Excavation adjacent to large Sugar Maple

Asked June 24, 2016, 9:08 AM EDT

The City is going to install a new water service to my home and will need to excavate to a depth of about 7.5 feet within the drip line adjacent to the trunk of this Sugar Maple. The top of the excavation would be approximately 14 x 14 due to oversizing. What will be the damage done to the tree? Will it survive? What would need to be done to reduce impact if possible? Thank you!

Hennepin County Minnesota

1 Response

Thank you for the question. You are to be commended for thinking about preserving your maple tree before construction begins. Many a large tree is thoughtlessly damaged, even fatally, during construction/excavation activities. Often, the damage doesn't show up right away but each season the tree looks worse until it eventually dies. By that time, the construction activities have been forgotten and no one can figure out why the tree is doing so poorly.

The very best thing you can do is hire (or ask if the city will provide?) a certified arborist who can evaluate the proposed construction in the context of preserving tree health. He or she can suggest preservation techniques to reduce soil compaction and root disruption. We have a very good Extension publication on how to protect trees from construction damage. The following paragraph from the document is pasted here for you so that you can generally understand the tree's root structure:
"approximately 90-95 percent of a tree's root system is in the top three feet of soil, and more than half is in the top one foot. The part of this root system in which construction damage should be avoided is called the Protected Root Zone (PRZ)".

Many construction sites have limited space so protecting the work zone can be a challenge but in this case you need to figure out something because a sugar maple is quite sensitive to root damage and soil compaction. This is where the arborist can be a big help to you in tipping the odds towards tree survival. This can't be stressed enough. Please read our entire publication to learn more: http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/protecting-trees-from-construction-damage/

Thank you for contacting Extension.