Application of Porous Pavement

May 12, 2006Richard Boase, P.Geo., CCEP

North Vancouver District

A Water Balance Perspective

Why Change at All

•Why is this an issue?

•How do we implement effective change?

•How do we monitor results of decisions made?

Single Family Rainwater Mgt.

DNV encompasses 16,237 Ha. (63 mi.2)

•64.5% Wilderness Area

•19.5% Residential

•8.3% Urban Parks

•3.3% Conservation

•2.1% Industrial

Single Family Rainwater Mgt.

•Population approximately 80,000

•27,319 dwelling units (incl. M/F)

•70% detached single family

•11% increase in dwelling units 1986-1991

Single Family Rainwater Mgt.

Science tells us that watershed health begins to deteriorate as a watershed moves beyond 10% total impervious surface area.

Aging SFD stock >50 years

Lower land value

Different appreciation for space

Total lot area = 1901 sq. m.

19% Hard Surface

53% Tree Canopy

15% Landscaping

13% Building Footprint

New SFD stock < 10 years

Higher land value

Different appreciation for space

Total lot area = 1972 sq. m.

24% Building Footprint

25% Hard Surface

23% Tree Canopy

By Covenant

28% Landscaping

59% increase 88% increase

Single Family Rainwater Mgt.

How do we implement change?

Single Family Rainwater Mgt.

2005 Rain Data (mm)

Over 80% of rain = small frequent showers < than 50 mm

We need a new approach

74%71%

21% 23%

4 % 6%

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2 0

4 0

6 0

8 0

1 0 0

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L e s s th a n 5 0 % o fM A R

5 0 % o f M A R to M A R G re a te r th a n M A R

R a in fa ll E v e n t S iz e (m m )

T y p ic a l V o lu m e D is tr ib u tio n o f A n n u a l R a in fa l l

S o u th C o a s t (B u rn a b y M o u n ta in ) O k a n a g a n (K e lo w n a A irp o rt)

N ote : B urnab y M oun ta in M A R * = 7 0 m m K e low n a M A R * = 20 m m (*2 4 -h o u r ra in fa l l )

Single Family Rainwater Mgt.

SiteSite

Watershed Watershed HealthHealth

WBMWBM

Building sizeBuilding size

Hard surfaceHard surface

LandscapingLandscaping

Single Family Rainwater Mgt.

Yes we can make a difference if we have;

• Policies

• Bylaws

• Standards for “greener” designs

Pervious Paving

We needed something to give us a nudge

Who would ever have thought it would come from a simple Council

discussion over a routine lane paving project!

Pervious Paving

Open Graded Asphalt

• Hot mix asphalt with inter-connecting voids• Developed as a highway safety feature to

reduce hydroplaning, skidding and tire noise

Pervious Paving

Could we adapt an existing use of open graded asphalt?

• Used as a tennis court surface

• Well draining

• More use year round

Pervious Paving

Project Area550 m2

Pervious Paving

Geotechnical Assessment First

• Variable permeability rates (50 -135 mm/hr)• High fines content (18 – 45 %)

• Organic content under existing lane surface

Pervious Paving

Geotechnical Assessment First

• Flat topography• No ability to raise grade • Concern about capillary action & fines

Pervious Paving

No alternative but to excavate and install a suitable sub base layer

• 300 mm thick base course

• 25 mm gravels with < 5% fines (75µm)

• 75 mm layer open graded asphalt

The End