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While the designs vary, all permeable pavements have a similar structure, consisting of a surface pavement layer, an underlying stone aggregate reservoir layer, optional <span title="An underground drain or trench with openings through which the water may percolate from the soil or ground above"> '''underdrains'''</span>, and geotextile over uncompacted soil subgrade. From a hydrologic perspective, permeable pavement is typically designed to manage rainfall landing directly on the permeable pavement surface area. Permeable pavement surface areas may accept runoff contributed by adjacent impervious areas such as driving lanes or rooftops. Runoff from adjacent vegetated areas must be stabilized and not generating sediment as its transport accelerates permeable pavement surface clogging. Additionally, the capacity of the underlying reservoir layer limits the <span title="The total drainage area, including pervious and impervious surfaces, contributing to a BMP"> '''[https://stormwater.pca.state.mn.us/index.php?title=Contributing_drainage_area_to_stormwater_BMPs contributing drainage area]'''</span>.  
 
While the designs vary, all permeable pavements have a similar structure, consisting of a surface pavement layer, an underlying stone aggregate reservoir layer, optional underdrains, and geotextile over uncompacted soil subgrade.  
 
 
From a hydrologic perspective, permeable pavement is typically designed to manage rainfall landing directly on the permeable pavement surface area. Permeable pavement surface areas may accept runoff contributed by adjacent impervious areas such as driving lanes or rooftops. Runoff from adjacent vegetated areas is often discouraged because sediment in runoff from adjacent areas increases clogging of the permeable pavement, especially at the edges. Additionally, the capacity of the underlying reservoir layer limits the contributing area.
 
  
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[[File:Schematic showing infiltration.png|thumb|300px|alt=schematic showing process of infiltration into permeable pavement during and after a rain event.|<font size=3>Schematic showing the process of infiltration into permeable pavement during and after a rain event. Note how infiltrating water includes precipitation falling directly on the pavement and runoff from the adjacent street directed onto the pavement. Caution should be used when runoff is diverted from impervious surfaces to permeable pavement.</font size>]]
  
 
==Benefits and limitations==
 
==Benefits and limitations==
*'''Benefits''': Permeable pavements allow for  conversion and/or design of typical impervious areas (i.e. parking lots) to infiltrate runoff as pervious areas. When compared to typical impervious areas, properly designed and maintained permeable pavements can reduce the runoff quantity, reduce total suspended solids (TSS) and total phosphorus (TP) loads into receiving water bodies, and reduce the runoff temperatures.
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*'''Benefits''': Permeable pavements allow conversion and/or design of typical impervious areas (i.e. parking lots) to pervious areas that infiltrate stormwater runoff. When compared to typical impervious areas, properly designed and maintained permeable pavements can reduce the runoff quantity, reduce total suspended solids (TSS) and total phosphorus (TP) loads into <span title="A stream, river, lake, ocean, or other surface or groundwaters into which treated or untreated wastewater is discharged"> '''receiving water bodies'''</span>, and reduce runoff temperatures. In addition, permeable pavements can reduce nitrogen, metals and process oils. Permeable pavements are well suited for high density urban areas with limited space (<span title="Highly urban and ultra-urban settings have a large percentage of impermeable surface and typically have limited space to install surface BMPs. An example would be a downtown area."> '''highly urban and ultra-urban environments'''</span>) for other BMPs such as <span title="A stormwater retention basin that includes a combination of permanent pool storage and extended detention storage above the permanent pool to provide additional water quality or rate control"> [https://stormwater.pca.state.mn.us/index.php?title=Stormwater_ponds '''wet ponds''']</span>, <span title="Are configured as shallow, linear channels. They typically have vegetative cover such as turf or native perennial grasses"> [https://stormwater.pca.state.mn.us/index.php?title=Dry_swale_(Grass_swale) '''swales''']</span> or <span title="Bioretention, also called rain gardens, is a terrestrial-based (up-land as opposed to wetland) water quality and water quantity control process. Bioretention employs a simplistic, site-integrated design that provides opportunity for runoff infiltration, filtration, storage, and water uptake by vegetation. Bioretention areas are suitable stormwater treatment practices for all land uses, as long as the contributing drainage area is appropriate for the size of the facility. Common bioretention opportunities include landscaping islands, cul-de-sacs, parking lot margins, commercial setbacks, open space, rooftop drainage and street-scapes (i.e., between the curb and sidewalk). Bioretention, when designed with an underdrain and liner, is also a good design option for treating Potential stormwater hotspots. Bioretention is extremely versatile because of its ability to be incorporated into landscaped areas. The versatility of the practice also allows for bioretention areas to be frequently employed as stormwater retrofits."> '''bioretention'''</span> systems.
*'''Limitations''': As with all BMP’s, permeable pavement has limitations that need to be considered before design and construction. Limitations are discussed in detail in the permeable pavement design section of this document.  
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*'''Limitations''': As with all BMP’s, permeable pavement has limitations that need to be considered before design and construction. Limitations are discussed in detail in the permeable pavement [[Design criteria for permeable pavement|design section]].
  
