Tree Roots & Sewer Lines

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Audra Jefferson
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1 Tree Roots & Sewer Lines Prepared for: Orange County Waste Discharge Requirements Steering Committee Prepared by: Michael Huff ISA Certified Arborist WE-4276A

4 Why do tree roots grow toward sewer and pipelines? Water, Nutrients, & Oxygen Roots grow toward an increasing water gradient and appear to need at least a continuous surface film to direct them to the water.

cooler than the surrounding soil, water may condense on the outer

5 Why do tree roots grow toward sewer and pipelines? Condensation When intact drains and other service pipes are cooler than the surrounding soil, water may condense on the outer surface and root growth may develop along the moisture gradient developed in the soil.

Why do tree roots grow toward sewer and pipelines? Heat Water flowing through sewer lines can be substantially warmer than the surrounding soil.

6 Why do tree roots grow toward sewer and pipelines? Heat Water flowing through sewer lines can be substantially warmer than the surrounding soil. Root growth and activity, including cell division and nutrient uptake is likely to be significantly greater than in other parts of the colder soil, leading to a mass of fine roots forming around the pipe. Thermal changes between materials provide fracture pore space.

7 Summary: Why do Tree Roots Grow so Well Near Pipelines? Pipeline Environments Promote Tree Root Development Greater Moisture Level in Trench Oxygenated Soil Less Soil Compaction Nutrients deeper in Trench Warmer Soil in Trench

8 Two Primary Types of Damage 1. Invasion of pipeline 2. Damage to pipeline

9 Why do tree roots invade sewer lines? Water, Nutrients, & Oxygen Damaged lines, faulty installation, inadequate leak tightness All tree roots are opportunistic

10 Why do tree roots invade sewer lines?

11 How Can Tree Roots Damage Pipelines?

12 How Can Tree Roots Damage Pipelines?

13 How Can Tree Roots Damage Pipelines?

14 How Can Tree Roots Damage Pipelines?

Conflict resolution and prevention Functional sewage systems and aesthetic tree environments are both essential elements of modern urban construction

15 Conflict resolution and prevention Functional sewage systems and aesthetic tree environments are both essential elements of modern urban construction We need to prevent and resolve conflicts through a broad interdisciplinary approach Education Research & Development Planning Implementation Maintenance

16 What types of trees can be more problematic? Large, fast-growing trees with aggressive root systems: figs (Ficus spp.) maples (Acer spp.) elm (Ulmus spp.) willows (Salix spp.) birch (Betula spp.) mulberry (Morus spp.) ash (Fraxinus spp.) poplar and cottonwood (Populus spp.) large eucalyptus (Eucalyptus spp.) Sweetgum (Liquidambar styraciflua)

18 What types of trees are Sewer-safe? There are no sewer-safe trees. Any tree will eventually take advantage of available water and colonize a sewer line.

What types of trees are less-aggressive? Small, slow-growing trees with less aggressive root systems: Japanese maple (Acer palmatum) crabapple (Malus spp.) Crapemyrtle (Lagerstroemia spp.

19 What types of trees are less-aggressive? Small, slow-growing trees with less aggressive root systems: Japanese maple (Acer palmatum) crabapple (Malus spp.) Crapemyrtle (Lagerstroemia spp.) Ginko (Ginko biloba) Thornless Honeylocust (Gleditsia triacanthos var. inermis) Golden Raintree (Koelrueteria paniculata) Little Gem Magnolia (Magnolia grandiflora Little Gem ) Saucer Magnolia (Magnolia x soulangiana) 'Winter King' hawthorn (Crataegus viridis)

20 How much of an issue are shrubs? Shrubs will exploit a broken line but root size and life span of shrubs is shorter than trees.

21 How far away should trees be planted? Dependent upon: Rooting Environment Species

23 Estimating rooting spread and depth Root System Depth Dependent on soil profile, species, and presence of turf grass and other landscaping Majority of fine roots in the upper 24 of soil Studies have found roots up to 200 deep

24 Estimating rooting spread and depth Roots are opportunistic will grow wherever environmental conditions permit Roots are not uniformly distributed around a tree Severely limited and highly irregular in urban settings

26 How far away should trees be planted? Randrup (2001) concluded that distances up to 20 constituted the high-risk zone.

Estimating rooting spread and depth Root System Spread Typical Rules 3 x canopy spread not accurate 1 1.

27 Estimating rooting spread and depth Root System Spread Typical Rules 3 x canopy spread not accurate x tree height not accurate Trunk Diameter = 38:1 young trees (cannot be applied to palms or mature trees) Mordelet et al. (1996) African fan palm (Borassus aethiopum) extended roots 65 before encountering nutrient-rich soil patch where root proliferation was 10x that in ordinary soil.

28 What Steps Can Help Control Root Growth? Root barriers with growth inhibitors Compact layers of soil Air gaps using large stones Solid barriers like plastic, metal, and wood. Landscape fabric (with slow release root inhibiting chemicals) Chemicals sulfur, sodium, zinc, borate, salt, or herbicides (may be harmful to trees)

29 What can municipalities and developers do? Replacement of the vitrified clay, brick, and concrete sewer systems with modern materials and joints between pipes should prevent most root problems in the future ($$). New sewer lines made of acrylonitrilebutadienestyrene (ABS) prevent many of the root problems.

30 What can municipalities and developers do? Trenchless pipe repair and replacement Relining Acid resistant polyester fiber with resin Penetryn liquid acrylic gel Pipe Sliplining Chemical control

What can municipalities and developers do? Standard construction methods on development sites compact the soil like a brick and then trench for the utility lines.

31 What can municipalities and developers do? Standard construction methods on development sites compact the soil like a brick and then trench for the utility lines. When a tree is planted, the only uncompacted area left around the trees is the trenched area. This leads to all roots following those channels which eventually may cause line breakage. View trees as a resource for storm water treatment Professional management of tree root growth is becoming more important for all infrastructure

What Steps Can Help Control Root Growth? Planting Location Determine the general location of the lateral on the property. Avoid planting or maintaining trees near the lateral.

32 What Steps Can Help Control Root Growth? Planting Location Determine the general location of the lateral on the property. Avoid planting or maintaining trees near the lateral. For information on where-to-plant considerations, visit the International Society of Arboriculture s (ISA) Webpage, Avoiding Tree & Utility Conflicts, at

33 What Steps Can Help Control Root Growth? Select an appropriate species For an extensive guide on tree selection, visit Cal Poly's site (selectree.calpoly.edu) and select "low" for "Root Damage Potential" along with the other tree attributes you seek.

34 Why Worry about it? Premature removal and replacement of large trees results in a substantial loss of net benefits formerly produced by the tree - approximately $70/year/tree (McPherson et al. 1999) Replacement trees are a net cost for the first 5 10 years because establishment costs are greater than benefits from the relatively small tree crown.

35 Why Should We Even Plant Trees Near Pipelines? Tree Benefits Improve air quality Decrease energy costs Aesthetics Reduce storm water run-off Filter and reduce impurities Reduce soil erosion Increase property values Longer pavement life Improve microclimatic conditions Rain, sun, heat and skin protection Attract businesses, patrons, and new residents to a community Carbon sequestration

36 Questions?

TREE SELECTION FOR DROUGHT RESISTANCE

TREE SELECTION FOR DROUGHT RESISTANCE by Dr. Kim D. Coder, Daniel B. Warnell School of Forest Resources University of Georgia 4/99 A fact of life in the Southeast is the mid-summer drought. In recent years