OP-ED: As Watertown Builds, What Can Be Done to Protect Trees Adjacent to Construction?

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This oak tree on Mount Auburn Street has been wrapped in 2×4’s to help prevent damage during road construction.

By James Briand, Trees for Watertown

Watertown is a city under construction. From major public works such as the Mount Auburn Street renewal to numerous private developments, streets and lots are being disrupted for improvements. While the projects may deliver important benefits, the heavy equipment and excavation work required sometimes presents difficulties for mature trees in the zone adjacent to construction. Protecting such large, mature trees is vital, because even if new trees are planted post-project, it will be years before they can deliver the same cooling impact as lost mature trees.  

Watertown residents may have noticed the vertical 2×4 lumber barriers on many trees along the Mount Auburn Street construction area. Such barriers have been put in place by project managers to address one potential threat to trees during construction — damage from mechanical equipment. Collisions with trees can shear off limbs or peel off bark, leaving the tree vulnerable to disease. Yet, such barriers are only a first step in protecting valued shade trees.

The number one threat to trees during construction is root damage. Contrary to frequent public perception, most of a tree’s roots spread out near the surface of the soil, not deep underneath. Most are, in fact, within 6-18 inches of the surface. This positioning leaves trees vulnerable to damage during construction.

Roots play an essential role in a tree’s nutrition engine, collecting oxygen from the soil as well as moisture needed for survival. When soil is compacted, either by heavy equipment or by frequent foot traffic in a constricted construction zone, it loses pores that allow oxygen to reach roots and becomes less able to retain water. Cutting off roots when digging utility trenches may also leave trees unstable, and vulnerable to wind damage.

So what can be done? Arborists and university extension experts recommend a few steps. First, consider the types of trees adjacent to the construction. Species such as white pines and beeches are more vulnerable to construction conditions than others such as Honey Locusts or sycamores. Extra efforts may be required to protect some more vulnerable trees.

Second, experts suggest installing protective fencing not just around the trunk, but where possible, out to the dripline, the furthest extent of branches from the trunk. This will help prevent soil compaction. Another positive step is to design projects to avoid major changes to the grade of the land around the tree during and after construction, as excess soil can smother the roots. Finally, water the trees generously during and after soil disruption, and keep an eye out for any dieback on the trees that may signal root damage. 

Watertown Tree Warden Mike Micieli, emphasizes the need to act early to preserve trees, even before construction begins. “Tree protection is essential to ensuring the survival of our shade trees. Ensuring adequate tree protection doesn’t just mean 2x4s on the trees. It also means mitigating canopy conflicts, reducing soil compaction, and ensuring the appropriate equipment is used when excavating under the dripline. However, a great way to protect trees during the construction process may happen before construction even begins. Transparency and communication through the design process often allows for adjustments to be made that may bring construction away from the tree entirely.”

If you have concern about the impact of construction on a tree near your home, reach out to the Watertown Forestry Department.

10 thoughts on “OP-ED: As Watertown Builds, What Can Be Done to Protect Trees Adjacent to Construction?

  1. For future projects, don’t plant trees in areas where you know the root zone will extend into utility trenches. Don’t plant trees in sidewalks where one day the roots will destroy the sidewalk. Don’t plant them under power lines where they will need annual trimming. You can find alternatives for street landscape that doesn’t involve large trees. Large trees don’t belong next to a roadway.

    • Mature trees provide so much value along roadways! I think a healthier approach for Watertown would be —“For future projects, design AROUND existing mature trees so that their root zones are PROTECTED. You can find alternatives that protect our mature public trees and the value provided by their canopy (Watertown: Let’s design and develop sustainably!). Losing street trees is a HUGE LOSS for Watertown and our future.”

  2. What happened to the trees that were nice and large at the corner of Main St. & Bacon St. Not one peep out of you, how about it now .

    • After listening to buzz saws and chippers for several days on Bacon Street behind my home, I went to have a look. All the trees along Bacon Street adjacent to the Halfway Cafe parking lot had been cut down and removed. A few days after that, a retaining wall had been built. I asked one of the contractors what they were building and was told the city hired them to remove trees, build up the land and erect a privacy fence for the extension of the bike path that runs behind Town Hall. While this will be an improvement over the trash and junk that had accumulated in the corner of the parking lot, I hope that the city plans to add trees along the unfenced side of the extension. What do we know about this?

