DISCUSSION FORUM
No-dig carbon reduction advantageJun 2011
Pipe Jacking Association News Release
The non-disruptive advantages of the microtunnelling and pipe jacking alternatives to the trenched installation of utility pipelines has long been appreciated and promoted. Today there is the additional consideration of sustainability and reduction of the carbon footprint when selecting methods of infrastructure construction.
In this regard too, the microtunnelling and pipe jacking alternatives have the advantage. According to early appraisals, savings of up to 95% of carbon emissions are achievable by using no-dig microtunnelling and pipe jacking methods.
To help quantify the potential advantages, the Pipe Jacking Association (PJA) has commissioned TRL, the UK's leading independent centre for international transport research and consultancy, to develop a web-based greenhouse gas emissions (GHG) calculator that will enable designers and utility companies make early assessments of the carbon savings offered by the no-dig methods.
An initial scoping study will assess the processes that consume energy and contribute to emissions, including vehicle movements to and from site for equipment, construction materials and spoil. It will analyse site processes and operations and include clear process mapping and protocol development to facilitate data collection on the separate installation techniques. The data gathered will be analysed and translated into a web-based tool that can 'carbon footprint' utility installations at the design stage and make a comparison between open-cut and no-dig methods. It is anticipated that as a project progresses the tool will enable updated and accurate emissions data to be calculated though the input of key project parameters.
Table 1. Comparing the environmental aspects of open trench and pipe jacked sewer construction at two typical sewer diameters
600mm ID pipeline 4m deep, 100m length
1200mm ID pipeline 4m deep, 100m length
Aspect
Open trench
Trenchless
Open trench
Trenchless
Excavated width
1400mm (trench width)
760mm (OD of jacking pipe)
2350mm (trench width)
1450mm (OD of jacking pipe)
Reinstatement width
1700mm
None
2650mm
None
Excavated volume per metre of pipeline
6.1m3
0.5m3
10.28m3
1.65m3
Imported stone fill and coated stone per metre of pipeline
11.9 tonnes
None
18.27 tonnes
None
Number of 20 tonne lorry loads per 100m pipeline (muck away and imported stone)
136
8
220
21
Programme development will include reference to the Publicly Available Specification (PAS) 2050 -Assessing the Life Cycle Greenhouse Gas Emissions of Goods and Services, and the Inventory of Carbon and Energy (ICE) compiled by the University of Bath which are used extensively to assess the GHG impact of many materials and processes used throughout the construction industry. The calculator will be a significant enhancement on many calculators available in that the impact of traffic disruption and delays will also be taken into account.
Both TRL and the PJA would like to hear from any stakeholders who are interested in the project, particularly client organisations and those working on related initiatives, who might have useful data to contribute. Contact Matt Wayman at mwayman@trl.co.ukor by telephone on +44 (0) 1344 770472.
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