Porous Asphalt Pavements for Storm Water Management
Porous Asphalt Pavements for Storm Water Management
Porous Asphalt Pavements for Storm Water Management
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<strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong> <strong>for</strong><br />
<strong>Storm</strong> <strong>Water</strong> <strong>Management</strong><br />
Dr. Will Rogers<br />
Technical Director<br />
Georgia <strong>Asphalt</strong> Pavement Associa=on
<strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong><br />
• Introduc=on<br />
• Applica=ons<br />
• Materials & Design<br />
• Construc=on Guidelines<br />
• Maintenance<br />
• Jobsite Pictures<br />
• Keys to Success
<strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong><br />
• Introduc=on<br />
• Applica=ons<br />
• Materials & Design<br />
• Construc=on Guidelines<br />
• Maintenance<br />
• Jobsite Pictures<br />
• Keys to Success
Introduc=on to <strong>Porous</strong> <strong>Pavements</strong>
Introduc=on: Benefits of <strong>Porous</strong><br />
<strong>Asphalt</strong><br />
• Reduce Earthwork Cut & Fill<br />
• GA Contractors Regularly place the OGFC used<br />
<strong>for</strong> <strong>Porous</strong> <strong>Asphalt</strong><br />
• Treats Runoff<br />
• Recharges Ground <strong>Water</strong><br />
• No Discharge Permit
Reference<br />
Prince<br />
William Site<br />
Rockville<br />
Site<br />
Univ. of<br />
New<br />
Hampshire<br />
Introduc=on: <strong>Water</strong> Quality<br />
Total<br />
Suspended<br />
Solids<br />
Total<br />
Nitrogen<br />
Percent Pollutant Removal<br />
Total<br />
Phosphorus<br />
Lead Zinc<br />
Petroleum Hydrocarbons<br />
in Diesel Range<br />
95 85 65 98 99 -‐-‐<br />
82 80 65 -‐-‐ -‐-‐ -‐-‐<br />
99 -‐-‐ 38 -‐-‐ 96 99
<strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong><br />
• Introduc=on<br />
• Applica=ons<br />
• Materials & Design<br />
• Construc=on Guidelines<br />
• Maintenance<br />
• Jobsite Pictures<br />
• Keys to Success
Applica=ons: Parking Lots
Applica=ons: Recrea=onal Facili=es
Applica=ons: Streets & Roads
<strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong><br />
• Introduc=on<br />
• Applica=ons<br />
• Materials & Design<br />
• Construc=on Guidelines<br />
• Maintenance<br />
• Jobsite Pictures<br />
• Keys to Success
Materials & Design: Subgrade Soil<br />
• Soil Inves=ga=on<br />
– Boring or Test Pits: 6 – 8’ Deep<br />
• Depth ≈ 2’ Below Expected Boaom of Recharge Bed<br />
• Number of Pits based on Pavement Use & Size<br />
• Soil Condi=ons Observed<br />
– Test Permeability<br />
– Depth to High <strong>Water</strong> Table<br />
– Depth to Bedrock<br />
– Soil should Drain:<br />
• Within 24 – 72 Hours
Materials & Design: Subgrade Soil<br />
Saturated Hydraulic ConducRvity of Hydrologic Soil Groups when a <strong>Water</strong> Impermeable Layer<br />
Exists between 20 and 40 inches<br />
Hydrologic Group A Hydrologic Group B Hydrologic Group C Hydraulic Group D<br />
A > 5.67 in/hr 1.42 < B ≤ 5.67 in/hr 0.14 < C ≤ 1.42 in/hr D ≤ 0.14 in/hr<br />
Saturated Hydraulic ConducRvity of Hydrologic Soil Groups when any <strong>Water</strong> Impermeable<br />
Layer exists at a Depth Greater than 40 inches<br />
Hydrologic Group A Hydrologic Group B Hydrologic Group C Hydraulic Group D<br />
A > 1.42 in/hr 0.57 < B ≤ 1.42 in/hr 0.06 < C ≤ 0.57 in/hr D ≤ 0.06 in/hr
Materials & Design: Hydrology -‐<br />
Kentucky
Materials & Design: Geotex=le<br />
• Non-‐Woven Geotex=le “Filter Fabric”<br />
Test Requirement<br />
Grab Tensile Strength<br />
(ASTM D4632)<br />
