PL01 Wroclaw
01.01.01An international success or third time is a charm
The “Sleza” sewer in Wroclaw, Poland, is an outstanding example for the application of three different pipe laying methods and one more prove for the universality of HOBAS CC GRP Pipe Systems.
The construction of the “Sleza” sewer already started in the 1970’s. Operating problems with the oldest sewer sections built with concrete pipes is the reason why HOBAS CCGRP Pipe Systems were used for developing the sewer since 1995. Because of varying soil conditions, some sections were built by the open
pipe trench method and others by trenchless technologies. One section was in very poor condition and had to be repaired as quickly as possible. A pipe laying method that was already successful in another project, namely the sewer “Podwale” was chosen. The sewer “Podwale” survived the floods in 1997 without any damages. Exactly this relining technology was chosen by Wroclaw waterworks authority in 1998 for the relining of the “Sleza” sewer. For further details, please see below:
In autumn 1995, the construction - which was started in the 1970’s - was continued with “Sleza – Stage IV”. HOBAS CC-GRP Pipe Systems of DN 1600, SN 10000 and SN 5000 were used. Based on a detailed technical and economical analysis, experts on site decided to use HOBAS CC-GRP Pipe Systems. Thanks to highly advantageous hydraulic parameters, the originally planned nominal diameter of DN 1800 could be reduced to DN 1600. The biggest challenge in this section was the laying depth of approximately 9 meters and the ground water, mainly in cohesive soils. In some sections, the soil conditions were extremely difficult. The contractor, the building company „Józef Iwaniszyn i Spólka”, decided to stabilize the bedding using a special technology, which was partially a breakstone layer of 0,5 m, and partially a concrete bench. On these layers, a gravel bed with granulation was laid before the HOBAS CC-GRP Pipe Systems were installed.
Due to the leaking of the concrete pipes and the doubtful load capacity in many sections, the investor decided to reline the full sewer length of 3.5 km. The designer wanted to reline only one short section in order to make some local reparations. The decision for HOBAS CC-GRP Pipe Systems was taken due to their successful realization of former projects.
In the less damaged sections, HOBAS CC-GRP Pipe Systems of DN 1600, SN 2500 were used. For the more corroded parts, HOBAS experts decided to use pipes with a stiffness of SN 5000. HOBAS CC-GRP Pipe Systems of 6 meters were assembled from 10 m long starting chambers. The annular space between pipes was filled with the mortar of cementsand proportion and with additives of foaming agents and stabilizers.
Until July 1999, 258 meters of the sewer in Redzinska Street and 284 meter in Szczecinska Street were relined.
In November 1999, the relining of the next section in Maslicka Street was completed and in December 1999 the acceptance inspection of the 1560 meter long relined section of the “Sleza” sewer in Redzinska and Maslicka Streets was successfully passed by HOBAS Poland.
The next section was assembled in 1999 using HOBAS CC-GRP Jacking Pipe Systems of DN 1600 (OD 1720), SN 32000 with a pipe wall thickness of 55 mm. This stage was divided into three sections, being 53.5 meters, 112 meters and 75 meters. The contractor was again the BETA SA company from Warsaw. Each section of approx. 240 m was assembled (after building of starting chambers) during three to six working days. The separate sections were connected with HOBAS tangential manholes.
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