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==Pretreatment considerations==
==Pretreatment Considerations==
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<span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''Pretreatment''']</span> that removes sediment from runoff draining onto permeable pavement from impervious surfaces is desirable since sediment can clog permeable pavements. For that reason, pretreatment areas should emit practically no sediment onto the permeable pavement surface. Locating such areas next to impervious surfaces upslope from the permeable pavement may not be possible on some sites. Permeable pavement itself can be considered a pretreatment device and included in a stormwater <span title="Multiple BMPs that work together to remove pollutants utilizing combinations of hydraulic, physical, biological, and chemical methods"> [https://stormwater.pca.state.mn.us/index.php?title=Using_the_treatment_train_approach_to_BMP_selection '''treatment train''']</span> if underdrains are utilized within the storage reservoir. The underdrains will typically be routed to a bioretention area.
Pretreatment to remove sediment from runoff draining onto permeable pavement from adjacent impervious areas is desirable since sediment tends to clog permeable pavements. This is usually accomplished through the use of a vegetative filter upstream of the pavement. Permeable pavement itself can be considered a pre-treatment device and included in a stormwater treatment train if underdrains are utilized within the storage reservoir. The underdrains will typically be routed to bioretention or a raingarden.
 
  
==Permit Applicability==
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==Permit applicability==
Permeable pavements can be utilized to assist in meeting stormwater permit requirements for volume, total suspended solids, and total phosphorus. The section on [[Calculating credits for permeable pavement|credits]] included in this document provides guidance on the implementation of permeable pavements that may be utilized to meet various credit goals.  
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Permeable pavements can be utilized to assist in meeting stormwater [[Regulatory information|requirements]] for volume, total suspended solids, and total phosphorus. The section on [[Calculating credits for permeable pavement|credits]] provides guidance on the implementation of permeable pavements that may be utilized to meet various runoff volume and pollutant runoff reduction goals (<span title="The stormwater runoff volume or pollutant reduction achieved toward meeting a runoff volume or water quality goal."> [https://stormwater.pca.state.mn.us/index.php?title=Overview_of_stormwater_credits '''credits''']</span>).
  
==Retrofit Suitability==
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==Retrofit suitability==
In most cases, existing impervious surfaces can easily be replaced with permeable pavements to achieve improved runoff conditions. Retrofit requires the removal of the old pavement and subgrade and the installation of the underlying reservoir layer and the permeable pavement. When possible, compacted subgrade soils should be removed or loosened to achieve the maximum infiltration rate possible.  
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In most cases, existing impervious surfaces can be replaced with permeable pavements to achieve improved runoff conditions. Retrofit requires the removal of the old pavement and subgrade and the installation of the underlying reservoir layer and the permeable pavement. For the greatest water quality credits, avoid compaction of subgrade soils. If this is not possible, compacted subgrade soils should be removed or loosened to achieve the maximum infiltration rate possible.
  
