Issue: December 6, 2008

It may be possible to replace a water line under a tree without harming the tree.

Question:

My water line is old and corroded. I need to replace it, but there were two Ponderosa pine trees planted over the line many years ago. I would hate to lose those trees. Is there some way to put in a new water line without damaging the roots of the trees?

Karen K.

Answer:

It may be possible to burrow below the major roots of the trees by using water pressure and rigid pipe connected to a water supply. This technique was used many years ago to burrow under my sidewalk when my water line needed replacing.

To avoid cutting and then repairing the sidewalk the plumber made a simple burrowing device by putting a hose fitting on one end of a piece of rigid plastic pipe. He dug a pit to allow starting the pipe tunnel horizontally at the level of the existing (leaking) water line. He attached this improvised tunneling device to the garden hose (attached to the neighbor's water with permission) then used water flowing through the pipe to excavate a tunnel under the sidewalk. On the other side of the sidewalk, a trench was dug in a traditional manner.

In your situation the tunnel excavated under the trees will need to be longer, but this may be possible. It will be easier and use less water following precipitation when the soil is already moist. The pine trees should have a relatively shallow root system with few sinker roots (going straight town). Most of the roots will be in the top two feet of the soil, so you should have little problem burrowing under them. You need to burrow deeply enough to keep the new water line from freezing. If you have shallow soil, rocky soil, or caliche, this may not work well.

Perhaps you can find a plumbing company that has experience doing this. The traditional trenching used to replace pipes will almost guarantee death of the pine trees. The water burrowing technique greatly increases the chance the trees will survive.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

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