Mullen Burst Strength<br />
(ASTM D3786)<br />
Flow Rate<br />
(ASTM D4491)<br />
UV Resistance Aper 500 Hours<br />
(ASTM D4355)<br />
≥ 120 lbs<br />
≥ 225 psi<br />
≥ 95 gallons / minute / SF<br />
≥ 70%
Materials & Design: Stone Recharge<br />
• Typically No. 3 Stone<br />
– Clean, Washed<br />
Bed<br />
• Typically Between 12 and 36 inches<br />
• ≈ 40% Voids<br />
– Typically stores Between 4.8 and 14.4 inches of<br />
Precipita=on<br />
– Since this Exceeds most <strong>Storm</strong> Events, Consider using<br />
Recharge Bed to Treat nearby Impermeable Surfaces.<br />
• Pretreatment by be Required
Materials & Design: Stone Recharge<br />
• In Most Cases:<br />
Bed<br />
– Recharge Bed Thickness Determined By:<br />
• <strong>Water</strong> Quan=ty<br />
• Soil Infiltra=on Rate<br />
– <strong>Porous</strong> <strong>Asphalt</strong> Thickness Determined By:<br />
• Traffic Loading<br />
• Same Structural Strength when Dry or Wet<br />
• Recharge Bed Geometry
Materials & Design: Flat Recharge Bed
Materials & Design: Choker Course<br />
• Op=onal<br />
• Typically No. 57 Stone<br />
• Typically 1” Thick<br />
• Designed to Provide Smooth Surface to Pave<br />
On<br />
– NOT Designed to fill Surface Voids of Recharge<br />
Bed
Materials & Design of <strong>Porous</strong> <strong>Asphalt</strong><br />
1. Consider Loca=on <strong>for</strong> <strong>Porous</strong> Pavement Early<br />
in Design Process<br />
2. Soil Infiltra=on Rates: 0.1 – 10 inches/hour<br />
work best<br />
3. Min. Depth to Bedrock / Seasonal High <strong>Water</strong><br />
Greater than 2 p.<br />
4. Boaom of Infiltra=on Bed must be Flat<br />
5. Max. Pavement Slope = 5%. Terrace if<br />
Needed.
Materials & Design of <strong>Porous</strong> <strong>Asphalt</strong>
Materials & Design of <strong>Porous</strong> <strong>Asphalt</strong><br />
6. Route Runoff from Nearby Impervious Areas<br />
7. Max. Ra=o of Impervious: Pervious Area -‐<br />
5:1. For Carbonate Soils – 3:1.<br />
8. Design Should Provide <strong>for</strong> Alternate Path <strong>for</strong><br />
<strong>Storm</strong>water to Enter Recharge Bed<br />
9. Include Overflow System as Required<br />
10. Recharge Bed should Drain within 12 – 72<br />
Hours
Materials & Design of <strong>Porous</strong> <strong>Asphalt</strong><br />
40" - 48" TO WATER TABLE<br />
ROOF LEADERS SHOULD BE<br />
EXTENDED INTO THE RETENTION<br />
BED WHERE POSSIBLE<br />
OPEN EDGE DRAIN<br />
DIRECT RAINFALL<br />
RUNOFF IF IMPERVIOUS<br />
SLAG RETENTION BED<br />
2" x 6" RECTANGULAR<br />
EMERGENCY OVERFLOW<br />
(3) 1" Ø ORIFICE(S)<br />
H-20 RATED CAST<br />
IRON GRATE<br />
WATER QUALITY<br />
SWALE
Materials & Design: Structural<br />
• Most <strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong> are Low<br />
Volume<br />
– Design Based on rain Event & Volume of <strong>Water</strong> to<br />
be Retained<br />
– Most <strong>Porous</strong> <strong>Pavements</strong> Overdesigned<br />
• Stone Recharge Bed is Structural<br />
• If Expec=ng Trucks / Heavy Loadings<br />
– Design these areas Separately<br />
– Consider Thickness & Mixture Type
Materials & Design: <strong>Porous</strong> <strong>Asphalt</strong><br />
• Open-‐Graded Fric=on Course (OGFC)<br />
– Same Pavement that Tops Interstates in GA<br />
– On Interstates, Typically:<br />
• Polymer-‐Modified PG76-‐22<br />
• Fibers<br />
– Controls Drain-‐Down, Scuffing<br />
– Also Available:<br />
• Crumb Rubber-‐Modified Binders<br />
– In Lieu of Polymer. S=ll Bumps PG Grade to PG76-‐22.<br />
– Allows Recycling of Crumb Rubber<br />
