Belfast Wastewater Treatment works

Causeway Geotech were appointed by Kier BAM JV to carry out ground investigation works for provision of geotechnical and environmental information to characterise ground conditions for a proposed upgrade to Belfast WwTW.

The scope of works included:

• 3 light cable percussion boreholes
• 8 boreholes by sonic drilling extended by rotary follow-on drilling to a maximum depth of 60m.
• Excavation of borehole starter pits by vacuum excavation methods
• UXO clearance of borehole locations using CPT mag-cone probing techniques
• Variable head permeability tests in selected boreholes
• A dual standpipe installation in all boreholes, with long term monitoring using water level loggers
• 21 machine dug trial pits
• Groundwater sampling using low-flow techniques
• Factual ground investigation report

The site is a busy operational wastewater treatment works and programming of the works in conjunction with the client and supply chain partners was critical to the success and safe execution of the works.

The works were supervised by a Causeway Geotech Site Agent, with the site team consisting of a vacuum excavation crew, UXO engineer & CPT crew, 3 drilling crews and a trial pitting crew.

A key aspect for the design was the determination of rock level across the site where previous investigations had proved unsuccessful. Through the use of Causeway Geotech’s dual purpose Fraste CRS-XL Duo roto-sonic drilling rig, boreholes were advanced to over 60mbgl which proved the bedrock level to vary between 17.5mbgl an 58.5mbgl across the site.