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Nalcor Energy Strait of Belle Isle HDD Project
Location
Strait of Belle Isle,
Newfoundland and Labrador,
Canada
Client
Nalcor Energy
Project Type
Ocean shoreline crossing /
HDD Installations
Services
Feasibility, Preliminary
Design, Final Design, and
Construction Management
Services
Duration
Aug 2010 to Present
HDD Contractor
Mears Group, Inc.
Mears Canada Corp.
2106-5th Street
Nisku, AB T9E 7X3
(780) 955-7155
Project Description
The required HDD installation lengths range from
5,250 feet (1,600 metres) to 8,900 feet (2,700
metres). The target water depths of the HDD exit
locations ranged between 230 and 260 feet (70 and
80 metres). These depths are required to avoid
potential damage from iceberg scour within the strait.
The anticipated geotechnical materials include sand,
gravel, cobbles overlying bedrock materials
consisting of shale, dolostone, limestone, sandstone,
and gneiss. The ocean floor sediments consist of
gravel, cobbles and boulders due to strong ocean
currents.
Nalcor Energy is undertaking the design and construction
of six (6) 20-inch (500 mm) diameter steel casing
pipelines installed using horizontal directional drilling
(HDD) methods to complete landfall/shoreline crossings
along the shorelines of Newfoundland and Labrador. The
steel casing pipelines will be used to house subsea
electrical cables that will be installed across the 10.6 mile
(17 kilometer) wide Strait of Belle Isle from Labrador to
Newfoundland.
HMM Role
HMM was retained to complete the feasibility study
and provide design and construction services for the six
(6) shoreline crossings. The feasibility study focused
on developing a risk register to identify and
characterize the specific risks for each crossing
location. Mitigation measures were also developed
with recommendations to be incorporated into the
design phase of the project. HMM compiled project
histories from several large HDD contractors to assess
and evaluate the current State-of-the-Practice in terms
of achievable HDD installation lengths at the required
pipeline diameters. Other tasks included developing preliminary plans and profiles, cost estimates,
and bid documents for additional geotechnical investigations. As part of these geotechnical
investigations, HMM completed full design and construction services for an HDD pilot bore
investigation which was used to validate the conceptual design of the six (6) shoreline crossings, test
contingency plans, and obtain geotechnical information.
Project Highlights
• Six (6) ocean shoreline crossings using
horizontal directional drilling methods.
• Target water depth of HDD exit locations
range between 230 and 260 feet (70 and
80 metres).
• HDD installation lengths ranging between
5,260 and 8,900 feet (1,600 and 2,700
metres).
• Critical assessment of the current State-ofthe-Practice
in terms of achievable HDD
installation lengths at the required pipeline
diameters.
• Development of a geotechnical investigation program including drilling an HDD pilot bore out
to a length of 5,111 feet (1,558 metres) to characterize the anticipated geotechnical materials
and to assess HDD drilling parameters such as bit wear, penetration rate, zones of lost
circulation, and grouting strategies.