The Capital Regional District (CRD) of Victoria is constructing a new wastewater treatment facility. To connect existing infrastructure to the facility, a pipeline was required to cross the Victoria Harbour between Ogden Point and McLoughlin Point. Due to the large volume of marine traffic, a trenchless methodology was chosen. Michels, and subsequently CCI, were subcontracted to deliver a design build approach to the crossing. CCI completed the engineering while Michels executed the pipeline preparation and trenchless installation.
The proposed pipeline installation consisted of a 940 m long NPS 42 HDD with complex curved geometry. The entry location was situated in downtown Victoria with restricted available workspaces at both the entry and exit locations.
The challenging formations identified throughout the crossing in the geotechnical investigation included highly fractured and low RQD granodiorite with the inclusions of faults. Additionally, the bedrock surface was probed and found to be heavily undulating, providing varying depths of cover over the proposed drill path. Detailed bathymetric surveys were required for design and to provide Michels with a model which could be trusted.
Due to heavy population density within the city limits, the pipeline was prepared along a busy street. The narrow street led to an A-typical pullback layout, requiring extensive analysis including street level lidar scanning and 3d modelling to determine the impact to residents, powerlines, and existing infrastructure. The road was shut down for pipe makeup and preparation.
The pullback operation lasted approximately three days and required the assistance of a pipeline hammer for the last 250 m of the pullback.
The total schedule for the project was 60 weeks. Execution was completed in 50 weeks. The completion of the project was largely due to the cooperation of varying groups of subject matter experts and a Contractor well versed with completing highly challenging trenchless projects with the highest level of safety.
Publication Date: 2018
2018 TAC/NASTT-NW Tunnelling and Trenchless Conference, Edmonton, Alberta
November 8-9, 2018
Sam Wilson, CCI Inc., Edmonton, Alberta
Patrick O Donoghue, Michels Canada Co., Nisku, Alberta