PROJECT DESCRIPTION
BACKGROUND
The excavation of trenches in roads is an unavoidable aspect of communal infrastructure development (e.g. for water, waste water). Road authorities have increasingly tightened the specifications for the backfilling of trenches due to the justified concern that inadequately compacted backfilled trenches can lead to road settlement threatening road safety (grooves and aquaplaning) and results in subsequent road repair costs. However, exaggerated demands have led to excessive increases in the cost of trenches and significant impact to the environment (e.g. backfilling with material from natural material resources such as sand, gravel). In a research project, sponsored by the Austrian Ministry of the Environment, Ministry of Economic Affairs and the Provincial Governments of Lower Austria, Upper Austria and Styria, a method has been developed that significantly reduces the negative environmental impact as well as the costs for pipeline construction in roads. The aim of this method is to: 1) re-use excavated material in the main backfill zone, if it is suitable for compaction, or 2) use quality sealed recycling material instead
OBJECTIVES
The new procedure for pipeline construction in roads (backfilling of pipeline trenches with excavation and/or recycled material), which was developed within the Austrian research project, was to be demonstrated in two different countries, Austria and Portugal. The objective was to make this a CEN standardised procedure and to disseminate the findings throughout the European Union. The following test methods within the control procedure were to be used: - preliminary tests: penetration test, core boring, water content, density, particle distribution; - tests during excavation: loadbearing plate (static, dynamic), water content, density, particle distribution, manual penetrometer; - tests during backfilling: loadbearing plate (static, dynamic), water content, density, particle distribution, manual penetrometer; - compaction tests: loadbearing plate (static, dynamic), penetration test.
RESULTS
The new “Vienna Trench Control” method for pipeline construction, with a simple but comprehensive compaction control, was first tested on five construction sites in Austria. To gain experience on a broader basis and under varying marginal conditions this method was demonstrated on some 40 construction sites in Austria, Italy and Germany, and prepared for demonstration in Portugal and Switzerland. Initially, it was foreseen to demonstrate the method in Portugal only. The demonstrations revealed the following: approx. 50% of excavation material could be re-used for backfilling, 33 % was backfilled with recycling material and 17% with imported natural material. The experience gained from the LIFE Demonstration Project showed that using the "Vienna Trench Control" method initially caused the following additional costs for tests: - for geotechnical tests/investigations by the client: -+ approx. 2 EUR per metre trench length - for geotechnical tests/test fields by the construction firm: -+ approx. 2 EUR per metre trench length On the other hand, using the new method could result in average savings of: -+ appro 10 EUR per metre trench length (based on the assumption that .50 % excavation material .33 % recycling material and .17% imported natural material are used for backfilling) The cost savings mentioned above however did not include costs for later restoration of roads nor subsequent costs of road accidents. The City of Vienna concluded a consortium contract with a company, Ökoreal GmbH, Chartered Consulting Engineer for Water Management, and delegated the operational and administrative management of the project. Partner contracts with 14 town councils in Austria, Germany and Italy were signed, who put 100m of trench at the disposal of Ökoreal to proceed with the demonstration works. There were some administrative and financial anomalies with the project (excavation of trenches by high number of “minor” project partners for dubious reasons, Ökoreal was more like a sub-contractor than a partner) and it underwent an audit. Furthermore, the benefits of the project from an environmental point of view were also questioned due to a lack of objective data to evaluate the project. The new “Vienna Trench Control” method for pipeline construction, with a simple but comprehensive compaction control, was first tested on five construction sites in Austria. To gain experience on a broader basis and under varying marginal conditions this method was demonstrated on some 40 construction sites in Austria, Italy and Germany, and prepared for demonstration in Portugal and Switzerland. Initially, it was foreseen to demonstrate the method in Portugal only. The demonstrations revealed the following: approx. 50% of excavation material could be re-used for backfilling, 33 % was backfilled with recycling material and 17% with imported natural material. The experience gained from the LIFE Demonstration Project showed that using the "Vienna Trench Control" method initially caused the following additional costs for tests: - for geotechnical tests/investigations by the client: -+ approx. 2 EUR per metre trench length - for geotechnical tests/test fields by the construction firm: -+ approx. 2 EUR per metre trench length On the other hand, using the new method could result in average savings of: -+ appro 10 EUR per metre trench length (based on the assumption that .50 % excavation material .33 % recycling material and .17% imported natural material are used for backfilling) The cost savings mentioned above however did not include costs for later restoration of roads nor subsequent costs of road accidents. The City of Vienna concluded a consortium contract with a company, Ökoreal GmbH, Chartered Consulting Engineer for Water Management, and delegated the operational and administrative management of the project. Partner contracts with 14 town councils in Austria, Germany and Italy were signed, who put 100m of trench at the disposal of Ökoreal to proceed with the demonstration works. There were some administrative and financial anomalies with the project (excavation of trenches by high number of “minor” project partners for dubious reasons, Ökoreal was more like a sub-contractor than a partner) and it underwent an audit. Furthermore, the benefits of the project from an environmental point of view were also questioned due to a lack of objective data to evaluate the project.
