Rita Leahy: Porous Pavements
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Water quality regulations have never been more stringent. Learn how you can effectively manage storm water runoff and earn LEED credits through the use of porous asphalt pavements on parking lots and other paved surfaces.
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Rita Leahy: Porous Pavements
- 1. PPoorroouuss AAsspphhaalltt PPaavveemmeennttss RRiittaa BB LLeeaahhyy,, PPhhDD,, PPEE TTeecchhnniiccaall CCoonnssuullttaanntt -- CCaallAAPPAA CCaallAAPPAA FFaallll CCoonnffeerreennccee 2299--3300 OOccttoobbeerr 22001144
- 2. AAcckknnoowwlleeddggeemmeennttss KKeenntt HHaannsseenn –– NNAAPPAA JJiimm HHuuddddlleessttoonn –– AAsspphhaalltt PPaavveemmeenntt AAssssnn ooff OOrreeggoonn RRoonn CCoommiinnsskkyy –– PPeennnnssyyllvvaanniiaa AAsspphhaalltt PPaavveemmeenntt AAssssnn MMaarrggoott YYaapppp && JJaassoonn PPuucccciinneellllii –– NNiicchhoollss CCoonnssuullttiinngg EEnnggiinneeeerrss BBrraannddoonn MMiillaarr -- MMeeaaddWWeessttvvaaccoo
- 3. PPrreesseennttaattiioonn OOvveerrvviieeww WWhhaatt aarree tthheeyy?? WWhhyy uussee tthheemm?? GGuuiiddeelliinneess ffoorr uussee RReessoouurrcceess
- 4. WWhhaatt aarree ppoorroouuss ppaavveemmeennttss?? Open-Graded HMA ~ 2½ to 6 in Choker Course ~ 1 to 2 in (#57 stone) Reservoir Course ~ 10 to 36 in Clean, Uniformly Graded Crushed Agg (#2 stone) ~ 40% Voids Non-Woven Geotextile Uncompacted Subgrade
- 6. Why should I use porous pavement? NNeeww ssttoorrmmwwaatteerr rreegguullaattiioonnss RReedduuccee vvoolluummee……nnoott jjuusstt ppeeaakk ffllooww LLiimmiitt iimmppeerrvviioouuss aarreeaa RReedduuccee rruunnooffff SSuussttaaiinnaabbiilliittyy ((ppoolllluuttaannttss,, iinnffiillttrraattiioonn))
- 7. PPrree--DDeevveellooppmmeenntt PPoosstt--DDeevveellooppmmeenntt 4455 iinncchheess rraaiinnffaallll//yyeeaarr 22 inches Evaporation 8 Runoff 15 Infiltration 2 inches 43 0
- 10. MMoorrrriiss AArrbboorreettuumm PPhhiillaaddeellpphhiiaa,, PPAA 11998844 DDeennssee-- PPoorroouuss GGrraaddeedd
- 11. MMoorrrriiss AArrbboorreettuumm,, PPhhiillaa DDeennssee-- GGrraaddeedd PPoorroouuss
- 12. KKaaiisseerr MMeeddiiccaall CCeenntteerr MMooddeessttoo,, CCAA
- 13. KKaaiisseerr MMeeddiiccaall CCeenntteerr AAllll rruunnooffff ffrroomm ssiittee ddiivveerrtteedd ttoo eeiitthheerr ppeerrmmeeaabbllee ppaavveemmeenntt ppaarrkkiinngg ssttrruuccttuurree oorr ppeerrccoollaattiioonn bbaassiinn.. NNOO SSuurrffaaccee RRuunnooffff lleeaavveess ssiittee..
