HDD Underbore on the Ribbon Gas Main Extension

As a part of the Ribbon Development in Darling Harbour, UEA was engaged to undertake extensive utility location with the objective of relocating the existing gas main in Darling Harbour. Stage 1 involved the use of dial before you dig requests, ground penetrating radar (GPR) searches and non-destructive digging (potholing) to identify the location and depth of existing services along the proposed underbore route. Once completed, UEA utilised GIS data to complete an underbore design which mapped all existing services, the new proposed gas route and possible obstructions including the concrete footings for the Western Distributor.

Based on UEA’s experience with completing complex underbores in highly congested locations and the completion of stage 1 works, UEA was also awarded stage 2 of the project following a competitive tender. Working within a brownfields site with over 200 years of redevelopment, historical mapping was utilised to show that the alignment of the underbore would traverse real estate that had changed significantly over the past 75 years.

Without any supplied geotechnical borehole data, the strata to be drilled could not be confirmed before the completion of the pilot bore, with the only known ground conditions to be sandstone at the HDD exit point.