Auger Boring Through Lecce Limestone With HOBAS Pipes
In the South-Italian city of Lecce, a new 3800 m long HOBAS GRP Interceptor Sewer has been installed. 800 m of the pipeline were successfully realized by means of auger boring. , The holding company Acquedotto Pugliese S.p.A. (AQP) offers water supply and wastewater services in the Italian regions of Puglia and Basilicata and counts among the most important sewer network operators worldwide. For the disposal of wastewater in the historical city center of Lecce, AQP planned a new interceptor sewer in order to improve the efficiency of the existing network. The old sewer already showed problems in handling even small precipitations, with frequents overflows upstream of the local wastewater treatment plant. It was decided to build a 3.8 km long GRP sewer line DN 800 as well as a new pumping system. Due to the busy traffic and the partly very narrow lanes in the city center of Lecce, it was decided to install 800 m of the new line with trenchless methods. , The soil in the Lecce area posed a particular challenge to the construction works: The marble-like and water-sensitive “Lecce stone” required a trenchless approach other than the conventional microtunneling with hydraulic conveyance. It was therefore decided to realize the no-dig section by means of auger boring, using the special Front Steer system by the company Bohrtec which has been developed especially for difficult soils. This solution allowed for the Lecce limestone to be conveyed dry and also turned out to be the easiest and most efficient way to implement this part of the project. , The construction company in charge, F.lli Andresini di Polignano a Mare, decided to use HOBAS GRP Jacking Pipes De 860, SN 32000 for the auger boring section and HOBAS GRP Sewer Pipes DN 800, SN 15000 for the remaining installation in open trench. Thanks to their easy jointing system, optimal hydraulic characteristics, and abrasion resistance, HOBAS CC-GRP Pipes proved ideal for the projects requirements. , “The centrifugally cast HOBAS GRP Pipes left me impressed”, says Vito Francesco Andresini, managing director of F.lli Andresini. “The easy cutting on site, the convenient coupling system, the high stiffness, allowing for the pipe to be installed even in difficult ground conditions, and the optimal standard length of 6 meters make the pipes an ideal solution for sewer lines.” Installation works were successfully finished in June 2016.