- 14. Placer CCoouunnttyy –– RRoosseevviillllee,, CCAA DDeemmoonnssttrraattiioonn PPrroojjeecctt PPaarrkkiinngg aarreeaa ffoorr ooppeenn ssppaaccee aacccceessss
- 15. PPoorroouuss PPaavveemmeenntt UUssee PPrriimmaarryy UUssee PPaarrkkiinngg lloottss RRooaaddss ww// lliittttllee ccuutt oorr ffiillll TTrraaiillss//SSiiddeewwaallkkss DDrriivveewwaayyss RRooaaddss//HHiigghhwwaayy CChhaalllleennggeess CCuuttss aanndd ffiillllss SSllooppee VVaarriiaabbllee ssooiill ccoonnddiittiioonnss UUttiilliittiieess LLiimmiitteedd uussee
- 16. DDeessiiggnn CCoonnssiiddeerraattiioonnss 1.20 1.00 0.80 0.60 0.40 0.20 0.00 0 5 10 15 20 Rainfal, inches Hours LLooccaattiioonn//SSiittee CCoonnddiittiioonnss HHyyddrroollooggyy SSttrruuccttuurraall Hours Rainfaill (inches)
- 17. LLooccaattiioonn//SSiittee CCoonnddiittiioonnss SSooiill ppeerrmmeeaabbiilliittyy//iinnffiillttrraattiioonn rraattee EEPPAA –– 00..55 iinn//hhrr 00..11 iinn//hhrr -- OOKK DDeepptthh ttoo bbeeddrroocckk >> 2fftt hhiigghh wwaatteerr >> 3fftt FFiillll –– nnoott rreeccoommmmeennddeedd http://websoilsurvey.nrcs.usda.gov
- 18. LLooccaattiioonn//SSiittee CCoonnddiittiioonnss SSllooppee –– lliimmiitt ssuurrffaaccee ssllooppee ttoo 55%% TTeerrrraaccee wwhheenn nneecceessssaarryy CCoonnvveennttiioonnaall HHMMAA ffoorr sstteeeeppeerr ssllooppeess
- 19. Terraced Gravel Stone edge provides alternative path for water to enter recharge bed if pavement is sealed or plugged.
- 20. HHyyddrroollooggyy -- SSttoorrmmwwaatteerr DDeessiiggnn RRaaiinnffaallll TTyyppiiccaall:: 66 mmoonntthh//244 hhrr ssttoorrmm CCoonnsseerrvvaattiivvee:: 255 yyeeaarr//244 hhrr ssttoorrmm LLooccaall && SSttaattee wwaasstteewwaatteerr mmiittiiggaattiioonn rreeqquuiirreemmeennttss 1.20 1.00 0.80 0.60 0.40 0.20 0.00 0 5 10 15 20 Rainfal, inches Hours
- 21. SSttrruuccttuurraall DDeessiiggnn -- AAAASSHHTTOO MMaatteerriiaall LLaayyeerr CCooeeffffiicciieenntt PPoorroouuss AAsspphhaalltt 00..4400 –– 00..442 AAsspphhaalltt TTrreeaatteedd PPeerrmmeeaabbllee BBaassee 00..300 –– 00..355 PPoorroouuss AAgggg BBaassee 00..1100 –– 00..1144 ((RReecchhaarrggee BBeedd))
- 22. SSttrruuccttuurraall DDeessiiggnn –– NNAAPPAA RReeccoommmmeennddeedd MMiinniimmuumm TThhiicckknneessss
- 23. CCaallttrraannss DDeessiiggnn GGuuiiddaannccee Category Examples Loading Speed Risk A Landscaped areas, sidewalks and bike paths (with no vehicular access), miscellaneous pavement to accept run-on from adjacent impervious areas (e.g. roofs) No vehicular loads N/A Low B Parking lots, park & ride areas, maintenance access roads, scenic overview areas, sidewalks and bike paths (with maintenance/vehicular access), maintenance vehicle pullout Few heavy loads Low speed (less than 30 mph) Low C Rest areas, maintenance stations Moderate heavy loads Low speed Low D Shoulders, some low volume roads, areas in front of noise barriers (beyond the traveled way) Moderate heavy loads High speed Medium E Highways, weigh stations High heavy loads High speed High California Department of Transportation Division of Design Office of Storm Water Management 1120 N Street Sacramento, California http://www.dot.ca.gov/hq/oppd/stormwtr/
- 24. OOtthheerr CCoonnssiiddeerraattiioonnss MMaatteerriiaallss CCoonnssttrruuccttiioonn MMaaiinntteennaannccee
- 25. PPoorroouuss AAsspphhaalltt -- OOGGFFCC CCaallttrraannss SSttaannddaarrdd SSppeecc SSeeccttiioonn 3399 ½--iinncchh oorr 11--iinncchh ggrraaddaattiioonn BBiinnddeerr:: PPGG 7700--1100;; PPGG--MM ((PPGG 7766--2222));; AAsspphhaalltt RRuubbbbeerr CCTT 336688 –– OOBBCC ((ooppttiimmuumm bbiinnddeerr ccoonntteenntt)) MMeetthhoodd ssppeecc ffoorr ccoommppaaccttiioonn