==Cold Climate Suitability==
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==Cold climate suitability==
The effective use of permeable pavement has been documented in a variety of climates. However, special consideration is necessary for cold climates, arid regions, or areas with high wind erosion [http://www.casqa.org/ (California 2003)]. Dramatic reductions in life span of the infiltration properties of the pavement may occur in these areas due to particulate clogging. In cold climates like Minnesota, the most notably special consideration is regarding the application of sand in the winter for added traction. This is not recommended. Fortunately, permeable pavements require significantly less use of de-icing sand and chemicals to maintain a safe walking or driving surface.  
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Favorable permeable pavement performance has been documented in cold climates. Air in the aggregate base acts as an insulating layer and the higher latent heat associated with higher soil moisture delays the formation of a frost layer while maintaining permeability and this condition also reduces frost depths when frozen. Winter sanding should be avoided when possible and if used, removed by vacuuming the following spring. Permeable pavements require significantly less use of, or in some cases, no deicing chemicals and sand to maintain a safe walking or driving surface. Other climate considerations include high wind erosion. Dramatic reductions in life span of the infiltration properties of the pavement may occur in these areas due to particulate clogging and this may require additional surface vacuum cleaning.
  
==Special Receiving Waters Suitability==
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==Special receiving waters suitability==
Many of the same design considerations and limitations apply to permeable pavement as to other infiltration practices. Infiltration of runoff from [[Potential stormwater hotspots|hotspots]] (e.g., gas stations, chemical storage areas, etc.) should be carefully considered and in many cases avoided. Special consideration also needs to be taken near [[Wellhead protection areas|wellhead areas]] and [[Stormwater infiltration and constraints on infiltration|basement foundations]]. Some designs may require consideration of storms in excess of the infiltration capabilities of the pavement. For these situations the design should ensure the excess runoff does not negatively impact [[Special waters and other sensitive receiving waters|special surface waters]] (e.g.,trout streams) through the implementation of additional BMPs.
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Many of the same design considerations and limitations apply to permeable pavement as to other infiltration practices.
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*Infiltration of runoff from <span title="Stormwater Hotspots (PSHs) are activities or practices that have the potential to produce relatively high levels of stormwater pollutants"> '''[https://stormwater.pca.state.mn.us/index.php?title=Potential_stormwater_hotspots stormwater hotspots]'''</span> (e.g., gas stations, chemical storage areas, etc.) should be carefully considered and in many cases avoided.
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*Special consideration also needs to be taken near <span title="The surface and subsurface area surrounding a well or well field that supplies a public water system, through which contaminants are likely to move toward and reach the well or well field (Minnesota Statutes, section 103I.005, subdivision 24)."> [https://stormwater.pca.state.mn.us/index.php?title=Stormwater_and_wellhead_protection '''Wellhead Protection Areas''']</span> and [[Stormwater infiltration and constraints on infiltration|basement foundations]].
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*Some designs may require consideration of storms in excess of the infiltration capabilities of the pavement. For these situations the design should ensure the excess runoff does not negatively impact <span title="Waters with qualities that warrant extra protection"> [https://stormwater.pca.state.mn.us/index.php?title=Construction_stormwater_program#Special_Waters_and_Impaired_Waters '''special receiving waters''']</span> (e.g.,trout streams) through the implementation of additional BMPs.
  
==Water Quality==
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The table below provides guidance regarding the use of permeable pavement practices in areas upstream of special receiving waters. Note that the suitability of a practice depends on whether the practice has an underdrain (i.e. filtration vs. infiltration practice).
In general, permeable pavement does provide removal of TSS and other pollutants through processes similar to other infiltration BMPs. However, permeable pavements are not suggested for areas that may receive high loading rates of TSS due to their propensity to clog. The expected volume and pollutant reduction for designs without an underdrain equals approximately 100% of the underlying reservoir storage volume. For designs with underdrains, the reductions are less. Of the water intercepted and draining through the underdrain, 45% of the total phosphorus and 74% of total suspended solids can be expected to be removed.
 
