4 Common Reasons for Trenchless Rehabilitation In Your Neighborhood
Sewer rehabilitation, water line replacements, fiber optic installation and gas line repair are among the common reasons for trenchless rehabilitation in residential neighborhoods.
Trenchless construction is growing in popularity, especially in residential areas. Property owners find that using trenchless technology in their construction work costs less and can have greater turnaround time than traditional subterranean construction techniques. While there are many uses for trenchless rehabilitation, there are only a few reasons to use this method in a residential environment.
A city’s sewer network forms part of its essential infrastructure. As pipes age, they can deteriorate forming cracks, leading to leaks and an increased inflow and infiltration entering the sewage system. The problems increase during wet weather when excess rainwater flows into the broken sewer system.
Trenchless construction allows for crews to push new plumbing in place without the need for large construction holes. Property owners who need to replace sewage lines on their property can expect to see relatively small insertion and retrieval holes dug in the yard, which allow the technicians to insert the new pipe along with an expansion head to burst or push the old plumbing out. (Learn more in "An Introduction to Pipe Bursting.")
Crews performing city sewer system repairs may still see small holes on properties for insertion and retrieval. However, city crews will attempt to use manholes for at least the insertion aspect of the job. In the event teams choose to perform sliplining rehabilitation instead of pipe bursting, the use of manholes as an access point is not an option.
Sliplining is the insertion of a smaller diameter pipe placed as a liner inside the existing plumbing. Grouting between the two tubes prevents leaks. Due to the grouting methods and the necessity of the lining to run the entire length of the new pipe, manholes are not a viable insertion point.
Water Line Replacements
As with the sewage system, water lines and water mains can deteriorate over time. On residential properties, tree roots and other debris can pose a problem to these underground pipes. Residential property owners can benefit from using trenchless construction to repair or replace these faulty lines.
In most cases, workers use pneumatic boring to replace the damaged water line by using a piercing tool with compressed air to bore a small round tunnel underground. Workers then insert the new lines, connecting them using advanced connection methods. In this case, homeowners can expect one or two small holes on the property as insertion points for the new water lines. Unlike with traditional trenching construction, these holes only minimally disrupt landscaping.
In some cases, workers use horizontal directional drilling for water line replacement; there are no insertion or receiving pits involved in this method. Instead, a directional drill, which is controllable to move in any horizontal direction, is the tool of choice. This work takes place completely underground and has the benefit of being able to lay more than just water lines. While residential areas can use this technique, it is more common on commercial properties involving additional utilities.
Gas Line Repair
Gas leaks are a serious matter. While it might seem like digging up and replacing the damaged pipe is the only option, trenchless construction is a viable choice.
Unlike traditional gas line repairs, trenchless repair does not leave the gas line in use while the repairs take place. To turn off the gas line, locating the service tee is the first step. The service tee location may be underneath the homeowner’s yard, sidewalk, adjacent roadway, or another paved area. Access to the service tee does require digging a hole to expose the tee. However, with gas line replacement, this should be the only substantial hole. (Read on in "Why the Oil and Gas Pipeline Industries are Eyeing HDD.")
After exposing the tee, workers attach the new pipe to a splitter head that has a guide wire. While pulling the new pipe into place, the splitter head expands the old line. This expansion method allows the old line to stay in place as a protective sheath for the new pipe. In some cases, the old line is removed by the split head while installing the new line.
Leaving or replacing the old line depends on its overall condition, local environmental laws and contractor preference.
Fiberlink Cable Installation
As technology grows, consumers want faster, better ways to transmit data from place to place. Fiberlink cabling does that by sending information, via pulses of light that contain the data, from one location to another through fiber optics. Companies offering Internet services, or telephone services use these lines to deliver clear content fast.
Residential neighborhoods often see current cable and telephone lines replaced by Fiberlink cabling. To best protect the lines of the optical fiber, burial underground is the best method of installation.
In areas free of rocks with flat land, direct burial using a plowing technique is the best choice, which requires skill and careful feeding of the cable. In some instances, the plow operator rips the area before laying the cable. This technique pre-plows the ground in preparation for laying the cable. It is useful to help determine if there are underground obstacles.
However, some contractors may choose to use directional boring techniques to bury the cables especially in areas where the cable needs to go across shallow waterways or roads. Construction workers, however, must know the exact location of other buried utilities. If not, there is a risk of damaging these lines during the boring process.
Risks and Benefits
As with any pipe replacement project, there are risks. The greatest danger is an obstruction during drilling, which poses the most significant problem for micro-tunneling. However, in a residential setting, where the job is to replace existing pipe, this risk is minimal when compared to other trenchless construction jobs.
Environmental factors are also considered a risk. Some contractors opt to use Cured-in-Place-Pipe or CIPP. While the utilization of this piping has benefits, it can leak harmful chemicals into the surrounding soil. Some states, such as California, prohibit the usage of these types of components. (Learm more in "Why CIPP is Growing Rapidly for Drinking Water Mains.")
Pipe diameter can be a risk as well, as some forms of tunneling see pipe breakage after a particular diameter. In cases of horizontal directional drilling, pipes over 30 inches in diameter have a greater risk of damage. While residential areas seldom use directional drilling, micro-tunneling is inversely affected. The smaller lines have an increased risk of harm.
Although there are some risks, many benefits can outweigh them. For homeowners, the reduced amount of digging on the property is essential. For traditional repairs, the cost increases when adding the need to landscape the damaged areas. Trenchless construction minimizes, and, in some cases, eliminates that concern. The base cost, before landscaping, is also less. For traditional repairs, the cost can run between $80 and $250 per pipe foot. Trenchless repairs usually cost between $60 and $200 per foot.
Of course, one of the biggest benefits is the overall work time. Traditional replacement and repair can take days or even weeks if the project is large. Project completion for trenchless construction is within the same day usually.
- What are the most common causes of residential water or sewer disruption?
- How does a tunnel boring machine (TBM) control the subsidence of the ground above the trenchless installation?
- What is the role of bypass pumping and when is it used?
- Is shoring and other trenching safety methods required during trenchless construction?