- 26. KKeeyy MMiixx PPrrooppeerrttiieess ““OOppeenn”” ggrraaddaattiioonn IInnccrreeaasseedd ppeerrmmeeaabbiilliittyy >>1188%% aaiirr vvooiiddss BBiinnddeerr ccoonntteenntt PPaavveemmeenntt dduurraabbiilliittyy DDrraaiinnddoowwnn ((<< 00..33%%)) CCoonnssttrruuccttaabbiilliittyy FFiillmm tthhiicckknneessss
- 27. CCoonnssttrruuccttiioonn SScchheedduulliinngg Plan ttoo bbuuiilldd llaattee iinn ccoonnssttrruuccttiioonn pprroocceessss WWaaiitt uunnttiill ““ddiirrttyy wwoorrkk iiss ddoonnee”” vveeggeettaattiioonn iiss eessttaabblliisshheedd EExxccaavvaattee bbeedd ttoo aabboouutt 11fftt aabboovvee ppllaannnneedd eelleevvaattiioonn aanndd uussee ffoorr SSWW ccoonnttrrooll EExxccaavvaattee ttoo ppllaann eelleevvaattiioonn wwhheenn rreeaaddyy
- 28. BBeedd EExxccaavvaattiioonn EExxccaavvaattee bbeedd ttoo ppllaann eelleevvaattiioonn uussiinngg eeqquuiippmmeenntt ww// ““ssoofftt ffoooottpprriinntt”” DDoonn’’tt ccoommppaacctt ssuubbggrraaddee
- 29. NNoonn--wwoovveenn GGeeootteexxttiillee SSpprreeaadd ggeeootteexxttiillee iimmmmeeddiiaatteellyy aafftteerr ffiinnee ggrraaddiinngg OOvveerrllaapp ffaabbrriicc >>1166iinn IInnssttaallll ddrraaiinnaaggee ppiippeess iiff uusseedd EExxcceessss ffaabbrriicc ((>> 44fftt)) ffoollddeedd oovveerr aagggg llaatteerr
- 30. SSttoonnee RReecchhaarrggee BBeedd PPllaaccee cclleeaann,, ssiinnggllee ssiizzee,, wwaasshheedd aaggggrreeggaattee DDoonn’’tt ddrriivvee ttrruucckkss oonn ffaabbrriicc SSpprreeaadd aanndd ggrraaddee wwiitthh ttrraacckkeedd eeqquuiippmmeenntt LLiigghhtt ccoommppaaccttiioonn -- ssttaattiicc PPrrootteecctt ppiippeess
- 31. CChhookkeerr CCoouurrssee PPllaaccee ““CChhookkeerr”” ccoouurrssee –– ½--iinncchh cclleeaann wwaasshheedd aaggggrreeggaattee PPuurrppoossee --lloocckk uupp ssuurrffaaccee ffoorr ssttaabbllee ppaavviinngg ppllaattffoorrmm 11 ttoo 22--iinncchheess tthhiicckk GGrraaddee aanndd ccoommppaacctt SSttaattiicc VViibbrraattoorryy?? llooww aammpplliittuuddee hhiigghh ffrreeqquueennccyy
- 32. MMiixx PPrroodduuccttiioonn WWaattcchh tteemmppeerraattuurree DDoonn’’tt ssttoorree ffoorr eexxtteennddeedd ppeerriiooddss iinn ssiillooss BBaattcchh ppllaanntt -- lloowweerr pprroodduuccttiioonn
- 33. PPaavviinngg RReeccoommmmeenndd ttrraacckk ppaavveerr MMiinniimmiizzee ttrruucckk mmoovveemmeennttss oovveerr aaggggrreeggaattee SSttaabbiilliittyy mmaayy bbee iissssuuee AAvvooiidd ddiissttuurrbbiinngg aagggg ssuurrffaaccee PPllaaccee mmiixx ~~ 220000°°FF ttoo 225500°°FF LLiimmiitt hhaannddwwoorrkk
- 34. CCoommppaaccttiioonn 11 ttoo 33 ppaasssseess wwiitthh 1100--ttoonn ssttaattiicc sstteeeell wwhheeeell LLeessss ssttaabbllee tthhaann tthhiinn OOGGFFCC,, mmaayy hhaavvee ttoo ccooooll Photo Courtesy of Cahill & Assoc Photo Courtesy of Cahill & Assoc
- 35. AAfftteerr CCoommppaaccttiioonn RReessttrriicctt ttrraaffffiicc ffoorr 2244 hhoouurrss KKeeeepp sseeddiimmeenntt ccoonnttrrooll iinn ppllaaccee ttiillll vveeggeettaattiioonn eessttaabblliisshheedd Photo Courtesy of Cahill & Assoc
- 36. MMaaiinntteennaannccee IInnssppeecctt ffiirrsstt ffeeww mmoonntthhss dduurriinngg ssttoorrmm eevveennttss;; aannnnuuaallllyy tthheerreeaafftteerr RReeppaaiirr//PPaattcchhiinngg--ddeennssee HHMMAA iiff <<1100%% ooff aarreeaa RReegguullaarr cclleeaanniinngg –– fflluusshheedd,, jjeett wwaasshheedd,, vvaaccuuuumm sswweeeeppiinngg
- 37. MMaaiinntteennaannccee DDoo NNOOTT uussee ttrraaddiittiioonnaall sseeaall ccooaatt ttrreeaattmmeennttss DDoo nnoott uussee ssaalltt oorr ssaanndd ffoorr ddee--iicciinngg SSaalltt -- ccoonnttaammiinnaattee ggrroouunnddwwaatteerr iinnffiillttrraattiioonn SSaanndd -- rreedduuccee ppeerrmmeeaabbiilliittyy Sand Salt Ash Seal Coat
