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Fairweather Tree Lovers and Moldy Basements

In the urban forestry world, there’s never a shortage of exciting challenges to lift the jaded city arborist’s spirits.  The fair-weather tree lover is one such challenge for me.  You know them, they are the folks that start sentences with, “I love trees, but. . .”  What invariably comes next is a sincere explanation of how life would be endless lollipops and unicorns if the tree in question would just kind of die and disappear through municipal intervention.  Preferably while they are away on vacation next week.  The tree is usually minding its own business while quietly photosynthesizing or making shade. 

Looking closer though, it is not exactly the tree that is the problem for the fair-weather tree lover, but the hole in the sidewalk where the tree is carrying out that quiet shade making.  The hole is a window that frames the soil behind it set in a wall made out of concrete.  This sidewalk is an impervious surface that sheds rain water into an overtaxed, aging storm drain system made out of dark, scary pipes that attempt to direct that water efficiently to the nearest creek or river where it can then be carried eventually to the ocean.   I think I read once that this approach to storm water management fails to replenish the water table under cities and as such is bad.  But looking even closer, for the fair-weather tree lover the water in the soil in the tree pit is the real problem.  The water soaks through the basement wall of the building they just bought and are renovating downtown.  They paid a lot of money for that building so they want the tree gone and the window to the earth behind it closed - permanently. 

Ok, so maybe putting living things that need to be surrounded by significantly more un-compacted soil than is available in the average tree pit into a place as dinky as a tree pit was a really dumb idea when it started catching on in cities years ago.  But heck, you have to put the trees somewhere and nobody important wants to let a good parcel of land go to waste growing trees when it could have a building on it instead.  On the bright side, some cities and their tree caretakers had the foresight to build some sidewalks that are better suited to cooperating with tree roots.  I try to do that every chance I get.  But again, the problem is the water touching the building.  I remember a similar case a few years ago that was more clear-cut.  The water that soaked into the earth through the tree pit (or wherever else it gets in) was coming through the round hole in the side of the basement wall.  The hole through which coal was delivered back when it was still popular to heat buildings with the stuff on site instead of by making electricity out of it.  So when the building owner claimed the city was responsible for the water coming in through that window to the earth they were figuratively patted on the head and told to run along and BS somebody else.

In the current situation there used to be a vault (a hollow place the building owner treated as their extra basement) under the sidewalk that was eliminated by building a wall and backfilling with soil to support the sidewalk (and tree pit).  So if water soaks through a poorly made wall is that really my problem?  By my I of course mean the city’s.  I’m trying to do some research on that.  I need to find out something kind of quick though.  The fair-weather tree lover can only be stalled so long while they wait for you to pull a rabbit out of your hat.  Because, as they said, they love trees.  (Email notification goes off)  Oh, an email from the risk manager.  He says that we are not bound to ensure that people’s buildings are watertight below ground.  Sweet!  My leafy friend just got a reprieve.  I love a happy ending.


Mark Foster

City Arborist

City of Asheville