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Useful Definitions

Auger Boring is technique for forming a bore from a drive pit to a reception pit, by means of a rotating cutting head. Spoil is removed back to the drive shaft by helically wound auger flights rotating in a steel casing.

Pipe Ramming is a non-steerable system of forming a bore by driving an open-ended steel casing using a percussive hammer from a drive pit. The soil may be removed from the casing using multiple methods.

Moling and Piercing generally require minimum excavation and are typically used as forms of online replacement, breaking aside the existing piping fabric and pulling through a new structural lining.

Pilot Tube is a multi-staged method of accurately installing a product pipe by use of a guided pilot tube and followed by an upsized product pipe.

Guided Boring is a method for the installation of pipes, conduits and cables using a surface-launched drilling rig. A pilot bore is drilled using a rotating drill string and is then enlarged by a back reamer to the size required for the product pipe.

Horizontal Directional Drilling (HDD) is a steerable trenchless construction system for the installation of pipes, conduits and cables in a shallow arc using a surface launched drilling rig. Traditionally, the term applies to large scale crossings of waterways or highways in which a fluid-filled pilot bore is drilled and is then enlarged by back reaming to the size required for the new inserted product piping.  This trenchless methodology has been successful used for installations of 700 to 7,500 feet depending on the size of the drilling rig and the site conditions.

Microtunneling is a trenchless construction method for installing pipelines by remote control or steerable laser controlled evacuation tunneling.  Developed in the 1970’s, Microtunneling uses a microtunnel boring machine (MTBM) which is operated from the surface without operator entry.  Piping is simultaneously installed as spoil is excavated and removed.  The laser guidance system can usually achieve the high degrees of accuracy required for gravity sewer line and grade.  Microtunneling machines are readily available to drive approximately 3,000 feet.

Pipe Jacking is a trenchless construction method usually applied to the smaller diameter of microtunneling.  Hydraulic jacks are utilized to push specially designed piping from as excavation is occurring.  The finished product is a watertight and structural sound pipe usually with short lengths and with specialized joints.  A cost effective alternative to traditional excavation, Pipe Jacking is most often used for tunneling under highways or railways.

Pipe Bursting is a technique for breaking existing pipe by fracture using applied mechanically force from within.  The pipe remains are forced into the surrounding ground by this action.  At the same time, a new pipe of the same or larger diameter is drawn in behind the bursting tool.

Sliplining is the insertion of new piping inside larger existing buried pipe and is often referred to as the grand-daddy of trenchless.  Generally, the host pipe must be cleaned before a segmented or continuous pipe is inserted either by pushing or pulling.  Grouting of the annular space is often recommended.

Spiral Lining is where a ribbed plastic strip is mechanically spirally wound to form a liner which is inserted into a defective pipeline. The annular space may be grouted or the spiral liner expanded to reduce the annulus and form a close-fitting installation.

Spot Repairs are repair work on storm and sanitary sewer piping at specific points between manholes.  Spot repairs can produce considerable savings fixing only what needs to be fixed rather than an entire length of sewer.

Grout in Place Lining Systems are designed to fill the annular space between the host pipe and the carrier pipe.  Grouting is also used to fill the space around laterals and between the new pipe and manholes.

Manhole Rehabilitation is the process of repairing an existing structure without excavation.  Numerous methods are commonly used such as a cured in place fitted liners; chemical grouting; hydraulically applied cement; etc.

Cured In Place Pipe is a trenchless or low dig rehabilitation technique whereby a flexible thermoset resin-impregnated sleeve or tube of polymer or glass fiber fabric is installed into an existing pipe, expanded by means of fluid pressure and then cured to a hard finish assuming the shape of the host pipe. Aggressive cleaning of the host pipe is required prior to insertion. Robotic systems are utilized to reopen any connections. Structural CIPP products are available for both pressurized and non-pressurized infrastructure.

Lateral Lining is accomplished by utilizing an inverted fabric bladder. Epoxy resins are impregnated into the tubing which is then inflated before the resin is cured. Curing can be via ambient temperatures or with steam. Lining can ensure a sound structural repair with no root intrusion or no leakage. This is an inexpensive, fast and non-intrusive technology that can resolve mayor infrastructure problems in mature urban areas.

Spray-on Systems are non-structural applications. Benefits include improved hydraulics and water quality plus, prevention of future corrosion. No excavation is required at service connections and long installations lengths are possible. Piping usually needs to be clean and dry before lining.

Tight Fit Systems have been utilized since the early 1980's and thousands of miles have been successfully installed worldwide. This technology generally uses a high density polyethylene liner from 2" to 48" in diameter with section lengths averaging 2 to 5,000 ft. Utilizing pits; the liner is winched into the cleaned host pipe through a mechanic reduction system. Once tension is released, the inserted liner expands to the host pipe.

-- Trenchless Technology Article --
Trenchless offers a sustainable option for a wide range of underground infrastructure projects. From the construction of interstate oil and gas pipelines, to sewer rehabilitation in high density urban areas, trenchless techniques can offer tangible environmental benefits. Here, we overview the ‘green’ potential of No-Dig, and survey several environmentally friendly trenchless projects around the world.
There are a number of reasons why Trenchless Technology is a sustainable and green alternative. In urban areas, trenchless reduces the carbon emissions generated from construction works, minimising both machinery use and traffic disruption.
No-Dig also protects natural environments – trees and root systems are usually unaffected, while it also avoids disturbing the habitat of local fauna. On pipeline projects, horizontal directional drilling (HDD) and microtunnelling can also be used to preserve fragile ecosystems such as coastal areas and wetlands, avoiding the disruption and damage caused by excavation.
--Sustainable cities
Sewer rehabilitation and replacement is a growing industry throughout the world, as existing water and wastewater infrastructure deteriorates due to age, corrosion and the demands of a growing population.
 --Cutting carbon emissions
Traditional open cut methods and equipment for the installation and replacement of underground infrastructure can be highly polluting. According to trenchless specialist and ISTT Chairman Dr Sam Ariaratnam “The construction industry, which consumes a large quantity of fossil fuels, has been tasked with reducing airborne emissions.
“Recognition of the urgency to curb emissions worldwide has led to an increase in research efforts aimed at developing methods to quantify and reduce emissions.”
Recent research has demonstrated that trenchless projects produce substantially fewer carbon emissions. A study conducted for the North American Society for Trenchless Technology (NASTT) by the University of Waterloo, located in Ontario, Canada, identified two areas in which a trenchless approach is more environmentally friendly than conventional open cut techniques.
First, traffic fuel consumption is lowered by trenchless methods. By avoiding traffic disruptions, trenchless projects prevent the delays and detours associated with conventional underground infrastructure projects. This lowers the amount of petrol consumed, and subsequently reduces carbon emissions. Fewer traffic delays also create social benefits, increasing the liveability of cities and minimising disruption to residents.
Second, trenchless job sites produce fewer emissions. They require minimal construction machinery and equipment as there is no need for excavation, compaction, back-filling and re-paving, dramatically reducing fuel consumption.
“The use of multiple construction equipment during open-cut construction invariably results in considerably more emissions in the atmosphere compared to employing trenchless methods, which have minimal on-site requirements,” said Dr Ariaratnam.
Also, trenchless works are typically more time efficient than open cut alternatives, meaning that machinery is operated for shorter periods. Dr Ariaratnam compared the use of pipe bursting versus open cut for a typical urban sewer rehabilitation project, and found that the pipe bursting took three days while open cut took seven days. The No-Dig approach, therefore, was over 50 per cent more time efficient.
Through these combined environmental benefits, Dr Ariaratnam’s study found that trenchless construction methods resulted in 79 per cent lower greenhouse gas emissions than open cut pipeline installation.
--No-Dig = no pollution
As well as reducing carbon emissions, Yeun J. Jung and Sunil K. Sinha have demonstrated that trenchless projects also avoid other forms of pollution typical of open-cut projects.
Contaminated soil is often discovered during open-cut pipeline construction, requiring specialised and costly disposal. In addition, rain and water created during open-cut construction can cause soil erosion and contaminated soils run-off, polluting streams, rivers and sewers. By only creating minimal surface disruption, trenchless projects avoid these environmental pitfalls.
Trenchless job sites also lack the dust caused by excavation, which can create air pollution and have a detrimental effect on the health of workers and residents.
Finally, the machinery required on open-cut job sites can create noise pollution in the surrounding environment, disturbing residents, schools, hospitals and businesses. With less machinery, No-Dig is a far quieter and less disruptive process.
--Maintaining existing infrastructure
Finally, avoiding excavation also prevents damage to adjacent structures, and therefore reduces the environmental and economic costs of replacing this infrastructure. Isabel Tardiff from the Centre for Expertise and Research on Infrastructure in Urban Areas in Montreal, Canada, cites research which indicates that trenching near a paved surface will diminish its lifespan by at least 30 per cent.
Also, as Dr Mohammed Nafaji and Dr Sanjiv Gokhale note in their reference guide to Trenchless Technology, during construction, the use of detoured roads not designed to take heavy traffic results in damage to the pavement structure.
“The heavy traffic decreases the life span of detoured road, which is an additional cost to municipalities and local governments,” Dr Nafaji and Dr Gokhale said.
--Calculating the benefits
Trenchless industry representatives are working to identify and quantify the ecological advantages of selecting trenchless techniques, which can assist suppliers and contractors in arguing for a certain technology.
For example, Dr Ariaratnam has introduced a commercially-available emissions calculator, known as eCalc, which has been developed to enable the comparison of the environmental impact of different utility installation methods.
“Now we actually have a way of calculating the sustainable solution,” said Dr Ariaratnam.
Developed by Arizona State University and Vermeer Corporation to aid stakeholders in calculating anticipated emissions from competing technology options, as of early 2009 eCalc had been successfully used on twelve projects and four different utility construction methods.
A similar Greenhouse Gas (GHG) calculator was also developed in 2007 by the British Columbia Chapter of the NASTT (NASTT-BC). In 2010, the NASTT-BC, with the assistance of Vancouver-based PW Trenchless Construction, released an upgraded Carbon Calculator designed by Habitat Enterprises of Vancouver, which is freely available for use on the branch website.
This device has indicated that, on average, Trenchless Technology produces 90 per cent fewer GHG emissions than open cut excavations, and can provide overall cost savings of 25–50 per cent.
--Protecting heritage trees
Trenchless can also play an important role in protecting historically and environmentally significant trees located in urban parks and gardens.
A major sewer replacement project at the Royal Botanic Gardens in London, UK, avoided tree root damage through the careful use of Trenchless Technology by Perco Engineering Services Ltd.
The project involved the installation of 160 m of 9 inch diameter pipe to expand the public facilities at these internationally renowned gardens.
“It was essential to avoid damage to the root systems of trees with scientific and historic value. An open cut method would have carried the risk of damage that Kew Gardens could not accept,” Dr Nafaji and Dr Gokhale said.
Perco worked according to the guidelines issued by the National Joint Utilities Group (NJUG) regarding the installation and maintenance of services close to trees, and only trenchless techniques were found to fulfil the high standards required by the NJUG.
The pipe bursting technique used by Perco avoided the need for excavation and only used existing manholes for access, thus guaranteeing tree safety. The pipebursting technique was employed to expand the existing 6 inch sewer, jacking a powerful expanding mole through the existing pipe, while 790 mm sections of segmental pipes were jacked into the existing annulus. These sections were then joined with an ethylene-propylene-diene-monomer (EPDM) rubber O-ring seals.
At ground level, it was impossible to detect that the pipe bursting was occurring beneath the surface. The royal opening of a new conservatory even took place in the midst of the project.
--Trenchless – the international choice
The use of trenchless techniques to reduce the environmental impact of pipeline projects is also a noticeable international trend.
--Trinidad and Tobago
For instance, the National Gas Company of Trinidad and Tobago is using HDD in the construction of a new offshore gas pipeline. The North – Eastern Offshore (NEO) pipeline will transport natural gas from the Angostura Field, located off the northeastern coast of Trinidad, to the New Abyssinia Accumulator Station, then on to the existing domestic gas distribution network.
The 93.5 km, 36 inch diameter pipeline will be composed of an 83 km offshore section, running from the Angostura Field to landfall at Mayaro Bay, as well as a 10.5 km onshore section which will traverse the remaining distance to the Accumulator Station. HDD will be used to install the landfall section of the pipe, to prevent cutting through the coastline and thereby minimise disruption to this sensitive environment. In addition, only water-based environmentally friendly bentonite will be used.
Similarly, HDD has been used by Gazprom to install sections of the Dzhubga – Lazarevskove – Sochi gas pipeline in Russia. The 177 km pipeline is intended to secure energy supplies to the mountain resort of Sochi and Olympic facilities under construction, and runs along the Black Sea to the Kudepsta gas distribution station near Sochi, with landfalls near Dzhubga, Tuapse, Kudepsta and Novomikhailovskove.
The Black Sea coast is part of the Sochi National Park and one of the most carefully conserved ecosystems in Russia. To avoid harming local wildlife, pipeline installation was scheduled to take into account the life cycle of native fauna. HDD was used to install the shore approaches near Tuapse and Kudepsta, further minimising disruption to this fragile coastal environment. According to a Gazprom spokesperson, this is the first time that HDD has been used in a shore approach in Russia.
The use of HDD not only helped preserve the coastal ecosystem, but also allowed the pipe to negotiate the steep coastal cliffs. Microtunnelling was also used to install the pipeline at all river crossings, which offered further environmental protection.
While making the project more expensive, these various environmental protection measures were considered by Gazprom to be more than worthwhile, and a company spokesperson reported that all works were conducted without impacting the surrounding landscape.
--Green award winner
The environmental benefits of trenchless are also being recognised by leading industry bodies.
At the 2008 ISTT International No-Dig awards, the Trenchless Project of the Year was selected for its innovative use of HDD to preserve an internationally renowned coastal ecosystem. The Strangford Lough Marine Turbine Cable in Northern Ireland is the world’s first commercial scale tidal energy system. Developed by Marine Current Turbine, the system was designed to generate 1.2 MW of energy – enough to supply electricity to 1,000 homes.
In addition to the engineering challenges inherent in such a ground-breaking project, the developers were faced with the daunting task of installing a high voltage power export cable in the protected wetland and intertidal environment of Strangford Lough. The Lough supports 75,000 migrating waders and wildfowl, colonies of breeding terns, Common and Grey seals, otters, porpoises, basking sharks, conger eels, octopodes, oysters, mussels and a giant leather backed turtle. It is a designated Special Area of Conservation, an Area of Outstanding Natural Beauty, a Ramsar Site, a National Nature Reserve, a Special Protection Area, a Marine Nature Reserve and a Site of Special Scientific Interest.
HDD was decided to be the best installation method for this fragile ecosystem, and Marine Current Turbines contracted Longbore TT to drill a bore deep into the bedrock. Longbore TT’s DD-140 rig and closed-loop fluids recycling system was rigged up on a purpose-built pad laid with pond liner to protect the ground from fluid spills. The top soil stripped from the site was used to form an acoustic barrier between the drilling operation and the foreshore, to minimise the disturbance to the seals.
In recognition of this outstanding example of environmental protection, Longbore TT was awarded the prize for New Installation (Small Project) at the UKSTT 2008 Awards Dinner. It then went on to win Trenchless Project of the Year at the 2008 ISTT Awards.
The ISTT said that the project “clearly demonstrates the environmental benefits of using directional drilling to cross one of the most sensitive marine environments in the world.
“Marine Renewable Energy Systems are helping to save the world’s resources and solve the planet’s energy supply problems. HDD makes a significant contribution to their objectives.”
Trenchless techniques reduce traffic congestion and minimise the excavation required, reducing energy consumption.
Meanwhile, marine environments, bushland and other waterways, not to mention landscaped gardens and yards, can all benefit from the ongoing promotion of the various innovative trenchless solutions.
--Green energy with No-Dig
Australian energy companies are increasingly concerned with reducing the environmental impact of large infrastructure projects. As a result, a large number of pipeline projects and LNG projects are currently avoiding surface disruption in environmentally sensitive areas through the use of trenchless installation techniques, such as HDD and microtunnelling.
--Gorgon LNG
Contractors working on the Gorgon LNG project will protect the pristine West Australian coast by drilling landfalls with HDD. The project includes the drilling of shore crossings to connect the upstream facilities for the Gorgon project to the onshore infrastructure on Barrow Island, located off the coast of northern Western Australia. AJ Lucas has been contracted to construct nine HDD landfalls: eight for gas flow lines and umbilical connections and one ‘water-wining’ hole to bring ashore the water needed for drilling fluid.
It is imperative that the project has minimal environmental impact as the landfalls come ashore under North Whites Beach, one of the principal rookeries for the green turtle (Chelonia mydas), which has a conservation status of vulnerable. Consequently, AJ Lucas ordered two new Herrenknecht HDD rigs, along with two new custom-built Brandt mud systems and five new Gardner-Denver PZ8 mudpumps. The equipment will be made soundproof and the site carefully designed to reduce the impact on local fauna and marine life.
--Australia Pacific LNG
HDD will also be used on the Australia Pacific LNG (APLNG) project in Queensland. The project includes the construction of a 42 inch diameter gas transmission pipeline from the Surat and Bowen basins to a proposed LNG processing site located at Laird Point on Curtis Island, Gladstone. Beginning east of Wandoan, the main pipeline extends 362 km north, veering east during the latter stages, with a marine crossing at The Narrows to arrive at the LNG facility.
In the project’s recently released Environmental Impact Statement, HDD was outlined as the preferred method for crossing the marine section of The Narrows, as it will limit potential impacts to the shoreline construction area, where workspace is required to set up the drilling rig and pipe-string.
The pipe will be pulled into place through the hole drilled under the sea bed, and tied into the rest of the pipeline, or capped, awaiting the tie-in.
--Desalination goes green
A number of desalination projects have been constructed or are in planning to secure water supplies across Australia. As the projects tend to be located in environmentally sensitive coastal areas, Trenchless Technology has been used when installing come components of the projects.
The $A1.2 billion Gold Coast Desalination Project is the first large scale water desalination plant on Australia’s eastern seaboard, having the capacity to provide up to 133 ML/d of water to southeast Queensland.
Trenchless Technology was used in two of the project areas. Tunnel boring machines were used for the construction of the marine intake and outfall tunnels, while microtunnel machines were used for the construction of road and creek crossings on the network pipeline.
In the case of marine tunnels, Trenchless Technology was chosen after a risk assessment process ascertained that microtunnelling would minimise the environment impact on the beach zone and remove potential damage from severe storms.
The marine tunnel works consisted of two tunnels, both with an outside diameter of 3.2 m lined with concrete segments providing an internal diameter of 2.8 m. The intake tunnel is 2.2 km long while the outlet tunnel is 2 km long. John Holland completed the marine tunnels using Herrenknecht machines and some Herrenknecht personnel.
Similarly, microtunnelling was used on the installation of pipelines associated with Sydney’s desalination plant. The southern shore of Botany Bay contains extensive seagrass beds, which are a valued and protected part of the estuarine environment.
Trenching through these seagrass beds would have required a seagrass management plan to be implemented during and after construction, and a compensatory seagrass package involving transplantation. Instead, Sydney Water selected microtunnelling for the Silver Beach construction area under Botany Bay for a distance of about 800 m in order to protect the seagrass.
--Water and wastewater silver lining
Trenchless Technology is also being used in the management and construction of traditional water and wastewater pipelines and projects.
Mardi–Mangrove Link Project Work commenced in February on the HDD installation of a 260 m section of pipe under Wyong River as part of the Mardi-Mangrove Link Project, located in New South Wales. Mardi–Mangrove Link Project Director Greg McDonald said “HDD allows us to cross the river with less need to disrupt the local environment. This site has a significant stand of trees, animal burrows in the river banks and a billabong on one side." Keeping Sydney green
Sydney Water has also highlighted the benefits of using Trenchless Technology in its efforts to reduce waste and minimise the environmental impact of its operations. In its 2010 Annual Report, Sydney Water said it continues to reduce the amount of waste it produces by using innovative measures to cut down the need for excavation.
“Relining old sewers, rather than excavating and replacing pipes, has prevented about 6,000 tonnes of potential waste generation.
“Trenchless excavation methods are significantly reducing waste generation in water delivery network renewal projects,” Sydney Water said.
Sydney Water also enlisted some HDD assistance as part of its Sewerfix Wet Weather Alliance (SWWA) Wet Weather Overflow Abatement Program.
UEA completed a 1,403 m horizontal directional drill of 500 mm HDPE from Brightmore Reserve in Cremorne for the SWWA as part of the Eaton Street Wet Weather Storage Facility (WWSF) in Neutral Bay, on the north shore of Sydney Harbour.
Primarily targeted at swimming sites, the program will provide benefits to the environment and human health, and is part of Sydney Water’s long-term SewerFix program of sewage system improvements.
Prior to this project, (diluted) sewage was discharged to Sydney Harbour via two overflows on the Mosman Submain approximately 185 times in ten years. The Eaton Street WWSF reduces this frequency to the catchment target frequency of 20 spills in ten years.
Trenchless techniques reduce traffic congestion and minimise the excavation required, reducing energy consumption.
Meanwhile, marine environments, bushland and other waterways can all benefit from the ongoing promotion of the various innovative trenchless solutions.
In Australia, the trenchless industry needs to take advantage of the move towards sustainable construction practises and promote these greener credentials to governments and the community at large.