Erosion and Sediment Pollution Control Program Manual.pdf

Repairing Construction Injury
The most common causes of tree injuries are worker carelessness, grade changes, soil compaction,
soil pollution, and the incorrect removal or trimming of trees. Depending on the extent of the injuries,
trees may die shortly after construction is completed or their
health may slowly decline over a number of years. Several
techniques can help correct injuries caused by construction
activities. Trees should be inspected for two years following
construction for declining health, branch dieback, or poor
foliage color.
Soil Techniques
Understanding structural fills
Structural fills are used to key-in slopes and provide heavily
compacted pads for construction. In a structural fill, all the soil is removed until a soil horizon with a
certain compaction rate is found. Removed soils are then replaced upon the compacted soil while
being compacted with water. It does no good to provide aeration systems or other preservation
techniques or to remove fills of this nature from near trees because roots have already been severed in
the fill process. Structural fills should be avoided within the TPZ of trees suitable for preservation.
Removing fill
Fill can kill trees quickly, or it can kill them gradually over a number of years. The effect fill has on trees
depends on a number of factors. If construction activity has changed the grade under or near a tree, all
efforts should be made to restore the area to its natural grade. Trees not surrounded by fill have a
noticeable trunk are at the soil line, while trees buried in fill have no trunk flare (see Figure 20). Test
holes can be dug at several points near the tree to determine how much fill has been added. Fill can
be removed safely within one year after construction. A backhoe can be used to remove fill to within
4 inches of the original grade, but the rest should be removed by hand with shovels and rakes. Fill that
has been in place for several years requires care during removal, and a qualified arborist should be
consulted. Some trees survive the initial application of fill because their roots grow into the fill. For
trees covered by fill for long periods of time, fill within 4 feet of the trunk should be removed to expose
the trunk and buttress roots. If it appears that many new roots have grown and become established in
the fill, the excavation should stop and the fill should be replaced. Fill should not be removed during
periods of hot, dry weather. Exposure under these conditions could shock a tree by drying out the roots
as well as the soil around them. The removal of fill can create a low spot around a tree that
accumulates water. If inadequate drainage is a problem, a French drain or other drainage system must
be installed to move standing water away from the tree.
363-2134-008 / March 31, 2012 / Page 475