  
==Water Quantity==
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{{:Infiltration and filtration bmp design restrictions for special waters and watersheds}}
The primary advantage of permeable pavements is their ability to provide volume reduction by reducing runoff from a site and/or providing attenuation during runoff events. The volume of water that will be reduced during a given rainfall event will be equivalent to the volume available for storage below the pavement or underdrain (if an underdrain is present). More discussion on this item is available in the section on [[calculating credits for permeable pavement|credits]].
 
  
[[category: Overview]]
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==Water quality==
 +
In general, permeable pavement provides removal of TSS and other pollutants through processes similar to other filtration and infiltration BMPs. However, permeable pavements are not suggested for areas that may receive high loading rates of TSS due to their propensity for surface clogging. The expected annual volume and pollutant reductions for designs without an underdrain are a function of the underlying reservoir storage volume. The greater the storage volume, the greater the annual volume and pollutant reductions.
  
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For designs with underdrains, reductions are typically lower depending on the drain outflow location that determines the volume of water removed by the underdrains before infiltration. Of the water intercepted and draining through the underdrain, 45 percent (with upper and lower 90 percent confidence bounds of 65 percent and 24 percent, respectively) of the total phosphorus and 74 percent (with upper and lower 90 percent confidence bounds of 93 percent and 33 percent, respectively) of total suspended solids removal can be expected. These event mean averages and ranges are derived from a literature review on research on permeable pavements. The literature includes 19 studies on pollutant reductions and 10 studies on volume reductions. (See the section on [[Calculating credits for permeable pavement|credits]] for more information on pollutant reduction credits and their relationship to the MIDS credit calculator).
  
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==Water quantity==
 +
The primary advantage of permeable pavements is providing volume reduction by reducing runoff from a site and/or providing attenuation from outflows. The volume of water that will be reduced during a given rainfall event will be equivalent to the volume available for storage below the pavement or underdrain (if an underdrain is present). More discussion on this item is available in the section on [[calculating credits for permeable pavement|credits]].
  
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<noinclude>
While the designs vary, all permeable pavements have a similar structure, consisting of a surface pavement layer, an underlying stone aggregate reservoir layer, optional underdrains, and geotextile over uncompacted soil subgrade.
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==Related articles==
 +
*[[Overview for permeable pavement]]
 +
*[[Types of permeable pavement]]
 +
*[[Design criteria for permeable pavement]]
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*[[Construction specifications for permeable pavement]]
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<!--[[Construction observations for permeable pavement]]-->
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*[[Assessing the performance of permeable pavement]]
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*[[Operation and maintenance of permeable pavement]]
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*[[Calculating credits for permeable pavement]]
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<!--[[Cost-benefit considerations for permeable pavement]]-->
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*[[Case studies for permeable pavement]]
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*[[Green Infrastructure benefits of permeable pavement]]
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*[[Summary of permit requirements for infiltration]]
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*[[Permeable pavement photo gallery]]
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*[[Additional considerations for permeable pavement]]
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*[[Links for permeable pavement]]
 +
<!--*[[External resources for permeable pavement]]-->
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*[[References for permeable pavement]]
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<!--*[[Supporting material for permeable pavement]]-->
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*[[Fact sheets for permeable pavement]]
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*[[Requirements, recommendations and information for using permeable pavement BMPs in the MIDS calculator]]
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<!--#[[Permeable pavement credits]]-->
  
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[https://stormwater.pca.state.mn.us/index.php?title=Permeable_pavement Permeable pavement main page]
From a hydrologic perspective, permeable pavement is typically designed to manage rainfall landing directly on the permeable pavement surface area. Permeable pavement surface areas may accept runoff contributed by adjacent impervious areas such as driving lanes or rooftops. Runoff from adjacent vegetated areas is often discouraged because sediment in runoff from adjacent areas increases clogging of the permeable pavement, especially at the edges. Additionally, the capacity of the underlying reservoir layer  limits the  contributing area.
 