- 38. CCoosstt?? SSttoonnee BBeedd SSWW PPiippeess && IInnlleettss EEaarrtthhwwoorrkk && EExxccaavvaattiioonnss DDeetteennttiioonn BBaassiinnss
- 39. CCoonncclluussiioonnss PPoorroouuss ppaavveemmeennttss ─ ggoooodd aalltteerrnnaattiivvee ttoo ccoonnvveennttiioonnaall ssttoorrmmwwaatteerr mmiittiiggaattiioonn SSiittee ccoonnddiittiioonnss ccrriittiiccaall PPrrootteecctt ppaavveemmeenntt ffrroomm ccoonnttaammiinnaattiioonn dduurriinngg aanndd aafftteerr ccoonnssttrruuccttiioonn PPrrooppeerrllyy ddeessiiggnneedd,, ccoonnssttrruucctteedd aanndd mmaaiinnttaaiinneedd wwiillll llaasstt tthhaann 2200++ yyeeaarrss
- 40. QQuueessttiioonnss?? CCoommmmeennttss?? Recharge Bed Permeability
- 42. RReessoouurrcceess Pervious Pavement Draft Design Guidance May 2013 California Department of Transportation Division of Design Office of Storm Water Management 1120 N Street Sacramento, California http://www.dot.ca.gov/hq/oppd/stormwtr/
Editor's Notes
- Impervious surfaces such as parking lots and paved roads are often cited as one of the causes of stormwater runoff. Water from rainstorms quickly runs off the impervious surfaces into storm drains and waterways washing the dirt and debris from these surfaces. Porous asphalt pavements dual purpose: pavements for parking lots and roads and stormwater storage, groundwater infiltration.
- From the bottom up, the standard porous structure consists of an compacted SG to maximize the infiltration rate of the soil a geotextile fabric that allows water to pass through but prevents migration of fine material from the SG into the stone recharge bed Stone recharge bed consisting of clean single-size crushed stone with about 40% voids which serves as a structural layer. This layer temporarily stores stormwater ~ 5 to 14 inches of precip - as it infiltrates into the soil below. Thickness f=(water quantity & soil infiltration rate). A stabilizing “choker course” consisting of a clean single-size crushed stone smaller than the stone in the recharge bed which helps to stabilize the surface for paving An open-graded asphalt surface with interconnected voids that allow stormwater to flow through the pavement into the stone recharge bed. Thickness = f(traffic load)
- Here’s some animation to demonstrate how the how porous pavement works. The porous asphalt course is ~ 2 to 6 inches thick with 16% air voids. The reservoir must not only provide stormwater storage but it must also carry the traffic loading. Given that most references recommend a subgrade soil infilgration rate of ½ inch/hour, porous pavement systems in most areas will be able to exfiltrate storms approaching the 100-yr/24-hr event. The depth of the stone reservoir should be such that it drains completely within 72hr.
- environmentally friendly tool for stormwater management conserve water, reduce runoff, promote infiltration which cleanses stormwater, replenish aquifers, and protect streams. Sustain the quality and quantity of our natural resources for use by future generations
- 45 inches precip over 1 acre site Land Development Reduces Infiltration Increases Direct Runoff Increases Pollutants Control Peak Rate of Runoff after Development to Pre-Development Rate Detention Basins - Temporary Storage - Sediment Control Does Not Address Increase in Volume of Runoff
- Picture of detention basin
- Picture of very ugly detention basin
- Developed - Franklin Institute 1972 Pilot Projects - 1970s Geotextiles - 1979 Current design since 1980 CA – 150+ projects since 1980
- Rain infiltrates through porous pavement. This system was built in 1983 and still operates with virtually no maintenance.
