Root control under Pathways 7

[looksatstars]

We have our park system that we are updating.
We have an existing asphalt trail about 7 ft across. The asphalt i think is about 2-3" thick on top of 6-8 inches of gravel subgrade.
Roots from nearby trees (poplar, alder, birch) are infiltrating in the area under the asphalt and over the gravel and pushing up the pavement and making huge cracks.
We are proposing to rip up the asphalt and put a new layer of asphalt and run a poly liner along side the pathway on either side to hopefully reduce the roots from coming underneath.
Has anyone used or know of another system that may work?
The contractor has proposed using a disc cutter going down about 6-8" on either side of the trail and cutting off the roots every season which sounds like a good idea.
any help would be great
thanks

 

[cvg]

the best, and cheapest way would be to keep the trees at a reasonable distance (farther) away from the sidewalk. Disking/edging mature tree roots may cause the tree to die anyway. What about the roots that go down more than 6 - 8"? They will still go under your sidewalk

 

[looksatstars]

I work for Parks so our main objective is to keep as many trees as possible and if that means redoing the trail every 5 years then so be it.
These trees are pretty hardy and can some of their roots being severed.
The roots seem to like the area right below the asphalt and above the gravel. Anything below the gravel about 8", the asphalt seems to be able to handle it.

 

[cvg]

The roots are seeking water source and the gravel under the sidewalk provides it. Can you grade the edges to prevent water from running towards the sidewalk?

 

[GeoPaveTraffic]

We have used a product called "Biobarrier" manufactured by Reemay to limit damage from tree roots. It is a geotextile fabric with a texture on the surface to help turn the roots. It seems to work in most cases.

One point, to install the system, you have to trench 18 inches deep along the side of the path cutting all of the roots in that zone. If the tree is not in good shape, that may be the end of the tree.

 

[ACtrafficengr]

Here's an option out of left field.

It seems Cornell University's horticulturists have determined the problem with tree roots is compacted subbase is too dense for tree roots to penetrate, so they grow between the pavement and subbase, lifting the pavement. The answer they came up with is a permeable structural soil that allows the roots to grow through unimpeded.

If I recall, it is a gap graded mix, like pervious HMA, only with a non-petroleum binder. The roots can grow through the voids without damaging the pavement.

Unfortunately, it seems the hort department's website is down at the moment, so the best I can give you is search results:

http://web.search.cornell.edu/searc...stylesheet=default_frontend&q=Structural Soil

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[jheidt2543]

Just a couple more thoughts to consider:

The annual disking alone the edges of the paths seems to me would kill the trees. The gap graded subgrades may work, but the roots eventually grow bigger and will still break up the asphalt.

My personal preference would be not to pave the paths! Leave them as compacted gravel trails, it is more "natural" and the money you save can be used for annual regrading of the trails, which you have to do in any case.

The compacted gravel can still be easily walked and biked on.

 

[kenvlach]

One more suggestion, can be used with those previously posted.

"The roots seem to like the area right below the asphalt and above the gravel." -- Maybe some sand between the gravel & asphalt?
Mix some lime into the sand. It will give a caustic burn to any feeler roots to let make them unwelcome. As the trail is 7 feet wide, and with enough grade to avoid runoff entering under the paving, the treatment should last until repaving needed.

 

[ACtrafficengr]

JHeidt - ADA regs may preclude this. Soft-surface paths are not really accessible, especially after rain, during spring thaw, etc.

If it was an accessible route for mobility impaired park users before, it must be accessible after reconstruction. If it wasn't accessible before but it could be with a reasonable effort, that it should be.

The Cornell mix has been used for 10 years in some places. Given the lifespan of a tree, this is a short test, I know, but still, it's something.

I doubt it would work if you let a really large tree grow next to the path, but if you plant crabapples, dogwoods, etc, closer to the path so their dripline didn't come too far over it, and kept the oaks and beeches further back, it would probably work.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[DMcGrath]

I heard about these "rubber sidewalks" last month on NPR, specifically about how the tree roots interact with the sidewalk.

http://www.washingtonpost.com/wp-dyn/content/article/2006/07/01/AR2006070101087.html

 

[moogbro]

They are using them in my area. Here is a link to a company which supplys them:

http://www.rubbersidewalks.com/default.aspx