  
 
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[[Category:Level 3 - Best management practices/Guidance and information/BMP overview]]
 
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[[Category:Level 3 - Best management practices/Structural practices/Permeable pavement]]
==Benefits and limitations==
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</noinclude>
*'''Benefits''': Permeable pavements allow for  conversion and/or design of typical impervious areas  (i.e. parking lots) to infiltrate runoff as pervious areas. When compared to  typical impervious areas, properly designed and maintained permeable pavements can reduce the runoff quantity, reduce  total suspended solids (TSS) and total phosphorus (TP) loads into receiving water bodies, and reduce the runoff temperatures.
 
*'''Limitations''': As with all BMP’s, permeable pavement has limitations that need to be considered before design and construction. Limitations are discussed in detail in the permeable pavement design section of this document.
 
 
 
 
==Pretreatment Considerations==
 
Pretreatment to remove sediment from runoff draining onto permeable pavement from adjacent impervious areas is desirable since sediment tends to clog permeable pavements. This is usually accomplished through the use of a vegetative filter upstream of the pavement. Permeable pavement itself can be considered a pre-treatment device and included in a stormwater treatment train if underdrains are utilized within the storage reservoir. The underdrains will typically be routed to bioretention or a raingarden.
 
 
 
==Permit Applicability==
 
Permeable pavements can be utilized to assist in meeting stormwater permit requirements for volume, total suspended solids, and total phosphorus. The section on [[Calculating credits for permeable pavement|credits]] included in this document provides guidance on the implementation of permeable pavements that may be utilized to meet various credit goals.
 
 
 
==Retrofit Suitability==
 
In most cases, existing impervious surfaces can easily be replaced with permeable pavements to achieve improved runoff conditions. Retrofit requires the removal of the old pavement and subgrade and the installation of the underlying reservoir layer and the permeable pavement. When possible, compacted subgrade soils should be removed or loosened to achieve the maximum infiltration rate possible.
 
 
 
==Cold Climate Suitability==
 
The effective use of permeable pavement has been documented in a variety of climates. However, special consideration is necessary for cold climates, arid regions, or areas with high wind erosion [http://www.casqa.org/ (California 2003)]. Dramatic reductions in life span of the infiltration properties of the pavement may occur in these areas due to particulate clogging. In cold climates like Minnesota, the most notably special consideration is regarding the application of sand in the winter for added traction. This is not recommended. Fortunately, permeable pavements require significantly less use of de-icing sand and chemicals to maintain a safe walking or driving surface.
 
 
 
==Special Receiving Waters Suitability==
 
Many of the same design considerations and limitations apply to permeable pavement as to other infiltration practices. Infiltration of runoff from [[Potential stormwater hotspots|hotspots]] (e.g., gas stations, chemical storage areas, etc.) should be carefully considered and in many cases avoided. Special consideration also needs to be taken near [[Wellhead protection areas|wellhead areas]] and [[Stormwater infiltration and constraints on infiltration|basement foundations]]. Some designs may require consideration of storms in excess of the infiltration capabilities of the pavement. For these situations the design should ensure the excess runoff does not negatively impact [[Special waters and other sensitive receiving waters|special surface waters]] (e.g.,trout streams) through the implementation of additional BMPs.
 
 
 
==Water Quality==
 
In general, permeable pavement does provide removal of TSS and other pollutants through processes similar to other infiltration BMPs. However, permeable pavements are not suggested for areas that may receive high loading rates of TSS due to their propensity to clog. The expected volume and pollutant reduction for designs without an underdrain equals approximately 100% of the underlying reservoir storage volume. For designs with underdrains, the reductions are less. Of the water intercepted and draining through the underdrain, 45% of the total phosphorus and 74% of total suspended solids can be expected to be removed.
 
