Shore Approach Horizontal Directional Drill Crossings into the Bay of Fundy, New Brunswick

摘要

New Brunswick Power Transmission Corporation (NB Power) is constructing the Fundy Isles Transmission PowerLine Project which consists of 69 kV Submarine Cables from Deer Island, NB to Campobello Island, NB and fromCampobello Island to Grand Manan Island, NB. This project will provide electricity to the islands and will replaceexisting cables installed in 1978 and nearing the end of their service life.NB Power requested that the connection between the submarine and the land-based sections of the project becompleted utilizing the Horizontal Directional Drill (HDD) methodology to mitigate any concerns of futureexposure due to erosion from the large tidal action within the bay. The HDD crossings were to include theinstallation of three (3) HDPE conduits, one (1) 16-inch O.D. HDPE conduit along with two (2) spare 3.5-inchHDPE conduits for future corrosion protection measures inside a 24” common borehole. The project included four(4) shore approach crossings, designed to be progressed through 0-50% RQD Mafic Tuft, Shale bedrock, andoverburden materials.Marathon Underground Constructors Corporation (Marathon) was successful in the tendering process for theproject. CCI Inc. (CCI) was subcontracted to assist with production of feasible designs and provide HDDconstruction experience and support.The unique nature of the shore approach methodologies, space constraints, marine activities, and difficult groundconditions at the crossing locations culminated in complicated conditions for HDD installations.Through comprehensive engineering design, significant combined HDD experience, and Marathon’s ability to adaptto onsite conditions, two of the four crossings were successfully completed by HDD methods and two werecompleted with open cut methodologies with all completion dates meeting the required in-service date.This paper will discuss the challenges faced during both the design and construction phases of the shore approachcrossings.