Are Construction Traffic Diversions Necessary for Trenchless Projects?

By Tabitha Mishra
Published: May 3, 2018 | Last updated: July 5, 2023
Key Takeaways

Traffic diversions are usually needed during conventional trenching construction projects, but during trenchless projects, minor diversions may still be needed to protect work crews.

Trenchless technology has gained popularity for many reasons, but the reason that makes it a sensation is its non-disruptive attribute. Trenchless construction methods such as horizontal directional drilling (HDD), horizontal auger boring (HAB), microtunneling, pipe ramming and pipe jacking are carried out with just two excavations, one at the launching site and the other at the receiving site.

Benefits of Trenchless Projects

Most trenchless rehabilitation projects do not require digging because they can easily be carried out from manholes.

The benefits offered by trenchless technology have inspired researchers to find even better ways to carry out subsurface construction work that leaves the surface relatively unscathed. This technology is here to stay, and it is just a matter of time before traditional open cut methods become a fact of history. Compared to trenching, trenchless methods:

Don't Require Construction Traffic Diversions

For most projects, traffic diversions are not necessary, however, in cases where the entrance pit is significantly closer to a roadway, a minor diversion may be used to protect the technicians working in the area. In this case, a Jersey barrier or K-rail is often used.

Reduce Energy and Financial Loss

Trenchless projects eliminate associated losses in terms of energy and economic losses to businesses in the vicinity. Since major roads are not blocked to carry out repairs and installations, businesses can continue to run their establishments without losing access to customers.

Drastically Reduce Noise

Noise, vibration and greenhouse gas emissions are significantly reduced using trenchless methods, as the roar of jackhammers and excavation crews are not present.

Eliminates Surface Disruption

Trenchless methods do not damage nearby structures, gardens, trees etc., therefore, the cost of repairing the unearthed sections is eliminated and landscaping costs are also reduced.

Utilizes Less Resources

Overall, the cost of trenchless projects is reduced due to the elimination of extra resources and crew. Excavators are not needed, less manual labor is required, so a smaller crew with technologically advanced equipment can carry out a repair faster and with less disruption. (Learn more in "Studies Claim the Trenchless Construction Cost Comparison is Massive.")

Trenchless technology in the pipeline industry is basically divided into two categories, trenchless construction and trenchless rehabilitation.

Trenchless Construction

Trenchless construction refers to the process of laying new pipelines under the earth’s surface without having to dig a trench as is still traditionally done to a certain extent. The route for the pipeline is first determined after conducting appropriate soil testing and geotechnical investigations.

Multiple surveys for the purpose of determining environmental and cultural sensitivity are carried out. If the pipeline project happens to require an entry/exit point or placing of men and machinery for a period of time on a private property, temporary easements are acquired from the owner. If, on the other hand, permanent structures such as valve chambers or block valve stations and manholes related to the project happen to fall on a private property, permanent easement contracts have to be acquired. (Read on in "Easement and Contract: The Legalities of Trenchless Projects.")

Planners get to work on setting out the pipeline route by carefully considering the above factors to minimize intrusion or disturbance to private owners. Potholing is carried out to confirm the existence of existing utility pipelines and service locations that pass through the proposed path in order to avoid cross boring. Other than these aspects, a trenchless project is invisible and unobtrusive to anyone on the surface. (Read "The Science of Getting it Right: Locating Underground Utilities.")

Trenchless construction requires the excavation of two pits – the entry pit for the purpose of aligning and launching the pipeline laying process, and the exit pit for the purpose of receiving the launched pipe. Once a project begins, entry and exit pits are marked and excavated for the sake of lowering equipment, machinery and men to the required grade and level for installing the pipeline. The area chosen for the excavations are cordoned off for safety reasons and do not require the closing of entire lanes and roads as in the case of open trenching.

Trenchless Rehabilitation

Trenchless rehabilitation refers to the process of repairing or replacing sections of old, worn out or damaged pipelines by using methods such as cured-in-place pipe (CIPP), sliplining, pipe ramming, mechanical spot repair and thermoformed pipe. These rehabilitation methods are carried out from manholes unless an excavation is required at an intermediate point.

The use of trenchless inspection methods makes it possible to locate problem areas without digging up the suspected problem pipeline. It also eliminates the danger of hitting electric cables and gas pipelines as has happened several times in the case of open trenching methods of repair.

The closed-circuit television (CCTV) camera, push rod camera etc. enable video inspection of the interior of an entire length of pipeline and also of laterals if required.

It is not an uncommon sight to see roads and lanes closed for the sake of rehabilitating pipelines where trenching is required to expose and inspect pipelines. Trenching requires construction traffic diversions because of the risk to pedestrians and vehicles. Trenchless rehabilitation methods at most require cordoning off the area around a manhole or two, to carry out the repair work.

Trenchless is Ideal for Cities

Cities are hubs of businesses, offices, leisure and residences. The maze of underground connections serving the people with electricity, telephone cables, and gas, water and sewer systems is a complicated system in itself. Any project requires utmost care while carrying out a new installation project or repairing an existing system because there is a danger of damaging existing utility lines which can cause contamination and serious injury in some cases. (See "Trenchless Installation of Utility Lines and Access Ports in Urban Areas.")

Thanks to guidance systems installed in trenchless construction equipment such as HDD, it is possible to maneuver through this maze without damaging surrounding utility lines. It is not only safe for the construction workers but also for people passing through the area because all the work is carried out underneath, out of sight. The sound pollution and vibration associated with trenching construction equipment has prompted contractors to opt for trenchless methods to minimize these effects and make cities more environmentally friendly. It has been observed in research studies that greenhouse gas emissions are reduced by over 90% in trenchless methods and up to 30% of cost-saving is achieved compared to open trenching methods.

No Construction Traffic Jams

Trenchless methods are not messy and do not create construction traffic jams because they do not require excavation of roads. Excavated earth piled up on street sides are an eyesore and sometimes smell offensive if a sewage line is struck by mistake.

Diverted construction traffic from these lanes affects businesses and productivity. This problem is completely eliminated if trenchless methods are employed. Thanks to trenchless methods, there is no need for diverting construction traffic.

Trenchless rehabilitation methods are cheaper for the customer as well as the contractor because the repairs are selective, can be carried out from entry points such as manholes, and do not disturb the property in any way. Trenchless construction methods are also cost-effective and eliminate the waste in time and cost that is involved in trenching of roads, and monetary losses to businesses in the area that ultimately affect a city’s economy.

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Written by Tabitha Mishra | Civil Engineer, Technical Content Writer

Tabitha Mishra

Tabitha has a Bachelors Degree in Civil Engineering from Mumbai University, India, and is currently freelancing as a technical content writer. Prior to writing, she has worked as a site engineer and site manager for various building construction, building rehabilitation, and real estate evaluation projects.

Tabitha is also certified as a Primavera project management professional and is well versed with Auto CAD. In her spare time, she does private consultation for small-sized home builders and assists with plans and permissions.

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