 
 
==Water Quantity==
 
The primary advantage of permeable pavements is their ability to provide volume reduction by reducing runoff from a site and/or providing attenuation during runoff events. The volume of water that will be reduced during a given rainfall event will be equivalent to the volume available for storage below the pavement or underdrain (if an underdrain is present). More discussion on this item is available in the section on [[calculating credits for permeable pavement|credits]].
 
 
 
[[category: Overview]]
 

Latest revision as of 19:28, 27 December 2022

image
a photo illustrating porous concrete
Example of a new retrofit permeable parking lot at the University of Minnesota
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.

Permeable pavements allow stormwater runoff to filter through surface voids into an underlying stone reservoir where it is temporarily stored and/or infiltrated. The most commonly used permeable pavement surfaces are pervious concrete, porous asphalt, and permeable interlocking concrete pavers (PICP). Permeable pavements have been used for areas with light traffic at commercial and residential sites to replace traditionally impervious surfaces such as low-speed roads, parking lots, driveways, sidewalks, plazas, and patios. While permeable pavements can withstand truck loads, permeable pavement has not been proven in areas exposed to high repetitions of trucks or in high speed areas because its’ structural performance and surface stability have not yet been consistently demonstrated in such applications.

While the designs vary, all permeable pavements have a similar structure, consisting of a surface pavement layer, an underlying stone aggregate reservoir layer, optional underdrains, and geotextile over uncompacted soil subgrade. From a hydrologic perspective, permeable pavement is typically designed to manage rainfall landing directly on the permeable pavement surface area. Permeable pavement surface areas may accept runoff contributed by adjacent impervious areas such as driving lanes or rooftops. Runoff from adjacent vegetated areas must be stabilized and not generating sediment as its transport accelerates permeable pavement surface clogging. Additionally, the capacity of the underlying reservoir layer limits the contributing drainage area.

schematic showing process of infiltration into permeable pavement during and after a rain event.
Schematic showing the process of infiltration into permeable pavement during and after a rain event. Note how infiltrating water includes precipitation falling directly on the pavement and runoff from the adjacent street directed onto the pavement. Caution should be used when runoff is diverted from impervious surfaces to permeable pavement.

Benefits and limitations

  • Benefits: Permeable pavements allow conversion and/or design of typical impervious areas (i.e. parking lots) to pervious areas that infiltrate stormwater runoff. When compared to typical impervious areas, properly designed and maintained permeable pavements can reduce the runoff quantity, reduce total suspended solids (TSS) and total phosphorus (TP) loads into receiving water bodies, and reduce runoff temperatures. In addition, permeable pavements can reduce nitrogen, metals and process oils. Permeable pavements are well suited for high density urban areas with limited space ( highly urban and ultra-urban environments) for other BMPs such as wet ponds, swales or bioretention systems.
  • Limitations: As with all BMP’s, permeable pavement has limitations that need to be considered before design and construction. Limitations are discussed in detail in the permeable pavement design section.

Pretreatment considerations

Pretreatment that removes sediment from runoff draining onto permeable pavement from impervious surfaces is desirable since sediment can clog permeable pavements. For that reason, pretreatment areas should emit practically no sediment onto the permeable pavement surface. Locating such areas next to impervious surfaces upslope from the permeable pavement may not be possible on some sites. Permeable pavement itself can be considered a pretreatment device and included in a stormwater treatment train if underdrains are utilized within the storage reservoir. The underdrains will typically be routed to a bioretention area.

Permit applicability

Permeable pavements can be utilized to assist in meeting stormwater requirements for volume, total suspended solids, and total phosphorus. The section on credits provides guidance on the implementation of permeable pavements that may be utilized to meet various runoff volume and pollutant runoff reduction goals ( credits).

Retrofit suitability

In most cases, existing impervious surfaces can be replaced with permeable pavements to achieve improved runoff conditions. Retrofit requires the removal of the old pavement and subgrade and the installation of the underlying reservoir layer and the permeable pavement. For the greatest water quality credits, avoid compaction of subgrade soils. If this is not possible, compacted subgrade soils should be removed or loosened to achieve the maximum infiltration rate possible.

