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Trees, Root Barriers and infrastructure

  • 1.  Trees, Root Barriers and infrastructure

    Posted 10 December 2019 17:14
    ​Hi everyone,

    Does anyone have any experience with root barriers and trees when it comes to water/sewer infrastructure?  There seems to be a constant war between the tree owners and the infrastructure engineers and the tree owners answer is always to "put in root barriers".  Does anyone have any experience on whether these work/if they do, which varieties they would recommend?

    Thanks
    Pro Cert 2


  • 2.  RE: Trees, Root Barriers and infrastructure

    Posted 15 December 2019 18:07
    Hi Michael,
    We have recently installed root barrier along a footpath that runs adjacent to a pine plantation. We used a product called "Root Guard", it comes in rolls of varying lengths and widths. The one we used was 900mm deep. The install was only appx 12 months ago so too soon to see if it has worked yet.
    Regards
    Shane
    NAC
    Pro Cert 2


  • 3.  RE: Trees, Root Barriers and infrastructure

    Posted 18 December 2019 22:58
    Hi Michael,
    We replaced a footpath that had been lifted by tree roots about 7 years ago with 900mm root barrier as mentioned by Shane, we dug the trench and cut the existing roots cleanly (after the excavator had mangled them). After doing a bit of reading it was suggested that the moisture can gather against the barrier and therefore the roots would follow it. To stop the roots going under the root barrier chasing water we lined the invert of the trench with salt, just using hand fulls of swimming pool salt, before backfilling. Not sure if the root trimming or the salt had any effect but can report that the path is still flat and the tree is still healthy seven years later.
    Regards,

    ------------------------------
    Luke Fayle

    Richmond Valley Council
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    Pro Cert 2


  • 4.  RE: Trees, Root Barriers and infrastructure

    Posted 15 December 2019 18:07
    Hi Michael,
    Put simply, the barriers work for some plants, but rarely for the sorts of trees these people want to plant on or near our infrastructure. That response is largely a throw away line and you need to push through it and make them engage. A tree policy endorsed by a Counci or WSP is a great weapon in your favour.
    Cheers

    ------------------------------
    Shaun Johnston
    Manager Water & Waste Water
    Burdekin Shire Council
    Shaun.johnston@burdekin.qld.gov.au
    ------------------------------

    Pro Cert 2


  • 5.  RE: Trees, Root Barriers and infrastructure

    Posted 15 December 2019 18:08
    If tree roots intrusion ​would only cause service problem, this problem could be alleviated through jet cleaning and trimming of roots. However roots intrusion could result in structure failure. This would require much more proactive mitigation step before any failure occurs. A risk matrix is to developed for possible likelihood and consequence's.
    Pro Cert 2


  • 6.  RE: Trees, Root Barriers and infrastructure

    Posted 15 December 2019 18:08
    Hello
    I personally have not seen tree barriers being effective in regards to drainage on tree species that have invasive root systems, if drainage is installed correctly such as collar joints fitted  together as per AS then the root systems have a more difficult task to get inside the drain, It is difficult when the incorrect trees are planted near Ministers mains and for some reason or another they can not be removed and the problem reoccurs and is costly to fix. It will be interesting to see other member replies on this issue as the clients I work for are often at wits end to minimise damage by trees mostly planted by government agencies and there seems to be no remedy to the problem

    Cheers
    Pro Cert 2


  • 7.  RE: Trees, Root Barriers and infrastructure

    Posted 15 December 2019 18:08
    Hi Michael,

    The link below provides an informative overview on the effectiveness of root barriers. I am not necessarily a fan of the additional costs, given the typical poor results, but they may be warranted in certain situations (i.e., repeat offender trees) especially if it prevents or prolongs a repeat failure or loss of service. You will need a really good specification to get a good result. Solid installations such as sheet pile or concrete definitely will work better and longer than flimsy mesh or modular plastic products.

    Another consideration is that your specification should be suited to the specific offending tree, further complicating the matter. It may be well worth contacting an arborist to determine the least impactful and most effective design of the barrier. Things like typical root depth and how far to extend the barrier above grade are best supported by the advice of an expert.

    https://shadetreeexpert.com/the-use-of-root-barriers-to-protect-infrastructure-from-%E2%80%A8roots/

    As an alternative you might want to consider treatments to the infrastructure itself. An example would be using a continuous piece of butt welded HDPE instead of jointed pipe (if possible). This will essentially eliminate the problem completely as there will no longer be a penetration pathway for root tips. If we are talking water mains or rising mains then going deeper than the root system is also an option. Although it does cause other problems such as ease of access for repairs or maintenance.  Although it will likely cost more in the short term this is far more long term cost effective solution in my opinion.

    I hope this info is helpful for you and best of luck with the roots!

    Regards,

    Earl DuPriest
    Asset Management Program Manager
    Charleston Water System
    103 St. Philip Street | Charleston, SC 29403
    Tel: 843-727-7202
    Mob: 843-214-4310
    E: dupriester@charlestoncpw.com


    Pro Cert 2


  • 8.  RE: Trees, Root Barriers and infrastructure

    Posted 15 December 2019 18:08

    I suggest checking with IKT in Germany. They have done some good work on root intrusion.  https://www.ikt-online.org/blog/international-research-project-ikt-tests-passive-root-protection-measures-in-a-globally-unique-experimental-setup/
    Contact the project manager

    Mirko Salomon, M.Sc.
    Project Manager
    tel.: 0209 17806-25
    e-mail: salomon@ikt.de
    Thanks,

    Walter


    Pro Cert 2


  • 9.  RE: Trees, Root Barriers and infrastructure

    Posted 18 December 2019 22:57
    ​Hello Michael,

    I run a Root management business and can give some insight for you. There are a lot of misconceptions around root barriers in the public space along with a lot of poorly installed barriers.