• Warm Mix Addi=ves<br />
– Reduces/Eliminates Draindown
Materials & Design: <strong>Porous</strong> <strong>Asphalt</strong><br />
• Bump Binder Grade from PG64-‐22 to PG76-‐22<br />
– Two Grades up from Standard Grade<br />
• Air Voids: Min. of 16%<br />
• <strong>Asphalt</strong> Content: Min. of 5.75%<br />
• Moisture Suscep=bility – These mixes have<br />
very low Stripping Poten=al<br />
– Rule of Thumb: If Dense-‐Graded Mix using this<br />
aggregate requires An=-‐Strip Agent, Use it.<br />
– Georgia is a Lime State, but may also consider<br />
WMA addi=ves like EvoTherm
Materials & Design: GDOT Sec=on 828:<br />
OGFC
Materials & Design: <strong>Porous</strong> <strong>Asphalt</strong><br />
Mix NMAS ApplicaRon Layer Thickness<br />
3/8” [9.5mm]<br />
OGFC<br />
1/2” [12.5mm]<br />
OGFC<br />
3/4” [19 mm]<br />
OGFC<br />
3/4” [19 mm]<br />
ATPB<br />
Parking/Recrea=on Facili=es 1.5 – 3.5 Inches<br />
Wearing Surface, Streets, Heavy Commercial 2.0 – 4.0 Inches<br />
Wearing Surface, Roads, Heavy Commercial 2.0 – 5.0 Inches<br />
Base Course 3.0 – 6.0 Inches
Materials & Design – Minimum<br />
<strong>Asphalt</strong> Thickness
Materials & Design: Structural – Heavy<br />
• ADOT Constructed Structural <strong>Porous</strong><br />
Pavement Roadway<br />
– Constructed in 1986<br />
– 6” of 3/8” NMAS Open Graded <strong>Asphalt</strong><br />
• SN = 0.40<br />
– 6” <strong>Asphalt</strong> Treated Permeable Base<br />
• SN = 0.20<br />
– 8” Stone Recharge Bed<br />
• SN = 0.11<br />
• Per<strong>for</strong>ming Well as of 2008<br />
– MR of <strong>Porous</strong> <strong>Asphalt</strong> ≈ 32 – 45% of Dense HMA
Materials & Design: Overflow Systems<br />
• In General, Used if:<br />
– Soil Will Not Drain in 24 – 72 Hours<br />
– Security Against Larger <strong>Storm</strong> Events<br />
• Discharge to:<br />
– Rain Garden<br />
– <strong>Storm</strong> Drain System<br />
– Body of <strong>Water</strong>
Materials & Design: Overflow Systems
Materials & Design: Overflow Systems<br />
Outflow to<br />
Other BMP<br />
Overflow<br />
Weir
Materials & Design: Other<br />
Considera=ons<br />
• Rou=ng <strong>Storm</strong>water from Impervious Areas<br />
– Roofs, Adjacent Roadways, ect…<br />
– Open Pipe Directly into Recharge Bed<br />
– Consider Sediment Control Devices<br />
– Remember 5:1 Ra=o<br />
• Provide Alternate Path<br />
– Good Prac=ce to Provide Alt. Path <strong>for</strong> Runoff to<br />
Enter Recharge Bed<br />
– Extreme <strong>Storm</strong>s, Clogging
Materials & Design: Other<br />
Considera=ons<br />
• Overflow Structures<br />
– For Soils unable to Drain w/in 72 Hours<br />
– For Higher-‐Level <strong>Storm</strong> Events & Slow Draining<br />
Soils<br />
• Protect from Sedimenta=on<br />
– Construc=on is Dirty<br />
– Ideas:<br />
• Construct Late in Schedule, if Allowed<br />
• Blend Impervious/<strong>Porous</strong> <strong>Pavements</strong> on-‐site<br />
• Cover <strong>Porous</strong> Pavement with Geotex=le to Protect<br />
from Clogging
<strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong><br />
• Introduc=on<br />
• Applica=ons<br />
• Materials & Design<br />
• Construc=on Guidelines<br />
• Maintenance<br />
• Jobsite Pictures<br />
• Keys to Success
Construc=on Guidelines<br />
• Protect Site from Excessive Heavy Equipment<br />
– Low Ground-‐Pressure Equipment<br />
• Wider Tracks or Over-‐Sized Tires<br />
– Prevent Compac=ng Soil & Reducing Permeability<br />
• When Placing the Filter Fabric:<br />
– Min. 16” Overlap<br />
– Extend Min. 4’ Outside Recharge Bed to Prevent<br />
