ISTT Award 2011 Goes to Rehabilitation Project in Sofia, Bulgaria

At the 2011 International No-Dig show Stroitelna Mehanizatsia and SEKISUI SPR Europe (SSPRE) received the renowned No-Dig Award 2011 of the International Society for Trenchless Technology (ISTT) for an outstanding rehabilitation project in Sofia, Bulgaria.

This year Stroitelna Mehanizatsia AD, Bulgaria received the No-Dig Award 2011 for a rehabilitation project carried out together with SEKISUI SPR Europe using the NORDIPIPE pressure liner.
“The ISTT has honored one of the most exciting construction projects with its renowned award. That makes us and our partners very proud,” says Edmund Luksch, CEO of the international SSPRE Group.

The conditions in Sofia presented a real challenge: in the middle of the worst Bulgarian winter, the team from Stroitelna Mehanizatsia renewed a steel water pipe with a working pressure of 7 bar and a diameter of 1,220 mm within the space of only a few weeks. A new inversion vessel with a diameter of 3,000 mm was specially developed for the purpose.

Stroitelna Mehanizatsia rehabilitated a 850-m section of a 30-year-old pipeline below the narrow streets of an old residential district of Sofia, including a crossing under a railway. Population pressure meant that the pipeline could not be taken out of service for an extended period. Construction work had to be completed by mid-January 2011, but could not be started until December. In view of the large diameter and 8-mm thin walls the NORDIPIPE pressure liner was used as a semi-structural solution from SSPRE.

The severe cold that was well below freezing hindered not only the pressure water jet cleaning of the host pipe but also the impregnation, because it was difficult to keep the resin fluid. A further challenge was that with the required minimum thickness of the impregnated liner only sections of maximum 90 m could be rehabilitated. Stroitelna Mahanizatsia therefore developed a new inversion vessel for the liner – likewise within the extremely tight deadline – tailor-made for rehabilitating sections of up to 110m in length in this project. This enabled the inversion to be completed successfully in all nine sections.

Maximum Performance from Man and Technology

“The biggest challenge with this project was to motivate my team to complete the work in the short time and to believe in themselves,” Stefan Zhelyazkov, General Manager of Stroitelna Mehanizatsia, explains. “Our employees did a great job and we were able to count on the full support of SEKISUI SPR Europe. Our success is thus thanks to the complete family of SSPRE companies, who gave optimum cross-border support for the installation of the NORDIPIPE liner.”

Successful Cooperation

A total of 45 tonnes of liners and resin were installed in only 35 days, including Christmas and New Year holidays. “Due to the complexity of the construction project we had of course hoped for the recognition of the ISTT. Nevertheless, the announcement of the award came as a surprise and we are absolutely thrilled. The award is an endorsement of the successful partnership between Stroitelna Mehanizatsia and SEKISUI SPR Europe,” said Zhelyazkov at the presentation at a gala dinner for the International NoDig Fair in Berlin on May 4.

The SEKISUI SPR Europe Group, headquartered at Schieder-Schwalenberg (Germany), offers advanced technological solutions for underground infrastructure to local authorities and construction companies all over the world. An international sales and support network of 19 offices combines the competence of construction and technology companies. SEKISUI SPR has the two leading key technologies – the spiral-wound and cured-in-place pipe lining methods – for the rehabilitation of water, sewage and gas pipelines. The products for trenchless pipe rehabilitation are manufactured at four plants in Australia, Germany, Belgium and the United States. SEKISUI SPR Europe has a total workforce of 450 and operates in over 40 countries with the aim of achieving optimum results for its customers, from the drawing board to installation

 This article was submitted by SEKISUI SPR Europe.