  3. I agree with a couple of Nick’s points, but not with the last. Large shade trees along the street are an essential part of a healthy city.

    — The generous canopies of street trees significantly cool nearby hardscape and parked cars, lowering the urban “heat island effect” which dangerously raises city temperatures. (Reminder: Boston had 23 days this summer with temperatures of 90F and above, and will have more 90F+ days in future.)

    — Shade tree canopies shade pedestrians and bicyclists from excessive heat and bad weather.

    — The presence of shade trees lining a busy city street makes the street safer by slowing traffic and by providing a barrier between pedestrians and traffic.

    — The stately beauty of large shade trees is a living symbol of municipal health and history.

    And more! See https://www.treepeople.org/22-benefits-of-trees for a detailed list.

    The key to correcting the concerns Nick addresses is to plan road reconstructions so that street trees can have long healthy lifetimes and will not disrupt power lines or sidewalks. This means:

    1) Street reconstructions should be designed intentionally for the long term health of street trees, with healthy soil in planned tree pits, enough soil volume in those planned tree pits to support trees of planned size and species, and adequate provision for maintenance, especially for watering during the first three years after transplanting.

    2) To avoid aerial power line conflict with tree branches, the rule nowadays is to plant shorter trees under power lines. Larger trees can be planned on the opposite side of the street where power lines aren’t an issue.

    3) Sidewalks near trees should be designed with structural soil underneath, and porous pavement above. What are “structural soil” and “porous pavement”?

    — Structural soil is a soil medium designed both to support sidewalks to engineering specifications, and to allow roots to grow under the sidewalk at their natural depth, rather than on top at the soil-sidewalk interface as happens without structural soil. (Roots growing right at the soil-sidewalk interface will eventually damage the sidewalk as they grow, which can be dangerous for pedestrians and ultimately brings damage to the roots when the sidewalk is repaired.)

    — Porous pavement is a form of asphalt which allows rain and snow melt to sink below the pavement surface into the soil, where the moisture is available to trees. Porous pavement brings special advantage to pedestrians in winter, since it significantly reduces the build-up of treacherous ice on sidewalk surfaces.

    The many benefits that big shade trees on our streets bring us make for a more healthy and livable city. We just need to plan well so that our street trees can have long, healthy lifetimes with minimal power line or sidewalk conflicts.

  4. Nick Kondek, Surely it has come to your attention that street trees absorb tons of CO2 every year, saving millions in energy costs. Trees can be a stimulus to economic development, attracting businesses. Commercial retail areas are more attractive to shoppers. Apartments rent more quickly, tenants stay longer, and space in a wooded setting is more valuable to sell or rent. Healthy, mature trees add an average of 10 percent to a property’s value.

    Trees mean improved water quality, resulting in less runoff and erosion. This allows more recharging of the ground water supply. Wooded areas help prevent the transport of sediment and chemicals into streams.

    Nationally, the 60 million street trees have an average value of $525 per tree. A Swedish study found that a high number of street trees resulted in a 17 percent increase in land values.
    The collective value of trees makes a difference in people’s health and quality of life in cities and towns everywhere.

  5. Dennis and Anne: TFW didn’t hear about the tree loss along Bacon Street until after it happened either. It seems the community had little or no notice that this would be happening, nor why.

    If these were healthy public shade trees, by Massachusetts State Law (MGL Chapter 87) they should have received a Public Tree Hearing. We’ve sent a message to the Planning Office to ask for information.

    • Seeing how the Editor didn’t allow my response to this earlier lets try this. I’m very surprised by this, that a community path which I’m sure Bike/Ped was full aware of this and sadly to the demise of the trees [how long to replace that same canopy] could have been constructed with gravel saving the poor trees. So I have to really wonder was this all necessary, when your trying to save trees.

      • This huge loss of mature public shade trees right off of Main St. —trees that are protected by LAW!!—- is very concerning. People use bike paths to enjoy NATURE. Now it looks like this stretch will be instead full of hot sun, concrete and asphalt. Yet another urban forest of Watertown undervalued and totally DESTROYED, without any public forum to discuss it. This is the opposite of what the people of Watertown want for our city.

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