    Firstly, you need to understand that a tree is always going to find a way to water and the main ways are the magnetism the water provides while running in any form of water pipe. Irrigation, Stormwater, water mains etc. The tree roots will always be drawn to those forms of infrastructure. Further to this, Barriers are only a management of troublesome roots not a stop or a complete fix. While that tree is living it will continue to spread it's root system, down, up over (where possible) around etc.

    If a barrier is installed correctly which in general terms down to 1.5m depth is sufficient with a stabilized sand 3% cement mix between the root system and the membrane you will get a good result. All services must have butyl tape well wrapped to stop penetration as well. The greatest deterrent is the stabilized sand barrier. The tree root gets a lick of the cement and actually fossilizes and hence a change of direction in the root system occurs. backfilling with mediums things like crushed rock or soil backfill against a membrane is nowhere near as effective as that actually promotes growth back into that space with additional airflow, water and oxygen in that void. If the butyl tape has not been installed correctly you will get roots sneak through that space and straight through the barrier.

    You will never get a guarantee on a barrier for the simple fact a tree is a living organism and can find ways adjust, it is a management mechanism and the surrounds should be checked periodically.

    Additional notes to consider. Barriers are best installed into asphalt or concrete paths. If the barrier is left proud of the surface and then the top embedded into the re-instatement you will get a great outcome at the most vulnerable place in a barrier - the top. All too often civil contractors will cut or bend the barrier over to install concrete and asphalt rendering that top are useless. Roots head straight for it.

    Base line is, installed correctly barriers are very effective for many many years
    Pro Cert 2


  • 10.  RE: Trees, Root Barriers and infrastructure

    Posted 05 January 2020 17:50
    ​Can you explain "magnetism the water provides while running in any form of water pipe"
    Wouldnt a copper pipe act as a faraday shield. Is there any peer reviewed evidence of roots being attracted to  magnetic fields

    Pro Cert 2


  • 11.  RE: Trees, Root Barriers and infrastructure

    Posted 05 January 2020 18:21
    ​Hi Michael,

    I don't know that Lavleen means magnetism literally.  I would suggest they mean magnetism as in the tree roots are attracted to the water within the pipes.

    Regards
    Pro Cert 2


  • 12.  RE: Trees, Root Barriers and infrastructure

    Posted 05 January 2020 17:50

    Thanks everyone,

    I've been looking for this thread for a couple of days, I knew I'd posted it.

    The information has been very interesting (particularly the use of stabilised sand, thanks Lavleen).  I must admit to a bit of surprise that the use of pool salt didn't kill the tree.
    Part of the issue I guess is getting people from other branches of this organisation to take the issue seriously (e.g. we had a water main burst, wanted to cut some tree roots so we could repair it and the parks section asked us why we installed under a tree in the first place.  The water main had been there for a very long time).

    We do have issues with intrusive species (e.g. Camphor Laurels, Jacarandas) so I doubt we'll be able to stop them being installed, but at least maybe we can think about how we treat them.


    Thanks for your help


    Pro Cert 2


  • 13.  RE: Trees, Root Barriers and infrastructure

    Posted 05 January 2020 17:50
    ​Hi Michael,

    Vegetation is opportunistic. Trees, plants and grass are not 'drawn to ' water or pipes necessarily. If infrastructure is faulty and moisture is evident in soil, trees will take advantage of this and incursions will occur. If trees and infrastructure are located in areas where the soil volume is insuffucent for the size of the tree, roots will cause pipes to crack and break, Furthermore, infrastructure is not always installed at the appropriate depths. If you wish to undertake DNA analysis, in most circumstances, you will find grasses and shrubs will be first collonisers at pipe faults as they often grow faster due to the plant lifecycle. Pipe relining , replacement and rerouting is more often than not the superior option even though it will be slightly more costly initially. Any works should be undertaken in accordance with AS4970 and appropriate use of directional boring under the trunk of the tree may be necessary. The product you refer to is more a root deflector and correct installation is paramount but again, these will fail if you are restricting the overall soil volume if the tree is still vigourously growing as the root volume as they expand still need to displace and soil in the vacinity. In circumstances where ive been asked to investigate the 'failure of a root barrier', i have found grass and shrubs are the recollonisers as the small stuff is often overlooked, or the barrier has been installed too close to young vigourous stock.

    In estimating appropriate tree volumes, you can then decide the most sustainable option. Theres a great chat re AS 2303 and soil volumes here : http://www.treesimpact.com.au/articles/estimating-soil-volumes-needs-of-trees-in-urban-situations. Sometimes a deflecting 'barrier' is simply a bandaid for a bigger problem.

    Limiting interacting can sometimes mean moving either of your assets. In the current political climate witht the premiers tree planting priority in NSW, we have a lot to consider in this space.




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    Lisa Murphy
    Tree Management Officer
    Hornsby Council
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    Pro Cert 2