Do Tree Roots Impact Pipeline Safety

At the bottom of an 8-foot hole in the middle of a California vineyard, two arborists carefully remove soil from where grape roots have wrapped around a Pacific Gas & Electric (PG&E) gas transmission pipeline. The work is slow-going, but the information gathered will benefit utility customers nationwide and make natural gas systems safer.

A 2010 study by the U.S. Department of Transportation’s Pipeline and Informed Planning Alliance highlighted the potential damage tree roots can cause to pipelines. Utilities like PG&E are trying to learn more.

“When we started investigating some of our pipe and the trees next to it, we found that the tree roots were going much deeper (than three feet),” explains Marvin Penner, a PG&E manager of land asset management.

Arborists, horticulturists and soils experts from Fresno State University joined pipeline risk management and environmental consultants to investigate how different types of tree species, soil and irrigation can impact pipelines. The study was sponsored by PG&E and included data gathered from 53 locations along the operator’s pipeline system in California.

“Some trees have a more aggressive root system or the pattern of root development would go deeper where it would be more likely to encounter a pipeline. And other trees have a more shallow root system or smaller roots that just don’t reach that deep. We got involved, basically, to map that,” said Dr. Charles F. Krauter, a professor of soils and water at Fresno State University.

Results of the study along PG&E’s system indicate the need for continued research across the country and reconfirm that tree roots can wrap around and damage a pipeline’s protective coating. Contact pipeline operators in your community to learn more about their Integrity Management Plans and vegetation management strategies designed to prevent tree root damage to their pipelines.

Portions of this article are reprinted with permission from an article that appeared in PG&E Currents.

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