permeable pavements REPORT
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Seminar Report 2015-2016 Pavements.
Permeable
CHAPTER-1 INTRODUCTION 1.1 Permeable Pavements Permeable Pavements, an alternative to traditional impervious pavement, are one of the most environmental friendly paving solutions that are available to builders, landscaping contractors, engineers, and property owners. Permeable pavement is ideal for sites with limited space for other surface storm water These paver types provide different benefits and are applied in various outdoor areas in public, private, and commercial properties. Permeable paving allows for filtration, storage, or infiltration of runo runoff ff and and can can redu reduce ce or elimi elimina nate te surfa surface ce stor storm m water water flow flowss comp compare ared d to traditional impervious paving surfaces like concrete and asphalt. Permeable pavement systems represent alternative paving surfaces that capture and temporarily store the design volume by filtering runoff through voids in the pavement surface into an underlying stone reservoir. Filtered runoff may be collected and returned to the conveyance system, or allowed to partially infiltrate into the soil. This allows permeable pavement systems to provide measurable reductions in postconstruction storm water runoff rates, volumes, and pollutant loads. Permeable pavement is a method of paving that allows storm water to seep into the ground as it falls rather than running off into storm drains, waterways and eventually to water bodies. Permeable pavements function similarly to sand filters, in that they filter the water by forcing it to pass through different aggregate sizes and typically some sort of filter fabric. Therefore most of the treatment is through physical (or mechanical processes. !s precipitation falls on the pavement it infiltrates down into the storage basin where it is slowly released into the surrounding soil. "ong term research on permeable pavers shows their effective removal of pollutants such as total suspended solids, total phosphorous, total nitrogen, zinc, motor oil, and copper. #n the void void spaces, spaces, natura naturally lly occurr occurring ing micro-o micro-org rgani anisms sms break break down down hydroc hydrocarb arbons ons and metals adhere.
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Seminar Report 2015-2016 Pavements.
Permeable
CHAPTER-2 TYPES OF PERMEA!E PA"EMENTS. Ther Theree are are a vari variet ety y of perm permea eabl blee pave paveme ment nt surf surfac aces es avai availa labl blee in the the commercial commercial marketplace, marketplace, including pervious concrete, permeable permeable pavers, pavers, concrete concrete grid pavers, and plastic grid pavers with turf. $ach of these permeable pavement surfaces is briefly described below%
2.1 Perv#$%s C$n&rete. Pervious concrete (also known as porous concrete is similar to conventional concrete concrete in structure and form, but consists of a special open-graded open-graded surface course, typically & to ' inches thick, that is bound together with Portland cement. This opengrad graded ed surfa surface ce cour course se has has a void void rati ratio o of )* )* to +)* +)* (conv (conven enti tion onal al conc concre rete te pavement has a void ratio rat io of between * and )*, which gives it a high permeability that is often many many times more than that that of the underlying underlying native soils, and allows allows rainwater and stormwater runoff to rapidly pass through it and into the underlying stone reservoir. !lthough this particular type of permeable pavement surface may not reuire an underlying base layer to support traffic loads, site planning and design teams may wish to provide it to increase the stormwater storage capacity provided by a pervious concrete system.
Fig no.+.% Pervious oncrete on Palm /each 0ardens,Florida .
Department of Civil Engineering.
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Seminar Report 2015-2016 Pavements.
Permeable
CHAPTER-2 TYPES OF PERMEA!E PA"EMENTS. Ther Theree are are a vari variet ety y of perm permea eabl blee pave paveme ment nt surf surfac aces es avai availa labl blee in the the commercial commercial marketplace, marketplace, including pervious concrete, permeable permeable pavers, pavers, concrete concrete grid pavers, and plastic grid pavers with turf. $ach of these permeable pavement surfaces is briefly described below%
2.1 Perv#$%s C$n&rete. Pervious concrete (also known as porous concrete is similar to conventional concrete concrete in structure and form, but consists of a special open-graded open-graded surface course, typically & to ' inches thick, that is bound together with Portland cement. This opengrad graded ed surfa surface ce cour course se has has a void void rati ratio o of )* )* to +)* +)* (conv (conven enti tion onal al conc concre rete te pavement has a void ratio rat io of between * and )*, which gives it a high permeability that is often many many times more than that that of the underlying underlying native soils, and allows allows rainwater and stormwater runoff to rapidly pass through it and into the underlying stone reservoir. !lthough this particular type of permeable pavement surface may not reuire an underlying base layer to support traffic loads, site planning and design teams may wish to provide it to increase the stormwater storage capacity provided by a pervious concrete system.
Fig no.+.% Pervious oncrete on Palm /each 0ardens,Florida .
Department of Civil Engineering.
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Seminar Report 2015-2016 Pavements.
Permeable
2.2 P$r$%s As'(alt. Porous Porous asphalt asphalt is similar to pervious pervious concrete, and consists of a special opengraded surface course bound together by asphalt cement. The open-graded surface course in a typical porous asphalt installation is to 1 inches thick and has a void ratio of between )* and +2*. Porous asphalt asphalt is thought thought to have a limited ability to maintain its structure and permeability during hot summer months and, conseuently, is currently not recommended for use in coastal region. #f it is used on a development site in the coastal region, it should be carefully monitored and maintained over time.
Fig no.+.+% Porous !sphalt.
2.) Permeable Pavers. Permeable pavers (PP are solid structural units (e.g., blocks, bricks that are installed in a way that provides regularly spaced openings through which stormwater runoff can rapidly pass through the pavement surface and into the underlying stone
Department of Civil Engineering.
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Seminar Report 2015-2016 Permeable Pavements. reservoir. The regularly spaced openings, which generally make up between '* and
Fig no.+.% Permeable /lock Pavers.
