What is Air Excavation in Construction?


The use of air, in the excavation process, is a relatively new technique. Similar to hydro excavation ( the use of water in excavation ), the use of air, is intended to be a non-destructive means of utility excavation. Like hydro excavation, the need to excavate around sensitive utilities, has become more and more of an issue, due to the concentration of utilities in the ground, the deterioration of old utility lines, as well as the need to install new utility lines in concentrated areas.

One of the benefits of air excavation, is that the technique does not introduce a second element to the operation. Using water to soften the earth for non – destructive excavation, introduces water to the soil.   This introduction of water, causes a re-activation of any type of dry pollutants that exist within the soil. Therefore the introduction of water into the soil, causes the material excavated from the utility trenches to become contaminated and must be handled and disposed as hazardous waste. This situation creates an entirely new prospective to the actual excavation of the utilities, if the material removed must be treated as a hazardous material. This is one of the primary reasons that air excavation is preferred over hydro excavation.

The use of air velocity, to breakdown the soil, allows the reuse of this soil as a backfill material, without the need to handle and remove the material as a hazardous product.

Air excavation has its limitations. The use of air only, does not breakdown the soil and the backfill around utilities, as easily and affectively, as the use of water. The ability to direct the heavy and powerful stream of water, breaks down the matrix of earth and rock, much more efficiently than only air. Although air has an intrinsic ability to move particles, due to the push of the air, it is not another element, it is simply the movement of the air around the earthen material. Air must be more concentrated and directed at the individual particles to breakdown the matrix, water has the overall tendency of breaking the matrix, together with softening the material and creating a flow able mixture. The creation of this flow able mixture is another consideration that must be added to the pros and cons of hydro verses air excavation. This flow able mixture must be deposited in an area that will allow the mixture of soil and water to flow out of the truck. This normally will require that an area of disposal be constructed with a raised perimeter, to limit the movement of the flow able material. The use of air does not require any special disposal area or consideration. The use of air, produces a product similar to a normal backfill material, and can be used to backfill the utilities after the excavation has taken place.

In comparison to the creation of a flow able mixture by the use of water to excavate, the use of air causes a basic cloud of dust that will rise into the air and cause breathing and respiratory issues with the operators of the equipment. One technique ( hydro excavation ) creates a slurry mixture and the other technique ( air excavation ) creates a dust cloud. Due to these respiratory concerns with air excavation, special breathing equipment, must be worn by the operators of any equipment involving air cutting, or excavation. In addition to the respiratory issues caused by air being used as a cutting force, the push of the air, moves the material in a basic random fashion. This random and uncontrolled excavation makes the resultant material not easily accumulated or vacuumed into a container. Unlike the use of water and the creation of a resultant slurry, the use of air, pushes the broken down earth in all directions, and causes the suction of the resultant material to be much more difficult and inefficiently excavated and accumulated.

Technology and research has advanced the physical process of air cutting and excavation. Large suction hoods have been developed, that will tent the excavation, and draw the dust and material out of the tented enclosure. This technology reduces the overall dusting of the entire surrounding environment, and contains the dust and the excavated products into a more concentrated area, allowing an easier management of the dust and broken down earth. Respiratory apparatus is still required for all operating personnel, even with the use of the advanced hoods and suction.

Another new technology being introduced in the development of air excavation, is the use of spin heads that rotate, due to the movement of the air pressure against a turbine type cutting head. This technology has increased the efficiency and the ability of the air nozzle, to more efficiently and accurately excavate the material around the utilities. A hooded assembly, over the tip of the air nozzle, has also advanced the efficiency of dust accumulation and focused material into the vacuum tube.

Air excavation and development of new techniques has been advancing, from its simple use of pointing a compressor nozzle towards the earth to excavate delicate tree roots to its current use as a primary means of utility excavation. The landscaping business has used the theory of air excavation for years. However, this usage was simply based on the disrupting occurrence of a high pressure air nozzle, functioning off of a normal air compressor, to remove and breakup the material that may be compressed around sensitive horticulture plants, roots, trees, etc. For many years, any delicate and non destructive requirements in the earthwork excavation business was focused on horticulture. However, as construction became more concentrated and utilities aged, the need for delicate and non destructive forms of excavation expanded to today’s current demand.

Unfortunately, like many other facets of technological development, a stimulus must occur that makes the need for a non destructive form of excavation necessary and financially competitive. In the utility field, this would entail a disastrous utility break caused fire and explosion or the loss of a primary utility service to hundreds of customers. These types of stimulus are becoming more common as construction advances within our inner Cities and existing utilities continue to erode.

Air excavation, like hydro excavation, has an extremely exciting future, and the continued technological gains will create air excavators that will be capable of inner city, non destructive, utility excavation which will be unchallenged by conventional excavation methods.

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