- 50 acre site, 4 buildings, 10 acres of pavements 4,400 tons of permeable asphalt Other projects in Roseville, Fremont, San Diego, Crystal Bay, NV (N Shore of Lake Tahoe)
- Key factors to consider soil characteristic, underlying geology (limestone & dolomite may require more detailed site investigation) local topography climate site use traffic loading First and foremost, consider the location early in the design process.
- Consider soil type, infiltration rate, depth to bedrock or seasonal high water table. Bottom of the recharge bed should exceed the frost depth Soil investigations: soil borings, test pits Simple test pits 6 to 8 ft in depth, obviously vary depending upon the depth of the bottom of the reservoir bed. Perform infiltration measurements at the approximate bed bottom location. Simple percolation tests and infiltrometer readings at multiple locations should be done to determine average infiltration rate. Double-ring infiltrometer – estimates vertical movement of water through the bottom of the test area Percolation test allows water movement through both the bottom and sides of the test area
- Use on sites with gentle slopes, permeable soils. On steeper slopes, terrace Spread infiltration; for carbonate soils where there is a risk of sinkholes, the max ratio should be 3:1
- The parking lots are terraced due to slope.. The other important thing is the gravel at the edge of the driveway. This is a clean stone that is connected to the stone recharge bed so if the pavement surface ever becomes plugged or sealed the water will still be able to flow off the surface and into the recharge bed below the pavement surface.
- The hydrologic design should be performed by a licensed engineer proficient in hydrology and SW design. The two most common methods for modeling SW runoff are the Curve Number (CN) and the Rational method. Porous pavement has the same runoff coefficient as a conventional dense-graded pavement, eg, CN = 98. Typical designs can use the 6-month/24-hr storm event. More conservative design - the 25-yr/24-hr storm. In the US values range from 1.4 to 15 inches
- Work done by Oregon and Arizona DOT led to the recommendations shown above for structural layer coefficients. These are used in the AASHTO structural design system. Arizona State U – 1.7 inches of OGFC – 1 inch of dense-graded HMA based on elastic layer analysis Resilient modulus of OGFC ~ ⅓ modulus of dense-graded HMA
- Category A 0.20 feet OGFC over 0.50 feet AB Class 4 Category B Maintenance vehicle pull out , Recovery zone outside shoulder area and Gore area 0.10 foot OGFC over 0.35 feet ATPB on 0.50 feet Class 4 AB Driveway or Sidewalk at driveway, Maintenance access road 0.10 foot OGFC over 0.40 feet ATPB on 0.70 foot Class 4 AB Parking area for passenger vehicles including trafficked area Design per procedures in HDM Topic 633. Use Gf=0 for OGFC, Gf=1.4 for ATPB, and Gf=1.0 for Class 4 AB. Use TI values from HDM Table 613.5B for all auto parking areas. Category C Parking area for heavy vehicles (e.g. rest area on highway with AADTT &gt; 3000) TI&lt;9 (See Note) Design per procedures in HDM Topic 633. Use Gf=0 for OGFC, Gf=1.4 for ATPB, and Gf=1.0 for Class 4 AB.
- Or keep runoff controls in place until vegetation is established
- Don’t produce higher than tested by draindown
- Limit hand work during paving operations Reduces mix temperature Difficult to work with modified binders Can reduce permeability
- On a yard-by-yard basis, the asphalt costs is about the same as conventional asphalt. The underlying stone bed is usually more expensive than conventional compacted subbase, but this cost difference is generally offset by the significant reduction in SW pipes and inlets. Because porous pavement is designed to fit into the topography of the site, there is generally less earthwork and no deep excavations. When the cost savings provided by eliminating the detention basin are considered, porous pavement is generally an economically sound choice. Asphalt portion similar to conventional HMA Gravel bed costs more than conventional subsurface construction Significant savings when accounting for Permitting Conventional storm water management techniques
- Porous pavements have been used for more than 30 years to minimize environmental impact of pavements. In addition to providing hard surfaces for parking and driving, they serve as SW storage and infiltration systems. They offer the opportunity to manage SW storage in an environmentally friendly way as they promote infiltration, improve water quality, recharge GW and keep the flow of runoff in line with non-developed areas.
- Port of Portland