Romanian remediation requires best of both worlds

Repairing the neglected sewers of Bucharest required the use of a combination of glass-reinforced plastic and cured-in-place pipe techniques, writes Ian Clarke on behalf of Insituform Technolgies

The drainage system in the historic centre of Bucharest, the capital of Romania, had fallen into disrepair during the communist era. But, since joining the EU in 2007, the Romanian economy has been boosted by about £6.5B of foreign investment and this has allowed some major reconstruction works to be carried out.

The City of Bucharest introduced a road and utilities refurbishment project of the

historic zone of Bucharest. It began in October 2006 and runs to April 2008, with the potential for subsequent further work. The current phase of the works is valued at nearly £15M and includes the renovation of sections of central Bucharest’s sewer network.

A tender was drawn up and, through its branch office in Romania, Yorkshire-based Insituform Technologies was named as the renovation subcontractor in a £2.1M contract. In mid-2007, Insituform Balcani was formed in Romania.

The project duration was expected to be 370 days and the works began with the cleaning and CCTV inspection of 3,000m of the sewer network. Subsequently, Insituform was required to develop a full and detailed construction design of the scheme that would be required to completely refurbish the surveyed sections of sewer.

The project ultimately required the use of both glassfibre reinforced plastic (GRP) segmental lining and cured-in-place pipe (CIPP) lining. Works included the rehabilitation of the mainline sewers lengths, internal rehabilitation of the existing manholes using grout injection techniques over a surface area of 2,037m2, lining of the lateral services connecting to the mainline sewers using CIPP techniques (a length of some 1,200m) and a final CCTV survey and report of the completed works.

In April 2007, work started on the GRP installations for the rehabilitation of an egg-shaped pipe in Gabroveni Street. This 225m length was completed on May 31.

Installation continued with a GRP 50m lining in an egg-shape sewer beneath Selari Street, which was completed on June 25.

In July work started in another egg-shape pipe beneath Lipscani Street. This 205m length was completed on August 27. In early September,` the next stage of the project started with the GRP lining of an egg-shape sewer beneath Franceza Street. At the time of writing, this 314m long section had also been completed.

GRP lining is classed as a segmental lining system. This means that it uses prefabricated liner sections as the basis of the lining system. A GRP liner is essentially a fibre-glass/resin product, which is factory manufactured and moulded to the precise size and shape of the pipeline it is designed to rehabilitate.

The design is normally based on the minimum dimension permissible within the deteriorated pipeline under repair. This ensures that the liner can be installed throughout the pipe length without any deformation in the host pipe preventing access. GRP liners can be also used to negotiate bends in pipes by using short-length liner pipes.

Preformed segments

As the GRP liner segments are preformed to the minimum dimension of the host sewer, their installation is normally achieved manually with specially fabricated end profiles. This allow the segments to knit together closely to ultimately form the completed lining length. Within the sewer, the liner segments are positioned using spacer blocks to create the lining, with an annulus between the liner outer wall and the pipe inner wall.

Normally this annulus is grout-filled as the lining construction advances. This provides the necessary bond between the host pipe and the new liner and adds to the structural integrity of the completed system.

Once a lining length is completed, the pre-surveyed positions of any laterals are reopened to remake the connection. It is only once the main GRP sewer lining is completed that the lateral connections are renovated. For the Bucharest project, the GRP liner segments were manufactured by Stanton-Bonna in the UK and taken to Romania by road.

The CIPP lining installations for these laterals is undertaken from within the main sewer. Subsequent to each lateral lining, the main/lateral connection is sealed completely using the new extended lateral connection repair connection seal.

Insituform has recently developed this in conjunction with lining product specialist Trelleborg-epros.

The works are being funded by a £1.3M grant from the Dutch government, £5.7M EU funds administrated by the European Bank for Reconstruction and Development and £7.8M from the budget of Bucharest City Hall. The project is being managed for the city by general contractor Sedesa constructions and Services Rom on behalf of Sedesa Obras y Servicios of Spain.

Trenchless future

In other works, the mainline sewer CIPP linings on the project will comprise1,711m in length and will use the Insituform process lining technique using water inversion/hot-water curing techniques.

Lateral connection linings for these sections will be done once CIPP work has been completed and the lateral connections have been remade into the mainline sewers. Sealing of the connections will be completed again using the new lateral connection repair seals.

Insituform also recently won a major GRP installation contract with Thames Water in the UK for lining work on the Crossness sewerage treatment plant. The contract is valued at over £1M and comprises the installation of GRP liners of 1,400mm diameter, 945mm x 1,400mm ovoid and 2,000mm x 1,370mm ovoid cross-section over a total length of some 1,000m.

The contract also includes the renovation of 13 access shafts, including new ladders and landings. This work began in October 2007.

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