rita leahy: porous pavements
TRANSCRIPT
Porous Asphalt PavementsPorous Asphalt PavementsRita B Leahy, PhD, PERita B Leahy, PhD, PE
Technical Consultant - CalAPATechnical Consultant - CalAPACalAPA Fall ConferenceCalAPA Fall Conference29-30 October 201429-30 October 2014
AcknowledgementsAcknowledgements
Kent Hansen – NAPAKent Hansen – NAPA Jim Huddleston –Jim Huddleston – Asphalt Pavement Assn of OregonAsphalt Pavement Assn of Oregon Ron Cominsky –Ron Cominsky – Pennsylvania Asphalt Pavement AssnPennsylvania Asphalt Pavement Assn Margot Yapp & Jason Puccinelli –Margot Yapp & Jason Puccinelli – Nichols Consulting EngineersNichols Consulting Engineers Brandon Milar - MeadWestvacoBrandon Milar - MeadWestvaco
Presentation OverviewPresentation Overview What are they?What are they? Why use them?Why use them? Guidelines for useGuidelines for use ResourcesResources
What are porous pavements?What are porous pavements?
Open-Graded HMA ~ 2½ to 6 in
Choker Course ~ 1 to 2 in(#57 stone)
Reservoir Course ~ 10 to 36 inClean, Uniformly GradedCrushed Agg (#2 stone) ~ 40% Voids
Non-Woven Geotextile
Uncompacted Subgrade
Why should I use porous pavement?
New stormwater regulationsNew stormwater regulationsReduce volume…not just peak flowReduce volume…not just peak flowLimit impervious areaLimit impervious areaReduce runoffReduce runoff
Sustainability (pollutants, infiltration)Sustainability (pollutants, infiltration)
Pre-DevelopmentPre-Development Post-DevelopmentPost-Development
45 inches rainfall/year45 inches rainfall/year
22 inches Evaporation
8 Runoff
15 Infiltration
2 inches
43
0
Morris ArboretumMorris ArboretumPhiladelphia, PAPhiladelphia, PA
19841984Dense-Dense-GradedGradedPorousPorous
KaiserKaiserMedicalMedicalCenterCenter
All runoff from site diverted to either permeable All runoff from site diverted to either permeable pavement parking structure or percolation basin. pavement parking structure or percolation basin. NO Surface Runoff leaves site.NO Surface Runoff leaves site.
Placer County – Roseville, CAPlacer County – Roseville, CA Demonstration ProjectDemonstration Project Parking area for open space accessParking area for open space access
Porous Pavement UsePorous Pavement Use Primary UsePrimary Use
Parking lotsParking lots Roads w/ little cut or fillRoads w/ little cut or fill Trails/SidewalksTrails/Sidewalks DrivewaysDriveways
Roads/Highway ChallengesRoads/Highway Challenges Cuts and fillsCuts and fills SlopeSlope Variable soil conditionsVariable soil conditions UtilitiesUtilities Limited useLimited use
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0 5 10 15 20
Rainfall, inchesHours
Design ConsiderationsDesign Considerations
Location/Site ConditionsLocation/Site Conditions
HydrologyHydrology
StructuralStructural
HoursR
ainf
aill
(inc
hes)
Location/Site ConditionsLocation/Site Conditions Soil permeability/infiltration rateSoil permeability/infiltration rate
EPA – 0.5 in/hrEPA – 0.5 in/hr 0.1 in/hr - OK0.1 in/hr - OK
Depth toDepth to bedrock > 2ftbedrock > 2ft high water > 3fthigh water > 3ft
Fill – Fill – not recommendednot recommended
http://websoilsurvey.nrcs.usda.gov
Slope – limit surface slope to 5%Slope – limit surface slope to 5% Terrace when necessaryTerrace when necessary Conventional HMA for steeper slopesConventional HMA for steeper slopes
Location/Site ConditionsLocation/Site Conditions
Terraced
Gravel
Stone edge provides alternative path for water to enter recharge bed if pavement is sealed or plugged.
