What is hydro excavating? This is a commonly asked question when the term is referenced.
Hydro- excavation is the use of water under pressure, in conjunction with a vacuum, to excavate the earth. The use of the water to loosen the soil, and the suction to remove the broken down soil, has been developing for the last several years. Why is hydro excavating becoming especially popular? The fact that there are a tremendous amount of utilities located under our city streets, and more are being installed on a continual basis, is the reason . Anyone who has been involved with a power outage, sewer break, or gas explosion, will understand the importance of excavating carefully and non- destructively, in areas that have a high concentration of utilities. The gas explosions in NYC in recent years, have identified the need for a non destructive means of excavation around utilities and within the inner Cities. The difficulty in trying to excavate complex utility lines, that are nested together, under our streets, is becoming more and more dangerous especially as old utilities deteriorate and new utilities are installed.
The basic, hydro excavating piece of equipment, is simply a high pressure washer and vacuum assembly, mounted on a piece of equipment, which will allow movement as needed. In some instances, this could be on a truck chassis, in others; it can be a towable trailer.
The third aspect of the equipment, is the ability to store the excavated material in a tank or truck body, to enable disposal in an area that is remote from the point of excavation. In many cases the use of water to loosen the soil in an area of possible contaminated soil, will require that this material be removed from the construction site. This is one of the negative aspects of hydro excavation; normally the use of the excavated material cannot be used as backfill due to the introduction of water. This is where the use of an air excavation methodology could be the next wave of excavation technology. However, this technology is still in its infancy.
What are some of the common situations that would benefit by the use of a hydro excavator and the ability to loosen the soil with water and vacuum the slurry into a waiting truck?
1.) Daylighting . The term daylighting is the process of exposing utility lines of any kind to the daylight. Due to the inherent dangers of excavating around underground utilities, as well as the inability to actually observe the location of the underground utilities, the exposure of these utilities without dangerous destructive excavation is invaluable. Daylighting of utilities is the primary purpose of a hydro excavator. Theoretically, if you know where the utilities are, you will not damage or break them.
2.) Potholing. The term potholing is a process of exposing utility lines in specific spots along the utility route. For example, if a gas line is known to exist along a roadway, however its exact and specific location is not accurately known, a process of potholing will be performed. At specific distances along the assumed routing of the gas line, a hydro excavator will be used to excavate a small hole in the vicinity of the assumed underground gas line. This small excavation will be enlarged, only to determine the specific location of the utility line. Once the line has been exposed, or daylighted, the location will be accurately marked. Based on the specific location of each of the potholes and the utility exposure to the daylight, the gas line route between the points can be more accurately determined. Once this route is more positively determined, then standard excavation equipment can be used to excavate the remaining portion of the line.
3.) Broken utility. The use of hydro excavation to excavate for a broken utility, is a common application of the technique. If a waterline has been broken, and there is water exiting the line, the areas around the broken utility are wet and difficult to excavate. The use of a hydro excavator, due to its ability to vacuum the material into a vessel on a truck, is extremely efficient and successful.
4.) Difficult excavations. This is an extremely broad category, however, the proper use of a hydro excavator can facilitate the excavation in difficult conditions. For example, I have had the need to excavate on difficult and extreme hillside conditions. We were installing airport lighting on a hillside that exceeded 30 degrees in pitch. This hillside would not safely support a common excavator. The use of a hydro excavator allowed the excavator itself to be positioned at the top of the slope. Both the waterlines, as well as the vacuum hose, were accessed remotely, to the location of the excavation. Dependent upon the manufacturer of the hydro excavator, the use of the water and suction can be as far as 600 lineal feet away from the equipment. By utilizing a hydro excavator, the excavation which was a 4 foot by 20 foot deep cylindrical excavation, was accomplished in 4 hours. In addition, the excavated materials were vacuumed into the tank of the hydro excavator for removal to a disposal area. There was no need to stockpile the excavated material on the hillside, no need to double handle the material, and no requirement to reclaim the area around the excavation, due to the lack of any type of damage, made by the process.
5.) Low clearance excavations. In many instances, especially in renovation projects, the need to excavate utility trenches and additional foundation excavations must occur under a building, or within areas of very limited headroom. The use of a remote hydro excavator, on the exterior of the structure, and the maneuvering of only the waterlines and vacuum hoses under the structure, allows an economic and efficient means of excavation. In addition, the removal of this material is performed during the excavation operation due to the vacuuming into the holding tank on the truck.
6.) Underpinning applications. The term underpinning, references a process by which an existing foundation is stabilized, to allow an excavation alongside to be below the existing bottom of footing. An underpinning operation is a serious structural technique that requires specific excavation in a systematic manner. The use of a hydro excavator to perform this excavation is both efficient and economical. In addition, the lack of any type of trauma to the surrounding soil is beneficial to the requirement, not to disturb the surrounding earth.
7.) Material removal. The best way to explain this process is to describe a project where I used a hydro excavator to remove difficult to reach material. We had to replace the sand in a sand filtration system, within a water treatment facility. This sand had been contaminated and needed replacement. Although the top of the filtration beds were actually open to the daylight, the area of the plant did not allow easy access for mechanical equipment of any kind. Due to this difficulty, we decided to use a hydro excavator to remotely vacuum the sand from the filtration bed, into the tank on the hydro excavator. In this manner, we eliminated all of the coordination and difficulty in trying to maneuver excavation equipment into the plant to remove the material.
