Protecting Trees – Construction Sites

There has been a lot said in recent months – between friends, at council meetings and on the Our Town Facebook Group – about the absolute need, and the general wish of residents, to protect and preserve as many trees as we possibly can in Baie-D’Urfé.

At the same time, we are a prosperous community and quite a lot of development, with or without demolition, takes place here. During the process permits are applied for and given for the felling of mature trees while others are to be “spared” and the construction work proceeds around them.

Unfortunately, simply ensuring that an excavator or truck does not hit a standing tree is insufficient to ensure it will survive and flourish in future years.  There is as much tree below ground as above it and soil compaction due to heavy machinery kills as many trees as it does if those machines run into the trunks. To prevent this, trees have to be fenced off so that soil compaction does not occur and so that materials are not dumped close to protected trees.

Unfortunately, it seems apparent that either Baie-D’Urfé does not have regulations to look after trees on construction sites or does not enforce them. For example, here are pictures of typical construction sites in our town in recent years:

Useless “fence”, ground compaction, pile of rubble right up to the trunk of the tree
This picture shows boards protecting the trunk (good) but the roots are buried under tons of rubble (bad). Heavy machines will be used to remove the rubble and make the soil compaction even worse.
Hard to know what that yellow tape is doing – it certainly isn’t going to protect the tree and its wide root system from anything much at all

What are other towns doing?

Dorval and Beaconsfield are much more conscious of their responsibilities in this matter … for example:

A very clearly demarcated protection zone around these trees with a prominent sign explaining clearly what is required of the public and contractors.
Clear, comprehensive, simple to understand

And away from the4 West Island, here’s a quite extensive tree protection zone on a construction site near Victoria:

What might our regulations have to say about this?

Beaconsfield set us a very good and practical example – for example, have a look at this short page setting out proposed guidelines on their website:

https://www.beaconsfield.ca/en/notre-ville-1/seances-du-conseil-et-documentation/237-municipal-fields/special-permits/194-protecting-our-trees

Then consider these quite reasonable requirements that Beaconsfield propose developers be required to adhere to. This proposal includes explanations (in italics) of why each recommended practice is needed. Could we not have something similar?

BEACONSFIELD – PROPOSED GUIDELINES:

a) Protection Perimeter

  • A minimum protection perimeter around the tree must be established to prevent circulation of any machines, storage of soil or materials, any type of excavation, spillage of toxic substances or permanently raising the actual level of the land. This perimeter should be outlined by a fence at least 1.2 meters high, which should be erected for the duration of any work (construction, renovation, landscaping).
  • Minimum dimensions recommended for the protection perimeter are in accordance with the size of the tree:
    • Protection perimeter distance (radius) = 8 × DBH (measure taken from the tree trunk). DBH: diameter of the tree trunk measured 1.4 m above ground level
      • Example: a tree with a 30 cm diameter trunk would have a protection perimeter radius of 2.4 m all around the trunk. The maximum size proposed for the protection perimeter of a tree is 4.5 m radius.
      • This perimeter constitutes a minimum to provide minimum protection of the anchoring root system as well as a certain amount of the smaller roots used for absorbtion of water and mineral elements and the flow of sap. In the case of an “outstanding” tree [see Paragraph 3.6], it might be appropriate for the City to increase the radius of protection to 12 or 15 times the diameter of the trunk, up to 7.5 m. This would protect most of the rootlets and the feeding roots (less than 2 cm in diameter), and ultimately result in reducing the risk of decline subsequent to this work to a very low level.

b) Excavation Inside the Protection Perimeter

  • In the case where excavation is required inside the protection perimeter, such as repair work on water pipes or sewers, among others, steps to shore up the ground must be adopted. This approach would permit the size of the trench or pit opening to be limited, as well as enable vertical excavation. City of Beaconsfield – Tree Policy 15
    • Even so, all root sections that are exposed to the air or that have been broken must be properly cut at right angles in order to fill the excavation pit.  This step, while appearing banal, generally permits a tree to recover more easily from the harmful consequences of losing roots, facilitates growth of new rootlets, and limits rotting of the anchoring root system.
    • During final clean up of the trench or pit, the final 30 cm of surface soil must be composed of topsoil to facilitate the formation of new roots.
    • It is also strongly recommended that the tree be watered every 15 days, especially during dry periods, for the first two years following the excavation.
    • When the closest section of the excavation is less than 2 m from the trunk, it is considered that 50% of the anchoring root system is generally lost for trees of 30 cm diameter and up. The tunnel method (horizontal drilling) should be used for reasons of safety of people and survival of the tree, otherwise felling of the tree must be anticipated in the short/medium term.

c) Circulation Inside the Protection Perimeter

  • In the event that it is absolutely necessary to allow machinery to circulate inside the protection perimeter, a geotextile fabric must be placed directly on the existing soil and covered with a 30 cm layer of crushed stone or wood chips. This measure will help maintain physical and mechanical conditions and properties of the soil intact, and avoid any type of asphyxiation of the underlying root system.

d) Permanent Raising of the Soil Level

  • For any permanent raising of the soil level over 20 cm high inside the protection perimeter of a tree, the following measures must be taken to ensure the tree’s survival:
    • place a minimum 20 cm thick layer of clean stone (¾, 1” or 2”) on the ground over the whole of the minimum protection perimeter, separating the layer of clean stone from the natural ground below and the fill above with a geotextile fabric (to avoid asphyxiation of the root system)
    • create a natural well around the trunk, without disturbing the fill in any way, at a distance of at least 30 to 50 cm from the trunk (to prevent rotting of the base of the trunk and thereby preclude danger of the tree trunk breaking during strong winds)

Other town and cities

There is a lot of useful information on the following site about what other towns and cities have done and are doing. The site is run by “Tree Canada” who are “… the leading national tree planting charity in Canada.  We’re dedicated to improving the lives of Canadians by planting and nurturing trees while teaching about their value.”

This is not new and not innovative, it is simply what has to be done protect our urban and peri-urban environment.

https://treecanada.ca/resources/canadian-urban-forest-compendium/13-tree-protection-during-construction-trees-and-building-foundations/ 

What can we do?

If you think best practice could and should be followed on construction sites in Baie-D’Urfé in order to protect as many as possible of the mature trees we are so proud of, please consider making your views known to Council. Don’t forget, the town repeatedly says how much it values its tree cover and we give away trees twice a year to citizens to plant and help maintain that cover. We have an active and expensive multi-year programme to deal with the emerald ash borer and the disease they carry – so why are we not doing everything we can to ensure that the mature trees we already have are better looked after when construction is authorised?

Your comments here and on the Our Town Facebook Group will be very helpful.

Genuinely Independent Information & Comment from Baie-D'Urfé