The project is one of the largest and most important infrastructure investments presently underway in the city. The work has been designed and the project managed by Atkins Consultants, on behalf on Northern Ireland Water. As part of the seven year £100 million Belfast Sewers Project, Insituform Environmental Techniques Ltd has recently been involved in a significant pipe lining project in the vicinity of May Street.

Records of May Street date back to the 1800s. The area includes the famous St George’s Market and the historic Belfast Court House, just two of the district’s well known tourist attractions. The recently built Victoria Square shopping centre is also attracting increased numbers of the public to the area.

In order to minimise disruption and reduce the environmental impact on the local community, a number of low-dig and trenchless techniques have been adapted where possible across the city. This has allowed continuous public and business access and the uninterrupted flow of traffic.

The project as a whole covers a number of new installations, pipe replacements and rehabilitation works. Northern Ireland Water aims to provide a modern sewerage system for the 250,000 people living in the greater Belfast area. Major works include the construction of a 9 kilometre tunnel of up to 4 metres in diameter, the construction of new sewers, storm water tanks and the repair of 500 existing sewers. The project started in 2005 and is scheduled for completion in 2012.

The Belfast Sewers Project involves two key contracts. The Sewer Rehabilitation Works – contract one started in 2005 will ultimately upgrade the 500 sewers originally found to be in poor condition. Insituform Environmental Techniques has played a significant role in the trenchless operations of these works.

Lining Works

Working for Northern Ireland Water, through main contractor John Graham (Dromore) Ltd, Insituform Environmental Techniques recently utilised its renowned CIPP lining technology to rehabilitate the pipes. The lining rehabilitated some 133 metres of a seriously deteriorated 1,200 mm x 900 mm egg shaped culvert running beneath May Street.

The red brick built culvert had suffered mortar and brick loss as well as extensive deformation in several areas and was in urgent need of rehabilitation. Given the location of the culvert, and the traffic requirements on May Street, an effective structural renovation technique was required that could be applied in a short time frame with minimum disruption to the area. After careful consideration of the available options, it was decided that the Insituform CIPP system offered such a solution.

The traffic management system was set up late on Friday 18 July 2008 to ensure sufficient access to the work site for men, materials and equipment. The lining work was completed and the pipeline placed back in service by Sunday.

Once the site was accessible to Insituform Environmental Techniques’ crews on the Saturday, the rehabilitated culvert section was accessed at both ends via existing manholes. After inspecting the culvert and ensuring that it was clean and ready for the lining process to a five metre high scaffold tower was erected at the launch end of the culvert and the necessary liner launch guide and liner reception structures were positioned in the respective manholes.

The liner comprised a 1,200 mm thick resin impregnated, needle felt ‘sock’ which was prepared off-site at Wellingborough, North Hampshire. The liner was delivered to the site in a refrigerated truck to ensure that the thermo-sensitive resin used did not cure during transport.

The end of the liner was fixed to one end of the launch guide structure and, using the water pressure head provided by the scaffold tower, the remainder of the liner was inverted through the fixed end into the deteriorated culvert. When the liner was fully inverted into position in the culvert, the water pressure ensured that the liner remained tight against the inner wall of the host pipe. The inversion water was then circulated through a boiler to heat it to the correct temperature. The increased temperature of the water caused the thermo-sensitive resin to cure and harden. The water pressure head continued to hold the liner tight against the host culvert inner wall. In the case of the May Street lining the cure time was approximately twelve hours.

On completion the liner formed a new pipe in its own right and the inversion/curing water was cooled and removed. The site was demobilised by the end of the Sunday shift, after a post-lining CCTV survey had been completed, and the culvert was placed back in service.

Commenting on the works, a representative of Northern Ireland Water stated “We have tried very hard to minimise the effects of what is one of Belfast’s largest ever civil engineering projects on the community at large. The use of minimum dig and trenchless technologies has enabled us to keep the city moving, businesses working and allowing our population to continue with their daily lives without serious interruption.

“This work, once completed in 2010, will give Belfast’s citizens one of the most modern and effective sewer systems in the country, ensuring that wastewater flows are collected, moved and treated effectively whilst also reducing local flooding at times of heavy rainfall.”