Hydrology - Stormwater DesignHydrology - Stormwater Design RainfallRainfall
Typical: 6 month/24 hr stormTypical: 6 month/24 hr storm Conservative: 25 year/24 hr stormConservative: 25 year/24 hr storm Local & State wastewater mitigation Local & State wastewater mitigation requirementsrequirements
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0 5 10 15 20
Rainfall, inches
Hours
Structural Design - AASHTOStructural Design - AASHTO
MaterialMaterial Layer CoefficientLayer Coefficient
Porous AsphaltPorous Asphalt 0.40 – 0.420.40 – 0.42
Asphalt Treated Permeable BaseAsphalt Treated Permeable Base 0.30 – 0.350.30 – 0.35
Porous Agg BasePorous Agg Base(Recharge Bed)(Recharge Bed)
0.10 – 0.140.10 – 0.14
Structural Design – NAPAStructural Design – NAPARecommended Minimum ThicknessRecommended Minimum Thickness
Caltrans Design GuidanceCaltrans Design GuidanceCategory 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
loadsN/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
DShoulders, some low volume roads, areas in front of noise barriers (beyond the traveled way)
Moderate heavy loads High speed Medium
E Highways, weigh stationsHigh heavy
loads High speed High
California Department of TransportationDivision of Design Office of Storm Water Management 1120 N Street Sacramento, Californiahttp://www.dot.ca.gov/hq/oppd/stormwtr/
Other ConsiderationsOther Considerations
MaterialsMaterialsConstructionConstructionMaintenanceMaintenance
Porous Asphalt - OGFCPorous Asphalt - OGFC
Caltrans Standard Spec Section 39Caltrans Standard Spec Section 39 ½-inch or 1-inch gradation½-inch or 1-inch gradation
Binder: PG 70-10; PG-M (PG 76-22); Binder: PG 70-10; PG-M (PG 76-22); Asphalt RubberAsphalt Rubber
CT 368 – OBC (optimum binder content)CT 368 – OBC (optimum binder content) Method spec for compactionMethod spec for compaction
Key Mix PropertiesKey Mix Properties ““Open” gradationOpen” gradation
Increased permeabilityIncreased permeability >18% air voids>18% air voids
Binder contentBinder content Pavement durabilityPavement durability
Draindown (< 0.3%)Draindown (< 0.3%) ConstructabilityConstructability Film thicknessFilm thickness
Plan to build late in construction processPlan to build late in construction process Wait untilWait until
““dirty work is done”dirty work is done” vegetation is establishedvegetation is established
Excavate bed to about 1ft above planned Excavate bed to about 1ft above planned elevation and use for SW controlelevation and use for SW control Excavate to plan elevation when readyExcavate to plan elevation when ready
Construction SchedulingConstruction Scheduling
Bed ExcavationBed Excavation Excavate bed to Excavate bed to
plan elevation using plan elevation using equipment w/ “soft equipment w/ “soft footprint”footprint”
Don’t compact Don’t compact subgradesubgrade
Non-woven GeotextileNon-woven Geotextile
Spread geotextile Spread geotextile immediately after fine immediately after fine gradinggrading
Overlap fabric >16inOverlap fabric >16in Install drainage pipes Install drainage pipes
if usedif used Excess fabric (> 4ft) Excess fabric (> 4ft)
folded over agg laterfolded over agg later
Stone Recharge BedStone Recharge Bed
Place clean, single size, Place clean, single size, washed aggregatewashed aggregate
Don’t drive trucks on Don’t drive trucks on fabricfabric
Spread and grade with Spread and grade with tracked equipmenttracked equipment
Light compaction - staticLight compaction - static Protect pipesProtect pipes
Choker CourseChoker Course Place “Choker” course – ½-inch clean Place “Choker” course – ½-inch clean
washed aggregatewashed aggregate Purpose -lock up surface for stable Purpose -lock up surface for stable paving platformpaving platform
1 to 2-inches thick1 to 2-inches thick Grade and compactGrade and compact
StaticStaticVibratory? Vibratory?
low amplitudelow amplitudehigh frequencyhigh frequency
Mix ProductionMix Production
Watch temperatureWatch temperature Don’t store for extended Don’t store for extended
periods in silosperiods in silos Batch plant - lower productionBatch plant - lower production
PavingPaving Recommend track paverRecommend track paver Minimize truck movements Minimize truck movements
over aggregateover aggregate Stability may be issueStability may be issue Avoid disturbing agg surface Avoid disturbing agg surface
Place mix ~ 200Place mix ~ 200°°F to 250F to 250°°FF Limit handworkLimit handwork
CompactionCompaction
1 to 3 passes with 1 to 3 passes with 10-ton static steel 10-ton static steel wheelwheel
Less stable than thin Less stable than thin OGFC, may have to OGFC, may have to coolcool
Photo Courtesy of Cahill & Assoc
Photo Courtesy of Cahill & Assoc
After CompactionAfter Compaction Restrict traffic for 24 hoursRestrict traffic for 24 hours Keep sediment control in place till Keep sediment control in place till
vegetation establishedvegetation established
Photo Courtesy of Cahill & Assoc
MaintenanceMaintenance
Inspect first few months during storm events; Inspect first few months during storm events; annually thereafterannually thereafter
Repair/Patching-dense HMA if <10Repair/Patching-dense HMA if <10% of area% of area Regular cleaning – fRegular cleaning – flushed, jet washed, vacuum lushed, jet washed, vacuum
sweepingsweeping
MaintenanceMaintenance Do NOT use traditional seal coat treatmentsDo NOT use traditional seal coat treatments Do not use salt or sand for de-icingDo not use salt or sand for de-icing
Salt - contaminate groundwater infiltrationSalt - contaminate groundwater infiltration Sand - reduce permeabilitySand - reduce permeability
SandSaltAsh
Seal Coat
Cost?Cost?
Stone BedStone Bed
SW Pipes & InletsSW Pipes & Inlets
Earthwork & ExcavationsEarthwork & Excavations
Detention BasinsDetention Basins
ConclusionsConclusions Porous pavements Porous pavements ─ ─ good alternative good alternative
to conventional stormwater mitigationto conventional stormwater mitigation Site conditions criticalSite conditions critical Protect pavement from contamination Protect pavement from contamination
during and after constructionduring and after construction Properly designed, constructed and Properly designed, constructed and
maintained will last than 20+ yearsmaintained will last than 20+ years
Pervious PavementDraft Design Guidance
May 2013
California Department of TransportationDivision of Design Office of Storm Water Management 1120 N Street Sacramento, Californiahttp://www.dot.ca.gov/hq/oppd/stormwtr/
ResourcesResources