CORE SERVICES
Our Core Competencies
Tree Survey specialise in the detailed assessments of large tree populations.
Our key areas of expertise are as follows:
A Preliminary Tree Assessment (PTA) is a comprehensive survey or assessment of trees within a designated site or parcel of land. These reports are often used in the earliest stages of development planning, prior to the development application (DA) or detailed design. The preliminary tree assessment provides base data and information to guide the layout of the development, including opportunities to retain existing trees.
The first stage of a preliminary tree assessment comprises of numbering, tagging and collecting data for each tree within the site. The second stage of the preliminary tree assessment consists of using the data collected on site in conjunction with a site survey plan to compile a report. General information for each individual tree will include:
- Identification: Allocated number and botanical name.
- Dimensions: Tree height, canopy spread and trunk diameter at breast height (DBH)
- Condition: Tree health, structure and age class.
- Significance: Tree significance, useful life expectancy and priority for retention.
- Protection zones: Tree protection zone (TPZ) and structural root zone (SRZ).
Our PTA include a tree location plan prepared using ArcGIS software. The tree location plan shows the identifying number and location of each tree, the extent of the tree protection zone, and will be colour coded to reflect the retention value of each individual tree (low, medium and high priority for retention).
Arboricultural Impact Assessments (AIA)
An Arboricultural Impact Assessment (AIA) is a detailed and comprehensive report that reflects the potential impacts of a development on trees within and adjacent to a proposed development site. The assessment provides detailed information on the impact of building, infrastructure, storm water drainage and landscape construction on the trees within and adjacent to the proposed footprint. The AIA will identify any trees that may need to be removed and trees that can be successfully retained. General information for each individual tree will include:
- Identification: Allocated number and botanical name.
- Dimensions: Tree height, canopy spread and trunk diameter at breast height (DBH)
- Condition: Tree health, structure and age class.
- Significance: Tree significance, useful life expectancy and priority for retention.
- Protection zones: Tree protection zone (TPZ) and structural root zone (SRZ).
- Impacts: Any conflict between the development footprint and the tree protection zone.
The AIA will include recommendations for site specific tree-sensitive construction methods, and other measures which may mitigate the likely impacts of the works. Our AIA includes a tree protection plan prepared using ArcGIS software. The tree protection plan displays the identifying number and location of each tree, the extent of the tree protection zone (TPZ) and structural root zone (SRZ) and will be colour coded to reflect any conflict between the development footprint and the protection zone of each individual tree (no encroachment, minor encroachment, major encroachment).
Tree Risk Assessments (TRA)
A Tree Risk Assessment (TRA) is a detailed analysis of the risk posed by a single tree or group of trees within a specific site. Tree risk assessments are often carried out at schools, universities, holiday resorts, parks and other public spaces where trees have potential to cause harm to the persons who occupy that space. There are three components to calculating the risk posed by a tree:
- Target: The persons, property, or asset at risk and the likelihood of that target being present/impacted in the event of partial or whole tree failure.
- Size: The size of the tree or branch most likely to impact the target. The size of the failure determines the likely force exerted upon impact.
- Probability: The likelihood of a failure occurring within the assessment period based on the structure and condition of the tree.
The first stage of a TRA comprises a visual tree assessment of all trees within the site. The visual tree assessment comprises a walkover risk assessment in accordance with the Quantified Tree Risk Assessment (QTRA) method. Where the walkover risk assessment identifies conditions or defects that present an increased risk of tree failure, the identified tree will be assessed using the full QTRA method and a stage one Visual Tree Assessment (VTA) as formulated by Mattheck & Breloer (1994).
Trees identified as posing an increased risk of harm are spatial located, tagged and allocated an identification number. Following the site inspection, a comprehensive report is prepared detailing the overall structure of each identified tree, the subsequent likelihood of tree failure and potential risk of harm posed by that individual tree. General information for each individual tree will include:
- Identification: Allocated number and botanical name.
- Dimensions: Tree height, canopy spread and trunk diameter at breast height (DBH)
- Condition: Tree health, structure, age class and any significant/visible defects.
- Risk: Risk of harm, risk rating and mitigation actions.
Our TRA includes management/mitigation options to reduce or eliminate the risk posed by each of the identified trees and a tree location plan prepared using ArcGIS software. The tree location plan displays the location of each identified tree, their allocated number and risk rating. A photo of each identified tree will is provided and included in the report to allow for identification and verification purposes. Any tree assessed for pruning will be accompanied with photographs marked with the proposed pruning locations to allow for clear instructions be passed onto the tree trimming suppliers.
Project Arborist Services
The project arborist is responsible for carrying out the inspections, supervision, monitoring and certification of trees during a development project. Details of the project arborist are often required to be submitted to the consent authority prior to construction.
There are many stages in the development process (from site acquisition to completion) where the AQF level 5 project arborist is required to monitor or provide certification (a written statement of compliance). Three key stages of the development are outlined below:
- Pre-construction: A pre-construction meeting should be attended by the site manager, the project arborist and contractors to introduce the tree protection plan and its requirements. Fencing and other protection measures are to be installed in compliance with conditions of consent and as detailed in the tree protection plan. Once the tree protection measures have been installed, they must be certified by the AQF level 5 project arborist.
- Construction: The project arborist will generally be required to undertake monthly site inspections to monitor and record the ongoing health and condition of the trees during construction. The project arborist will also be required to supervise and certify any work carried out within the tree protection zone (TPZ). If there is non-compliance with tree protection measures or if trees have been damaged, a time frame for compliance and remedial works should be specified by the AQF level 5 project arborist. The determining authority may need to be notified of non-compliance issues.
- Post-construction: Practical completion assumes that all construction and landscaping works are finished. At practical completion all remaining tree protection measures (such as tree protection fencing, trunk protection and ground protection) should be removed. Following the final inspection and the completion of any remedial works, the project arborist should certify (as appropriate) that the completed works have been carried out in compliance with the approved plans and specifications for tree protection. Certification should include a statement on the condition of the retained trees, details of any deviations from the approved tree protection measures and their impacts on trees.