+2* of the total pavement surface, are typically filled with gravel. Typical PP systems consist of the pavers, a .)- to -inch thick fine gravel bedding layer and an underlying stone reservoir.
2.* C$n&rete +r#, Pavers. oncrete grid pavers (0P are precast concrete units that allow rainfall and storm water runoff to pass through large openings that are filled with gravel, sand, or topsoil and turf. 0P are typically .) inches thick and have a void ratio between +2* and )2*, which means that the material used to fill the spaces between the grids has a large influence on the overall permeability (i.e., void space of a 0P system. ! typical 0P installation consists of the pavers, - to .)- inch sand or pea gravel bedding layer, and an underlying stone reservoir. 3oid 4tructured oncrete is a similar
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Seminar Report 2015-2016 Permeable Pavements. design type that utilizes molded cast in place concrete rather than pavers.
Fig no.+.&% oncrete 0rid Pavers.
2. Plast#& +r#, Pavers. Plastic grid pavers (P0P are similar to 0P. They consist of fle5ible, interlocking plastic units that allow rainfall and stormwater runoff to pass through large openings that are filled with gravel, sand, or topsoil and turf. 4ince the empty plastic grids have a void ratio of between 62* and 6'*, the material used to fill the spaces between the grids has a large influence on the overall permeability (i.e., void space a P0P system.
7hen designing a permeable pavement system, planning and design teams must not only consider the storage capacity of the system, but also the structural capacity of the underlying soils and the underlying stone reservoir. The infiltration rate and structural capacity of the native soils found on a development site directly influence the size of the stone reservoir that is needed to provide structural support for a permeable pavement system and measurable reductions in post-construction storm water runoff rates, volumes, and pollutant loads. 4ite planning and design teams should strive to design permeable pavement systems that can accommodate the storm Department of Civil Engineering.
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Seminar Report 2015-2016 Permeable Pavements. water runoff volume generated by the target runoff reduction rainfall event.#f this cannot be accomplished due to site characteristics or constraints, site planning and design teams should consider using permeable pavement systems in combination with other runoff reducing low impact development practices.
Fig no.+.)% Plastic 0rid Pavers
CHAPTER-) PERMEA!E PA"EMENT CRITERIAS
).1 Permeable Pavement Feas#b#l#t Cr#ter#a 4ince permeable pavement has a very high retention capability, it should always be considered as an alternative to conventional pavement. Permeable
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Seminar Report 2015-2016 Permeable Pavements. pavement is sub8ect to the same feasibility constraints as most infiltration practices, as described below. ).1.1 Re/%#re, s'a&e.
! prime advantage of permeable pavement is that it does not normally reuire additional space at a new development or redevelopment site, which can be important for space constrained sites or areas where land prices are high. ).1.2 S$#ls.
4oil conditions do not typically constrain the use of permeable pavement, although they do determine whether an underdrain is needed. 9nderdrains are reuired if the measured permeability of the underlying soils is less than 2. in:hr. #nfiltration may be promoted in these designs, however, by incorporating an infiltration sump (i.e., a layer of stone below the invert of the underdrain. 7hen designing a permeable pavement practice, designers must verify soil permeability by using the on-site soil investigation methods provided. #n fill soil locations, geotechnical investigations are reuired to determine if the use of an impermeable liner and underdrain are necessary or if the use of an infiltration sump is permissible. ).1.) C$ntr#b%t#n0 ,ra#na0e area.
The portion of the contributing drainage area that does not include the permeable pavement should not e5ceed ) times the surface area of the permeable pavement (+ times is recommended, and it should be as close to 22* impervious as possible to help prevent clogging of the pavement by sediment from pervious surfaces. ).1.* Pavement s%ra&e sl$'e.
4teep pavement surface slopes can reduce the stormwater storage capability of permeable pavement and may cause shifting of the pavement surface and base
materials. The permeable pavement slope must be less than )*. ;esigners may consider using a terraced design for permeable pavement in areas with steeper slopes. #n all cases, designs must ensure that the slope of the pavement does not lead to flow occurring out of the stone reservoir layer onto lower portions of the pavement surface. ).1. M#n#m%m (,ra%l#& (ea,.
The elevation difference needed for permeable pavement to function properly is generally nominal, although + to & feet of head from the pavement surface to the Department of Civil Engineering.
Seminar Report 2015-2016 Permeable Pavements. underdrain outlet is typically necessary. This value may vary based on several design factors, such as reuired storage depth and underdrain location. ).1. M#n#m%m ,e't( t$ 3ater table.
! high groundwater table may cause runoff to pond at the bottom of the permeable pavement system. Therefore, a minimum vertical distance of 2.) feet must be provided between the bottom of the permeable pavement installation (i.e., the bottom invert of the reservoir layer and the seasonal high water table. ).1.4 Setba&5s.
To avoid the risk of seepage and to prevent damage to building foundations and contamination of groundwater auifers, permeable pavement areas should be located at least%
)2 feet from septic systems
2 feet from property lines
)2 feet from water supply wells
2 feet up gradient from building foundations. 7here the 2-foot setback from building foundations is not possible, an impermeable liner may be used along the sides of the permeable pavement practice (e5tending from the surface to the bottom of the practice.
).1.6 P$ll%tant ($ts'$t lan, %ses.
Permeable pavement is not appropriate for certain pollutant-generating sites. #n areas where higher pollutant loading is likely (i.e. oils and greases from fueling stations or vehicle storage areas, sediment from un-stabilized pervious areas, or other pollutants from industrial processes, appropriate pretreatment, such as an oil-water separator or filtering device must be provided, or the areas should be diverted from the permeable pavement. months following construction, the practice and ;! should be inspected at least twice after storm events that e5ceed :+ inch of rainfall. onduct any needed repairs or
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