Hollystown – Foul Drainage Works

Project Name

Hollystown – Foul Drainage Works


Glenveagh Homes




Hollystown, Co. Dublin

Main Contractor:

M&N Civil Engineering

Contract Period:

March 2022 - July 2022

M&N’s PSCS role included the construction of a 3.2-kilometer foul drainage line, manholes, and associated drainage systems, all compliant with Irish Water (IW) standards. The depths reached up to 8 meters, necessitating rock breaking in trenches amounting to 4,500m3 at significant depths.

The initial phase involved setting up the compound and site facilities to accommodate the project team. Additionally, M&N installed 3 kilometres of fencing to secure the works area and adhered to ESB guidelines by installing overhead ducting at three crossing points within the site.

Restrictors were integrated into plant machinery to prevent potential clashes with overhead structures. We also constructed a 2km internal haul road and installed silt-fences at watercourses and stream crossings to mitigate against the potential for contamination.

For sewer pipe installations, M&N installed SN8 sewer pipes with diameters of 225mm and 300mm, as well as precast concrete pipes in diameters of 450mm and 525mm. These pipes were laid at depths ranging from 3 meters to 8 meters, using excavators of up to 50 tons.

Throughout the project, we worked closely with Fingal County Council one of the statutory stakeholders. Site visits were conducted for inspections, air testing, and the final assessment of works by Irish Water before handover. Collaboration with Fingal County Council was also vital in managing the interface with watercourses during the project’s progression.

The main challenge encountered during this project was the groundwater issues that arose in areas where rock was encountered during trench excavation. This was addressed by installing 600mm diameter wells below our excavation levels. These wells allowed us to pump groundwater to sediment tanks and then safely discharge it into local streams. This approach was coordinated and agreed upon with Fingal County Council.

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