Research sponsored by the UK’s Pipejacking Association (PJA) and delivered by Transport Research Laboratory (TRL) shows that savings of up to 75 per cent in carbon emissions can be demonstrated comparing trenchless pipe placement to open cut. The method uses a new web based carbon calculator: www.pipejackingco2calculator.

com which was launched in mid-2013 and evaluates the carbon footprint of pipejacking or microtunnelling compared to open cut placement of sewers and other utilities in urban highways. "This level of savings in carbon emissions was achieved by comparing the installation of 500m of 600mm pipeline, 6 metres deep, using non-disruptive techniques with open-cut construction," says Brian Ashton, chairman, Pipe Jacking Association and director, DCT Civil Engineering. "In this comparison the saving equates to more than 370t of carbon emissions. In addition, the construction period for the trenchless installation was projected to be less than half that of the open-cut construction. At shallower depths carbon savings are more typically in the range of 50 to 60 per cent."

The comparison tool has been developed by TRL and is the third carbon calculator that it has produced to date. Previous projects were conducted for government supported recycling body WRAP comparing primary with recycled aggregate; and creation of the asphalt pavement embodied carbon tool (asPECT) which calculates the carbon footprint of asphalt . "It took just over a year to develop the new calculator," says TRL project manager Matthew Wayman. Wayman is an expert in carbon footprinting based on life cycle assessment. "It is really data intensive so getting all of the required information was quite a task and it required some software development to create the web application."

The tool can compare all kinds of pipe materials in all ground conditions. Data for the calculator has been drawn from a number of authoritative sources that include the University of Bath’s Inventory of Carbon and Energy for construction materials, the Concrete Pipeline Systems Association, and outputs from the Department for Transport’s QUADRO program (Queues and Delays at Roadworks) also developed by TRL. To complement these data sources the calculator uses a range of datasets that were developed by PJA engineers to enable the application to calculate carbon emissions.

These include:

  • Comprehensive materials schedule for all pipe diameters from 200 – 2400mm to include manholes, shafts, base slabs and all other components that impact on carbon emissions
  • Plant schedules for both scenarios together with energy Usage
  • Machinery selection for all diameters in differing ground conditions, using both slurry and dry techniques
  • Project duration – realistic outputs and daily hours worked
  • Average haulage distances for plant and materials

Reports can be produced that not only provide comparative emissions data for open-cut and non-disruptive options, they also detail data sources and assumptions utilised in the calculations.

The carbon dioxide emissions calculator is free to use and has been verified by WRc plc. The PJA says that the new tool will add further pressure to utility companies to consider non-disruptive alternatives at design stage to mitigate carbon emission under their statutory obligations. These obligations include the CRC Energy Efficiency Scheme and Environmental Key Performance Indicators which form part of the Government’s commitment to reduce carbon emissions by 80 per cent on 1990 levels by 2050. The Department of Energy & Climate Change’s CRC Energy Efficiency Scheme (formerly Carbon Reduction Commitment) is a mandatory scheme aimed at improving energy efficiency and cutting emissions in large public and private sector organisations that are responsible for around 10 per cent of the UK’s emissions.

Development of the tool was inspired by earlier work in the US which had been put on hold. The North American Society for Trenchless Technology (NASTT), in association with the Action on Climate Change Team (ACT) of Simon Fraser University in British Columbia had been developing a similar carbon calculator.

The project was then transferred to NYSEARCH, a New York based research group that works on behalf of North American gas and water utilities and the project was then put on hold. As a result the Pipe Jacking Association decided to sponsor a new tool.

In developing the calculator the PJA established key parameters for the project. These parameters being, that it should be easy to use, transparent, comprehensive, authoritative and verified.

The PJA believes that by using TRL, an international consultancy well versed in all aspects of transport, as contractor, and WRc to verify its integrity and performance, these parameters have been more than adequately met.