application of porous pavement may 12, 2006 richard boase, p.geo., ccep north vancouver district a...
TRANSCRIPT
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%
0
2 0
4 0
6 0
8 0
1 0 0
Pe
rce
nt
of
To
tal
An
nu
al
Ra
infa
ll
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