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<Jim Clark>
posted
I'm looking for documentation or evidence that compares the impact of pavers versus a "standard" street section. As a general rule, I'd say that anything that reduces the depth of cut (i.e. section) required reduces impacts. But I'd like more detailed information if anyone has it!

Thanks.
 
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<Scott Cullen>
posted
Reply to post by Jim Clark, on September 13, 1999 at 19:30:42:

Jim, Unilock, one of the bigger paver manufacturers, has toll free 1-800-unilock . They may have typical specs which show section detail to be compared to traditional paving, if that comparison helps you.
 
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<Wayne Cahilly>
posted
Reply to post by Jim Clark, on September 13, 1999 at 19:30:42:

Jim,

Have you contacted Nina Bassick at Cornell? She has done a lot of work with trees in urban street plantings and may have accumulated some data on impacts or potential impact differences. Worth a call anyway.

Wayne
 
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<Garry Clubly>
posted
Reply to post by Jim Clark, on September 13, 1999 at 19:30:42:

G'day Mr. Clark,

Up until recent times, I would have agreed with this idea, and on smaller residential developments where tolerances for typical paver sub-grade and sub-base are less critical, pavers may still be preferable to concrete or ashphalt (due to the depth of excavation and sub-base preparation required by these latter pavement types).

But, as you know with the type of large development sites that I deal with here in Sydney, I am increasingly becoming disillusioned with the idea that pavers are a more tree friendly approach. Basically what I am comming across more and more is that engineers are not prepared to sign off on pavement installations using pavers unless sub-grade preparation and sub-base materials are comparable with those typically found under ashphalt and concrete.

Another point (although slightly away from your question), there has been some interestion research carried out by Prof. Shackle (an expert in pavers, uses and construction) here at the University of NSW regarding the porousity of pavers. In short they block up very quickly where a typical gap graded sand (washed river sand) is used for sub-base and joint infill. This is were some of the work we have been doing with porous pavers comes in to reduce this problem.

The problem of course with this latter approach is that for it to work properly, porous pavements (i.e. pavers with specially design cut-out sections such as the "Ecolock pavers") require appropriate sub-base materials (e.g. a larger gap graded aggregate sub-base and infill). Even if structural soils are used (as we have done), it may not necessarily be suitable to retrofit pavements around existing trees and root plates (although I have tried this a couple of times now where the site conditions and tree species might tolerate it - but its still a bit of an experiment).

If you would like some more in formation on Brian Shackles work, please get in touch.

Garry Clubley
 
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<Scott Cullen>
posted
Reply to post by Garry Clubly, on September 13, 1999 at 19:30:42:

Hello Gary,

It sounds like there are a range of issues in design and selection -- from both an engineering and an arboricultural standpoint.

-Are we trying to preserve existing trees (seems like the thrust of Jim's query)? And are we trying to do that by minimizing excavation and compaction (root damage) or maximizing pavement porosity / permeability / permitivity / perviousness (?) or both?

-Or are we trying to create an hospitable root area for new plantings (the typical application for structural soils)?

-Are we needing to support vehicular traffic on a regular basis, parking, occassional traffic (like emergency vehicle access) or pedestrian traffic? Is pedestrian activity routed (a path here to there) or is it an open mall type affair?

-And once the engineering, design and hort types have plugged in all their data the economics of the development need to support it. My principal occupation these days is real estate and I know that budgets rule in most cases. And it's often hard to make a case for additional allocations for such mundane things as paving... "just that stuff they drive on, it's not going to increase my market price."

Have you found much acceptance or effectiveness with using heavy grade geotextiles either to spread loads / prevent infiltration of aggregate grades or for filtration to prevent silt up?

Scott
 
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