We discovered we have issues with our wastewater lateral and it needs to be replaced. Not to get too into the details but where we expected to find a 4” cast iron lateral that could be cleaned and lined we instead found a 6” terra cotta lateral with multiple issues that mainly stem from extensive root infiltration from the maple tree that was planted about 4 feet away from it.
The photo shows the tree and very close to where the line runs. The plan from our contractor is to dig up either side of the stairs and replace with PVC since lining isn’t possible. The excavation is planned to be only in the mulch beds shown, since the main runs in the grass about three feet away from the end of the bed. The existing terra cotta will be left under the stairs and to the main and lined then connected to the PVC.
Our concern is how close the excavation is to the tree and how it will impact the trees health. Ideally we would use trenchless but that isn’t really an option, and rerouting isn’t really possible due to needing to reuse the existing house and main connections. So what should I be sure our contractor is doing to best protect the tree, and how should we take care of it once everything is complete. We are expecting some die off in the canopy but it’s a really healthy tree so we are hoping that with good care we can save it overall.
Utility engineer here.
Find a new contractor, yours is working with the tools they have have, but a specialist will be able to cut the roots that have infiltrated the pipe, then run a structural epoxy liner through the old one (called CIPP).
Tree roots look for oxygen, so once you have a solid cured in place pipe, they’ll grow around it instead of trying to intrude.
From an arborist perspective, usually limiting the trenching to 30% of the root zone (a radius based on the drip line of the tree) will leave keep the tree alive, but it’s still a gamble.
The 30% will include the arc of the circle it cuts off, and if the tree is large enough that it could fall on a house, it’s not worth the risk.
CIPP was the original plan for the entire run until they got into it. The existing pipe doesn’t have the right fall over the run, being flat in a few places with it seeming as though it rises in at least one spot. They were able to clear the roots from 85% of the line with one area towards the very end giving them the most trouble.
While I have issues with our contractor, the scope of work isn’t really one of them. They are using CIPP for the last few feet to the city main tap, and for the section under the steps to avoid needing to dig that up, as well is along the interior portion before the trap where it is clear 4” cast iron. The only trenchless option we might have in this case is pipe bursting and I’ve not seen anyone in our area that really does that, and it would mean pulling a new 6” pipe which we don’t really. I appreciate the opinion but in this case trenching is really the right option unfortunately for the job being done.
No, trenching is not the right option. Find a pipe-bursting contractor even if it’s hard.
Or, ya know, expect to lose the tree.