Sedimenta=on from Entering Bed<br />
– Fold Excess Over Recharge Bed un=l Paving
Construc=on Guidelines: Bed<br />
Excava=on
Construc=on Guidelines: Geotex=le
Construc=on: Drain Pipes
Construc=on: Drain Pipes
Construc=on Guidelines<br />
• Install Drainage Pipes, if Required, Just aper<br />
Placing Geotex=le<br />
• Place Aggregate <strong>for</strong> Stone Recharge Bed<br />
– Dump Aggregate at Edge of Bed, where Possible<br />
– Place 8 – 12 Inches Using Track Equipment<br />
– Compact/Seat with a Single Pass from a Light<br />
Roller or Vibratory Plate Compactor<br />
• Install Choker Course, if Required
Construc=on Guidelines: Recharge Bed
Construc=on Guidelines<br />
• Pave ATPB (if Required) and OGFC in 2 – 4” Lips<br />
– Tracked Paver Recommended<br />
– Follow GDOT Guidelines <strong>for</strong> OGFC/PEM<br />
– GA Contractors place OGFC/PEM Regularly<br />
• Compact w/ 10 TN Sta=c Roller<br />
– 2 – 4 Passes<br />
– Remove Roller Marks w/Lighter Roller aper Cooling<br />
• Limit Traffic <strong>for</strong> First 24 Hours<br />
– Mix may be more Tender than Usual
Construc=on: Paving
Construc=on: Paving
Construc=on: Rolling
<strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong><br />
• Introduc=on<br />
• Applica=ons<br />
• Materials & Design<br />
• Construc=on Guidelines<br />
• Maintenance<br />
• Jobsite Pictures<br />
• Keys to Success
Maintenance<br />
• Keep Sediment Control In-‐Place un=l<br />
Vegeta=on is Established<br />
• NEVER use Sand or Ash <strong>for</strong> De-‐Icing<br />
– Clogging<br />
– Less De-‐Icer needed with OGFC<br />
• Consider Placing Sign to Alert Maint.<br />
Personnel<br />
• NEVER Apply Seal Coat
Maintenance
Maintenance<br />
• All <strong>Porous</strong> <strong>Pavements</strong> should be Inspected<br />
– Several Times in First Few Months<br />
– Annually<br />
– Aper Large <strong>Storm</strong>s to check <strong>for</strong> Ponding/Clogging<br />
• Preventa=ve Maintenance VITAL<br />
• Cleaning:<br />
– Pressure Washing (Not High Pressure)<br />
– Vacuum Truck<br />
– Recommended: Vacuum Clean 2x Per Year
<strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong><br />
• Introduc=on<br />
• Applica=ons<br />
• Materials & Design<br />
• Construc=on Guidelines<br />
• Maintenance<br />
• Jobsite Pictures<br />
• Keys to Success
Clemson <strong>Porous</strong> Pavement
<strong>Porous</strong> Parking Bays
<strong>Porous</strong> Parking On Street
<strong>Porous</strong> Parking on Street
<strong>Porous</strong> <strong>Asphalt</strong> <strong>Pavements</strong><br />
• Introduc=on<br />
• Applica=ons<br />
• Materials & Design<br />
• Construc=on Guidelines<br />
• Maintenance<br />
• Jobsite Pictures<br />
• Keys to Success
Keys to Success<br />
• Make Sure Site Condi=ons are Acceptable<br />
– Soil Infiltra=on / Permeability<br />
– Depth to Groundwater and/or Bedrock<br />
• Design<br />
– Boaom of Recharge Bed should be Level<br />
– Limit Surface Slope to < 5%<br />
– Runoff from Adjacent Areas will not Plug<br />
Pavement<br />
– 5:1 Impervious to Permeable Area Ra=o
Keys to Success<br />
• Construc=on<br />
– Don’t Compact Subgrade<br />
– Protect Pavement from Contamina=on<br />
• Build <strong>Porous</strong> Pavement Late<br />
• Stabilize Adjacent Areas Be<strong>for</strong>e Construc=on<br />
• ALWAYS PROTECT RECHARGE BED<br />
• Maintenance<br />
– Do NOT Sand or Ash <strong>Pavements</strong><br />
– Install Signage to Warn Maintenance Personnel<br />
– Can Patch with Conven=onal <strong>Asphalt</strong> < 10%
Ques=ons?
References