An air spade tool is an air powered selective excavation tool that is designed specifically for working around tree roots, utilities, and in sensitive areas.
The Airspade uses compressed air, that in the case of Arboraeration is supplied via our vehicle mounted, 150 CFM (Cubic Feet per Minute) diesel air compressor. This allows air to be jetted out of the end of the Airspade at extremely high velocities, almost 12,000 MPH, or the equivalent of Mach 2!
With all of this power, what can an airspade be used for?
Airspade use in arboriculture has been a recent advance in its use and is now being practiced in many parts of the world to manage urban trees. Common uses include excavation to plot the location of tree roots prior to planning applications, excavating tree roots to undertake root pruning, services installation or root barrier installation and using them to de-compact soil surrounding trees. Below we are going to discuss how Airspades can be use in each of the above scenarios:
Airspade Investigations – Locating and Plotting Tree Roots
Within current planning guidance all applications for construction projects must comply with British Standards 5837:2012 – Trees in relation to Design, Demolition and Construction. Within this document generic guidelines are given to consultants on the size of the root protection area (RPA), however where planned works conflict with these RPA’s we are able to excavate trial pits in strategic locations in order to find the exact location and size of tree roots and offering clients far more information to take to the planning process, enabling greater chance of reducing the RPA’s size or shape to facilitate construction. Without using a selective excavator such as an airspade these works would not be possible.
Root Barrier and Services installation
In the same way that airspades can be used to excavate trial pits to look for tree roots we also use the same methodology for root barrier installation – whereby tree roots are pruned away from the target area and then a barrier is installed. Working in this way ensures the roots can be pruned carefully and in the correct locations, maximising the trees ability to recover.
Services installation (Water, Gas, Electric Etc) is an often overlooked area of building layout and design and also needs to take into account RPA’s, where encroachment is not avoidable, such as sites with limited access or areas of trees at the front of the property we can carefully excavate the line of the utilities using the air spade, providing a straight line for the services to be routed without causing damage to the trees root systems.
Decompaction
Compressed air decompaction – This is where a modified airspade is driven 30cm into the ground and high pressure compressed air is injected into the soil, creating fractures and gaps.
Typically this de-compacts a radius of 1m surrounding the injection site and to a depth of up to 1m. this is usually recommended on heavily compacted areas and can also have the benefit of having a targeted fertilizer added to the soil at the same time to spread this around the area.
Vertical mulching – this is a method of excavating and breaking up the top 20-30cm of soil using our airspade. Typically, we only undertake 50% of the rooting area at a time to reduce any risk of destabilising the tree. This method of decompaction is generally recommended when lighter surface compaction has taken place, such as in parks or heavily used areas.
Airspade Root Collar Investigations
Another use of the air spade for trees is that we can undertake below ground investigations of the root collars of trees, checking for signs of fungal decay and softening of the main structural roots.