Cold climate suitability

Favorable permeable pavement performance has been documented in cold climates. Air in the aggregate base acts as an insulating layer and the higher latent heat associated with higher soil moisture delays the formation of a frost layer while maintaining permeability and this condition also reduces frost depths when frozen. Winter sanding should be avoided when possible and if used, removed by vacuuming the following spring. Permeable pavements require significantly less use of, or in some cases, no deicing chemicals and sand to maintain a safe walking or driving surface. Other climate considerations include high wind erosion. Dramatic reductions in life span of the infiltration properties of the pavement may occur in these areas due to particulate clogging and this may require additional surface vacuum cleaning.

Special receiving waters suitability

Many of the same design considerations and limitations apply to permeable pavement as to other infiltration practices.

  • Infiltration of runoff from stormwater hotspots (e.g., gas stations, chemical storage areas, etc.) should be carefully considered and in many cases avoided.
  • Special consideration also needs to be taken near Wellhead Protection Areas and basement foundations.
  • Some designs may require consideration of storms in excess of the infiltration capabilities of the pavement. For these situations the design should ensure the excess runoff does not negatively impact special receiving waters (e.g.,trout streams) through the implementation of additional BMPs.

The table below provides guidance regarding the use of permeable pavement practices in areas upstream of special receiving waters. Note that the suitability of a practice depends on whether the practice has an underdrain (i.e. filtration vs. infiltration practice).

Infiltration and filtration bmp1 design restrictions for special waters and watersheds. See also Sensitive waters and other receiving waters.
Link to this table

BMP Group receiving water
A Lakes B Trout Waters C Drinking Water2 D Wetlands E Impaired Waters
Infiltration RECOMMENDED RECOMMENDED NOT RECOMMENDED if potential stormwater pollution sources evident RECOMMENDED RECOMMENDED unless target TMDL pollutant is a soluble nutrient or chloride
Filtration Some variations NOT RECOMMENDED due to poor phosphorus removal, combined with other treatments RECOMMENDED RECOMMENDED ACCEPTABLE RECOMMENDED for non-nutrient impairments

1Filtration practices include green roofs, bmps with an underdrain, or other practices that do not infiltrate water and rely primarily on filtration for treatment.
2 Applies to groundwater drinking water source areas only; use the lakes category to define BMP design restrictions for surface water drinking supplies


Water quality

In general, permeable pavement provides removal of TSS and other pollutants through processes similar to other filtration and infiltration BMPs. However, permeable pavements are not suggested for areas that may receive high loading rates of TSS due to their propensity for surface clogging. The expected annual volume and pollutant reductions for designs without an underdrain are a function of the underlying reservoir storage volume. The greater the storage volume, the greater the annual volume and pollutant reductions.

For designs with underdrains, reductions are typically lower depending on the drain outflow location that determines the volume of water removed by the underdrains before infiltration. Of the water intercepted and draining through the underdrain, 45 percent (with upper and lower 90 percent confidence bounds of 65 percent and 24 percent, respectively) of the total phosphorus and 74 percent (with upper and lower 90 percent confidence bounds of 93 percent and 33 percent, respectively) of total suspended solids removal can be expected. These event mean averages and ranges are derived from a literature review on research on permeable pavements. The literature includes 19 studies on pollutant reductions and 10 studies on volume reductions. (See the section on credits for more information on pollutant reduction credits and their relationship to the MIDS credit calculator).

Water quantity

The primary advantage of permeable pavements is providing volume reduction by reducing runoff from a site and/or providing attenuation from outflows. The volume of water that will be reduced during a given rainfall event will be equivalent to the volume available for storage below the pavement or underdrain (if an underdrain is present). More discussion on this item is available in the section on credits.


Related articles

Permeable pavement main page

This page was last edited on 27 December 2022, at 19:28.