Sustainable Stormwater Management in

Road Environments:

Porous Asphalt for Local Roads

Robert Roseen, PE, D.WRE, PhD, Thomas Ballestero, PE, PhD, PH, CGWP, PG,

James Houle, CPSWQ, Alison Watts, PhD, Tim Puls

The UNH Stormwater Center

Environmental Research Group, Department of Civil Engineering

University of New Hampshire

Ohio Transportation Engineering Conference

Columbus, OH

10/19-10/20/2010

Dedicated to the protection of water resources through effective stormwater management

• Research and development of stormwater treatment systems

• To provide resources to stormwater communities currently involved in design and implementation of Phase II requirements

Gregg Hall ● 35 Colovos Road ● Durham, New Hampshire 03824-3534

603.862.4024 ● http://www.unhsc.unh.edu

Introduction - Objective

We can do better at stormwater

management in roadways and

road corridors

Case Study –

Porous Asphalt Road

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Boulder Hills, Pelham, NH

2009 Installation of 900’ of first PA private

residential road in Northeast

Site is nearly Zero discharge

LID subdivision 55+ Active Adult Community

Large sand deposit

Conventional Site

Design

LID Design

The Scope

Built on 9% grade

14 acres of previously undeveloped land

5 multi-family buildings, a community well,

and a private septic system

All driveways and sidewalks in the

development are porous asphalt

Fire lanes consisting of crushed stone that

also serve as infiltration systems for rooftop

runoff. 7

The Design

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Gravel Filter Layer over 3/8-in stone base

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Cutoff for Stone Layer Flow

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Choker Course ¾-in Stone

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Choker Course Compaction

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Infiltration

Testing of

Gravel

Layer

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15

16

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THE FINISHED PRODUCT

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2009 Porous Asphalt Paving Costs

DMA $100/ton,

PA $125/ton placed by machine for

parking and residential road and

driveways

Complicated jobs with handwork are more

expensive $170/ton

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Cost Avoidance

Avoided use of 1616’ of curbing, 785’

pipe, 8 catch-basins, 2 detention basins, 2

outlet control structures

1.3 acres less of land clearing

Conventional SWM=$789,500 vs LID

SWM=$740,300, $49,000 savings (6.2%)

Comparison of Unit Costs

6% savings on total cost of SW infrastructure for a ~zero discharge site

But There is More….

Salted twice, then never again (less salt to

receiving stream)

Better traction than standard DMA

Fire fighting storage from rooftop capture

No concern about mosquitoes in the ponds

Very little site runoff (pollutant load to

stream very small, no thermal pollution)

Receiving stream in geomorphic equilibrium

not taxed 23

State of the Practice with Porous

Pavements

Significant advancements in porous asphalt

strength, durability, and production costs have

been achieved

Large increase in significant PA installs for

light duty, residential, commercial, and state

road applications

However, a large number of installations STILL

continue to be sub-standard

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Common Pitfalls Inappropriate porous asphalt mix selection with

respect to durability leads to raveling and low

durability

Poor subbase compaction—tendency to under-

compact due to concerns regarding infiltration (leads

to rutting)

Poor asphalt compaction—tendency to under-

compact due to weaker subbase (leads to low

pavement durability)

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All issues can be addressed through

qualified engineering oversight

MODERATE

DURABILITY: Pre-

Blended PG 64-28*

SBR with 5 pounds of

fibers per ton of

asphalt mix. This mix

is recommended for

large projects > 1

acre where high

durability pavements

are needed.

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*or PG binder typical to

region; **PG binder 2

grades stiffer

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Sieve Size (inch/mm) Percent Passing (%)

0.75/19 100

0.50/12.5 85-100

0.375/9.5 55-75

No.4/4.75 10-25

No.8/2.36 5-10

No.200/0.075 (#200) 2-4

Binder Content (AASHTO T164) 6 - 6.5%

Fiber Content by Total Mixture Mass 0.3% cellulose or

0.4% mineral

Rubber Solids (SBR) Content by Weight of the

Bitumen 1.5-3% or TBD

Air Void Content

(ASTM D6752/AASHTO T275)

16.0-22.0%

Draindown (ASTM D6390)* < 0.3 %

Retained Tensile Strength (AASHTO 283)** > 80 %

Cantabro abrasion test on unaged samples

(ASTM D7064-04)

< 20%

Cantabro abrasion test on 7 day aged samples < 30%

Hydraulic Performance

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Lag Time (kL) Peak Reduction (kP)

5 2 1 0.5 0.1

TSS Removal Efficiencies

100

90

80

70

60

50

40

30

20

10

0

TS

S %

Rem

oval

Eff

icie

ncy

Weighted Skid Resistance (BPN)

0

10

20

30

40

50

60

70

80

90

100

100 50 25 0

% Salt Application

Skid

Resis

tan

ce (

BP

N)

Dense Mix Asphalt

Porous Asphalt

0

10

20

30

40

50

60

70

80

90

100

100 50 25 0

% Ic

e C

ov

er

% Salt Application

% Ice Cover

Dense Mix Asphalt

Porous Asphalt

Weighted Skid Resistance (BPN)

0

10

20

30

40

50

60

70

80

90

100

100 50 25 0

% Salt Application

Skid

Resis

tan

ce (

BP

N)

Dense Mix Asphalt

Porous Asphalt

Repairs and Replacement

Damage can occur to PA from non-design loads

Repairs may be needed from cuts for utilities

Repairs can be made with standard HMA for most

damages up to 15% of surface area

PA can be repaired by heating and rerolling at

$2,000/day at approximately 500’ of trench

When pavement reaches end of life, it is replaced

by milling to choker coarse.

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Repairs

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We would like to extend our sincere

gratitude to the

Cooperative Institute for Coastal and

Estuarine Environmental Technology

and the National Oceanic and

Atmospheric Administration

for their generous support.

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Questions?