Info Request Response Traffic Management Plan 25-9-25 - JN1006_2-Bennett-3FergusonSt-AIA092025

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4.      POTENTIAL CONSTRUCTION IMPACTS

4.1      General construction impacts not specific to site operational works
Trees situated within the design footprint will need to be removed.
Another development impact that may affect trees is earthworks. Earthworks can be
separated into three categories.
4.1.1     Cutting (excavation)
Cutting within the Notational Root Zone (NRZ) can result in root damage, with the severity of
impact influenced by factors such as the size and number of roots affected, overall tree health,
structural attributes (e.g. weight distribution), and soil characteristics. Minor or low-level
incursions into the NRZ—defined as less than 10%—may lead to short-term health effects, such
as isolated twig dieback within the crown, but typically do not result in long-term decline. In
contrast, moderate (10–20%) or high (>20%) NRZ encroachments carry a greater risk of
significant health deterioration, compromised structural integrity, or even tree mortality. The
extent of impact depends on the cumulative root mass affected, species-specific tolerance to
root disturbance, and the excavation techniques. These effects often present immediately and
may worsen post-development, particularly under harsh environmental conditions.
4.1.2     Fill
Soil (fill) affects trees in various ways. All-purpose landscape soil is often reused from other
areas of the site or imported from other sites and is often not favourable for tree health. It may
contain contaminants, soil pathogens, or low-quality nutrients and therefore not consistent
with the requirements of the existing vegetation. Furthermore, increasing depths of fill
decreases soil moisture of existing tree roots. Even during wet conditions, where surficial
landscape plantings and turf are performing well, established trees can decline. Structural
soils such as those found in road base, below concrete pads ect. are made up of fine particles
(pores), which do not provide enough interconnected gaps (pore space) for water and gases
to be exchanged from air and precipitation that the tree is reliant on to survive. The processes
to achieve the desired level of compaction can also cause physical damage to tree roots and
limit their extension. Fill often causes a health decline, but over a longer period in comparison
with cutting. Impacts depend on various factors such as fill type, compaction requirements,
species tolerance, environmental conditions, individual tree attributes such as health and age
class ect.
Additionally, cutting and filling within a site can indirectly impact tree health regardless of
whether it is within their respective NRZ, by altering groundwater levels or disrupting natural
hydrological flows. Symptoms of decline may not be immediately apparent and often emerge
only after construction is complete.
4.1.3     Surfacing
Surfacing can influence tree health in several ways, particularly through soil compaction and
changes to water availability. Load-bearing surfaces are more likely to compact the soil, which
restricts air and water movement and limits root development. Impervious surfaces such as
concrete or asphalt can also redirect stormwater away from the tree’s root zone, reducing



Tree Management Plan (TMP)                Ref: JN0823                                 Page 8 of 33