Tree Damage During Construction

Could your tree damage be due to construction damage?

When your trees and construction projects collide your trees may suffer.

Tree damage from construction sometimes takes years to detect. The construction itself, now long past, isn’t readily suspected. The tree however is suffering and you need a remedy.

A thorough inspection of your property, prior to building or remodeling, (or better yet prior to site planning), may save thousands of dollars and future headaches. And, possibly avoid that tree damage entirely. Sadly, it’s common for homeowners to pay a premium for a beautiful wooded lot - construction begins and ends and the homeowner is faced with trees damaged by construction activities which must now be removed. This removal is always more expensive with the home and landscape in place, than prior to construction.

A tree preservation plan put in place prior to planning and construction can save you years of headaches and thousand of dollars. We specialize in pre-construction consultations. We work in coordination with the homeowner and/or the builder to put into place a tree preservation plan to avoid those unnecessary pitfalls. Too often, though, we are called in after the tree damage, with no recourse but to remove the once beautiful and valuable trees.

Through a thorough examination we can help you determine your alternatives.

Some of the more common construction injuries:

Soil Compaction

Equipment used in construction such as backhoes, bulldozers, payloaders, cranes, dump trucks, equipment trailers, utility vehicles, and skid-steers can damage trees in a very short period of time. As equipment is driven over soil, the vehicle weight compresses the soil. The valuable air space in the soil is crushed. Soil aeration refers directly to the amount of oxygen available in the soil pores. When the air space is compacted, the soil has a reduced capacity to hold both oxygen and water for the tree roots. Water from rain and even irrigation is more likely to run off the top of the soil instead of soaking in the soil, thus causing an altered drainage pattern.On-site storage areas, parking areas, and foot traffic from construction workers also compacts the soil.

Altered Drainage Patterns

In addition to compacting soil, placing sewers, streets, curbs, and gutters at a site will greatly alter drainage patterns. Water that once had a chance to soak in after a shower now is whisked into the storm sewer, bypassing the ground water system. Less ground water is available to tree roots. The soil dries out faster since less water is stored, and the effects of droughts are heightened. This effect is worse at the bottom of a hill where plants requiring moist, but well-drained soils are often found.

Decreased Grades

Reducing the grade around existing trees causes serious injury. The majority of fine roots are found in the top 6-12 inches of soil. Large portions of the fine roots thus are lost by soil removal, causing a reduced root zone. This situation results in an altered drainage pattern.

Reduced Root Zones

Trenching, cuts for roads and/or sidewalks, and decreased grades result in the mechanical severing of fine roots, decreasing the size of the root zone. Since most of the fine roots are near the surface, even a shallow trench or cut for a sidewalk can damage the tree. The tree now has a decreased ability to absorb water and nutrients and store carbohydrates.

Disturbed Soil Profiles

Builders are often faced with a disposal problem with the soil removed from digging the basement. The lowest cost solution is to spread the spoil from the basement over the existing soil. The spoil is often finer textured than the original soil, resulting in a disturbed soil profile and increases the grade. Water does not move downward from a fine textured soil such as clay into a coarser textured soil such as a sand or gravel. Water remains in the fine textured soil at the interface of the soil types until the head pressure is sufficient to force the water into the coarser soil.

This is called a perched water table, and the impounded water can kill sensitive plants such as yews. This explains why adding gravel into the bottom of a planting hole will not increase drainage.

Increased Grades

Distributing soil from construction excavations can also bury tree roots. The result is decreased aeration to the fine feeder roots and a disturbed soil profile.

Adding soil over the root zone of existing trees is problematic. As little as four inches of fill may kill a mature forest tree.

Mechanical Injury

Bark damage as well as broken or damaged limbs are often damaged by construction equipment. The tree is further weakened and subjected to invasion by decay organisms.

Debris in the Soil

In many cases, virtually anything and everything is buried at a construction site. Concrete spills, sheetrock, and plywood are examples of construction debris that cause disturbed soil profiles and alter soil moisture distribution patterns. One example found a site where plants had been failing for several years. A soil probe identified the problem -- an entire 4x8 sheet of plywood buried about one foot below the soil surface.

Impounded Water

Sometimes altered drainage patterns and/or disturbed soil profiles can cause water to be impounded, creating a boggy site from one that had been well drained. Many native trees will not tolerate poor drainage. Upland species are most vulnerable. Oxygen levels in the soil are reduced as water fills the pore spaces that formerly held oxygen.

Increased Competition

Often little thought is given to the effects of altering plant communities. For example, it is uncommon to see an attractive sugar maple growing in an attractive bluegrass lawn. Either the healthy sugar maple shades out the grass or the tree slowly declines due to competition from the lush, highly competitive grass.

Increased Light

Another alteration of the suburban landscape relative to the woodland it replaces is increased light. Reduced numbers of trees and the resulting increase in reflected light contribute to a much higher light level.

Reflected light alone can double the incident light levels to which a plant is exposed. Thin barked trees, such as beech, seem particularly sensitive to this problem.

Increased Temperatures

The heat island effect of our cities is well known. Soil and air temperatures both rise in the city. Plants may be more sensitive to soil temperature changes since air temperatures normally fluctuate more.

Plants that are at the southern part of their natural range are most likely to be sensitive in this situation.

Interrupted Nutrient Cycling

This is not a factor that is likely to have severe consequences itself, but it is one more stress with effects that are additive. Micronutrients are likely to be the ones that are found to be deficient. In a woodland situation, nutrients are recycled as foliage, branches, and stems that decompose over time. Removal of leaves and other organic debris takes the nutrients they contain out of the system.

Insects and Disease

Increased stress levels predispose the tree to insect infestations and disease.

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