Arborist Involvement in the Development Process

When it comes to development projects, trees should be viewed as an asset. Aside from providing various advantages to the environment, healthy and established trees can increase the amenity and land value of a site. They not only have aesthetic qualities, but also reduce excessive heat by providing shade and cooling by respiring, absorb carbon dioxide, store air pollutants, and can even be linked to the heritage curtilage of a site.

However, tree roots can take up a significant amount of space on a potential development site which can have a substantial impact on how the land is used. Many people forget that trees extend far below ground level and construction activities can have a significant impact on their roots if they are not carefully considered throughout the development process.

The Australian Standard AS4970-2009 Protection of trees on development sites provides guidance for arborists, architects, builders, engineers, land managers, landscape architects and contractors, planners, building surveyors, those concerned with the care and protection of trees, and all others interested in integration between trees and construction.

It's crucial to remember that while most trees take decades to reach their full potential, they may be severely damaged or even killed in a matter of minutes by a backhoe or careless contractor working on a site. It’s also important to remember that not all trees are equal when it comes to site development. Deciding which trees on development sites need to be retained and protected or removed at an early stage will allow for a more comprehensive approach to a site development. 

To ensure efficiency and effectiveness in the development’s design, arborists are called to properly assess the trees’ constraints and benefits in accordance with industry best practice and consent authority requirements.

What is an Arborist?  

Arborist, in general, is a term used for tree specialists who are well-versed in the science of tree planting, care, maintenance, and arboriculture. Meanwhile, a Certified Arborist pertains to a person who has been in the industry for a certain amount of time and is recognized by a professional organization such as the International Society of Arboriculture (ISA). 

However, not all certified arborists are qualified as consultants.

Consulting Arborists or Project Arborists are sought to carry out tree assessments, identifying tree protection measures, consultation, report preparation, and monitoring. They are skilled, experienced, and have acquired the minimum qualification framework which is generally a Diploma in Arboriculture - known as AQF Level 5. 

Why do you need a Consulting Arborist?

Most municipalities and government departments today require a minimum AQF Level 5 Arborist to be engaged through the construction process. Where trees are involved on a potential development site, It is generally a condition of consent or an RFQ to, at minimum, have an Arboricultural Impact Assessment (AIA) or Tree Protection Plan (TPP) in place to allow construction to proceed.

Planning and Design - Preliminary Development Assessment Report (Pre-DA) 

A consulting arborist visits the site generally after the site survey has been completed and scrutinizes the trees through a comprehensive arboricultural assessment before a preliminary design is sketched for the proposed construction. The assessed trees are evaluated to determine their quality in the landscape and suitability to be retained through the construction process. It is important to remember that many councils require the retention of good quality trees so this step is crucial.

The consultant will then provide a Preliminary Development Assessment Report (Pre-DA) outlining trees which should be retained based on their quality. It is better to have this information early in the development  process as it is easier for architects and engineers to design around trees when these designs are more fluid and less set in concrete - so to speak. 

The Consulting Arborist will then review these plans and provide feedback and make suggestions or alterations to design so trees of good quality can be successfully retained.

Arboricultural Impact Assessment (AIA)

Once the design is finalised and ready to be sent to the consent authority for approval, the Consulting Arborist will take the plans and complete an AIA report. This report must be objective and not argue for or against a development.

This report again covers the quality or ‘retention value’ of the trees and analyses the impacts of the proposed development on the above and below ground components of a tree. AS4970-2009 provides offset calculations for the Tree Protection Zone and Structural Root ZOne which are based on the lower trunk dimensions of a tree. These calculations are made and the design footprint, methods of constructions and additional construction considerations are overlaid and the impact to the trees, determined. 

The report then makes recommendations for the retention or removal of trees and provides guidance on protecting trees on development sites.

Tree Protection Management Plan (TPMP)

The TPMP is sometimes completed during the AIA or may be required after as a condition of development consent. Canopy Consulting generally provides this information as part of our AIA reports so it’s important to remember this when comparing our services with another company.

The TPMP outlines the specific tree protection requirements and usually comprises a geographical plan along with a written specification. The plan makes recommendations on managing trees which are to be retained throughout the construction process. 

Pre-construction  

The arborist’s work does not end in the early phase of the project, they need to be involved throughout the process. This is when the role of the ‘Project Arborist’ comes into play. During Pre-construction, the Project Arborist will visit the site and physically mark trees which are approved for removal. These trees are then removed by a tree contractor.

Next, tree protection measures as per the TPMP are installed. This is usually in the form of protective fencing installed at offsets from the tree - normally at the edge of the Tree Protection Zone. These tree protection measures are inspected and certified by the Project Arborist. The certification is provided to the council or private certifier.

A few mistakes can throw away years of careful and painstaking tree preservation.

Construction

A regular site visit from a consultant is needed during the construction phase as their mere presence can prevent numerous negative impacts on the protected trees. Their years of experience, knowledge, and awareness are significant during unexpected accidents during the development. Depending on the site and type of construction, regular inspections may be undertaken on a fortnightly, monthly or quarterly basis for the duration of construction.

Besides preventing accidents, they are tasked to maintain or amend the protective measures installed prior to the construction. They closely monitor the entire project, as there are situations that call for the temporary removal of selected protective measures. When this occurs, the Project Arborist must be on site to supervise these activities to make sure that ‘accidents’ don’t happen.

Post Construction

The presence of the Project Arborist on a construction site cannot guarantee that no damage will be inflicted on the tree if they are not involved and regularly inspected. The entirety of the development takes constant communication and collaboration between the contractors, designers, local government, owners, and the arborist to ensure that the existing trees are healthy and stable. 

Once practical construction is completed, tree protection measures are dismantled under instructions from the Project Arborist. This is typically to allow landscaping works to take place.

At the completion of the project, the Project Arborist will visit the site and inspect the trees and provide final certification. In the event that the consent conditions relating to tree protection have been contravened, the Project Arborist will make recommendations to remediate the soil environment or may recommend pruning to repair broken or damaged branches.

Once these recommendations are completed, the Project Arborist will provide final certification which is submitted to the certifier so an Occupancy Certificate can be issued.

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Canopy Consulting
Macquarie Park NSW 2113
1300 122 667
(1300 1CANOPY)
info@canopyconsulting.com.au

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