Comparative Study between Hydro and Air Excavation Technologies

• Author / Creator

  Rijal, Roshan

• Infrastructure development is in demand throughout the world. Rebuilding and redeveloping are happening in urban areas across the globe, whether for installation of underground pipes for sewer, gas, water supply or for deployment of telecommunications and electrical cables. Given the ever-increasing demand for construction work for underground utilities, the requirement for excavation is also increasing. Traditionally, hand tools or mechanical excavators were used for underground utilities construction. However, this type of tools and machinery can be unsafe in certain circumstances, i.e. excavation near existing utilities or excavation for existing electrical cables or excavation for existing telecommunication lines. Also, traditional mechanical excavation equipment produces a large amount of greenhouse gases, whereas alternative methods such as Suction excavation technology (SET) are more cost efficient, and have less social and environmental impacts. Innovations in technology in recent years have led to suction excavation (hydro and air excavation) for underground utilities projects. Hydro excavation uses water during excavation and produces a waste mixture of solids and liquid which is known as slurry. Strict government guidelines/regulations must be followed before disposing slurry or backfilling at legal dumping site. However, air excavation uses pressurized air for excavation and produces less negative impacts on the environment. The excavation industry and government regulatory bodies have yet to recognize the benefits of air excavation, since it is a new technology compared to hydro excavation. This research provides a comparison between traditional and suction excavation, as well as hydro and air excavation technologies to determine which excavation method is the best solution for underground utility projects. The factors considered include productivity rate, cost, safety considerations, and environmental impact, and the choice of excavation method under different conditions i.e. ground conditions, moisture content, and applicable temperature ranges is also considered.
  The study began with determining the overall cost of excavation for daylighting an underground utility by the traditional open-cut excavation using hand tools, mechanical excavation, and suction excavation. In addition, a comparative study was conducted between traditional and suction excavation technology in terms of life-cycle costs from pre-construction to post-construction for underground utility projects, considering the social and environmental costs. Furthermore, the Analytical Hierarchy Process (AHP) was applied to determine the most cost-effective method of excavation among hydro and air excavation with respect to direct, indirect, environmental, and social costs for underground utility installation and rehabilitation projects in urban areas. Finally, an online pilot survey questionnaire was conducted to investigate hydro and air excavation technology in detail to gain a thorough understanding of the conditions under which it is appropriate to use air and hydro excavation technologies.
  Considering the life-cycle costs for a typical urban underground utility project, suction excavation was found to be more cost effective than traditional excavation methods. Also, after conducting an AHP considering direct, indirect, social and environmental costs with their respective weights based on expert opinion, air excavation was found to be the most cost-effective method for excavation project in urban areas. Furthermore, based on the responses collected from an online pilot survey, the total savings in terms of cost and time from excavation to management of slurry or dry earth is greater for air excavation than hydro excavation. In addition, air excavation is considered to be environmentally friendly due to reduced emission of greenhouse gases, and lack of requirement for fresh water during excavation, reducing the requirement for regulated disposal of excavated material at a waste management facility. However, air excavation is not suitable for conducting excavation during extremely cold (winter) conditions.

• Subjects / Keywords

  • excavation technologies

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-sjt8-xs83

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.