Vacuum excavation, such as hydro excavation, is a growing technology utilized to prevent job-site damages throughout the world. This technology continues to grow in use due to the proven success in preventing costly and sometimes catastrophic damage to underground utilities by being a non-mechanical method to excavate.
Vacuum excavation is a combination of two non-mechanical sources to excavate. The first source is pressurized water or air, which is used to loosen and break up the soil. Once the soil is loosened, the second non-mechanical source, vacuum and airflow, removes material from the excavation and stores it in a debris body or hopper. The material is contained in the debris body where it can then be transported offsite for disposal, loaded into another transportation vehicle, or even dumped on site and used as backfill. Because vacuum excavation is non-mechanical, the potential to damage an underground utility such as gas lines, fiber optics, or electrical lines is significantly reduced.
As evidence, many states have excavation best practices stating a tolerance zone around a utility. The tolerance zone is a distance on each side of the utility where only hand tools or vacuum excavation can be employed. However, when talking about hand tools, the belief is we excavate like archeologists and dig slowly, but digging by hand with a shovel is not archeologist-like and can be very damaging. How many of us have dug up and damaged a coaxial cable or a buried electrical line in the back yard? I know I have.
To validate further, the Common Ground Alliance (CGA) tracks and publishes a report every year on underground damages, facility type, and their cause. The CGA’s most recent report from 2015 showed there were 288,346 known reported events of underground facility damage in North America – that is one every two minutes! The key here is known incidents and the actual number of incidents is likely much higher due to unreported damages. In addition, CGA tracks excavation method employed, and the leading cause of underground damage was backhoes and trenchers with over 40% of all damages. Backhoe and trenchers are used more frequently for excavations and can be very destructive, so being number one on the list would be logical. However, the second leading cause of underground damage is hand tools, with over 26% of all known and reported utility damage. Conversely, vacuum excavation accounted for less than 0.2%. Going back to the tolerance zone and recommended excavation practices, you can see, only one of those methods is truly non-destructive. Employing vacuum excavation versus hand tools would reduce almost 45,000 known damages a year – over 100 damages a day!.
Even though vacuum excavation accounted for 234 events in 2015, many of these events could have been prevented. It is likely these events were improper use of the equipment. I am often asked for recommended operating techniques and pressure for vacuum excavators, and I always refer them to the Technical Standards and Safety Authority (TSSA) of Ontario’s Guideline for Excavation in the Vicinity of Utility Lines and the Gas Technology Institute’s (GTI) hydro excavation best practice and guideline. Both documents align in their best practices and are both great references for the continued non-destructive use of vacuum excavators.
Some key best practices are:
- Never use over 3,000 PSI of water pressure when hydro excavating. Too high of water pressure can damage underground utilities.
TSSA and GTI both recommend:
3,000 PSI maximum when used with a spinning or rotating nozzles.
2,500 PSI maximum when using a straight jet nozzle.
1,500 PSI maximum when 18” or more below surface.
Always keep the digging lance moving so as to not concentrate the pressurized air or water at a single point.
Maintain 8” between the end of the pressure wand and underground facility
Never heat water over 115° F.
Always be properly trained on the equipment and its safe operation.
The potential misuse of equipment by exceeding site or industry pressure recommendations is what lead Vactor to develop an industry exclusive, patent pending DigRight technology. You can learn more here. This technology will ensure proper operation of the equipment and help prevent those 234 vacuum excavation events.
It is also important to use equipment designed for the application. I too often see homemade digging lances or vacuum tubes that do no utilize proper protective coatings. It is important that the digging nozzles be protected on the end with a non-conductive coating. Similarly, vacuum tubes should be protected on the end with a soft, non-conductive end to prevent damages to underground utilities. Utilizing steel crowned ends can cause damage to underground facilities and should never be used when vacuum excavating. When employed properly, vacuum excavation is the only safe way to excavate safely, especially around buried utilities.
Article Supplied by:
Product Manager at Vactor – www.vactor.com
I guess that the person never has had to cut through a layer of shale. You can not do it at 1500 PSI below surface.
1,500 PSI maximum psi over hydro lines and nothing over 70 degrees on the water