So, did my installer and I make a mistake when putting in the septic system at my Wisconsin Northwoods cabin?

We bought a fully wooded lot, and for my wife and me, saving trees was a priority. We hated seeing the builder cut the trees within 15 or so feet of the structure; they allowed us to keep just a few slender red oaks standing inside that envelope so that the site would not look quite so barren.

Creating the drainfield also cost us some trees – but here, at our request, the installer left a few cheek by jowl with one side of the field. Since then I've received a couple of bits of information that lead me to question that decision. Should we have been less tree-conscious and cared more about the possible impacts on our system?

Comments from readers

What led me to question the decision we made? A couple of comments from readers. Jay Hodgens, P.E., of Hodgens Engineering Service in the Hudson Valley Region of New York, noticed in this magazine a picture of a drainfield trench abutting a tree and wrote a letter that we published a few months ago.

"I looked at the tree abutting the trench and envisioned difficulties in years to come: tree root damage, the tree coming down at an inappropriate time, the uprooted tree causing damage to the drainfield, or tree root intrusion into the drainfield, causing premature failure." He noted that some states have 10-foot separation distances from trees and observed that
dripline plus five to 10 feet might be a suitable separation.

Then came a letter from Bob Carey, an arborist, horticulturist and radio garden talk show host in Mechanicsburg, Pa. He noticed the same picture and observed, "I think any arborist would advise that excavating an area so close to an established tree is a recipe for tree failure and hazard creation. While those conditions are developing, it's likely that the infiltration area will be functionally degraded."

Apparently onsite trench excavations near trees are not highly unusual, as Carey added, "I know better than to say that the situation depicted in that photo is exceptional. I've learned to inquire about odd failures of trees by asking about onsite system layouts."

Worth watching

In any case, where our system is concerned, the die is cast. The excavation for our trenches definitely cut into the root systems of two or three trees. The installer told the machine operator to remove a couple of other trees that were even closer, and so perhaps in his professional judgment, those we did leave will be all right.

I guess time will tell. We will need to watch those trees for signs
of deterioration. In the meantime, I would be interested in other professionals' perspectives – for my own curiosity and for the benefit of this magazine's readers.

How close do you allow drainfield excavations to come to mature trees? Where do you draw the line when deciding whether a tree stays or goes?
Why? What is your experience with trees that have been allowed to stand next to drainfields?

Drop a note to editor@onsiteinstaller.com with your opinions, observations and experiences. I promise to respond to each note, and we will print a sampling of the comments in a future issue.