Insituform Environmental Techniques was subcontracted to reline twin culverts as part of the Ballyogan Landfill Site Carrickmines Dublin 28 works project. The twin culverts, which extend through the body of the 62 hectare landfill site, convey the Ballyogan Stream through the landfill.

Prior to commencing the CIPP rehabilitation, CCTV reports detailed a number of structural faults along the length of the culverts, ranging from Grade 1 to Grade 4 status, assumed to have been caused by overburden loading or hydrostatic pressure.

Rehabilitation works took place using two single shot installations, each 271 metres long, using CIPP lining technology. The project was the largest CIPP lining job in Ireland to date.

Although cost efficiency was one of the primary reasons for rehabilitation using CIPP there were a number of other considerations including:

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  • The need to retain the internal diameter of the culverts required thin wall rehabilitation
  • The liner chosen was needed to improve hydraulic capacity
  • A short installation period was needed, as works were being carried out in a live stream flow
  • Health and safety considerations meant that the method chosen should not require any man entry into the culverts.

Both of the liner installation took just three days each to complete, including installation and hot water curing.

Challenging CIPP

There were a number of challenges that the company overcame when undertaking this project.

The first challenge was the proximity of the installation site to the Arklow Carrickmines 220 kilovolt electricity substation, the powerlines of which pass directly over the inlet of the river culverts. This meant that there was a maximum permissible machinery reach and height restriction of 4.5 metres. The remote location of the site also made access difficult for the necessary installation equipment.

These challenges were overcome by building an access road and introducing roller beds to convey the liner from the liner delivery vehicle to the culvert insertion point, minimising the headroom required.

The challenge of working in a river environment was incentive for the team to complete the work quickly, as the flow had to be diverted on a continuous basis. Works on the lining project were completed in two 36 hour shifts.