[CANUFNET] Constructing Driveways within Critical Root Zones

[Julian Dunster]

My experience is that most so called permeable paving system do not last 
more than a few years. Then the fines clog up the pores and the surface 
becomes impermeable. Pavers are particularly bad for that. There is a 
better chance of infiltration if the paved area is flat and horizontal. 
If it has a slope, runoff is more likely, and in fact, most surfaces are 
sloped to prevent ponding and flooding, so designing for water 
infiltration is counter intuitive for the engineers. Gravel is the most 
effective long-term permeable solution, so grasscrete, ecoraster and 
similar contained gravel products work well. The porous concrete is a 
nice idea but again, if not cleaned, the pores clog up over time. If the 
surface must be sloped, slope it so that the water goes to a place where 
it can infiltrate in such a way that it helps tree roots. Oddly enough, 
asphalt sometimes works well because it tends to sweat, and underneath 
it there is a moisture layer than is root friendly, but then the roots 
grow close to the surface and heave the asphalt.

jd

On Behalf of Dunster and Associates Environmental Consultants Ltd.


Dr. Julian A Dunster R.P.F., R.P.P.., M.C.I.P., ISA Certified Arborist,
ASCA Registered Consulting Arborist # 378,
ISA Tree Risk Assessment Qualified
Honourary Life Member ISA + PNWISA

North American distributor for Rinntech
www.dunster.ca
www.treelaw.info
www.rinntech.info

On Tue/7/14/2020 7:51 AM, Naomi Zurcher via CANUFNET wrote: