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Not only is trenchless works typically more time efficient than open cut alternatives, meaning that machinery is operated for shorter periods, but 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.

In addition, according to a study conducted for the North American Society for Trenchless Technology (NASTT) by the University of Waterloo, located in Ontario, Canada, it found that trenchless job sites produce fewer emissions.

They require minimal construction machinery and equipment as there is no need for excavation, compaction, backfilling and re-paving, dramatically reducing fuel consumption.

With the industry focused on preserving the environment and reducing emissions, the ASTT created a Carbon Calculator to promote innovation in the trenchless technology sector.

The purpose of the ASTT is to advance the science and practice of trenchless technology for the public benefit, while promoting education, training, study and research and practice for the public benefit and to publish the useful results of the same.

With this in mind, paralleled with the global goal of reducing carbon emissions, the ASTT formed a Special Interest Group (SIG) of leading industry professionals to create a solution that supports the mitigation of climate change impacts.

ASTT Councillor Matthew Boyle says the ASTT embarked to create a SIG to look at the impact trenchless technology has in reduction carbon generation in construction projects. “The SIG’s purpose was to provide members with access to a Carbon Calculator to quantify, and therefore promote, trenchless technology as a lower carbon emissions alternative to Excavate and Lay,” he says.

“The primary focus of the SIG was to provide members a tool to compare greenhouse gas emissions using comparative approaches in the capital delivery of services.”

As a result, the SIG approached the market for the development of the calculator and selected the Moata Carbon Portal from Mott MacDonald in August 2020.

At the time of release, it was the first carbon calculator capable of measuring the capital and operational carbon footprints of building information modelling (BIM) designed assets.

Boyle says following Mott MacDonald agreeing to be on board with the ASTT, the SIG moved into trial phase where asset owners were selected to use to the tools in their businesses for best use practices in Australia.

However, it was here where the process stalled and the use of the calculator in the trial was limited, little feedback was submitted, and the pandemic hitting Australia.

Boyle says the SIG has currently been suspended until further legislation and member support.

“We went with Mott McDonald because in New Zealand there is a legislative requirement to monitor carbon emissions, but until there is something in place like this in Australia, the SIG has come to a halt.”

In December 2021 the Australian Government released the June 2021 quarterly update of Australia’s National Greenhouse Gas Inventory.

Australia’s greenhouse gas emissions fell by 2.1 per cent in the year to June 2021, and have fallen by 20.4 per cent since 2005

Boyle says he sees the awareness of carbon emissions driving the trenchless community to look deeply into its supply chain to innovate and come up with new techniques and products to drive zero emissions further into the future.

“I see the specification of low emitting trenchless technology by asset owners and government organisations to be the standard across Australia and New Zealand,” he says. “I believe this will be backed up by legislation and the trenchless community will be well placed to help deliver on a low carbon future.”

With the trenchless community already doing its part to reduce emissions, Boyle says the rehabilitation process for overall asset installation can be measured, quantified, and improved into the future.

This is where the Carbon Calculator could demonstrate how the use of trenchless technology can reduce project carbon emissions.

“This is great evidence for asset owner members, contractor members and supplier members. It could also be used to see what part of the process emits more carbon, allowing innovation to occur to effect overall emission reduction,” Boyle says.

The ASTT says its Carbon Calculator is not to be relied on to make commercial decisions nor is it a tool that will accurately define Capital Carbon Baselines, noting that there is no specific, quantified carbon goal that the calculator aims to reach.

Rather, the tool will be used to promote best practices across the industry.

The three steps the calculator aims to take is:

1. Reduction – reduce the carbon impact of infrastructure.

2. Behaviours – improve the behaviours of designers, constructors, and entire supply chains to reduce infrastructure carbon.

3. Union – create a common way of working to calculate carbon reductions across the industry, setting the narrative.

Boyle says with the ASTT’s overall goal being to advance the science and practice of trenchless technology for the public benefit and to promote education, training, study and research and practice for the public benefit, it is hoped the calculator will be used on individual projects and tested across various areas, with the onus on contractors and client organisations to use the tool and consider their own impacts.

“With this as our goal, we will support all measures that our members are taking to reduce emissions and promote to educate the greater community into the advancements and benefits of trenchless technology,” he says.

Aussie Trenchless’s SRP EXP Spiral Lining System is designed to rehabilitate pipes from DN150 to DN1200 using a selection of six different sized profiles.

The SRP EXP sizes range from a profile type E7-050-5 for DN150 to DN250 pipes, E9-085-6 for DN300 to DN450 pipes, E14-085-6 for DN375 to DN600 pipes, E20-085-6 for DN600 to DN900 pipes.

Wastewater and sewer pipeline networks are under stress, as time goes by, underground pipeline networks continue to age and breakdown, with repairs using traditional civil open cut methods being far too costly and disruptive on communities.

Aussie Trenchless director Chris Meredith says trenchless rehabilitation techniques continue to grow in volume as they are a cost-effective repair solution.

“The SRP EXP Spiral Lining System can be installed under flow conditions, with no by-pass pumping needed it is quick and efficient using a third-generation high quality profile to ensure ease of installation, providing a value-added outcome for the network owners,” he says.

The SRP EXP Winding Unit and Cages are a standard design. Each winding unit supplied is the same, the cages vary in diameter to suit the underground pipe size and all parts that make up the cages are standard and interchangeable on some cage sizes.

If a client requires a special diameter cage outside of the SRP EXP product range, Meredith says the company can design and supply it.

“I am looking forward to No-Dig Down Under in June this year where we will be displaying our equipment and technologies for the first time in two years following the pandemic,” he says.

“It will be good to see a wide range of trenchless products and services on offer. From construction tools like drilling and micro tunnelling rigs, to location and mapping services, with many and varied lining systems and products.

“In general, all agree that the trenchless industry is in good shape. The industry has solutions for most underground issues to ensure the above ground footprint and disruption is minimised during a trenchless installation.”    

Spiral lining is now available to all trenchless rehabilitation contractors in Australia and overseas through Aussie Trenchless.

Meredith says it is no longer benefiting the special few, with the spiral lining market now continuing to increase due to its availability, versatility, and competitiveness.

It can be installed under flow conditions, used in a wide range of pipe sizes, it has expanding tight fitting profiles and fixed diameter profiles with a grouted annulus gap.

“Spiral Lining profiles will continue to advance, with improved installation techniques and site application as a wide range of contractors become involved in spiral installations,” he says.

For more information visit Aussie Trenchless. 

If the pumps are down, the drilling stops

In the Australian HDD sector there is a limited number of available maxi-rigs and powerful mud pumps. Having ready access to additional maxi-rigs and powerful mud pumps is a key means to maintaining project productivity and mitigating the impact of unscheduled repairs. If the pumps are down, the drilling stops.

Mud pressure is lost as it moves through the surface piping and a lot more as it moves down the drill string. Most of the pressure is expended in a jet stream at the drill bit and as it passes through the stages of a downhole motor if being used. At this point the mud pump needs to provide additional pressure to push the mud back along the annulus to the surface, while maintaining an operational long term duty cycle.

It is also important that the mud pump is sized appropriately to adequately cope with the volumes of drilling fluid required and to maintain adequate annular velocity in the borehole to ensure cuttings remain in suspension in the drilling fluid until the fluid exits the borehole.

The capacity of the mud pumps is commonly misunderstood and misrepresented. It is common for people to promote their mud pumps as having a 500gpm (1,892lpm) capacity and a 500 psi pressure rating. While both numbers may be on the spec sheet, promoting the pumps as a 500 gpm pump at 5000 psi is almost certainly incorrect.

For example:

A common HDD pump such as the EWECO 446 – a good all-round pump for smaller projects – is often quoted as having an output of 56 5gpm with pressure rating of 5000 psi. While both numbers are true, they are not true together.

The spec sheets show that the pump will do 565 gpm at 1200 psi at 440 rpm max with 6-inch diameter liners.

Or, if the liners are changed to 3-inch diameter, the pump will output 5000 psi, but even at a max of 440 rpm, the flow output is only 141 gpm.

For a long duration longevity on a project, it is good drilling practice to limit the operation to 60 per cent – 70 per cent of the capacity, particularly pressure capacity.

Assuming for small HDD projects where flow is more important than pressure, the minimum pump in the example above with the largest liners which should be considered is a 565 gpm x 65 per cent = 367gpm pump. Applying the same logic to the pressure rating 1200 psi x 65 per cent = 780 psi

While there are many contributing factors to pressure such as choke points, valves, drill pipe joint ID, pipe internal roughness, jet nozzle diameter and number to name a few, it would not be uncommon to see 500psi of pressure on a 1000 m jetting hole running 3 x #16 jets at a flow rate of 360 gpm flow rate.

If a downhole motor forms part of the bottomhole assembly (BHA) where the formation is rock, it would not be unreasonable to add 150 – 200 psi to the pressure to operate the motor effectively on bottom i.e. 200 psi + 500 psi =700psi. For long term operation, the pump is effectively at maximum capacity.

In general terms, additional pumps can be coupled together to increase flow rate but not increase pressure.

A longer bore or a higher flow motor would break a single pump in a short time. Double pumps don’t provide additional pressure.

To solve the problem, the pump liner diameter must be reduced, which in turn increases pressure output but decreases flow output. So to drill a longer bore (>1500 m) with large downhole motors (>8-inch), triple or quadruple pumps would be required to provided operational longevity.

Or get bigger pumps

Maxibor has a fleet four of the largest pumps in the HDD industry: two Gardner Denver PZ9 pumps with 1000 HP engines and two Gardner Denver PZ8 pumps with 750 HP engines. 

These are 100 per cent duty rated oil well servicing pumps, primarily due to the low-speed design (130 rpm stroke rate compared to the 440 rpm in the previous example).

They have proven project after project to operate at high flow AND high pressure all day every day for months on end.

From an HDD perspective, dual PZ 8 / 9 pumps have delivered bores in Australia at lengths of 2,500 m in the civil industry and at lengths of 4,000 m in the gas drainage industry.

These pumps allow very long bores to be drilled to solve infrastructure installation challenges or they allow forward motor reaming. This is another technique to solve particular requirements where exit site sensitivities exist, or it is not possible to drill a mud return line. It is these types of pumps that allow high-performance, cutting-edge HDD bore designs to be achieved.

Pumps of this capacity are invaluable, if not a prerequisite, on long bore (+1000 m) and large diameter hole (+800 mm) projects requiring larger maxi-rigs such as the Gallagher 660e, Gallagher 600, American Auger 660 and the Vermeer D330x500, which are a key part of the Maxibor HDD fleet. They are most often required in Australia on river and harbour crossings and long and deep water and sewer projects.

Maxibor will be using its Gardner Denver mud pumps on two landmark projects requiring a total of seven bores each averaging over 2.2 km in length. Availability of the pumps has been one of the key factors in the selection of Maxibor as the HDD provider on these projects.    

A HDD provider like Maxibor, with its sizeable fleet of powerful pumps and maxi and other rigs, provides added comfort to project stakeholders that these key plant items will be available to enable the construction schedule to be maintained.

For more information visit Maxibor’s website.