[CANUFNET] sidewalk bridging over roots

[Trevor Thistle]

Hi All,

Here in Edmonton we are doing Neighborhood renewal (street, sidewalk and curb reconstruction) on a massive scale (8 neighborhoods a year and 12 starting next year). There are thousands of mature trees affected by this construction every year and at this scale it is impossible to do hand work around every tree.

This is what we do:


 *   Sidewalk and curb removal is done mechanically around all trees, paying close attention to minimizing root damage and excavation depths as we pass the tree. Root damage is often unavoidable but in the past few years we have come a long way and we seldom have to cut or shave a structural root for sidewalk construction. Most of the root damage is peeled bark, which is still not ideal but is progress and a good compromise between productivity and tree conservation.


 *   We narrow streets whenever possible to allow sidewalks and curbs to be reconstructed further from the roots. This results in less root damage and the addition of rooting area for the trees.


 *   We have abandoned the idea that sidewalks have to be straight. Where property lines allow us and drainage issues keep us from raising grades to get sidewalks over roots, we bend sidewalks around roots. So, we may have sections of separate sidewalk that are serpentine. For the most part our citizens quite like the finished product.


 *   Where we cannot change sidewalk alignments, we have developed what we call a "Tree Treatment". This is a process where we minimize the excavation depth where the structural root plate of the trees and the sidewalk overlap. Through a combination of grade raising and adjusting the thickness of the base and concrete we manage to overcome most root obstacles. Also the section of concrete that passes the tree (the length varies depending on the tree size) is reinforced with extra rebar to resist heaving. In addition, the concrete is scored every 12-16 inches, the theory is that these scores will allow the concrete to crack where we can hide the cracks and allows the sidewalk to bend and not become disjointed as the tree grows.


 *   Finally, an urban forester monitors the projects and makes a list of trees that have sustained moderate to severe root damage. Very rarely do we need to remove a tree that has been rendered hazardous due to root damage. The trees that make this list are watered and fertilized for 3 years to aid them in recovery from construction damage.


If you have any question fell free to contact me.


Trevor Thistle B.Sc. (Forestry)
Urban Forester & ISA Certified Arborist
The City of Edmonton,
Neighbourhoods and Parks
Forestry Services
Ph: (780) 944-7833
Fax: (780) 496-4978
Cell: (780) 913-5893

________________________________
From: canufnet-bounces at list.web.net [mailto:canufnet-bounces at list.web.net] On Behalf Of Ian Wilson
Sent: Tuesday, May 22, 2012 8:12 AM
To: 'Canadian Urban Forest Network'
Subject: Re: [CANUFNET] sidewalk bridging over roots

Jeremy, that will likely be part of the strategy.  However conventional sidewalk construction would probably damage a lot of roots in this case even if we raise the grade - and the sidewalk is likely to crack in a few years.  Thus we are looking at the bridging or rubber sidewalks options

Thanks Ian

From: canufnet-bounces at list.web.net [mailto:canufnet-bounces at list.web.net] On Behalf Of Jeremy Gye
Sent: Saturday, May 19, 2012 10:21 AM
To: 'Canadian Urban Forest Network'
Subject: Re: [CANUFNET] sidewalk bridging over roots

Hi Ian,
Is there any latitude to play with the grading/profile of the sidewalk, in order to accommodate the roots using a more conventional sidewalk construction approach?

Jeremy

E-mail: jgye at shaw.ca

From: canufnet-bounces at list.web.net [mailto:canufnet-bounces at list.web.net] On Behalf Of Ian Wilson
Sent: May-18-12 2:57 PM
To: 'Canadian Urban Forest Network'
Subject: [CANUFNET] sidewalk bridging over roots

ALL-

Kelowna is looking at a new sidewalk installation next to some mature street trees (red oaks).  In the past we have successfully used rubber sidewalks in these types of situations but in this case it's going to be a multi-use corridor and there are concerns that the rubber surface is not as suitable for roller blades, etc. because of the seams.

I have a couple of questions:


1)       Anybody else have experience with rubber sidewalks in these situations and whether the bumps are an issue?

2)      Another possible solution is reinforced concrete bridging over the roots.  Does anybody have specifications for bridged sidewalk construction that they could send to me?

Thanks

Ian



Ian Wilson, Park Services Manager
Park Services

TEL 250 469-8842
FAX 250 862-3335

City of Kelowna 1359 KLO road, Kelowna, BC  V1W 3N8  kelowna.ca<http://www.kelowna.ca/>
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