8.) Post hole digging . This is a basic reference to a technique to excavate a hole for a post or pole, such as a telephone pole. I have been on hydro excavators in the center of Washington DC, excavating for telephone poles, with extreme efficiency and economy. The ability to simply move along the side of the street and excavate as required, without the need for additional room for excavated materials or separate excavation equipment is extremely efficient. In addition, the safety aspect for pedestrians is important, there are no backhoes backing up, or working, and there are no open excavations, left without being covered. The use of a hydro excavator to excavate deep, cylindrical excavations is very efficient.
9.) Contaminated waste removal. The use of a hydro excavator to remove hazardous waste is another great method of utilizing the hydro excavating technology. The ability to vacuum material into a truck from a remote area, removes the issue of heavy equipment or dust producing apparatus from the operation.
10.) Excavation of frozen material. The use of a a hydro excavator to remove frozen earth is a very efficient method of digging through frost. The majority of hydro excavating equipment is equipped with a water heater that will heat the water used to breakdown the soil. This heated water will literally cut through frost and frozen material like a knife through butter. If you have ever experienced the frustration, time and money expended to excavate through frozen ground, you will understand the benefit of this feature.
Hydro excavating is an excavating technique that , unfortunately, will require a number of disasters to stimulate the need and ultimate use of this type of technology. What will be required to occur, is a compromised gas line or electrical transmission line, within a major City, to acknowledge to the industry that hydro excavating is a useful technique, and a practical means of non- destructive excavation. I have personally tried to promote the industry in the New England area with less than stellar results. I believe the entire construction industry must understand the following concepts regarding utility excavation, prior to the acceptance of hydro excavation as a legitimate technique for utility exposure.
- Utility excavation will continue to get more crowded and difficult as development throughout the United States continues to expand, and larger and more complicated projects are constructed.
- Inner City streets are becoming overly congested with utilities, both old and new.
- Demand for more advanced services, with more advanced technology, will demand that excavation time be reduced and safety increased.
- Skill level of equipment operators is on the decline, and the ability of the old and seasoned operators to feel their buckets as they carefully excavated for utilities, is becoming an obsolete skill.
- Additional gas lines and fiber optic transmission lines have increased the extent of hazardous and exceptionally important utilities which are installed underground. The demand to cluster more utilities within the same small areas, will continue to expand and their safe excavation will become more and more difficult.
- Deterioration of existing utilities as well as reduction in maintenance money to clean sewer and storm systems will increase the vulnerability of existing utilities and new utilities to compromise.
- Consumer demand for immediate service, and intolerance for utility disruption, will require quicker response times for excavation and repair.
- Competition will not allow mistakes, and tolerance for mistakes will erode regarding utility maintenance. The demand for new installations will grow as well as the need to excavate old and deteriorated existing lines .
- Cost for damaged utility repair is constantly increasing, and will continue to increase as more utilities are installed, and the demand for quicker and more efficient utility service increases.
- Population growth in Cities and urban areas is demanding a safer and more efficient method of utility excavation and daylighting.
- Liability issues will not allow the continuance of maverick excavators that feel they can touch and feel the utilities with their backhoes. This will not be tolerated as the exposure to liability increases.
Unfortunately I feel that the use of hydro excavating as a technology and legitimate means of excavation will need to be stimulated by issues that will compromise individual’s health and their pocketbook. There will have to be losses, both in life and property, to convince the industry that the hydro excavation technology is a legitimate and a logical means of utility excavation.
Currently the cost of hydro excavation is substantially higher than the standard means of excavation.
What do we mean by standard excavation techniques?
Standard excavation techniques, for utility excavation includes the use of mechanical equipment to perform the excavation of utilities. The infamous backhoe, whether a John Deere 450 or a small Ford Tractor attachment is considered a backhoe. No matter which piece of equipment is used, the use of a mechanical bucket to excavate very fragile and dangerous utilities, is a macho technique, that is extremely difficult to argue against, especially when that method of utility excavation is less than ½ the cost of performing the same excavation with a hydro excavator. Most experienced and very seasoned excavators, who have had their business for an eternity, and have probably inherited it from their fathers, who inherited it from their fathers, will very arrogantly indicate that they have never lost a gas line or a major electrical utility line.
This is probably accurate, for the time being.
However, what must be identified, is the potential for such a disaster to occur. Once is enough. I have personally witnessed, very severe construction disasters, that no one would have ever thought could occur. I was personally involved with a company that performed a technique called lift slabs. The industry, like the current excavation industry, laughed at the individuals that promoted safety, and tried to convince the construction industry that this type of construction needed to be controlled. It was not. The end result was a catastrophe call L’Ambiance Plaza in Bridgeport, Ct. This disaster claimed the lives of 28 construction workers on April 23, 1987, and ended in litigation that resulted in a total claim of 41 million dollars in damages.
I was a part of the lift slab industry, we had just completed several office structures in Rye New York using this same lift slab technique.
It was the best method since sliced bread, for the time being!
The point I am making, is that the use of hydro excavation, as the proper and most efficient technique for utility excavation, will only be firmly entrenched within the industry, when failure by the other proven techniques causes death and destruction, resulting in the loss of money and the inability to obtain any type of liability insurance.
Unfortunately the world is motivated by money, and until the use of hydro excavation can be PROVEN, by a savings in money, it will continue to be resisted.
Until the utility companies demand that the use of hydro, or even air excavation be used to excavate their utilities, it will not be done!
Hydro excavation is a technology that will be used and demanded
Unfortunately it will require the loss of life, property and money, to establish the technology, as the only proper and safe method of utility excavation.
Further research and investigation should be done, by you the consumer, to fully understand the benefits of using hydro excavation as a safe and legitimate technique for the excavation of complex utilities.